Golden Jubilee photos

Events, activities and celebrations are being organised in all the Member States as CERN prepares for its fiftieth anniversary next year. A detailed programme of the festivities will be available in early 2004. In the meantime, the Weekly Bulletin and the special Fiftieth Anniversary Website are launching a series of photographs recounting the Laboratory's fifty-year history. A different event will be commemorated each week. The series begins with one of the first Council sessions.

1952

[ The SC, the first Machine ]

In 1952, before CERN was officially founded, two accelerator projects were launched: one for an innovative accelerator to operate at an energy level unequalled at the time, the other for a more standard machine, a Synchro-Cyclotron (SC) to operate at 600 MeV. Design work on the SC was started in 1952 and carried out by teams scattered throughout Europe. Once construction began in 1954, CERN had to arrange road transport for the first of what has since been a long series of spectacular component deliveries, such as those of the machine's two magnetic coils each weighing 60 tonnes and measuring 7.2 metres in diameter. Above, one of them is seen passing through the village of Meyrin. The SC was commissioned in 1957 and was operational for 34 years!

1958

[ The first experiments ]

A year after the commissioning of the Synchrocyclotron (SC), the first experiments were already starting to bear fruit. In July 1958, Tito Fazzini, Giuseppe Fidecaro, Alec Merrison, Helmut Paul and Alvin Tollestrup produced conclusive evidence that approximately one pion in ten thousand decayed into an electron and a neutrino, as predicted by the weak interaction theory. This, the first of CERN's great discoveries, effectively put an end to the controversy that had been raging at the time.
A few years later, Giuseppe Fidecaro began a collaboration at CERN with his wife Maria. In the image, Giuseppe and Maria Fidecaro in 1963, surrounded by spark chambers, inside the detector for the experiment on the decay of the rho into a pi and a gamma meson.

1959

[ The Proton Synchrotron - Energy record ]

Standing before the CERN personnel in the Main Auditorium on 25 November 1959, John Adams held not a bottle of champagne but a bottle of vodka. It had been presented to him a few months earlier during a visit to Dubna in the Soviet Union, where the world's most powerful accelerator had just been commissioned. He had been given strict instructions not to open the bottle until Dubna's energy record of 10 GeV had been broken. On 24 November, the record was smashed by CERN's brand new machine, the Proton Synchrotron, which accelerated protons at 24 GeV, over twice the energy of the Dubna machine. Before sending the empty bottle back to the Soviet Union, John Adams, who had headed the accelerator's construction, placed the recording of the signal in it as proof of the record.
More than 40 years later, the PS is still going strong, delivering beams with particle densities a thousand times greater than when it first started operation. Over the years, other accelerators have grown up around it and the PS is now the hub of the CERN accelerator complex, supplying the other machines with all types of particles.

1959

CERN is one of the few laboratories to have its own fire station. The CERN fire brigade was set up in July 1956 to provide a rapid response in the event of an accident and to tackle the risks specific to the Organisation's activities. Pierre Vosdey, a fireman from Paris and founder of the fire station, was CERN's first fireman. He was joined two years later by a second fireman. It was not until the 1960s that some thirty further firemen were recruited to ensure the safety of the PS (Proton Synchrotron). Their mission was not only to fight fires on the whole CERN site and in the surrounding area but also to run the infirmary for work-related and road accidents, fulfil general security and safety-related duties, such as theft prevention, road safety and site surveillance, and to perform a variety of other duties, including passing on urgent telegrams, manning the switchboard, handling liquid hydrogen and nitrogen and receiving and unloading goods. The fire brigade's complement reached its peak in 1975, when 90 firemen were recruited following the construction of the SPS (Super Proton Synchrotron).
Nowadays, the fire brigade comprises 57 members from 9 different nationalities, many of whom are at CERN on secondment from their home units for a period of three years. They provide a service 24 hours a day, 365 days a year. The CERN fire brigade works in close collaboration with firemen in the Host States, and takes part in a training exchange programme incorporating the Fire Brigade of the City of Geneva (SIS), the Geneva Airport Fire Brigade as well as those of the City of Neuchâtel and the Département de l'Ain.

1960

[ Computers for physics ]

CERN's first computer, a huge vacuum-tube Ferranti Mercury, was installed in building 2 in 1958. With its 60 microsecond clock cycle, it was a million times slower than today's big computers. The Mercury took 3 months to install and filled a huge room, even so, its computational ability didn't quite match that of a modern pocket calculator. "Mass" storage was provided by four magnetic drums each holding 32K x 20 bits - not enough to hold the data from a single proton-proton collision in the LHC. It was replaced in 1960 by the IBM 709 computer, seen here being unloaded at Cointrin airport. Although it was taken over so quickly by transistor equipped machines, a small part of the Ferranti Mercury remains. The computer's engineers installed a warning bell to signal computing errors - it can still be found mounted on the wall in a corridor of building 2.

1950-1960

[ The first CERN bubble chamber ]

In the 1950s and 1960s, bubble and spark chambers were the dominant experimental tools in high-energy physics. While spark chambers were usually built and fitted to specific experiments, bubble chambers were constructed as general purpose devices that could be used for a variety of experiments.
At CERN, the bubble chamber programme started under Charles Peyrou in the late 1950s. The first of CERN's bubble chambers, a 30 cm hydrogen chamber, is seen here being inserted into its vacuum tank. The HBC30, as it was called, took its first beam from the SC in 1959. One of the first pictures taken, of a positive pion-proton interaction, began a long series of pretty images for which bubble chambers would become famous. When it stopped operating in spring 1962, the HBC30 had consumed 150 km of film in its 3 years of operation.

1963

[ The Swiss site expands into France ]

In this photograph taken in the winter of 1963, CERN still looks quite bare under its mantle of snow. The Proton Synchrotron (PS), resembling a bicycle wheel in shape, had been in operation since the summer of 1959. A proposal had just been made for the site of CERN's second large project, the Intersecting Storage Rings (ISR): France was to house the world's first proton-proton collider. In September 1965, the French authorities signed an agreement making more than 40 hectares of land available for the extension of the CERN site established in Switzerland into French territory. The ISR project received final approval from the CERN Council in December 1965. The civil engineering work on the French part began in November 1966.

1963

[ Remembering CESAR ]

Few today remember CESAR, the CERN Electron Storage and Accumulation Ring. Although a minor chapter in CERN's history, this little accelerator made a lasting impact. It was designed to investigate the challenges posed by the beam accumulation, stability and lifetime factors required for a two ring proton collider.
CESAR was completed in mid-1963. Electrons were injected, but refused to circulate for many months. The reason was the low magnetic fields compounded by the fact that the magnets were made from solid iron. After switch-on, their field took days to creep towards its final value, and even the position of the overhead crane influenced electron trajectories. Success came just before Christmas. The results of CESAR studies were used to design the ISR, intersecting storage rings, collider.
In 1964, the experimental programme began, and it lasted until the end of 1967. In 1968, CESAR was dismantled, some components found use at CERN, its van de Graaff injector was shipped to the University of Swansea, and the CESAR team dispersed to other accelerator activities at CERN. In the photograph, R.Nettleton (left) and H.Burridge (right) are preparing the van de Graaff for shipment to the University of Swansea.

1966

[ CERN celebrated ]

21 February 1966. The Swiss post office issued a stamp in CERN's honour. This stamp showed the flags of the thirteen Member States at the time arranged in the geometrical outline of Switzerland against a background of a track photograph.

1967

[ Testing ISOLDE ]

This picture was taken in 1967 during the first test of the Isotope On-Line Separator (ISOLDE) installation at the 600 MeV CERN Synchro Cyclotron. When ISOLDE began operation, it was unique in the world. It used a new technique to overcome the problem of rapidly separating interesting atoms from the rest of the nuclear target. Through a combination of chemical and electromagnetic methods the different isotopes were separated and converted into an ion beam made of just one isotope.
On-line production of radioactive nuclei, in this way, offered many new opportunities for physicists as it allowed them to perform previously impossible experiments on short-lived nuclei.
ISOLDE has become one of CERN's major installations and it supports a broad scientific programme by providing beams to different experiments. The techniques developed at ISOLDE have opened up a new field of radioactive ion-beam accelerators, both at CERN and worldwide.

1970

[ A New Class of Detectors ]

In the 1960s, detection in particle physics mainly meant examining millions of photographs from bubble chambers or spark chambers. This was slow, labour intensive and not suitable for studies into rare phenomena, so there was a bottleneck that could have affected further progress in high energy physics.
The transistor revolution triggered new ideas. While a camera could detect a spark, a detector wire connected to an amplifier could 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 techniques - without a camera in sight.
Today practically every experiment in particle physics uses some type of track detector that is based on the principle of the multiwire proportional chamber. The technology is also used in many other fields using ionising radiation such as biology, radiology and nuclear medicine.
Georges Charpak, who won the Nobel Prize in 1992 for his work on particle detectors, is pictured on the left along with Fabio Sauli and Jean-Claude Santiard, working on one of CERN's first large multiwire proportional chambers.

1971

[ ISR - The first proton-proton interactions ]

At the inauguration ceremony for the Intersecting Storage Rings (ISR) on 16 October 1971, the man in charge of their construction, Kjell Johnsen, presented the "key" to the machine to Edoardo Amaldi, President of Council. Seated on the stage with them for this symbolic event were Victor Weisskopf, Marcel Antonioz, Willy Jentschke (seen on the left of the photo) and Werner Heisenberg (on the far right).
On 27 January that year, in a world premier, signals produced by proton-proton collisions had been observed at the ISR. The protons, supplied by the PS, were injected into two identical rings, each measuring 300 metres in diameter, and collided head on at the 8 points where the rings intersected. The installation, which remained in operation until 1984, gave physicists access to a wide range of energies for hadron physics, hitherto restricted to the data from cosmic ray studies.
The many technological challenges that were met at the ISR, in the fields of vacuum technology and stochastic cooling for instance, paved the way for luminosity records to be broken.¹ From June 1974 onwards, the nominal current of the beams stored in the rings - 20 A per ring - allowed the 10³¹ cm^-2s^-1 luminosity threshold to be exceeded. A further increase in luminosity was achieved when superconducting magnets were introduced in November 1980, the first time they had been used in an accelerator.

¹ Luminosity is directly proportional to the number of collisions occurring in a given amount of time.

1971

The vessel of the Big European Bubble Chamber, BEBC, was installed at the beginning of the 1970s. The large stainless-steel vessel, measuring 3.7 metres in diameter and 4 metres in height, was filled with 35 cubic metres of liquid (hydrogen, deuterium or a neon-hydrogen mixture), whose sensitivity was regulated by means of a huge piston weighing 2 tonnes. During each expansion, the trajectories of the charged particles were marked by a trail of bubbles, where liquid reached boiling point as they passed through it.
The first images were recorded in 1973 when BEBC, equipped with the largest superconducting magnet in service at the time, first received beam from the PS. In 1977, the bubble chamber was exposed to neutrino and hadron beams at higher energies of up to 450 GeV after the SPS came into operation.
By the end of its active life in 1984, BEBC had delivered a total of 6.3 million photographs to 22 experiments devoted to neutrino or hadron physics. Around 600 scientists from some fifty laboratories throughout the world had taken part in analysing the 3000 km of film it had produced.

1972

In 1972, the OMEGA spectrometer was commissioned in the West Area and more than a million collisions were recorded that very first year. OMEGA was equipped with spark chambers - replaced at the end of the 1970s by electronic detectors - and a 15 000-tonne superconducting magnet. On this photo we can see the magnet's lower coil and, in the foreground, the support plate for the upper coil.
No fewer than 48 experiments made use of this device, exploiting beams of various particles at various energies - from the PS at the beginning, and then from the highest energy beams of the SPS. OMEGA thus played a key role in many physics results and activities, notably the production of the J/psi particle, the study of particles carrying charm or beauty quarks, the study of «gluonia», and the CERN heavy ion programme.
The OMEGA experiments ceased in 1996 when the facilities in the West Hall were shut down in preparation for the construction of the LHC.

1972

CERN's first large accelerator, the Proton Synchrotron (PS), had hardly come into operation at the beginning of the 1960s, when physicists started to dream of a machine ten times more powerful, operating at 300 Gigaelectronvolts. The construction of such an accelerator required a new laboratory to be built and several European sites were candidates. John Adams, the project leader, suggested using the PS as an injector for the new machine, to achieve the higher energy level at a lower cost. The new Laboratory was therefore to be built on a site adjacent to CERN. The project was approved in 1971, but the CERN Convention, which only provided for a single laboratory, had to be amended.
An agreement was signed with France on 16 June 1972 (see photograph), establishing a new site at Prévessin, in the Pays de Gex. The two laboratories, which each had their own administrative structures and Directors-General, were merged in 1976.

1973

In July 1973, a groundbreaking discovery was announced in CERN's Main Auditorium: the Gargamelle group had found proof of the weak neutral current. The discovery confirmed the electroweak theory, which had predicted that the weak force and the electromagnetic force were different facets of the same interaction. This paved the way for the Grand Unified Theory, which holds that just after the birth of the Universe all forces were actually the same...
Gargamelle, whose "body" now reposes in the Microcosm garden, was a huge bubble chamber weighing around 1000 tonnes, filled with 18 tonnes of liquid freon. Its size, worthy of the giant Gargantua - the son of Gargamelle - was mighty enough to catch neutrinos, the elusive neutral particles which career through space without leaving any tracks. In the photograph, an unseen neutrino interacts with an electron and emerges as a neutrino instead of changing into a muon - what is seen (horizontally) is the track of the electron. This lepton event offers proof of the existence of neutral currents.

1974

A few months after the signature of the agreement giving the go-ahead for the expansion of CERN into French territory, work began on the Super Proton Synchrotron (SPS). Two years later, on 31 July 1974, the Robbins tunnel-boring machine excavating the SPS tunnel returned to its starting point (see photograph). It had excavated a tunnel with a circumference of 7 kilometres, at an average depth of 40 metres below the surface. The tunnel straddled the Franco-Swiss border, making the SPS the first cross-border accelerator.
More than a thousand magnets were needed to equip the ring. The civil engineering and installation work was completed in record time after only four years. The SPS was equipped with a control system which was ahead of its time, consisting of 24 small control computers distributed in the tunnel and the control room and communicating by means of a high-rate data transmission system. The main control room housed only four consoles as opposed to the banks of electronic equipment usually used at the time.
On 17 June 1976, the project leader, John Adams, announced to the members of Council gathered for their June round of meetings that the first circulating proton beam at 400 GeV had been achieved. The SPS experimental programme began the following year.

1978

Catching neutrinos isn't easy. They interact only rarely with matter, so they have a good chance of passing straight through the Earth without stopping. However, when they do interact it is possible to see what effect they have on other particles.
CERN had been doing this type of research for more than a decade by the time the detector in the picture was finished in 1977. The picture shows Klaus Winter, who worked on the 100 tonne CHARM experiment. CHARM is seen here in the West Area where it was set up with the 1250 tonne CDHS experiment.
Researchers used these machines to help develop the Standard Model of particle physics and further our understanding of the structure of the atomic nucleus.
The research also helped expand physics into a new field aimed at understanding the peculiar behaviour of neutrinos. There are three 'flavours' of neutrino - the electron, muon, and the tau neutrino. Over a long enough distance, they oscillate from one flavour to another.
In 2006, CERN will try to make more progress on understanding neutrinos by sending a beam of muon neutrinos through the Earth's crust to the Gran Sasso National Laboratory in Italy, 730km away. The new detectors there will be able to measure the change in flavour when the beam arrives.

1979

CERN organised celebrations for its tenth, twenty-fifth, thirtieth and fortieth anniversaries. Over the years, as its educational and outreach activities expanded, the festivities placed more and more emphasis on the general public, who were invited to come and see science in the making. The tenth-anniversary celebrations were confined to an official ceremony in the presence of representatives of the thirteen Member States and to a party for the personnel.
Those marking the Organization's twenty-fifth anniversary were more grand and included, in addition to the official ceremony, an exhibition of CERN technology, a concert by the Suisse Romande Orchestra at the Victoria Hall in Geneva, an exhibition at the Balexert shopping centre, an open day for the local population and a special day for the staff consisting of talks, competitions and numerous other attractions. In particular, a competition was held to find the most unusual anecdotes about life at the Laboratory. A photographic record of the Organization's first twenty-five years, with which many people at CERN are familiar, was also published.
King Juan Carlos I of Spain was the most important guest at the official thirtieth-anniversary ceremony on 21st September 1984, marking Spain's return as a CERN Member State the previous year. The Suisse Romande Orchestra gave a concert in Geneva's Victoria Hall on this occasion too and an open day was organised for the general public. The greatest thirtieth-anniversary gift of all, however, was the first Nobel Prize awarded for research conducted at CERN, which went to Carlo Rubbia and Simon van der Meer a few weeks later.
The fortieth anniversary celebrations, which consisted of an open day for the personnel, were certainly the least formal of all. For a day, the CERN site was transformed into a huge fête with entertainment put on for all the family.

1983

At the beginning of the 1980s, CERN embarked on the enormous Large Electron-Positron Collider construction project. The excavation of the 27-kilometre LEP tunnel was a huge technical challenge. The tunnel-boring machines excavated the tunnel in 3.3 km octants and had to be operated with extraordinary precision to ensure that they reached their destination - the bottom of the next vertical shaft - precisely on target. The tunnel was excavated before high-performance instruments were developed for the construction of the Channel Tunnel. As no firms were willing to perform the surveying work, CERN's own surveyors, with experience from the SPS behind them, took up the challenge.
At the surface, the surveyors established the world's most accurate geodetic network, performing measurements to an accuracy of 10-7, or 1mm per 10 km, using the Terrameter (see photo). The excavation of the tunnel was completed in 1988 and the finished tunnel's trajectory was found to diverge from the theoretical value specified by the physicists by only one centimetre. Such precision had never before been achieved.
In addition to successfully aligning accelerator components with an accuracy of 0.1 mm, the surveyors' other celebrated achievement was that they managed to align the LEP machine around all 27 km of its circumference with a discrepancy of only 1 cm compared to the subsequent monitoring radiofrequency measurements done with the beam.
Such precision surveying work is essential for CERN. CERN's surveying team is currently responsible for checking the alignment of some 8 500 components over 63 km of beam lines and they will have to align some 3 000 new components for the LHC machine.

1983

On 25 January 1983, this historic press conference announced the observation of W particles in the UA1 experiment at CERN, and was followed by another in May when Z particles had been found.
Natural phenomena at this scale are described by four forces, gravity, electromagnetism and the strong and weak nuclear forces. But in 1968 a new theory predicted that electromagnetism and the weak nuclear force were manifestations of a single 'electroweak' interaction, proposing that it would be communicated by the charged W+ and W- bosons and the neutral Z0 boson. In 1979 Sheldon Glashow, Abdus Salam and Steven Weinberg won the Nobel Prize for Physics for this work.
Finding the bosons predicted by the theory involved a huge effort. CERN had to develop new technology and engineering. Innovations included making crucial advances in techniques for producing, gathering and controlling antimatter (see Bulletin 26/2004), converting the SPS into a proton-antiproton collider, and building two new detectors, the 2000 ton UA1 and the 200 ton UA2.
In recognition of these efforts, the two most instrumental collaborators in the discoveries, Carlo Rubbia, head of the UA1 project, and Simon van der Meer, inventor of the stochastic cooling technique, were awarded the Nobel Prize for Physics, 1984.

1986

[ The Big Dig ]

The excavation of the LEP tunnel was the most formidable civil-engineering venture in the history of CERN and Europe's largest civil-engineering project prior to the Channel Tunnel.
Siting a 27-km long underground ring in the corridor between the Jura mountains and Lake Geneva was no easy matter. After several proposals, the decision was made to install the ring along the foot of the Jura range. However, owing to geological features the tunnel had to be built on a gradient of 1.4 %, sloping towards the Lake.
Three tunnel-boring machines started excavating the tunnel in February 1985. One year into the project there was a major geological accident when substantial quantities of high-pressure water, sand and mud burst into the tunnel, halting operations for several months. Once the problem was overcome, work resumed and the ring was completed on 8 February 1988.
Despite its size, the tunnel accounted for less than half the 1.4 million cubic metres of spoil excavated from the site. The LEP facility also included a number of access shafts as well as four huge experimental caverns and numerous galleries and service tunnels.

1989-2000

In their day, LEP and its four detectors were the biggest of "big science," both in the size of the detectors and the international collaborations that produced them. Initially each detector had certain measurements in which it excelled, and with later upgrades they all performed well across-the-board. By making overlapping measurements, but using different methods, the results from the four detectors reinforced each other.

For detecting the direction and momenta of charged particles with extreme accuracy, the ALEPH detector had at its core a time projection chamber, for years the world's biggest. The experiment also became renowned for its innovative software for visualizing particle collisions.

Of the LEP detectors, DELPHI was the most innovative, including what was the world's largest superconducting magnet. One of DELPHI's main strengths was its ability to unambiguously identify many types of charged particles.

L3's strong point was accurate measurements of the momenta of electrons and their heavier cousins, muons. The detector was surrounded by a magnet that weighed as much as the Eiffel Tower and created the world's largest magnetic volume, 2700 cubic metres.

Based on tried-and-true technology, OPAL was the safest bet among the LEP detectors. It was also the first LEP detector to record data, observing a Z boson decay on 14 August, 1989.
Registering 17 million Z boson decays in its first six years, and later 40 000 pairs of W bosons, LEP's highly-accurate results confirmed the Standard Model of particle physics, extended the model to much higher energies and pointed the way to future discoveries at future accelerators, such as the LHC.

1991

Commissioned in 1989, the Large Electron-Positron Collider (LEP) was the largest ever electron-positron accelerator. Its 27 km circumference was chosen on the basis of synchrotron radiation considerations. When the trajectory of charged electrons is curved, they emit radiation and lose energy. The greater the radius of curvature, the smaller the energy loss. It was therefore necessary to find a compromise between the cost of building the ring and the costs involved in operating the accelerator. The PS and SPS accelerators were used to pre-accelerate particles before injecting them into the LEP machine.
LEP had 5176 magnets, 128 accelerating cavities (to re-accelerate the energy lost in the bends of the ring) and four enormous detectors, ALEPH, DELPHI, L3 and OPAL. The detectors were designed to study the reactions of the electrons as they collided at high energies with positrons (the antimatter counterpart of electrons).
The first collisions took place in August 1989. LEP operated at 100 GeV for seven years and produced Z particles, one of the vectors of a fundamental force of Nature, the weak force. In 1995, LEP was upgraded for a second phase of operation known as LEP2, and spent the rest of its career operating at almost twice its original energy (over 200 GeV). This led to the production of W+ and W- pairs, the other two vectors of the weak force. 272 superconducting accelerating cavities had to be added to achieve this energy.
After 11 years of successful research, the LEP was closed down on 2 November 2000 to make way for the construction of the LHC, which will operate at an energy of 7000 GeV.

1992

Particle physicists don't always need ever more powerful accelerators to study interesting physics. LEAR, the Low Energy Antiproton Ring, was designed to help explore the properties of antimatter, with the annihilation of protons and antiprotons becoming the main theme.
LEAR was commissioned in 1983 and contributed to more than 30 experiments with great success.
LEAR took part in the discovery of a 'glueball', a particle composed entirely of gluons, the carriers of the strong nuclear force. LEAR also observed that neutral kaons and antikaons decay at a slightly different rate, offering physicists another insight into the mystery about why matter prevails over antimatter in the Universe.
Uniquely, LEAR combined both the electron and stochastic beam cooling techniques, used to control and refine the beams. It also pioneered a technique using white noise and magnetic resonance to extract one antiproton for every 30 km the beam travelled around the machine (400 revolutions).
In 1995 the machine produced the first nine antihydrogen atoms. As antimatter is a potential power source and rocket propellant, and is well known to followers of science fiction, this triggered a considerable amount of media interest.
LEAR was closed in 1996 and is now being converted to LEIR (Low Energy Ion Ring): it will provide lead ion beams to the LHC.

1993

Theory might provide the scaffolding of physics, but it takes experiments to put up the brickwork. The Large Electron-Positron Collider project (LEP), which included four experiments (ALEPH, DELPHI, L3 and OPAL), was designed to test the Standard Model of particle physics.
With more than 17 million Z boson decays observed in the first five years, and 40 thousand W boson pairs collected later, LEP allowed physicists to test the Standard Model to an unprecedented level of precision. LEP also measured the number of families of matter particles (three), and predicted the mass of the Top quark, which was later discovered in the US.
Occasionally, the LEP data showed small anomalies, but most of them disappeared after closer scrutiny: mainly, it revealed the coherent pattern of particle physics that the Standard Model had predicted.
Perhaps the most tantalising result came at the end of LEP's 11-year career when it saw signs of what might have been a Higgs boson, the particle thought to be responsible for the existence of mass. However, the data at hand did not allow the observation to be confirmed, so the result was only "perhaps".
LEP closed in 2000 to make way for the LHC, which will continue to challenge the Standard Model. However, LEP generated a body of work that will be useful for years to come, even after the Standard Model is superseded.

1994

At the end of the 1980s, the Internet was already a valuable tool to scientists, allowing them to exchange e-mails and to access powerful computers remotely. A more simple means of sharing information was needed, however, and CERN, with its long tradition of informatics and networking, was the ideal place to find it. Moreover, hundreds of scientists from all over the world were starting to work together on preparations for the experiments at the Large Electron-Positron (LEP) collider.
In 1989, Tim Berners-Lee (see photo), a young scientist working at CERN, drafted a proposal for an information-management system combining the internet, personal computers and computer-aided document consultation, known as hypertext. In 1990 he was joined by Robert Cailliau and the weaving of the World Wide Web began in earnest, even though only two CERN computers were allocated to the task at the time. The Web subsequently underwent a steady expansion to include the world's main particle physics institutes.
The Web was not the only information-sharing system developed for the Internet. Other notable examples included the Gopher system, developed at the University of Minnesota in the United States. The turning point that allowed the CERN system to win through was the decision by the CERN Management to release the Web into the public domain, thus ensuring that users would always be able to use it free of charge.
While a single CERN server was used to develop the Web at the time of its inception, there are more than 46 million Web servers throughout the world today.

1994 -

ATLAS

CMS

LHCb

The four LHC experiments are on an unprecedented scale. The detectors will record particle collisions far more powerful than those at any other particle accelerator. One of the detectors, ATLAS, will be the largest-volume particle detector ever, a cylinder 45 metres long and 25 metres high. And the collaborations are a step beyond LHC's predecessor, LEP, involving even more people from more countries. Together, these four experiments promise to open a door to new realms of physics.
CMS and ATLAS are both general-purpose detectors, whose major quarry include the Higgs particle, which could give other particles their mass, and supersymmetric particles, which would bolster theories beyond the Standard Model. A major technical challenge for CMS has been acquiring 61 000 large, precision-grown crystals, denser than iron, for catching high-energy photons and electrons (1st bottom photo). ATLAS includes the world's largest superconducting magnets (2nd bottom photo), eight coils arranged into a large barrel shape that will physically support the rest of the detector while wrapping it in a massive magnetic field.
LHCb (1st top photo) aims to help explain why the Universe is all matter and practically no antimatter. This experiment is specially tuned to sort through billions of collisions that create pairs of beauty and antibeauty quarks, searching for matter-antimatter differences. ALICE (2nd top photo) will study collisions of lead nuclei that create a state of matter, the quark-gluon plasma, that probably existed in the first moments of the universe.

1996

Antiparticles were predicted in the work of Paul Dirac in the 1920's, since when physicists have identified all the necessary antiparticle constituents of an antiparticle atom - antielectrons (positrons), antiprotons and antineutrons. However, an antihydrogen atom wasn't produced until the PS210 experiment at CERN in 1995.
PS210 used the LEAR accelerator, which was then nearing the end of its lifetime (see Bulletin 28/04), so everything in the experiment had to work first time.
After installing the equipment in spring 1995, the experiment took place in the autumn, in two hour periods over 4 weeks. The experiment team collided energetic antiprotons from LEAR with a heavy element, a challenge for them as well as the LEAR operators.
Proving that antihydrogen atoms had been formed required several more weeks of data analysis, but the announcement that nine antihydrogen atoms had been produced came on 4 January 1996.
Some of the press coverage focused on applications that were more science fiction than science. The real value of the experiment was that it proved antimatter atoms were possible, and paved the way toward producing sufficient amounts of 'cold' antihydrogen for basic research, opening the way to a new realm of fundamental science.

1997

Even before digging the LEP tunnel, in the early eighties CERN scientists began laying the plans for the second-generation collider to go in the tunnel. From the beginning, physicists had their eyes fixed on certain goals such as finding the Higgs boson and signs of supersymmetric particles.
To reach the desired energies within the LEP tunnel, instead of LEP's electrons and positrons, the next collider would need to use more massive particles that radiate away less energy as they travel around the circular tunnel.
Also, since the United States was planning the Superconducting Super Collider (SSC) with a circumference even larger than LEP's, CERN scientists conceived of their next collider as a "high-luminosity" machine that would excel at producing a high number of collisions. But since making a strong antiproton beam is laborious, this collider would have to smash together two proton beams.
Thus the LHC project was born. Since the LHC would use two proton beams running in opposite directions, it required two sets of magnets-a "two-in-one" collider. Also, to reach the desired energies, the accelerator would need to use superconducting magnets, rather than conventional magnets as in CERN's previous colliders.
Through several years of building prototype magnets and sections of the accelerator, CERN scientists were able to work out the technical difficulties and show the project was feasible. In 1993 the U.S. Congress canceled the SSC. A year later, the CERN Council gave the go-ahead for the LHC, the most powerful collider in the world.

1998

The technology developed at CERN for accelerators and detectors has been put to a wide range of uses in fields other than particle physics. Medicine has been one of the main beneficiaries, both in the area of diagnostics and in therapeutics. Scientists at CERN have been contributing to medical research for almost 40 years.
In the mid-1970s, new detectors based on the multiwire proportional chamber began to be used for medical imaging. They were much more sensitive than previous devices and considerably reduced the doses of radiation to which patients were exposed during medical examinations.
Some years later, CERN developed a prototype for a positron camera, paving the way for the construction of the Hôpital Cantonal Universitaire de Genève's first Positron Emission Tomography (PET) scanner (photograph).
During the same period, CERN physicists investigated the applications for carbon ions and protons in cancer treatment. This was because although the high energy x-rays normally used in the treatment of deep-seated tumours are effective, the surrounding healthy tissue is exposed to high doses of radiation. Light ion and proton beams cause less exposure and are therefore preferable when the tumour is close to a vital organ. Furthermore, carbon ions, whose nuclei deliver 24 times more energy to a cell than those of a proton, are more effective in fighting tumours that are resistant to radiotherapy (this accounts for 10% of the 40 000 tumours per million of the population each year).
Between 1996 and 2000, CERN led the Proton Ion Medical Machine Study (PIMMS), which was then adapted for use in radiotherapy by the Italian Tera Foundation, and became known as PIMMS-TERA.
More recently, CERN and the GSI in Germany have collaborated in setting up the European Network for research in LIGHt ion Therapy (ENLIGHT).

1998

Antimatter isn't normally just sitting around, waiting to be studied. As far as scientists know, hardly any antiparticles—the mirror-image versions of regular particles, with the same mass but opposite electric charge—exist in the Universe. This absence of antimatter is somehow mysterious and motivates physicists to look for tiny differences between particles and antiparticles.
One way to do this is by studying antimatter very precisely. The simplest antimatter atom, antihydrogen, is made from an antiproton and a positron (an anti-electron). The first nine atoms of antihydrogen emerged from particle collisions at CERN in 1995, but they moved at nearly the speed of light.
To produce slow-moving antihydrogen atoms, better suited for precision studies, scientists have gone against the prevailing methods at CERN. Instead of smashing together highly-accelerated particles, they built the Antimatter Decelerator (AD) to put the brakes on antiprotons, slowing them down so they can be caught and combined with positrons.
The 188-metre-circumference AD cools the antiproton beam and slashes the particles' momentum by a factor of 35. Since starting up in 2000, the AD has fed these particles to three different studies, ATHENA, ATRAP and ASACUSA. With these experiments, scientists hope to see whether antimatter behaves the same as matter-and if not, whether this explains why the Universe has so little antimatter.

2000

Fourteen thousand million years ago, less than 10 microseconds after the Big Bang, the Universe was too hot and too dense for the formation of protons and neutrons, the particles of which atomic nuclei are made. Theory suggested that their constituents, quarks and gluons, were able to move around freely in a 'particle soup' known as quark-gluon plasma (QGP). Physicists at CERN began trying to verify this in 1986.
To do that quarks and gluons had to be 'deconfined' from their usual place within protons and neutrons. It was thought that this could be achieved by accelerating a beam of ions (atoms from which the electrons have been removed) and firing it at a fixed target. When CERN's heavy ion programme first started, the relatively light nuclei of oxygen and sulphur were used.
Having refined its experimental techniques, CERN was able to use heavy ions (lead ions) in 1994. Within the framework of the fixed target heavy ion programme at the Super Proton Synchrotron (SPS), several experiments were designed to detect the signals which, according to theory, should be triggered by the formation of the plasma. In 2000, CERN announced the discovery of a new state of matter. However, it was not possible to tell whether this new state was actually the QGP or simply a precursor state. There were two routes for further study. CERN chose, with the NA60 experiment, to perform certain measurements again but with greater precision, thanks to technological developments made for the LHC. Meanwhile, the Brookhaven Laboratory, in the United States, chose to increase the collision energy by using the colliding beam mode rather than the fixed-target method and constructed the Relativistic Heavy Ion Collider (RHIC).
Research is still continuing: the next step, using higher energies, will be taken by CERN's LHC experiments, ALICE in particular.

2000

CERN: Where the Web was born, but much else as well. The multiwire proportional chamber, developed at CERN, not only revolutionized particle detection for physics experiments but also for medical imaging. CERN physicists also paved the way for the first positron-emission tomography (PET) scanner.
For most of CERN's history, though, technology transferred from the Laboratory to industry without organized promotion or follow up. CERN's culture was dedicated to basic research, and its Convention states that the fruits of its research be made freely available. Confidentiality before receiving patents, and restrictions on publications to protect industry, seemingly ran counter to CERN's openness.
But by the 1980s, the expense of grand equipment such as the Large Electron-Positron (LEP) collider required substantial justification before funding.
Following an external committee's recommendation, the Organization began to formalize technology transfer, first cataloging technologies developped at CERN that had already found applications. Then came an industry liaison office and in 2000 a dedicated technology transfer group. In retrospect, the Web took off partly because it was given away, but to find eventual use in industry, some technologies need protection and aid along the way.

2002

New accelerator projects take many years to make and mature. When the LHC project was still only a twinkle in CERN's eye, research was already starting on a new machine. A small team at CERN was setting about the task of studying a high-energy, compact, lepton linear collider, known as CLIC. This is possibly set to become the collider of the future. A machine of this kind has all the advantages of a collider (the total collision energy is equal to the sum of the energies of the two colliding beams) without the drawback of synchrotron radiation, which is produced when particles are accelerated around a ring and thus puts a limit on the energy of such colliders.
But in a project as technically challenging as CLIC, considerable technological hurdles must be overcome. To limit the linear collider's length to some tens of kilometres, the beams must acquire a considerable quantity of energy per metre travelled. The collision rate (luminosity) must also be sufficiently high. Consequently, each beam must contain an enormous amount of densely packed particles and the two beams must be aligned with tremendous precision so that the beam could be less than one nanometre at the collision point! The CLIC design is based on the two-beam acceleration concept, where a "drive beam" transfers its energy to accelerate a main beam.
Tests of the various solutions and options for CLIC began as early as 1991, with the first CLIC Test Facility (CTF). The second facility, CTF2, performed tests from 1996 to 2002. And from this year onwards, a new test facility - CTF3 - has taken over. Its aim? To demonstrate the feasibility of the key parameters for such a collider.