All events

The Canton of Geneva acquires the CDC 3800 for the University of Geneva

The Canton of Geneva bought the CDC 3800 from CERN, and installed it at the University of Geneva. At CERN, the CDC 3800 was replaced by a CDC 6400. 

Timelines
Computing at CERN

Spain quits

At the request of the Spanish government, Spanish contributions to the CERN budget for 1964, 1965 and 1966 were reduced by 50%, 35% and 20% respectively. In a letter on 21 September 1996 to the Director-General the government asked for a further reduction of 35% from 1967 onwards. The CERN finance committee rejected the request.

Minutes of the CERN council, 19-20 June, 1969:

At the 40th Session of council last year, Spain asked that her notice of withdrawal from the organization contained in her letters of 8 August and 30 October should be held in suspense whilst her authorities studied further the possibility of her remaining in CERN.

By letter of 2 June 1969, Spain notified the Director-General that no solution had been found possible and that consequently her withdrawal from the organization would take effect as from 31 December 1968.

The council is now invited to take note of the withdrawal of Spain from the organization.

Spain formally withdrew from CERN on 31 December 1968.

Timelines
Member states

T. D. Lee lectures to CERN’s summer students

Summer at CERN means summer students – and a succession of distinguished speakers from within and outside the organization who share their knowledge with young scientists each year. This photo shows Nobel Prize-winner T. D. Lee explaining symmetry principles in physics to the 1968 intake.

The summer student programme was set up in 1962 as an extension of the existing fellows and visitors scheme. In its first year, 70 students were selected from around 500 applicants; they stayed for 68 weeks, lodging at the University in Geneva or in temporary barracks on the CERN site. Since then the programme has continued to grow, and the combination of work experience, lectures, discussions and workshops and an active social life remains just as popular.

Timelines
From the archive

CERN’s new telephone exchange

Dialling zero for an outside line could be frustrating in 1965. With just 17 lines serving 1,000 CERN extensions, callers faced long waits – and if the overloaded battery failed no-one could got through at all. Phone traffic had increased by 70% between 1963 and 1965, complaints were frequent and the exchange staff were feeling overloaded too.

No more lines, extensions or operators’ desks could be added to existing exchange, so a new one was commissioned. Stop-gap measures until it was ready in August 1968 included pleas for patience and strict rationing of the only 140 new internal phone numbers remaining at CERN.

Timelines
From the archive

The 55th Tour de France comes to CERN

CERN’s internal magazine carried detailed instructions about closed roads, blocked entrances, and suggested detours. Staff were invited to respect the parking ban and to obey police instructions, but plenty of them took the opportunity to pile outside and watch as well. On 19 July 1968 the Tour de France came right past CERN’s main entrance!

CERN staff joined fans lining the route to encourage riders on Stage 20, which took the riders 242.5 km from Sallanches to Besançon, over the Faucille pass in the nearby Jura mountains. This was the last year that the Tour ran on a national team format; stage 20 was won by Jozef Huysmans (Belgium A), who finished 32nd overall when the race ended two days later.

Timelines
From the archive

Muons are like drunken cowboys

In March 1968 staff were invited to watch the new documentary film about CERN. They probably enjoyed themselves, as Guido Franco’s aim was to inform the public through entertainment. He sought to engage an audience’s attention and make them want to learn, rather than forcing information on them. If that sounds uncontentious, you might be surprised at the strength of feeling the film aroused.

 

Despite considerable editing at the end of 1967 to meet criticisms of the first version, opinion still varied widely. Some were enthusiastic, feeling it captured the spirit and excitement of particle physics research; others found it frivolous, mocking scientists and portraying them as playboys having a wonderful time at the taxpayers’ expense. Even the fiercest critics thought it reflected great credit on Franco as a film-maker, however, they just feared it could do untold damage to the reputation of CERN.

Timelines
From the archive

Georges Charpak revolutionizes detection

In the 1960s, detection in particle physics mainly involved examining millions of photographs from bubble chambers or spark chambers. This was slow, labour-intensive and unsuitable for studies into rare phenomena.

Then came a revolution in transistor amplifiers. While a camera can detect a spark, a detector wire connected to an amplifier can detect a much smaller effect. In 1968, Georges Charpak developed the “multiwire proportional chamber”, a gas-filled box with a large number of parallel detector wires, each connected to individual amplifiers. Linked to a computer, it could achieve a counting rate a thousand times better than existing detectors. The invention revolutionized particle detection, which passed from the manual to the electronic era.

Charpak, who joined CERN in 1959, was awarded the 1992 Nobel prize in physics "for his invention and development of particle detectors, in particular the multiwire proportional chamber".

Today practically every experiment in particle physics uses some track detector based on the principle of the multiwire proportional chamber. Charpak has also actively contributed to the use of this technology in other fields that use ionizing radiation such as biology, radiology and nuclear medicine.

Timelines
The history of CERN

First proton beams at ISOLDE

(image: ISOLDE experimental hall. The magnet of the ISOTOPE separator, the collection chamber and the control desk were placed in the same area as most of the experiments.)

The underground hall for ISOLDE is ready in 1967 and the first proton beam bombards the target on October 16. The first experiments are successful and prove that the online technique meets the expectations of the experimentalists. During the next year, a number of experiments produce short-lived isotopes of a several elements. The first paper is published early in 1969 and presents results for short-lived isotopes of the noble gases Ar, Kr, Xe and Rn and several other elements like Ag, Cd, I, Pt, Au, Hg, Po and Fr.

Timelines
ISOLDE

The Finance Committee approves the purchase of a CDC 6400

At its 81st meeting on 16 February 1967, CERN's Finance Committee authorized the purchase of the CDC 6400 computer, a small CDC 3100, and four magnetic tape units. The costs exceeded the funds available in the 1967 budget by 7-8 million Swiss francs. In its next meeting the Committee recommended the use of CERN's own funds for the purchase, "only raising a bank overdraft if this is necessary to cover the cash requirements". 

The CDC 6400 was installed at CERN later that year. 

Timelines
Computing at CERN

The CDC 3800 boots up temporarily

The 3800 was a member of the 3000 series Control Data Corporation family of computers, incompatible with the 6000 series machines. The 3800 had a 48-bit architecture. Its 64 Kword core memory was replaced by a faster, 800-nanosecond memory during its stay at CERN. This machine was eventually acquired by the State of Geneva and installed at the local University of Geneva. At CERN it was replaced by a CDC 6400. It is worth noting that CERN acquired other machines of the 3000 series, such as a 3100 for the FOCUS project offering semi-interactive facilities and quick sampling of experimental data at the central computers, and a 3200 for interactive graphics applications.

Timelines
Computing at CERN

Synchrocyclotron shuts down

(image: excavation work for ISOLDE underground hall in 1966)

On 8 May 1966, the CERN Synchrocyclotron begins a long shutdown until mid-July. During this time major modifications are carried out as part of a programme to improve the capacity of the machine and its associated facilities. One of the main items of work during the shutdown is the construction of a new tunnel for an external proton beam line to the new underground hall for the ISOLDE experiments. This tunnel is constructed underground to keep external radiation levels down and the existing proton room is kept for experiments that use beams of lower intensity.

Timelines
ISOLDE

A CERN stamp

On 21 February 1966 the Swiss Postal Authorities issued a 50 centime postage stamp in honour of CERN. Five Swiss artists visited CERN and were shown around the site, then each presented two designs. The judges selected a design by H. Kumpel  showing the flags of the thirteen Member States of CERN superimposed on a bubble chamber photograph. The flags are arranged to represent the approximate outline of the Swiss border.

A further commemorative stamp was produced by France in 1977 for the inauguration of the Super Proton Synchrotron, and another Swiss stamp marked CERN’s 50th anniversary in 2004.

Timelines
From the archive

No parking problems with a palanquin

A suggestion to ease parking problems on the CERN site by allocating spaces didn’t go down well in 1965. Possibly the priority given to senior staff, and remarks about the benefits of an invigorating walk, gave offence. In any case, an alternative was proposed:

‘May I suggest instead that “senior administrators, division leaders" and the like, be provided with sedan-chairs or palanquins, in which they could be transported swiftly and effortlessly from corner to corner of the site. Other members of the staff would of course function as bearers. This would not only provide them with invigorating exercise, but also inculcate a due sense of their social position.’

A worried prospective bearer suggested motor scooters, as used by nuns on the wards of an Illinois hospital, instead. To prevent congestion indoors, use of the corridors could be limited to senior staff. Other people would get from office to office via the window ledges, not only enjoying healthful exercise but also freeing up more parking spaces as staffing levels gradually decreased when they fell off. The suggestion does not seem to have been adopted, but remains on file

Timelines
From the archive

First observations of antinuclei

By 1965, all three particles that make up atoms (electrons, protons and neutrons) were known to each have an antiparticle. So if particles, bound together in atoms, are the basic units of matter, it is natural to think that antiparticles, bound together in antiatoms, are the basic units of antimatter.

But are matter and antimatter exactly equal and opposite, or symmetric, as Dirac had implied? The next important step was to test this symmetry. Physicists wanted to know how subatomic antiparticles behave when they come together. Would an antiproton and an antineutron stick together to form an antinucleus, just as protons and neutrons stick together to form the nucleus of an atom?

The answer to the antinuclei question was found in 1965 with the observation of the antideuteron, a nucleus of antimatter made out of an antiproton plus an antineutron (while a deuteron – the nucleus of the deuterium atom – is made of a proton plus a neutron). The goal was simultaneously achieved by two teams of physicists, one led by Antonino Zichichi using the Proton Synchrotron at CERN, and the other led by Leon Lederman, using the Alternating Gradient Synchrotron (AGS) accelerator at the Brookhaven National Laboratory, New York.

The CERN paper, Experimental Observation of Antideuteron Production was published in the Italian particle-physics journal Il nuovo cimento on 1 September 1965 (the journal ended when it was merged into the European Physical Journal in 1999.

Timelines
The story of antimatter, The history of CERN

The CDC 6600 arrives at CERN

The CDC 6600, made by the Control Data Corporation, arrived at CERN on 14 January 1965. It was the first multi-programmed machine in the CERN Computer Centre, with about 10 times the processing capacity of the IBM 7090. 

The 6600 was used to analyse the 2-3 million photographs of bubble-chamber tracks that CERN experiments were producing every year. Human operators recorded significant observations from frames of bubble-chamber film onto punched cards. A machine called a  Hough-Powell digitizer (HPD) scanned the cards and sent the information to the 6600. A device called YEP also measured significant tracks on bubble-chamber photographs, coded them onto paper tape, and sent this information to the computer. A third device – "Luciole" –  provided the 6600 with fully automated measurements of spark-chamber film. 

The CDC 6600 filled a large room. It consisted of 12 data channels, 10 peripheral processors, a central magentic-core memory and a central processor. Devices such as the HPD were connected directly to the computer by data channels. The 6600 was also connected to card readers that ran about 500 FORTRAN problems per day, and to two online computers – the SDS920 and the IBM 1800 – via CERN-made data links. The results of calculations on the 6600 were printed on paper or punched onto cards for further study.

The change-over from the IBM 7090 was planned to take 3 months starting in January 1965. Major engineering overhauls were needed during the first few years, which led to a 2-month shut-down in 1968 to modify the 6600: CERN's pre-production model needed to incorporate the logic and packaging improvements that had been introduced in CDC's production machines. During this period of struggling with hardware instability and software development, computing work at CERN was done partly by sending jobs to outside computers and partly by processing data on a CDC 3400, and later on a 3800, temporarily made available by the Control Data Corporation.

Find out more

Technical specifications

CDC 6600, serial number 3 (pre-production series machine)
Ran at CERN from 1965 to 1975
Transistor machine
Central Processing Unit clock cycle: 100 nanoseconds
Core memory: 128K words of 60 bits (converted to modern terms, with 8-bit bytes, this is 0.94 MB)
Memory access: 1 microsecond (but independent memory banks allowed for up to one access per clock cycle)
Instruction prefetch function
Ten overlapping functional units
Ten autonomous peripheral processor units (PPU's) each with 4K 12-bit words of core memory
Huge disks over 1 metre in diameter held 500 million bits each
Tape units (half inch tape: 7 tracks, recording 200, 556 and 800 bytes per inch; one-inch tape: 14 tracks recording 800 bytes per inch)
High-speed card reader (1200 cards per minute)

 

Timelines
Computing at CERN

CERN approves the online separator project

On 10 April 1963, a number of European nuclear physicists meet at CERN to discuss the isotope separator project. A first outline is presented in an internal nuclear physics division report.

A Working Party is set up and a series of meetings are held from May to September. In a memorandum dated 26 October 1964 the chairman of the Nuclear Structure Committee Torleif Ericson recommends the on-line isotope separator project to CERN and on 9 November the Working Party submit a formal proposal.

On 17 December 1964 the Director-General gives formal permission to the groups behind the proposal to carry out the experiment.

 

 

Timelines
ISOLDE

Fun and games at the traditional CERN Christmas party

The tradition of holding a Christmas party for CERN children began in the first year of CERN’s existence and still continues. In the early 1960s it was decided to hold two parties, so there would be room to invite non-CERN children from the neighbouring districts as well. In 1964 (on  December 6 for those with names from A to K, and December 13 for the rest) children aged between four  and twelve years old enjoyed a film, a conjurer and musical clowns, followed by refreshments. Transport was arranged for those requiring it, and parents were informed that although they would not be admitted to the party itself, arrangement had been made to keep the bar open for those wishing to remain during the festivities - Happy Christmas!    

Timelines
From the archive

Higgs, Brout and Englert independently work out the Higgs mechanism

British physicist Peter Higgs, and independently Robert Brout and Francois Englert publish papers describing a mechanism which explains how particles could get mass. Higgs calls the hypothetical particle the "Higgs boson" in his paper Broken Symmetries and the Masses of Gauge Bosons, published on 19 October 1964 in the journal Physical Review Letters.

Timelines
The search for the Higgs boson

Cronin and Fitch detect a difference between matter and antimatter

In 1964, James Cronin and Val Fitch at Brookhaven National Laboratory in the US did an experiment with particles called neutral K-mesons, or "kaons". The types of kaons they chose to study can be regarded to consist of one half ordinary matter and the other half antimatter. They started with two types of kaon that had seemingly identical masses but different lifetimes. Kaons of the long-lived type exist for 5.2 × 10-8 seconds before each decays into 3 pions. Kaons of the short-lived type exist for only 0.89 × 10-10 seconds before each decays into 2 pions.

Cronin and Fitch shot the two types of kaon down a 17-metre beamline and detected the resulting pion-decays at the other end.

Given the different lifetimes of the kaon types and the length of the beamline, you would expect only to see decays from the long-lived kaon type at the detector. Cronin and Fitch expected the short-lived kaon type to decay long before it reached the end of the beamline, and so its decay products would not be detected. In other words you would expect to detect only 3-pion decays and no 2-pion decays at all.

But in their experiment, Cronin and Fitch did detect 2-pion decays: 45 of them, out of a total of 22,700 decay events – a ratio of about 1 in 500. The result violated a fundamental principle of physics – the symmetry between matter and antimatter.

The pair announced their result in the paper "Evidence for the 2-pion Decay of the K Meson", published in the journal Physical Review Letters on 27 July 1964. They shared the 1980 Nobel prize in physics "for the discovery of violations of fundamental symmetry principles in the decay of neutral K-mesons."

Timelines
The story of antimatter

CERN Open Day!

If you were one of the estimated 70,000 visitors to CERN during the 2013 Open Days – or one of the 2,000+ volunteers busily organizing visits, games and all manner of weird and wonderful activities – you might not recognize this photo! Fifty years ago CERN’s Open Days were conducted on a much more modest scale.

Limited to families and guests of staff, CERN’s third Open Day on 25 April 1964 welcomed 1,100 visitors. Various CERN departments displayed their laboratories and equipment, and a kindergarten looked after the youngest visitors while their parents toured the site. A technical press day was also arranged on 19 May, with 36 visiting journalists. CERN’s Public Information Office reported good coverage of CERN’s activities during the year, despite “the general disinterest of the daily press in basic science”.

Timelines
From the archive

Just add "0": The IBM 7090 replaces the IBM 709

The IBM 7090 was installed at CERN in 1963. It was about four times more powerful than the 709. The computer was connected to a device call a Hough-Powell digitizer (HPD) – a machine that scanned films from bubble chambers, measured important tracks, and sent the information directly to the 7090. A second device, "Luciole", was also connected to the computer, providing fully automatic measurements from spark-bubble chambers. Over 300,000 frames of spark-chamber film were automatically scanned and measured in this way, beginning the trend towards online use of computers for processing experimental data. 

Technical specifications
IBM 7090
Ran at CERN 1963 to 1965
Transistorized second-generation machine with a 2.18-microsecond clock cycle
Core storage: 32K words of 36 bits, 4.36-microsecond access time
Card 1/0, Tape units wrote on 7 tracks at 112.5 inches per second, 200 to 556 bytes per inch
8 data channels
Interrupt system
FORTRAN compiler
Basic monitor operating system (IBSYS)
Connected online to flying-spot digitizers (HPD and Luciole) to measure bubble and spark chamber films

 

Timelines
Computing at CERN

Fast ejection of protons from the PS

This remarkable photo, used on the cover of the May 1963 CERN Courier, captures the passage of protons extracted from CERN’s Proton Synchrotron (PS).

Initially, the PS had operated with internal targets, but when a beam of higher intensity was needed the fast ejection system was developed to eject the beam towards external targets. During the afternoon of Sunday 12 May 1963 the PS became the source of the world's first beam of 25 GeV protons to travel freely in air.

This photo was taken the following day by members of CERN’s Public Information Office. They placed blocks of plastic scintillator along the path of the beam and set up a camera to record the effect. As expected, the scintillators glowed brightly as the beam passed through them.

You can read more in the May and June 1963 editions of the CERN Courier, and there are more photos here.

Timelines
From the archive

The lighter side of neutrino experiments

A buzz of excitement marked the start of neutrino experiments at CERN in 1963. As many years of hard work were about to be put to the test, this spoof advertisement appeared on the concrete shielding near the heavy liquid bubble chamber.

CERN inventions such as the fast ejection system, proposed in 1959 by Berend Kuiper and Günther Plass, and the magnetic horn, which earned Simon van der Meer his share of the Nobel prize for physics in 1984, had enabled CERN to produce the most intense beam of neutrinos in the world. The first run in June was anxiously awaited, but everything ran smoothly. During seven weeks a total of 4000 events were observed in the spark chamber and 360 in the bubble chamber, comparing very favourably with the 56 spark chamber events found in the previous neutrino experiment in Brookhaven.

Timelines
From the archive

CERN on ice

It needed more than a broom to tackle the giant icicles decorating CERN’s labs and offices during the great freeze of 1963. The village of La Brévine, 150km away, lived up to its reputation as Little Siberia with temperatures down to -38°C, while cyclists - and even motorists - enjoyed themselves riding across Europe’s frozen lakes and icy rivers.

The Swiss electricity network struggled to cope with high demand, reduced production and the failure of a high-tension cable bringing power from Germany. In response, CERN limited its consumption as much as possible, modifying or cutting the experimental programme until things improved. See more photos of CERN in the 1963 snow here.

Timelines
From the archive

Summoning the Founding Fathers

By 1962, with CERN’s long-term accelerator construction plans still not fixed, some member states were growing impatient to pursue their own projects. A meeting was called for January 1963, where Europe’s top high-energy physicists would thresh out the whole question of coordinating national initiatives with those carried out at CERN.

Reaching agreement between so many countries was never going to be easy, so Director-General Weisskopf suggested a pre-meeting of even more important people – CERN’s “Founding Fathers”. He felt an “informal exchange of view among people who are beyond the pure scientific level” - people committed to CERN’s aims and with experience in governmental matters – would help find “the best way in which to prepare a sympathetic response for the various European countries”. Discussions began over dinner at Le Béarn in Geneva on 19 December, and continued the next day. You can read the minutes of the meeting here. The top physicists duly met January, and became the European Committee for Future Accelerators. 

Timelines
From the archive

John Linsley detects the first 10^20 eV cosmic ray

John Linsley detected first cosmic ray with an energy higher than 1020 electronvolts (eV) in New Mexico, US, in 1962. This was the highest energy cosmic ray particle ever detected at the time.  He made this discovery using a ground-based array of detectors. His observations suggested that not all cosmic rays are confined to the galaxy and gave evidence for a flattening of the cosmic ray spectrum at energies above 1018 eV. This discovery clarified the structure of air showers and provided the first evidence of ultra-high energy cosmic ray composition and arrival directions. 

Timelines
Cosmic rays

Yugoslavia quits

On 29 September 1961, the Federal Republic of Yugoslavia gave formal notice to CERN of its intention to withdraw from the organization at the end of the year, after Yugoslavia struggled to pay its yearly contributions. This formal notice confirmed an informal advance notice given on 19 May, by a letter that was circulated to the CERN council.

Timelines
Member states

Inauguration of the IBM 709

On 6 March 1961 François de Rose pressed the button to run the first program on CERN’s new IBM 709.  The existing Ferranti Mercury computer had been working at full stretch, but increasing user demand left CERN with a backlog of computing work by the end of 1959. A larger and faster machine was essential, though with the two operating together CERN soon got its first taste of compatibility problems.

Planning the inauguration of the IBM required a certain delicacy. CERN’s choice of an American computer over European ones had provoked some grumbling, and it was also important that no major Swiss academic institution was overlooked when issuing the invitations. There had been discussion of “a press conference when we could provide a reasonable number of journalists with information and, since this seemed to be required, drinks”, but in the end CERN provided facilities for a press gathering but let IBM organize this themselves. The inauguration remained a more scholarly affair; guests were treated to lunch, speeches, and a CERN visit – and a short musical performance by the new computer.

Timelines
From the archive

CERN inaugurates the IBM 709

The IBM 709 arrived at CERN in January 1961. It was inaugurated at an official ceremony on 6 March that year, where computer engineer Lew Kowarski delivered a speech (see image).

With Mercury and the 709 operating together, CERN had its first experience of compatibility problems. This was a continuing source of difficulty as various different computers came into operation at CERN.  Many of CERN's programs were also used on a range of computers in its 13 member states. 

A high-level computer-programming language called "FORTRAN" (short for "FORmula TRANSlating")that made its CERN debut with the 709, and this language quickly became the only programming language in general use at the laboratory. A new generation of programs, written in FORTRAN to exploit the greater speed of the IBM 709, were brought in to analyse measurements from bubble-chamber photographs. 

The IBM 709 was a vacuum-tube machine with a core memory size of 32K 36-bit words. The central processing unit (CPU) was 4-5 times faster than that of the Mercury, but compiling a typical FORTRAN program could still take several minutes. Tape bins made way for card trays. As many as six peripheral devices could be attached via their controllers to data channels on the 709, to access core memory buffers while the CPU performed other work. The Direct Data Connection – an innovation of the machine – allowed for direct transmission of data from external equipment to memory via a channel. The speed was in principle up to 1 megabit per second.

After one year of experience, CERN added a small IBM 1401 to speed up the input/output, job sequencing and operations. The concept of SPOOLing (Simultaneous Peripheral Operation On-Line) with its 1/0 files (virtual reader/printer) has its origins in the days of 709 operations.

Technical specifications
IBM 709
Ran at CERN from 1961 to 1963
Vacuum-tube machine
12-microsecond clock cycle, 2 cycles to add and 15 on average to multiply 36-bit integers
Hardwired division and floating-point arithmetic, index registers
Core storage: 32K words of 36 bits, 24-microsecond access time
Card reader (250 cards per minute) and card punch (100 cards per minute)
Line printer
Magnetic-tape units (7 tracks, 75 inches written per second at 200 bytes per inch)
Introduction of the Data Channel
FORTRAN compiler
FORTRAN monitor system

 

Timelines
Computing at CERN

Matter in question

If you’re not ready to start the New Year yet, how about a trip back in time instead? In January 1961 staff were invited to watch CERN’s first documentary film.

CERN was of growing interest to journalists, including those in ‘the field of television and moving pictures, news and featurial films’, and by the end of 1958 the organization decided it was time to make a film of its own. The contract was awarded to Georges Pessis in May, and filming soon began. A team of CERN advisors carefully considered all aspects of the work, including what it should be called. After some brainstorming they settled on Matter in Question for the English version. The first private viewing took place on 12 July 1960; the head of the Public Information Service told Pessis that the photography had been very favourably received, and no one had been too critical of the music – possibly jazz wasn’t to everyone’s taste.

Timelines
From the archive

Miss Steel and the Scientific Conference Secretariat

Conferences are a great way to promote international scientific communication, and CERN soon acquired considerable experience in running them.  In January 1961 it set up a Scientific Conference Secretariat to share this expertise, organizing conferences in collaboration with local scientific institutions abroad as well as those on-site. In the early days the Secretariat had a staff of just one person - Miss Steel.

A keen traveller and one of the great characters of CERN, E. W. D. Steel brought experience from an international career in refugee work when she joined the Organization as a secretary in 1955. She soon discovered that conference organizing committees generally had plenty of scientific knowledge, but were less skilled in dealing with the practicalities. She also observed that “most theoretical physicists are delightful people but they are often nervous and highly strung and need to be handled with care”! Her autobiography A ‘One and Only’ Looks Back is filled with anecdotes of a rich and rewarding life.  

Timelines
From the archive

Spain joins

From the minutes of the CERN council, dated 14 June 1960:

In a letter dated 22 April 1960, the president of the council asked delegates of the member states whether their governments would be prepared to confirm the attitude which they had adopted in 1956 regarding an application by Spain for membership of CERN.

Agreement has already been received from Austria, France, the German Federal Republic, Greece, the Netherlands, Sweden, the United Kingdom and Yugoslavia, and it is expected that by the time of the council session agreement will have been received from all the other member states. The only question to be settled is the amount of the special contribution Spain would have to pay.

Spain joined CERN on 1 January 1961.

Timelines
Member states

CERN commemorates Wolfgang Pauli

CERN has the privilege of housing the scientific archive of 1945 Nobel-prizewinning physicist Wolfgang Pauli. This small but historically valuable collection was donated by Pauli’s widow who, with the help of friends, tracked down originals or copies of his numerous letters. This correspondence, with Bohr, Heisenberg, Einstein and others, provides an invaluable resource on the development of 20th century science.

Franca Pauli can be seen here with two of CERN’s founding fathers, Francis Perrin and François de Rose, at the inauguration of CERN’s Pauli Memorial Room (Salle Pauli) on 14 June 1960 (press release, in French). The Archive also includes photographs, manuscripts, notes, and a rare audio recording of Pauli lecturing in 1958. Many items have been digitized and are available online; more information is available here.

Timelines
From the archive

Plans for an isotope separator are published

(image: The isotope separator in 1960)

Plans for an isotope separator are published in the proceedings of the International Symposium held in Vienna, May 1960. This isotope separator is built by CERN's Nuclear Chemistry Group (NCG) and used to measure the production rate of radionuclides produced in different targets irradiated with 600 MeV protons from a CERN Synchrocyclotron (SC) beam. Researchers observe high production rates showing that the SC would be the ideal machine for setting up a dedicated experiment for on-line production of rare isotopes. 

Timelines
ISOLDE

First session of the CERN Computer Users’ Committee

Demand for CERN’s Mercury computer had increased rapidly since its arrival in 1958, and by 1960 it was time to impose some sort of order on the users: “The present informal arrangement where every programmer may contact any operator makes it impossible for the operators to work efficiently.” A Users’ Committee was set up (see the minutes of the first meeting here), a reception desk was established and some rules laid down.

“Programmers have always the strong tendency to ask the operator to perform various emergency actions as soon as their programmes fail. If the operator follows such directions computer time is usually lost unnecessarily. If she refuses (as she is supposed to do), experience shows that people tend to argue. Consequently every effort will be made to have no programmer in the computer room outside normal working hours.” Any questions were to be directed to the Office of the Programming King, Mr Lake. 

Timelines
From the archive

Inauguration of the Proton Synchrotron

The PS came into operation on 24 November 1959, breaking existing records as the world’s biggest and most powerful particle accelerator. The official ceremony a few months later (you can watch part of it in this 1960 documentary) was a celebration of the technical achievement but also of successful European co-operation that paved the way for progress in the aftermath of World War II. A special issue of the CERN Courier gave more information about the new machine.

A press conference and visit were followed by lunch, then the official inauguration by Niels Bohr, speeches and a reception. The guest list included several hundred eminent scientific and political figures. The back cover of the commemorative brochure also featured VIPs - the men and women who made up the PS team.

Timelines
From the archive

The Proton Synchrotron starts up

The Proton Synchrotron (PS) accelerated protons for the first time on 24 November 1959, becoming for a brief period the world’s highest energy particle accelerator. With a beam energy of 28 GeV, the PS became host to CERN’s particle physics programme, and provides beams for experiments to this day.

During the night of 24 November 1959 the PS reached its full energy. The next morning John Adams (pictured) announced the achievement in the main auditorium. In his hand is an empty vodka bottle, which he had received from Dubna with the message that it was to be drunk when CERN passed the Russian Synchrophasotron’s world-record energy of 10 GeV. The bottle contains a polaroid photograph of the 24 GeV pulse ready to be sent back to Dubna.

When CERN built new accelerators in the 1970s, the PS’s principle role became to supply particles to the new machines. Since the PS started up in 1959, the intensity of its proton beam has increased a thousandfold, and the machine has become the world’s most versatile particle juggler.

In the course of its history the PS has accelerated many different kinds of particles, feeding them to more powerful accelerators or directly to experiments.

Timelines
CERN accelerators, The history of CERN

The Proton Synchrotron is up and running

The Large Hadron Collider (LHC) is the world’s biggest and most powerful particle accelerator, but for a few months in 1959 the Proton Synchrotron (PS) shared the same distinction.

The PS reached its full design energy of 24 GeV (later increased to 28 GeV) during the night of 24 November 1959, and the following morning project leader John Adams announced the achievement to staff in CERN’s main auditorium. In this photo he holds a vodka bottle that he had been given during a trip to the Joint Institute for Nuclear Research in Dubna with instructions that the contents should be drunk when CERN passed the Russian Synchrophasotron’s world-record energy of 10 GeV. The bottle in his hand contains a photo of the 24 GeV pulse ready to be sent back to the Soviet Union!

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From the archive

CERN Courier No. 1

‘It is a pleasure to introduce our long expected internal bulletin,’ wrote Director-General Cornelis Jan Bakker, ‘I hope it will benefit not only from your attention but also from the many suggestions which will certainly arise in CERN's fertile minds.’

The first CERN Courier featured visiting  VIPs, a forthcoming trip to Russia, feedback on the 13th CERN Council Session and a round-up of news at CERN and abroad (Other Peoples' Atoms). Behind the scenes, an introductory report from the editor discussed the objectives and format of the proposed journal, and also how to finance it. Disagreement about whether it would be ethically acceptable to include advertisements rumbled on for quite some time.

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From the archive

Austria joins

Austria signed as a member state of CERN on 1 June 1959. The press release announcing the accession noted:

Following applications made in 1958 by the Austrian government, the council agreed unanimously to accept Austria as the 13th European member state to participate in CERN. Welcoming Mr W Goertz, permanent representative of Austria to the UN, MF de Rose, president of CERN council said:

A country where cosmic rays were discovered and which gave such names as Hess, Boltzmann, Schrödinger and Pauli to physics has its natural place in CERN. The difficult post-war period only, M de Rose pointed out, prevented Austria from joining earlier. We are happy that the accession of Austria now marks the end of this period of post-war difficulties and the beginning of a new contribution of that country to international cooperation and European culture.

The release notes that the Austrian permanent representative was "particularly pleased" to see Austria's flag together with those of the other member states already flying when he arrived at the CERN entrance for the afternoon session of the council.

Read the press release here.

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Member states

Preparing CERN’s HBC30 bubble chamber for testing

The 30cm liquid hydrogen bubble chamber (HBC30) - here seen being inserted into its vacuum tank in March 1959 - was the first bubble chamber to be used for physics experiments at CERN. After testing with nitrogen and hydrogen it was placed in the Synchro-Cyclotron, and its first five days of operation in November yielded 100,000 photographs. In March 1960 it was moved to the proton Synchrotron, and by the time it ceased operations in spring 1962 it had consumed 150 km of film.

Bubble chambers were one of the main experimental tools used in high-energy physics during the 1950s and 1960s. They were filled with superheated liquid, and if a charged high-energy particle passed through the liquid started to boil along its path, producing a trail of tiny bubbles that could be photographed. CERN’s first bubble chamber was a small (10cm) trial model, developed to test this exciting new technique. Larger models soon followed, including the giantess Gargamelle and the Big European Bubble Chamber (BEBC).

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From the archive

Yesterday’s Tomorrow’s World

Fans of vintage British TV science documentaries might enjoy this early precursor to Tomorrow’s World. On weekdays (when the outside broadcast cameras weren’t needed to cover sports fixtures!) the Eye on Research crew visited scientific laboratories and research centres to discuss topical issues.

This was the BBC’s first regular science and technology series; it broadcast over forty episodes on a wide range of subjects between 1957 and 1962 (they are listed on BBC Genome). Presenting live from CERN on 24 February 1959, we see Raymond Baxter deploying all his famous interviewing skills to help some distinctly nervous scientists explain their work to the viewers. The soundtrack jumps a bit, but it’s still worth a look.

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From the archive

8th Annual International Conference on High Energy Physics

The 8th Annual International Conference on High Energy Physics – known as the Rochester Conference, from the name of its first venue – was held at the Physics Institute of the University of Geneva. The format for this meeting, which was also the 2nd CERN Conference on High Energy Nuclear Physics, differed slightly from previous years. To maximise use of time, rapporteurs were chosen summarise the developments in their field. You can read the proceedings here or look at some of the deliberations of the planning committee here.

Even if rapporteurs helped make the content clearer for participants, CERN’s Public Information Office pointed out that it ‘will probably be too hard to digest for the average reporter and reader, even if cleverly "popularized". Thus the main stress should be placed on personalities and the spirit of international cooperation.’ (See memo.) There were plenty of high profile physicists to choose from, including Nobel Prize winner Wolfgang Pauli; a rare recording of him speaking at the conference is online here.   

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From the archive

CERN installs its first electronic computer: The Ferranti Mercury

CERN's first computer, a huge vacuum-tube Ferranti Mercury, was installed in 1958. It was one million times slower than today's large computers. Though the Mercury took 3 months to install – and filled a huge room – its computational ability didn't quite match that of a modern pocket calculator. "Mass" storage was provided by four magnetic drums each holding 32K × 20 bits – not enough to hold the data from a single proton-proton collision in the Large Hadron Collider. The Mercury ran a simplified coding system called Autocode – a type of programming language with a limited repertoire of variables. 

At the end of its career the Mercury was connected online to the Missing Mass Spectrometer experiment. In 1966 it was shipped to Poland as a gift to the Academy of Mining and Metallurgy at Cracow. Although it was quickly taken over by transistor-equipped machines, a small part of the Mercury remains in the CERN IT department. The computer's engineers installed a warning bell to signal computing errors – the bell is mounted on the wall in a corridor of building 2.

See video: "Computing at CERN in 1965" (features the Ferranti Mercury)

Technical specifications

FERRANTI Mercury
Ran at CERN from 1958 to 1965
First generation vacuum tube machine
60-microsecond clock cycle, 2 cycles to load or store, 3 cycles to add and 5 cycles to multiply 40-bit longwords
No hardware division
Magnetic core storage (1024 40-bit words, 120-microsecond access time)
Processor with floating-point arithmetic and a B-Register (an index register)
Magnetic-drum auxiliary storage (16 Kwords of 40 bits, 8.75 msec average latency, 64 longwords transferred per revolution)
Paper tape I/0
Two Ampex magnetic-tape units added in 1962
Autocode compiler

 

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Computing at CERN

Wim Klein, CERN's first computer

Before electronic computers were available at CERN, a Dutchman called Willem "Wim" Klein performed astonishing feats of mental arithmetic to help his colleagues with their calculations.

Klein was born in Amsterdam in the Netherlands on 4 December 1912. He first displayed his mathematical talents in circuses around Europe. He joined CERN's Theory Division in 1958, where he was in considerable demand as a calculator in the days before the first electronic computers.

On 27 August 1976, Klein calculated the 73rd root of a 500-digit number in 2 minutes and 43 seconds, a feat recorded by the Guinness Book of Records. He became known as "the human computer".

Klein was found dead in his home in Amsterdam on 1 August 1986. He had been stabbed to death. The killer was never identified.

Find out more:

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Computing at CERN

Closure of CERN’s Theoretical Study Division in Copenhagen

During the construction of CERN in the 1950s, most staff were lodged in temporary offices nearby.  But the theoretical physics group (one of three study groups set up in 1952 as part of the ‘provisional CERN’) began life at the Theoretical Physics Institute, University of Copenhagen.  Niels Bohr led the group until September 1954, then handed over to Christian Møller. The photo shows CERN’s Director General Cornelius Bakker signing an agreement on the legal status of the group in Denmark in 1956.

It was always intended that the group would relocate back to the main CERN site over a period of five years, and the first theorists came to Geneva in 1954. They were based first at the University of Geneva, then in barracks near the airport, before finally moving to the new site in Meyrin. The Theory Group in Copenhagen officially closed on 1 October 1957.

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From the archive

The first circulating beam in the Synchrocyclotron

A log book entry written by Wolfgang Gentner, the head of SC Division, and signed by various colleagues, tells us that a short celebration was held on the 1st of August 1957 following the successful  appearance of the first circulating beam.

The 600 MeV Synchrocyclotron (SC)  was CERN’s first accelerator and provided beams for its earliest particle and nuclear physics experiments.  It was a remarkably long-lived machine, even when superseded by the larger Proton Synchrotron, and operated for 33 years before being decommissioned in December 1990. Work is currently underway to give the SC a new lease of life as an exhibition area and visitor attraction.

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From the archive

The P.A.U.L.I. and its uses

In June 1957, V. F. Weisskopf proudly announced acquisition of an instrument with unique possibilities - an intricate mechanism for testing complicated physics theories and producing new ideas. But it required careful handling! Inexperienced operators testing a theory would often see no reaction at first, or just hear faint noises reminiscent of German expressions such as “Ganz dumm” and “Sind sie noch immer da?” It was rather bulky, almost spherical in shape, and very much dependent on the correct fuel supply. Weisskopf said that, for reasons not yet fully understood, nobody had been able to make the machine work before noon.

In fact, Wolfgang Pauli had been acquired as a professor at the ETH Zürich in 1928, but a footnote explained that the paper had been classified since 1932, and partial publication was only now permitted since the U.S.S.R. had succeeded in building a similar gadget with a radius 1.5 times larger than the original model.

You can read the full report here (p.9) along with other fascinating articles in the spoof Revues of Unclear Physics, published at the University of Birmingham to celebrate the 50th birthday of R. E. Peierls.

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From the archive

CERN's first accelerator - the Synchrocyclotron - starts up

The 600 MeV Synchrocyclotron (SC), built in 1957, was CERN’s first accelerator. It provided beams for CERN’s first experiments in particle and nuclear physics. In 1964, this machine started to concentrate on nuclear physics alone, leaving particle physics to the newer and much more powerful Proton Synchrotron (PS).

The SC became a remarkably long-lived machine. In 1967, it started supplying beams for a dedicated unstable-ion facility called ISOLDE, which carries out research ranging from pure nuclear physics to astrophysics and medical physics. In 1990, ISOLDE was transferred to a different accelerator, and the SC closed down after 33 years of service.

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The history of CERN, CERN accelerators

The Bevatron discovers the antineutron

The journal Physical Review receives the paper Antineutrons Produced from Antiprotons in Charge-Exchange Collisions by a second team working at the Bevatron – Bruce Cork, Glen Lambertson, Oreste Piccione and William Wenzel. The paper – which announces the discovery of the antineutron – is published in the issue dated November 1956.

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The story of antimatter

Birth of the CERN fire brigade

Safety is top priority in any scientific research laboratory, and fire prevention was an important issue from the earliest days of CERN. The newly constructed buildings were fitted with smoke detectors, and voluntary fire brigades and first aid teams were set up among staff members.  

The appointment of CERN’s first fire service chief, Pierre Vosdey, in July 1956 marked the start of the professional firefighting service that CERN enjoys today. Experienced firemen were recruited, who trained more volunteers. The service expanded during 1957, providing 24-hour cover and acquiring a fire engine, an ambulance, a 14 metre ladder, a motor pump, smoke detectors and 250 fire extinguishers. This photo shows some of the team in 1959. Today the CERN fire brigade has around 50 members and continues to work closely with the Swiss and French fire services to ensure safety on-site.

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From the archive

Neutrinos detected at last!

On 14 June 1956 a telegram from Frederick Reines and Clyde Cowan informed Wolfgang Pauli that neutrinos had been detected from fission fragments - nearly 26 years after Pauli first postulated the neutral particle as a solution to the missing energy during beta decay.

Pauli had outlined his theory in a letter to the ‘Dear radioactive ladies and gentlemen’ at the Tübingen conference in December 1930, excusing his own absence from the conference on the grounds that he had to go to a dance in Zürich. The name “neutrino” was coined by Enrico Fermi in 1933.  

Apparently Pauli’s reply to the telegram did not arrive, so it survives only in the form of the draft sent by a secretary - Pauli simply says “Thanks for message. Everything comes to him who knows how to wait.”

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From the archive

Does CERN need to buy a computer?

When CERN was just over a year old, the Scientific Policy Committee was asked its opinion “as to the advisability of purchasing [an] electronic computer”. Lew Kowarski thought we should buy one, and his proposal (CERN/SPC/13) makes fascinating reading. He gives an overview of the current state of the market and outlines some issues to be considered. These included costs and staffing requirements, but also the fact that physicists were unlikely to bother learning to use this new machine unless it was clear that the effort was worthwhile!

He considered the pros and cons of hiring a computer or collaborating with other institutes, but felt that purchase would serve us better “if an electronic computation is to become a standard technique in high-energy physics”. His recommendation was accepted, and the Ferranti Mercury computer was installed in June 1958 (see photo).

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From the archive

The Bevatron discovers the antiproton

A paper titled "Observation of antiprotons," by Owen Chamberlain, Emilio Segrè, Clyde Wiegand, and Thomas Ypsilantis, members of what was then the Radiation Laboratory of the University of California at Berkeley in the US, appeared in the 1 November 1955 issue of Physical Review Letters. It announced the discovery of a new subatomic particle, identical in every way to the proton – except its electrical charge was negative instead of positive.

A month before the paper appeared, The New York Times had put the news on the front page:

New Atom Particle Found; Termed a Negative Proton

With the discovery of the antiproton, Segrè and colleagues had further proof of the essential symmetry of nature, between matter and antimatter. Segrè and Chamberlain were awarded the Nobel prize in physics in 1959 "for their discovery of the antiproton".

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The story of antimatter

Election of the CERN Staff Association Committee

Voting for the Committee members of CERN’s newly formed Staff Association closed at midnight on 11 July 1955; Messrs J.A. Giebel, K. Johnson, J. P. Stroot, E. Zaccheroni, J. Ball, R. Siegfried, Miss C. de Mol and Miss A. Schubert were duly elected, with 177 votes cast.

 

On 21 July the Chairman, Mr A. Sarazin, requested formal recognition of the Association as sole representative of CERN’s personnel. Cornelis Bakker, who was just taking over from Felix Bloch as Director-General, was happy to grant this, with the proviso that that staff could still approach him directly if they so wished. At this time, not all CERN staff were based in Geneva and he suggested that that those in Copenhagen, Uppsala and Liverpool should also be represented by the Association. The next step was a series of meetings between management and the Association, and the creation of a consultative committee. You can read some of the relevant letters here.

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From the archive

Laying the foundation stone of CERN

“On this tenth day of June, one thousand nine hundred and fifty five, on ground generously given by the Republic and Canton of Geneva, was laid the foundation stone of the buildings of the headquarters and the laboratories of the European Organization for Nuclear Research, the first European institution devoted to co-operative research for the advancement of pure science”

The stone was laid by the organization’s first Director-General, Felix Bloch, and speeches referred to the challenge of setting up the new laboratory, the cooperation and goodwill that had made it possible and a vision for the future.  The headquarters agreement with the Swiss Federation was signed the following morning, and in the afternoon the grounds of CERN were thrown open to the public. Construction had started long before the foundation stone, of course, so there was already plenty for visitors to see, and staff were on hand to act as guides. Want to know more? The commemorative booklet for the Foundation Stone Ceremony and the Open Day flyer are available here

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From the archive

Inaugural meeting of the CERN Staff Association

 “Wholeheartedly agree – the sooner the better!” – CERN’s personnel officer was enthusiastic about the idea of creating a Staff Association in 1955. The Director of Administration, Sam Dakin, was similarly encouraging, writing to the Director-General: “Very often I am conscious that in attempting to judge the needs and wishes of the staff, we have to rely on ordinary gossip and that for official comments we have only those of Divisional Directors who may not always accurately know or represent the feeling of their staff. […] In such matters as, for instance, the health insurance, scales of pay, annual leave and so on, I should feel much better satisfied that we were adapting our policy to meet the real needs of the case if we have discussed it with the staff representatives as well as with the Directors.” (You can read the letters here.)

The Association held its inaugural meeting in the large lecture theatre of Geneva’s Institut de Physique at 6.15pm on Wednesday 11 May 1955. The rules and statutes were approved at this meeting and the President (A. Sarazin) and Committee members were elected over the next few weeks.

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From the archive

Baby CERN’s first Christmas

In his seasonal greetings to CERN’s Director-General and staff, the President of the CERN Council acknowledged the difficulties faced by a young organization and the devotion shown by all those involved in overcoming them.

The reply, sent a few days later, emphasized how much had been achieved: “…Less than three months after its official birth, CERN finds itself in possession of an active programme of research and building in full progress, adequate accommodation and a considerable staff. The stage of teething troubles is behind us; our approaching adolescence will bring difficulties of its own but we can look ahead with confidence…”

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From the archive

“OERN is difficult to pronounce in most languages”

Has it ever struck you as odd that the initials CERN refer to an organization that ceased to exist when the current organization was created? If so, you’re not alone.

The Conseil Européen pour la Recherche Nucléaire was a provisional body set up in 1952 to establish a world-class fundamental physics research centre in Europe. It was dissolved when it had successfully accomplished its mission but by then, of course, the acronym CERN had stuck. Most people felt this wouldn’t cause any particular legal or other complications, though Lew Kowarski (second from the left in this 1955 photo) considered the idea “so silly as to be intolerable”. You can read Director of Administration Dakin’s memo here.

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From the archive

The new CERN Council

When the CERN Convention was signed in 1953, it was assumed that the long-awaited European laboratory would soon become a reality. But ratification formalities took longer than expected. Meanwhile work on the ground was forging ahead, so it was a relief for the interim governors when the new CERN Council finally took office some 15 months later.

An important item at the first Council meeting on 7-8 October 1954 was the transfer of all assets and liabilities of the interim organization. Council officers and senior CERN staff were also appointed, various procedural, financial and staff questions settled, and a provisional organizational structure adopted. This structure was approved at the second meeting in February 1955 (shown in photo) along with the headquarters agreement with Switzerland. CERN was finally starting to take shape! If you’re interested to know more, the minutes of the first meeting are available here.

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From the archive

Twelve founding members

The CERN convention was signed in 1953 by the 12 founding states Belgium, Denmark, France, the Federal Republic of Germany, Greece, Italy, the Netherlands, Norway, Sweden, Switzerland, the United Kingdom and Yugoslavia, and entered into force on 29 September 1954.

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Member states

The European Organization for Nuclear Research is born

At the sixth session of the CERN Council, which took place in Paris from 29 June - 1 July 1953, the convention establishing the organization was signed, subject to ratification, by 12 states. The convention was gradually ratified by the 12 founding Member States: Belgium, Denmark, France, the Federal Republic of Germany, Greece, Italy, the Netherlands, Norway, Sweden, Switzerland, the United Kingdom, and Yugoslavia. On 29 September 1954, following ratification by France and Germany, the European Organization for Nuclear Research officially came into being. The provisional CERN was dissolved but the acronym remained.

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The history of CERN

CERN exists!

A telegram from Jean Mussard informed Edoardo Amaldi (Secretary-General of the provisional CERN) that the CERN Convention had finally come into force on 29 September, when France and Germany deposited their instruments of ratification at UNESCO House in Paris.

Three more member states were yet to ratify – this took another five months – but the necessary conditions had now been met. The provisional Council ceased to exist and, after a few days during which Amaldi was the sole owner of all CERN’s assets, the new organization held its first meeting in Geneva on the 7-8 October 1954.

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From the archive

Construction of CERN begins

A historic moment passed almost unnoticed on 17 May 1954, as the first excavation work started in the Meyrin countryside and construction of CERN began. Future events of this kind were celebrated with speeches, press coverage and parties, but this was a quiet and purely unofficial ceremony.

Geneva had been chosen as the site for the proposed laboratory in October 1952 and approved by a referendum in the canton of Geneva in June 1953, but CERN’s status was provisional until completion of the ratification process at the end of September 1954. Nonetheless, CERN staff were already hard at work, and those based locally (at the Institut de Physique and Villa Cointrin) assembled in Meyrin along with representatives of the Genevan authorities and the chairman of the provisional CERN Council, Robert Valeur, to watch work begin on their new home.   

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From the archive

The Bevatron starts up at Berkeley, California

The Bevatron in 1958 (Image: Lawrence Berkeley National Laboratory)

In 1954, Ernest Lawrence oversaw the building of a proton accelerator called the Bevatron at the radiation laboratory in Berkeley, California. The machine's name comes from BeV, the symbol used at the time for "billion electronvolt", or 109 electronvolts. We now call this unit the gigaelectronvolt, symbol GeV – BeV is no longer used. The Bevatron was designed to collide protons at 6.2 GeV, the expected optimum energy for creating antiprotons.

The following is from Experiences with the Bevatron by then Berkeley physicist Edward Lofgren, who was present for the start-up of the machine:

Finally, on April 1, 1954, a feeble pulse was obtained at a magnetic field corresponding to 6 BeV. The intensity was measured by counting the tracks in nuclear emulsion that had been inserted into the beam. The intensity was in the range of 104 to 106 protons per pulse.

A team of physicists headed by Italian-American physicist Emilio Segrè designed and built a detector specialized to look for antiprotons. The Bevatron was up and running.

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The story of antimatter

Breaking ground

On 17 May 1954, the first shovel of earth was dug on the Meyrin site in Switzerland under the eyes of Geneva officials and members of CERN staff.

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The history of CERN

Settling into Geneva

Even before the official creation of CERN in 1954, staff began to settle into temporary offices around Geneva. On 5 October 1953 part of the PS (Proton Synchrotron) Group, including Frank Goward, John Adams, Mervyn Hine, John and Hildred Blewett, Kjell Johnsen and Edouard Regenstreif, arrived to take up residence in offices that had been made available in the University of Geneva’s Institute of Physics . In the same month plans were made to convert the Villa de Cointrin (see photo), which later became the first headquarters for the CERN Directorate,  Administration and Finance Groups. The building was currently empty and in need of repair, and was being offered for an annual rent of around 3,000 CHF.

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From the archive

Signing the CERN Convention

After long months of negotiation - success! The work of the provisional Council responsible for planning the new international laboratory for nuclear physics reached a successful conclusion on 1 July 1953 with the signature of the CERN Convention.

The drafting committee and the administrative and financial working group had worked at UNESCO House throughout the week leading up the Council’s sixth meeting in Paris (29-30 June) to finalize the document, and signature took place the next day at a conference held at the Ministry of Foreign Affairs. Delegates of nine countries signed, with the remaining three expressing their intention to do so shortly.

The convention was gradually ratified by the 12 founding member states (Belgium, Denmark, France, the Federal Republic of Germany, Greece, Italy, the Netherlands, Norway, Sweden, Switzerland, the United Kingdom, and Yugoslavia) and the European Organization for Nuclear Research officially came into being on 29 September 1954. The text of the Convention is available here.

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From the archive

The convention is complete

The draft convention was completed in the alotted 18 months and approved unanimously by the representatives of the eleven countries that had signed the original agreement plus the UK, and the document was made available for signature. 

The CERN Convention established financial contributions, which are calculated on the basis of net national income over recent years so that each Member State pays according to their means. 

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The history of CERN

Air Cherenkov discovery Galbraith & Jelley

The detector used for the first observations of atmospheric-Cherenkov radiation: a dustbin with a small parabolic mirror and phototube (Image: G Hallewell)

In September 1952 a simple experiment allowed the first observation of Cherenkov light produced by cosmic rays passing through the atmosphere. This experiment birthed a new field of astronomy. In 1952 armed only with a rubbish bin painted black on the inside from the UK Atomic Energy Research Establishment at Harwell, a recycled 25 cm searchlight mirror and a 5 cm phototube, Bill Galbraith and his colleague John Jelley set out to measure flashes of Cherenkov light in the night sky. They observed a count rate of about one pulse per minute, which confirmed Patrick Blackett’s assertion that Cherenkov light from charged cosmic rays traversing the atmosphere should contribute to the overall night sky intensity. In 1953, with improved apparatus at the Pic du Midi, the pair successfully demonstrated that the light signals they recorded had the polarization and spectral distribution characteristic of Cherenkov radiation. These experiments also revealed the correlation of the amplitude of the light signal with shower energy. The first steps towards Cherenkov astronomy had been taken.

Read more: "The discovery of air-Cherenkov radiation" – CERN Courier

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Cosmic rays

Where to build?

Geneva was selected as the site for the CERN Laboratory at the third session of the provisional council in 1952. This selection successfully passed a referendum in the canton of Geneva in June 1953 by 16,539 votes to 7332.

It was selected from proposals submitted by the Danish, Dutch, French and Swiss governments. But Geneva's central location in Europe, Swiss neutrality during the war and that fact that it already hosted a number of international organisations all playing a role gave it the edge. While preparations were being made to establish the laboratory in Geneva, theoretical work would be carried out in Copenhagen.

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The history of CERN

Redesigning the Proton Synchrotron

Too often trip reports are just boring administrative documents, but this one caused a radical rethink of the design for CERN’s Proton Synchrotron. Suddenly a relatively straightforward engineering challenge became a development project for an untested idea.

Plans were already underway for CERN’s large accelerator, a scaled-up version of Brookhaven’s Cosmotron, when Odd Dahl, Frank Goward and Rolf Wideröe visited Brookhaven in 1952. There they joined in discussions about a new strong-focusing (or alternating gradient focusing) technique, which meant smaller magnets could be used to guide particles round an accelerator provided they were arranged with their field gradients facing alternately inwards and outwards instead of the conventional outward-facing alignment. Dahl recommended laying aside plans for a 10 GeV accelerator for the time being in order to investigate the idea further (CERN-PS-S4).

It was a risky decision to follow this unexplored route, but one that paid off by allowing construction of a much more powerful machine at little extra cost. When the Proton Synchrotron came into operation in November 1959 it had an energy of 24 GeV, later increased to 28 GeV.

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From the archive

Early beginnings

The first meeting of the CERN Council quickly followed the signing of the agreement. It took place at UNESCO from 5-8 May 1952 with Switzerland’s Paul Scherrer in the chair. At this meeting, governments wishing to host the new laboratory were invited to submit proposals before the end of July and the first five officials were appointed.

Edoardo Amaldi was made Secretary General of the provisional organisation, Cornelis Bakker from Amsterdam headed the group that would draw up plans for the laboratory’s first machine --
 a synchrocyclotron with an energy of at least 500 MeV, Niels Bohr headed the theory group, and Odd Dahl from Norway got the job of exploring options for the originally conceived 'bigger and more powerful' machine that would bring together European science and scientists.

Lew Kowarski -- who originally proposed setting up a laboratory for fundamental research, unlinked to military goal, with a nuclear accelerator -- was tasked with organising and setting up an international laboratory, from financial procedures to buildings and workshops.

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The history of CERN, The history of CERN

CERN is born, mother and child are doing well

 

“We have just signed the Agreement which constitutes the official birth of the project you fathered at Florence. Mother and child are doing well, and the doctors send you their greetings.” This was the message sent to Isidor Rabi on 15 Feb 1952 by the signatories of an agreement establishing the provisional European Council for Nuclear Research.

Scientists and politicians had been pressing for the creation of a European laboratory to pool resources depleted after World War Two, and Nobel laureate Rabi added his support at the fifth UNESCO General Conference (Florence, June 1950), where he tabled a resolution to “assist and encourage the formation of regional research centres and laboratories in order to increase and make more fruitful the international collaboration of scientists…” 

The first resolution concerning the establishment of a European Council for Nuclear Research was adopted at an intergovernmental meeting of UNESCO in Paris in December 1951. The provisional Council, set up in 1952, was dissolved when the European Organization for Nuclear Research officially came into being in 1954, though the acronym CERN (Conseil Européen pour la Recherche Nucléaire) was retained.

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From the archive

The beginning of Positron Emission Tomography

William H. Sweet and Gordon L. Brownell at Massachusetts General Hospital in Boston suggested using the radiation emitted by positron annihilation to improve the quality of brain images by increasing sensitivity and resolution. They published a description of the first positron-imaging device to record three-dimensional data of the brain in their 1953 paper Localization of brain tumors with positron emitters in Nucleonics XI. This was the beginning of positron emission tomography. 

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Discovering the positron

Kofoed-Hansen and Nielsen produce short-lived radioactive isotopes

Danish physicists Otto Kofoed-Hansen and Karl-Ove Nielsen, working at the Institute for Theoretical Physics at the University of Copenhagen, are first to demonstrate how to produce radioisotopes with an on-line technique. In a paper entitled Short-lived Krypton isotopes and their daughter substances Kofoed-Hansen and Nielsen demonstrate the feasibility of on-line production of short-lived radioactive isotopes.

They used fast neutrons, produced in the Copenhagen cyclotron in an internal Be target, to bombard a uranium oxide target. The produced fission products arre swept directly into the ion source of an isotope separator. This direct coupling of the accelerator, target and separator gives access to isotopes with shorter half-lives than any earlier indirect production method.

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ISOLDE

Origins

At the end of the Second World War, European science was no longer world-class. Following the example of international organizations, a handful of visionary scientists imagined creating a European atomic physics laboratory. Raoul Dautry, Pierre Auger and Lew Kowarski in France, Edoardo Amaldi in Italy and Niels Bohr in Denmark were among these pioneers. Such a laboratory would not only unite European scientists but also allow them to share the increasing costs of nuclear physics facilities.

French physicist Louis de Broglie put forward the first official proposal for the creation of a European laboratory at the European Cultural Conference, which opened in Lausanne on 9 December 1949. A further push came at the fifth UNESCO General Conference, held in Florence in June 1950, where American physicist and Nobel laureate Isidor Rabi tabled a resolution authorizing UNESCO to "assist and encourage the formation of regional research laboratories in order to increase international scientific collaboration…"

At an intergovernmental meeting of UNESCO in Paris in December 1951, the first resolution concerning the establishment of a European Council for Nuclear Research was adopted. Two months later, 11 countries signed an agreement establishing the provisional council – the acronym CERN was born.

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The history of CERN

Clifford Butler and George Rochester discover the kaon, first strange particle

Stereoscopic photographs showing an unusual fork (a b) in the gas. The direction of the magnetic field is such that a positive particle coming downwards is deviated in an anticlockwise direction (Image: Nature)

Butler and Rochester discovered the kaon – the first strange particle – in an experiment using a cloud chamber. They took two photos – one of two cloud chamber photographs – one of them seemed to be a charged particle decaying into a charged particle and something neutral. The estimated mass of the particle was roughly 200 times that of the proton.

Their paper, Evidence for the existence of new unstable elementary particles, noted:

Among some fifty counter-controlled cloud-chamber photographs of penetrating showers which we have obtained during the past year as part of an investigation of the nature of penetrating particles occurring in cosmic ray showers under lead, there are two photographs containing forked tracks of a very striking character. These photographs have been selected from five thousand photographs taken in an effective time of operation of 1500 hours. On the basis of the analysis given below we believe that one of the forked tracks represents the spontaneous transformation in the gas of the chamber of a new type of uncharged elementary particle into lighter charged particles, and that the other represents similarly the transformation of a new type of charged particle into two light particles, one of which is charged and the other uncharged

Read more: "Evidence for the existence of new unstable elementary particlesG. D. Rochester & C. C. Butler, Nature 160 (1947) 855-857

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Cosmic rays

Pauli travels to Sweden to receive the Nobel prize

The date on this menu for Wolfgang Pauli’s Nobel prize festivities is 1946, yet he was awarded the  physics prize for his exclusion principle in 1945. In a letter to Niels Bohr (25 November 1945) he explains the delay:

“Dear Bohr! It was a great exciting surprise that the Nobel prize was awarded to me this year although I had thought already a week earlier, when the congratulation telegramm of you and your wife arrived, that it was a good omen …  The decision, whether or not I should go to Stockholm on December 10 was really not easy. The American authorities kindly offered me exit and re-enter permits for a trip to Stockholm and back for this very particular purpose. Considering all circumstances of the present situation, particularly the possibility of a delay by such a trip of my getting naturalized, I finally decided to postpone my participation in the ceremony in Stockholm to next year after having heard that Stern and Rabi are doing the same…”

Pauli was working in the USA during the war, and US naturalization was particularly important to him because his application for Swiss nationality had been turned down in 1938 and was not granted until 1949.

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From the archive

First air shower experiments (check)

Groups led by Bruno Rossi in the USA and Georgi Zatsepin in Russia started experiments on the structure of Auger showers. These researchers constructed the first arrays of correlated detectors to detect air showers.

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Wolfgang Pauli learns that he has been awarded the Nobel prize

Wolfgang Pauli was awarded the 1945 Nobel prize in physics for his Exclusion Principle. When he received the telegram from Arne Westgren (15 November 1945) Pauli was working at the Institute for Advanced Study in Princeton, having left Europe for the USA during the Second World War. Pauli was the first resident member of the Institute to receive a Nobel  prize; his colleagues greeted it with great enthusiasm and the Director organised an official ceremony. Unexpectedly, after speeches by various distinguished guests, Albert Einstein rose to give an impromptu address, referring to Pauli as his intellectual successor. Pauli was deeply touched by this speech, recalling it in a letter to Max Born ten years later (24 April 1955), and regretting that, since it had been entirely spontaneous, no record of it remained.

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From the archive

Pierre Auger and colleagues demonstrate extensive air showers

Pierre Auger, who had positioned particle detectors high in the Alps, noticed that two detectors located many metres apart both signaled the arrival of particles at exactly the same time. A systematic investigation of the showers showed coincidences between counters separated horizontally by as far as 75 metres. While the counting rate dropped sharply in going from 10 centimetres to 10 metres, the rate decreased slowly at larger distances.

Auger had recorded "extensive air showers," showers of secondary subatomic particles caused by the collision of primary high-energy particles with air molecules. On the basis of his measurements, Auger concluded that he had observed showers with energies of 1015 eV – 10 million times higher than any known before.

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Cosmic rays

Carl Anderson and Seth Neddermeyer discover the muon

The muon was discovered as a constituent of cosmic-ray particle “showers” in 1936 by the American physicists Carl D. Anderson and Seth Neddermeyer.

Because of its mass, it was at first thought to be the particle predicted by the Japanese physicist Yukawa Hideki in 1935 to explain the strong force that binds protons and neutrons together in atomic nuclei. It was subsequently discovered, however, that a muon is correctly assigned as a member of the lepton group of subatomic particles—it never reacts with nuclei or other particles through the strong interaction. A muon is relatively unstable, with a lifetime of only 2.2 microseconds before it decays by the weak force into an electron and two kinds of neutrinos. Because muons are charged, before decaying they lose energy by displacing electrons from atoms (ionization). At high-particle velocities close to the speed of light, ionization dissipates energy in relatively small amounts, so muons in cosmic radiation are extremely penetrating and can travel thousands of metres below the Earth’s surface.

Read more: "Note on the nature of cosmic ray particles" – Seth H. Neddermeyer and Carl D. Anderson, Physical Review Letters, 51 (1937) 884

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Cosmic rays

Anderson and Neddermeyer discover the muon

The muon was discovered as a constituent of cosmic-ray particle “showers” in 1936 by the American physicists Carl D. Anderson and Seth Neddermeyer.

Read the paper:"Note on the nature of cosmic-ray particles"

Because of its mass, it was at first thought to be the particle predicted by the Japanese physicist Yukawa Hideki in 1935 to explain the strong force that binds protons and neutrons together in atomic nuclei. It was subsequently discovered, however, that a muon is correctly assigned as a member of the lepton group of subatomic particles—it never reacts with nuclei or other particles through the strong interaction. A muon is relatively unstable, with a lifetime of only 2.2 microseconds before it decays by the weak force into an electron and two kinds of neutrinos. Because muons are charged, before decaying they lose energy by displacing electrons from atoms (ionization). At high-particle velocities close to the speed of light, ionization dissipates energy in relatively small amounts, so muons in cosmic radiation are extremely penetrating and can travel thousands of metres below the Earth’s surface.

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Pauli and Sommerfeld in Geneva

Wolfgang Pauli is seen here with his former teacher Arnold Sommerfeld attending a conference on the electron theory of metals in Geneva, 1518 October 1934. The conference proceedings don’t mention any leisure activities, but these included a cable car trip up the nearby Salève mountain to enjoy views of Geneva town, the lake and the Alps. The Salève is in France and Sommerfeld had no French visa, so conference organiser Jean Weiglé obligingly smuggled him up to join the others in his car. 

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From the archive

Ernest Lawrence patents the cyclotron

In 1929 Ernest Lawrence – then associate professor of physics at the University of California, Berkeley, in the US – invented the cyclotron, a device for accelerating nuclear particles to high velocities without the use of high voltages. Lawrence was granted US patent 1948384 for the cyclotron on 2 February 1934. The machine was used in the following years to bombard atoms of various elements with swiftly moving particles. Such high-energy particles could disintegrate atoms, in some cases forming completely new elements. Hundreds of artificial radioactive elements were formed in this manner.

Eventually, the cyclotron was able to accelerate particles such as protons to the energy of a few tens of megaelectronvolts (symbol: MeV. One MeV equals one million electronvolts). Initially driven by the effort to discover the antiproton, the accelerator era had begun, and with it the science of high-energy physics was born.

In 1939 Lawrence won the Nobel prize in physics, "for the invention and development of the cyclotron and for results obtained with it, especially with regard to artificial radioactive elements".

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The story of antimatter, CERN accelerators

Bruno Rossi: Cosmic rays are positive charged particles

Bruno Rossi (Image: Wikimedia Commons)

Rossi’s coincidence circuits form the basis of all modern electronic-counter experiments. In 1930, Bruno Rossi used electronic valves to register coincident pulses from the Geiger counters. He arranged the detectors in a triangle so that the cosmic rays could not transverse all three counters. In 1932 he found that 60% of the cosmic rays that pass through the 25 cm piece of lead could also traverse a full metre of lead. This was the first demonstration of the production of showers of secondary particles. Rossi also demonstrated that the cosmic ray flux contains a soft component easily absorbed in a few millimeters of lead and a hard component of charged particles with energies above 1 GeV. This ended Millikan’s theory that the cosmic rays consisted of gamma rays.

Rossi demonstrated that the Earth’s magnetic field bends incoming charged particle showers so that if they are more negative, more come from the east than from the west and vice-versa. In 1933, Rossi and others demonstrated an east-west effect that showed that the majority of cosmic rays were positive. Rossi noted coincidences between several counters placed in a horizontal plane, far in excess of chance coincidences. "It would seem that occasionally very extensive groups of particles arrive on the equipment," he noted in one of his papers.

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Cosmic rays

Results confirmed

 

The discovery was confirmed soon after by Occhialini and Blacket, who published Some photographs of the tracks of penetrating radiation in the journal Proceedings of the Royal Society A. Anderson's observations proved the existence of the antiparticles predicted by Dirac. For discovering the positron, Anderson shared the 1936 Nobel prize in physics with Victor Hess.

For years to come, cosmic rays remained the only source of high-energy particles. The next antiparticle physicists were looking for was the antiproton. Much heavier than the positron, the antiproton is the antiparticle of the proton. It would not be confirmed experimentally for another 22 years.

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Discovering the positron

Carl Anderson discovers the positron

Photograph from Occhialini and Blacket’s paper showing tracks of radiation (Image: Blackett, P.M.S., & Occhialini, G.P.S., Royal Society of London Proceedings Series A 139 (1933) 699)

In 1932 Carl Anderson, a young professor at the California Institute of Technology in the US, was studying showers of cosmic particles in a cloud chamber and saw a track left by "something positively charged, and with the same mass as an electron". After nearly a year of effort and observation, he decided the tracks were actually antielectrons, each produced alongside an electron from the impact of cosmic rays in the cloud chamber. He called the antielectron a "positron", for its positive charge and published his results in the journal Science, in a paper entitled The apparent existence of easily deflectable positives (1932).

The discovery was confirmed soon after by Occhialini and Blacket, who in 1934 published Some photographs of the tracks of penetrating radiation in the journal Proceedings of the Royal Society A. Anderson's observations proved the existence of the antiparticles predicted by Dirac. For discovering the positron, Anderson shared the 1936 Nobel prize in physics with Victor Hess.

For years to come, cosmic rays remained the only source of high-energy particles. The next antiparticle physicists were looking for was the antiproton. Much heavier than the positron, the antiproton is the antipartner of the proton. It would not be confirmed experimentally for another 22 years.

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Cosmic rays

Carl Anderson discovers the positron

In 1932 Carl Anderson, a young professor at the California Institute of Technology in the US, was studying showers of cosmic particles in a cloud chamber and saw a track left by "something positively charged, and with the same mass as an electron". After nearly a year of effort and observation, he decided the tracks were actually antielectrons, each produced alongside an electron from the impact of cosmic rays in the cloud chamber. He called the antielectron a "positron", for its positive charge and published his results in the journal Science, in a paper entitled The apparent existence of easily deflectable positives (1932).

The discovery was confirmed soon after by Occhialini and Blacket, who in 1934 published Some photographs of the tracks of penetrating radiation in the journal Proceedings of the Royal Society A. Anderson's observations proved the existence of the antiparticles predicted by Dirac. For discovering the positron, Anderson shared the 1936 Nobel prize in physics with Victor Hess.

For years to come, cosmic rays remained the only source of high-energy particles. The next antiparticle physicists were looking for was the antiproton. Much heavier than the positron, the antiproton is the antipartner of the proton. It would not be confirmed experimentally for another 22 years.

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The story of antimatter

The Copenhagen Faustparodie

Among the scientific documents in CERN’s Wolfgang Pauli Archive is a rather unusual item – a copy of the script parodying Goethe’s Faust performed at the Niels Bohr Institute conference, 3-13 April 1932 (exact date of performance not known). Written mostly by Max Delbrück, and decorated with caricatures of the protagonists, the skit features Pauli (Mephistopheles) trying to sell the idea of the neutrino (Gretchen) to a sceptical Paul Ehrenfest (Faust)!

Pauli had postulated the existence of this weightless particle in his famous letter to the ‘Dear radioactive ladies and gentlemen’ at the Tübingen conference in December 1930, but he had to wait until 1956 for experimental confirmation by Reines and Cowan, so in 1932 it was still the subject of debate. Pauli’s reputation for sharp wit made him ideal for his satanic rôle, but in his absence the part was played by Léon Rosenfeld. The rôle of God was assigned to Bohr. The script (in German), can be seen here. An English translation is given in George Gamow’s Thirty Years that Shook Physics.

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From the archive

Paul Dirac predicts the positron

Paul Dirac published a paper mathematically predicting the existence of an antielectron that would have the same mass as an electron but the opposite charge. The two particles would mutually annihilate upon interaction.

“This new development requires no change whatever in the formalism when expressed in terms of abstract symbols denoting states and observables, but is merely a generalization of the possibilities of representation of these abstract symbols by wave functions and matrices. Under these circumstances one would be surprised if Nature had made no use of it,” he wrote.

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Discovering the positron

December 1930 - Pauli’s Neutrino letter (now in music and art!)

On 4 December 1930, Wolfgang Pauli wrote his famous letter to the ‘Dear radioactive ladies and gentlemen’ postulating a neutral particle to solve the puzzle of missing energy during beta decay. This letter forms the basis of a new work by ART@CREATIONS, Liebe Radioaktive Damen und Herren, featuring music composed by Petros Stergiopoulos and Oded Ben-Horin.

 

Pauli had to wait nearly 26 years for experimental confirmation of the neutrino. As he wrote to its discoverers, Frederick Reines and Clyde Cowan, ‘Everything comes to him who knows how to wait.’

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From the archive

Geiger-Müller counters and the coincidence technique

Bothe and Kolhorster’s experiment (Image: L. Bonolis, American Journal of Physics, 79 (2011), 1133. Reproduced under Creative Commons license)

In 1929 Hans Geiger and Walter Müller developed a gas filled ionization detector – a tube that registers individual charged particles. This Geiger-Müller counter was ideal for studying high-energy cosmic rays. Two such tubes placed one above the other could register 'coincidences'  when an incoming particles passes through both tubes  and thus define the path of a cosmic ray. Walther Bothe and Werner Kolhörster connected two Geiger counters to electrometers and immediately observed these ‘coincidences’.

A gamma ray only fires a Geiger counter if it knocks an electron out of an atom. The observation of coincident signals suggests that a cosmic gamma ray had either produced two electrons or that a single electron had fired both counters. To test if it was an electron that had set off both counters Bothe and Kolhörster put gold 4 cm thick between the counters to absorb the electrons knocked off from the atoms. They found that the rays were not affected and concluded that cosmic rays consisted of electrically charged particles and not gamma rays. Interposing a 4 cm thick gold piece between the tubes only slightly reduced the coincidence rate proving that cosmic rays contain charged particles of much higher energy than the Crompton electrons that would be produced by gamma rays. 

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Cosmic rays

First sighting of positron disregarded

While studying cosmic rays in a Wilson cloud chamber, the Soviet academic Dimitri Skobeltsyn noticed something unexpected among the tracks left by high-energy charged particles. Some particles would act like electrons but curve the opposite way in a magnetic field. In an independent experiment that same year, Caltech graduate student Chung-Yao Chao observed the same phenomenon. The results were inconclusive, and both scientists disregarded the anomaly. 

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Discovering the positron

Robert Millikan coins the term ‘cosmic rays’

Robert Millikan originally set about to disprove Hess and Kolhörster’s discovery. He and Ira Sprague reached a height of 1500 m in a balloon over Texas where they recorded a radiation intensity of approximately one quarter of Hess and Kohörster's measurement. The difference was caused by a geomagnetic difference between Texas and Central Europe but was blamed on turnover in the intensity curve at high altitude.

Millikan and Harvey Cameron reported on experiments on high-altitude lakes in 1926. They measured ionization rates at various depths in lakes at altitudes of 1500 m and 3600 m. The underwater rate of the lower lake corresponded to the rate obtained 2 m deeper in the higher lake. The pair concluded that particles shoot through space equally in all directions. This demonstrated that two metres of water absorbed about the same as two kilometers of air, and convinced Millikan that rays do come from above.

Millikan was convinced that penetrating radiation entering the atmosphere was electromagnetic and coined the term ‘cosmic rays’ in a paper where he argued that cosmic rays were the ‘birth cries of atoms’ in the galaxy.

Read more: "The Origin of the Cosmic Rays" – R.A. Millikan, G.H. Cameron, Physical Review Letters, 32 (1928) 533

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Cosmic rays

Wolfgang Pauli appointed professor at ETH Zürich

Despite some reservations about his lecturing style, Wolfgang Pauli was appointed professor of theoretical physics at the ETH, Zürich, on 10 January 1928. He started on 1 April at a basic annual salary of 15,000 francs.

Pauli’s lectures could sometimes be challenging. The equations in this photo  (taken in Copenhagen in 1929) look fairly legible, but K. Alex Müller recalls his habit of standing at the centre of the blackboard and writing equations around himself, almost in circles, rather than horizontally. Students in the ETH’s famous lecture room 6c tended to sit in two groups, to his left and his right, in order to be able to see round him! Markus Fierz considered Pauli the sort of teacher whose defect it is to think about their subject while lecturing; consequently, the listener participates in a sort of soliloquy which, since it is not really addressed to him, is sometimes barely intelligible. But - Fierz added - this taught the student, above all, to think critically about a theory.

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From the archive

Dirac's equation predicts antiparticles

In 1928, British physicist Paul Dirac wrote down an equation that combined quantum theory and special relativity to describe the behaviour of an electron moving at a relativistic speed. The equation would allow whole atoms to be treated in a manner consistent with Einstein's relativity theory. Dirac's equation appeared in his paper The quantum theory of the electron, received by the journal Proceedings of the Royal Society A on 2 January 1928. It won Dirac the Nobel prize in physics in 1933.

But the equation posed a problem: just as the equation x2=4 can have two possible solutions (x=2 or x=-2), so Dirac's equation could have two solutions, one for an electron with positive energy, and one for an electron with negative energy. But classical physics (and common sense) dictated that the energy of a particle must always be a positive number.

Dirac interpreted the equation to mean that for every particle there exists a corresponding antiparticle, exactly matching the particle but with opposite charge. For the electron there should be an "antielectron" identical in every way but with a positive electric charge. In his 1933 Nobel lecture, Dirac explained how he arrived at this conclusion and speculated on the existence of a completely new universe made out of antimatter:

If we accept the view of complete symmetry between positive and negative electric charge so far as concerns the fundamental laws of Nature, we must regard it rather as an accident that the Earth (and presumably the whole solar system), contains a preponderance of negative electrons and positive protons. It is quite possible that for some of the stars it is the other way about, these stars being built up mainly of positrons and negative protons. In fact, there may be half the stars of each kind. The two kinds of stars would both show exactly the same spectra, and there would be no way of distinguishing them by present astronomical methods.

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The story of antimatter, Discovering the positron

First photographs of cosmic rays

Using a cloud chamber, Dimitry Skobelsyn took the first photographs of tracks left by cosmic rays. Skobeltsyn was the first to advance the idea of using the registration of recoil electrons (Compton electrons) in a gas-filled Wilson cloud chamber. In his 1927 experiments, Skobeltsyn worked out the momenta of charged particles passing through the chamber from their degree of deflection by a magnetic field.

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The Como congress 1927

Wolfgang Pauli, Werner Heisenberg and Enrico Fermi relax on Lake Como during the 1927 International Conference on Physics.

The 1927 conference (held in Como to commemorate the 100th anniversary of the death of Alessandro Volta) is famous for Niels Bohr’s first presentation of his ideas on complementarity. His lecture “The Quantum Postulate and the Recent Development of Atomic Theory” became the basis of the Copenhagen interpretation of quantum mechanics; a fuller version was presented at the Fifth Solvay Conference (Brussels) in October. Bohr had discussed his ideas with colleagues both before and after these conferences, and Pauli was particularly involved in the preparation of the final manuscript.  

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From the archive