The European Organization for Nuclear Research, also called the European Laboratory for Particle Physics and commonly known by the acronym CERN or Cern (from the name of the European Council for Nuclear Research, a provisional body established in 1952), is the most great particle physics center of the world. It is located a few kilometers from Geneva, Switzerland, straddling the Franco-Swiss border, in the municipalities of Meyrin, Prévessin-Moëns and Saint-Genis-Pouilly.
CERN aims to better understand what the Universe is made of and how it works. To do this, CERN provide scientists with a complex, unique in the world, of particle accelerators, enabling them to push the boundaries of human knowledge.Founded in 1954, the Laboratory has become a remarkable example of international collaboration. Our mission is to: provide a unique complex of particle accelerators enabling research at the cutting edge of human knowledge; to conduct world-class research in fundamental physics; bringing people together from around the world to push the boundaries of science and technology for the benefit of all.
CERN established in 1954, the organization is based in a northwest suburb of Geneva on the France–Swiss border and has 23 member states. Israel is the only non-European country granted full membership. CERN is an official United Nations Observer. The acronym CERN is also used to refer to the laboratory, which in 2016 had 2,500 scientific, technical, and administrative staff members, and hosted about 12,000 users.
CERN’s main function is to provide the particle accelerators and other infrastructure needed for high-energy physics research – as a result, numerous experiments have been constructed at CERN through international collaborations. The main site at Meyrin hosts a large computing facility, which is primarily used to store and analyse data from experiments, as well as simulate events. Researchers need remote access to these facilities, so the lab has historically been a major wide area network hub. CERN is also the birthplace of the World Wide Web.
The convention establishing CERN was ratified on 29 September 1954 by 12 countries in Western Europe. The acronym CERN originally represented the French words for Conseil Européen pour la Recherche Nucléaire (European Council for Nuclear Research), which was a provisional council for building the laboratory, established by 12 European governments in 1952. The acronym was retained for the new laboratory after the provisional council was dissolved, even though the name changed to the current Organisation Européenne pour la Recherche Nucléaire (European Organization for Nuclear Research) in 1954. According to Lew Kowarski, a former director of CERN, when the name was changed, the abbreviation could have become the awkward OERN, and Werner Heisenberg said that this could “still be CERN even if the name is “.
CERN’s first president was Sir Benjamin Lockspeiser. Edoardo Amaldi was the general secretary of CERN at its early stages when operations were still provisional, while the first Director-General (1954) was Felix Bloch.
The laboratory was originally devoted to the study of atomic nuclei, but was soon applied to higher-energy physics, concerned mainly with the study of interactions between subatomic particles. Therefore, the laboratory operated by CERN is commonly referred to as the European laboratory for particle physics (Laboratoire européen pour la physique des particules), which better describes the research being performed there.
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.
In 1983, the electroweak theory is almost completely confirmed, the weak and electromagnetic forces are almost unified. It is also this year, September 13, that the first work of LEP begins. In 1984, Carlo Rubbia and Simon van der Meer received the Nobel Prize in Physics in October for their discovery concerning the electroweak force. Following the inauguration of LEP in 1989, the predictions of the theory on the electroweak forceare confirmed, in particular the existence of charged particles (W bosons) whose mass is approximately 80 times that of the proton as well as a neutral particle (the Z boson) whose mass is approximately 91 times that of the proton.
Between 1989 and 1990, Tim Berners-Lee, joined by Robert Cailliau, designed and developed a hypertext information system, the World Wide Web.
In 1992, Georges Charpak received the Nobel Prize in physics for work carried out at CERN in 1968 (development of the multi-wire proportional chamber).
The November 18, 2010, researchers announce that they have succeeded in trapping antihydrogen atoms for the first time in a magnetic field.
The July 4, 2012, a new particle is identified, whose properties seem compatible with that of the Higgs boson as described by the theory. Additional results of this experiment processed during 2013 confirmed that this new elementary particle is a Higgs boson, whose properties are so far compatible with those described by Standard Model. The Nobel Prize in Physics was awarded in 2013 to theoretical physicists François Englert and Peter Higgs for their theoretical work on this particle, predicting its existence from the 1960s.
Several important achievements in particle physics have been made through experiments at CERN. They include:
1973: The discovery of neutral currents in the Gargamelle bubble chamber;
1983: The discovery of W and Z bosons in the UA1 and UA2 experiments;
1989: The determination of the number of light neutrino families at the Large Electron–Positron Collider (LEP) operating on the Z boson peak;
1995: The first creation of antihydrogen atoms in the PS210 experiment;
1999: The discovery of direct CP violation in the NA48 experiment;
2010: The isolation of 38 atoms of antihydrogen;
2011: Maintaining antihydrogen for over 15 minutes;
2012: A boson with mass around 125 GeV/c2 consistent with the long-sought Higgs boson.
In September 2011, CERN attracted media attention when the OPERA Collaboration reported the detection of possibly faster-than-light neutrinos. Further tests showed that the results were flawed due to an incorrectly connected GPS synchronization cable.
The 1984 Nobel Prize for Physics was awarded to Carlo Rubbia and Simon van der Meer for the developments that resulted in the discoveries of the W and Z bosons. The 1992 Nobel Prize for Physics was awarded to CERN staff researcher Georges Charpak “for his invention and development of particle detectors, in particular the multiwire proportional chamber”. The 2013 Nobel Prize for Physics was awarded to François Englert and Peter Higgs for the theoretical description of the Higgs mechanism in the year after the Higgs boson was found by CERN experiments.
The World Wide Web began as a CERN project named ENQUIRE, initiated by Tim Berners-Lee in 1989 and Robert Cailliau in 1990. Berners-Lee and Cailliau were jointly honoured by the Association for Computing Machinery in 1995 for their contributions to the development of the World Wide Web.
Based on the concept of hypertext, the project was intended to facilitate the sharing of information between researchers. The first website was activated in 1991. On 30 April 1993, CERN announced that the World Wide Web would be free to anyone. A copy of the original first webpage, created by Berners-Lee, is still published on the World Wide Web Consortium’s website as a historical document.
Prior to the Web’s development, CERN had pioneered the introduction of Internet technology, beginning in the early 1980s.
More recently, CERN has become a facility for the development of grid computing, hosting projects including the Enabling Grids for E-sciencE (EGEE) and LHC Computing Grid. It also hosts the CERN Internet Exchange Point (CIXP), one of the two main internet exchange points in Switzerland.
CERN operates a network of six accelerators and a decelerator. Each machine in the chain increases the energy of particle beams before delivering them to experiments or to the next more powerful accelerator. Currently (as of 2019) active machines are:
The LINAC 3 linear accelerator generating low energy particles. It provides heavy ions at 4.2 MeV/u for injection into the Low Energy Ion Ring (LEIR).
The Proton Synchrotron Booster increases the energy of particles generated by the proton linear accelerator before they are transferred to the other accelerators.
The Low Energy Ion Ring (LEIR) accelerates the ions from the ion linear accelerator LINAC 3, before transferring them to the Proton Synchrotron (PS). This accelerator was commissioned in 2005, after having been reconfigured from the previous Low Energy Antiproton Ring (LEAR).
The 28 GeV Proton Synchrotron (PS), built during 1954—1959 and still operating as a feeder to the more powerful SPS.
The Super Proton Synchrotron (SPS), a circular accelerator with a diameter of 2 kilometres built in a tunnel, which started operation in 1976. It was designed to deliver an energy of 300 GeV and was gradually upgraded to 450 GeV. As well as having its own beamlines for fixed-target experiments (currently COMPASS and NA62), it has been operated as a proton–antiproton collider (the SppS collider), and for accelerating high energy electrons and positrons which were injected into the Large Electron–Positron Collider (LEP). Since 2008, it has been used to inject protons and heavy ions into the Large Hadron Collider (LHC).
The On-Line Isotope Mass Separator (ISOLDE), which is used to study unstable nuclei. The radioactive ions are produced by the impact of protons at an energy of 1.0–1.4 GeV from the Proton Synchrotron Booster. It was first commissioned in 1967 and was rebuilt with major upgrades in 1974 and 1992.
The Antiproton Decelerator (AD), which reduces the velocity of antiprotons to about 10% of the speed of light for research of antimatter.
The AWAKE experiment, which is a proof-of-principle plasma wakefield accelerator.
The CERN Linear Electron Accelerator for Research (CLEAR) accelerator research and development facility.
Large Hadron Collider
Many activities at CERN currently involve operating the Large Hadron Collider (LHC) and the experiments for it. The LHC represents a large-scale, worldwide scientific cooperation project.
The LHC tunnel is located 100 metres underground, in the region between the Geneva International Airport and the nearby Jura mountains. The majority of its length is on the French side of the border. It uses the 27 km circumference circular tunnel previously occupied by the Large Electron–Positron Collider (LEP), which was shut down in November 2000. CERN’s existing PS/SPS accelerator complexes are used to pre-accelerate protons and lead ions which are then injected into the LHC.
Eight experiments (CMS, ATLAS, LHCb, MoEDAL, TOTEM, LHCf, FASER and ALICE) are located along the collider; each of them studies particle collisions from a different aspect, and with different technologies. Construction for these experiments required an extraordinary engineering effort. For example, a special crane was rented from Belgium to lower pieces of the CMS detector into its cavern, since each piece weighed nearly 2,000 tons. The first of the approximately 5,000 magnets necessary for construction was lowered down a special shaft at 13:00 GMT on 7 March 2005.
The LHC has begun to generate vast quantities of data, which CERN streams to laboratories around the world for distributed processing (making use of a specialized grid infrastructure, the LHC Computing Grid). During April 2005, a trial successfully streamed 600 MB/s to seven different sites across the world.
The initial particle beams were injected into the LHC August 2008. The first beam was circulated through the entire LHC on 10 September 2008, but the system failed 10 days later because of a faulty magnet connection, and it was stopped for repairs on 19 September 2008.
The LHC resumed operation on 20 November 2009 by successfully circulating two beams, each with an energy of 3.5 teraelectronvolts (TeV). The challenge for the engineers was then to try to line up the two beams so that they smashed into each other. This is like “firing two needles across the Atlantic and getting them to hit each other” according to Steve Myers, director for accelerators and technology.
On 30 March 2010, the LHC successfully collided two proton beams with 3.5 TeV of energy per proton, resulting in a 7 TeV collision energy. However, this was just the start of what was needed for the expected discovery of the Higgs boson. When the 7 TeV experimental period ended, the LHC revved to 8 TeV (4 TeV per proton) starting March 2012, and soon began particle collisions at that energy. In July 2012, CERN scientists announced the discovery of a new sub-atomic particle that was later confirmed to be the Higgs boson. In March 2013, CERN announced that the measurements performed on the newly found particle allowed it to conclude that this is a Higgs boson. In early 2013, the LHC was deactivated for a two-year maintenance period, to strengthen the electrical connections between magnets inside the accelerator and for other upgrades.
On 5 April 2015, after two years of maintenance and consolidation, the LHC restarted for a second run. The first ramp to the record-breaking energy of 6.5 TeV was performed on 10 April 2015. In 2016, the design collision rate was exceeded for the first time. A second two-year period of shutdown begun at the end of 2018.
Accelerators under construction
As of October 2019, the construction is on-going to upgrade the LHC’s luminosity in a project called High Luminosity LHC (HL-LHC). This project should see the LHC accelerator upgraded by 2026 to an order of magnitude higher luminosity.
As part of the HL-LHC upgrade project, also other CERN accelerators and their subsystems are receiving upgrades. Among other work, the LINAC 2 linear accelerator injector was decommissioned, to be replaced by a new injector accelerator, the LINAC 4 in 2020.
The original linear accelerator LINAC 1. Operated 1959–1992.
The LINAC 2 linear accelerator injector. Accelerated protons to 50 MeV for injection into the Proton Synchrotron Booster (PSB). Operated 1978–2018.
The 600 MeV Synchro-Cyclotron (SC) which started operation in 1957 and was shut down in 1991. Was made into a public exhibition in 2012–2013.
The Intersecting Storage Rings (ISR), an early collider built from 1966 to 1971 and operated until 1984.
The Large Electron–Positron Collider (LEP), which operated from 1989 to 2000 and was the largest machine of its kind, housed in a 27 km-long circular tunnel which now houses the Large Hadron Collider.
The LEP Pre-Injector (LPI) accelerator complex, consisting of two accelerators, a linear accelerator called LEP Injector Linac (LIL; itself consisting of two back-to-back linear accelerators called LIL V and LIL W) and a circular accelerator called Electron Positron Accumulator (EPA). The purpose of these accelerators was to inject positron and electron beams into the CERN accelerator complex (more precisely, to the Proton Synchrotron), to be delivered to LEP after many stages of acceleration. Operational 1987-2001; after the shutdown of LEP and the completion of experiments that were directly feed by the LPI, the LPI facility was adapted to be used for the CLIC Test Facility 3 (CTF3).
The Low Energy Antiproton Ring (LEAR), commissioned in 1982, which assembled the first pieces of true antimatter, in 1995, consisting of nine atoms of antihydrogen. It was closed in 1996, and superseded by the Antiproton Decelerator. The LEAR apparatus itself was reconfigured into the Low Energy Ion Ring (LEIR) ion booster.
The Compact Linear Collider Test Facility 3 (CTF3), which studied feasibility for the future normal conducting linear collider project (the CLIC collider). In operation 2001–2016. One of its beamlines has been converted, from 2017 on, into the new CERN Linear Electron Accelerator for Research (CLEAR) facility.
Possible future accelerators
CERN, in collaboration with groups worldwide, is investigating two main concepts for future accelerators: A linear electron-positron collider with a new acceleration concept to increase the energy (CLIC) and a larger version of the LHC, a project currently named Future Circular Collider.
CERN does not operate a single particle accelerator to study the structure of matter, but a whole chain of other machines (sometimes called injectors). The particles which pass through them successively are progressively accelerated, thus giving the particles more and more energy. This complex currently includes several linear and circular accelerators.
The buildings that make up the science complex are numbered without any apparent logic. For example, building 73 is wedged between buildings 238 and 119. The plurality of languages and nationalities (more than 80) within CERN partly inspired Cédric Klapisch in the creation of the film L’Auberge Espagnol.
Chain of particle accelerators around the LHC
The most powerful installation at CERN is the Large Hadron Collider (LHC), which was commissioned onSeptember 10, 2008 (initially planned in november 2007). The LHC is at the very end of the accelerator chain. In the case of an acceleration of protons, they take the following path:
It all starts with a source of protons called a “duoplasmatron”. This machine, the size of a tin can, uses hydrogen to produce protons with an initial energy of 100 k eV (the nucleus of ordinary hydrogen is made up of a single proton). This gas, coming from a bottle, is injected at a controlled rate into the source chamber, where it is ionized to extract the single electron from each atom. The resulting protons are then ejected by an electric field to the next step.
Linac-2 linear proton accelerator, which was commissioned in 1978. Constituting (along with the proton source) the first link in the chain, it is the most heavily used installation at CERN; its availability rate is 98 to 99% and its shutdown is scheduled for around 2017 when it will then be replaced by Linac-4. The Linac-2 accelerates the protons to one third of the speed of light, which results in an energy of 50 MeV by particle.
At the outlet of Linac-2, the protons are injected into the PS-Booster. It is a small synchrotron with a circumference of 157 m and which brings the energy to 1.4 GeV per proton, which corresponds to 91.6% of the speed of light. The protons are then injected into the PS.
The PS or Proton Synchrotron, with a circumference of 628 meters, and equipped with 277 electromagnets including 100 dipoles which are used to bend the particle beam. It is one of the oldest equipment at CERN, as it was commissioned inNovember 1959, but has undergone multiple modifications since. This machine is currently used to accelerate protons but also ions. During his career, it also acted as an accelerator of antiprotons, electrons, and positrons (antielectrons). It increases the energy of protons up to 25 GeV, accelerating them to 99.9% of the speed of light. From this step, the increase in speed is no longer significant because we approach that of light which constitutes, according to the theory of relativity, an insurmountable limit. The increase in the energy of particles is now mainly the result of an increase in their mass.
The Super Proton Synchrotron (SPS), with a circumference of 7 km, equipped with 1,317 electromagnets including 744 dipoles. It propels protons to 450 GeV. It was commissioned in 1976 as an accelerator simple, converted Collider proton-antiproton in 1983, before becoming a new injector chain from 1989 to the LEP, then for his replacement, the LHC. Like the PS, the SPS has accelerated various particles during its career (protons, antiprotons, more or less massive ions, electrons, positrons). Since the start of the LHC, the SPS only works with protonsor ions.
And finally the LHC or Large Hadron Collider (Large Hadron Collider, in French), with a circumference of 26.659 km, using superconductors, and where protons can reach 7 TeV (i.e. an energy level per particle 70 million times larger than that produced by the source duoplasmatron).
As part of the ALICE experiment, the LHC also accelerates lead ions, and for the latter the course is slightly different: produced by an “ECR source” from vaporized then ionized lead, the lead ions undergo their first acceleration in the Linac-3 linear accelerator, then they pass through the LEIR (Low Energy Ion Ring). It is only then that the ions follow the same path as the protons, via the PS, the SPS, and the LHC (the ECR source, Linac-3 and LEIR therefore replace the duoplasmatron, Linac-2 and “Booster” respectively). As they accelerate, these ions are stripped of their electrons in several stages, until all that remains is “naked” atomic nuclei which can reach an energy of 574 TeV each (i.e. 2, 76 TeV per nucleon).
Each CERN installation has one or more experimental halls, available for experiments. This is how the accelerated protons of the Booster, the PS, and the SPS can be directed either to the next accelerator in the chain, or to experimental areas, most often with a fixed target (collision between the beams and a target in order to produce new particles).
Other facilities and experiments at CERN
Although the LHC is currently the largest and most publicized facility, other equipment and research work is present at CERN.
AD, the antiproton decelerator
The antiproton decelerator (en) is a device intended to produce low energy antiprotons. Indeed, during their creation (by impact of protons, coming from the PS, on a metallic target) the antiprotons usually have a speed too high to be able to be exploited during certain experiments, and moreover their trajectories and their energies are disparate. The antiproton decelerator was built to recover, control, and ultimately slow down these particles to about 10% of the speed of light. For this, it uses electromagnets and powerful electric fields. Once “tamed”, these antiprotons can be used in other experiments:
ACE (Antiproton Cell Experiment): an experiment that studies the effectiveness of antiprotons to fight cancer, by injecting a beam of these particles into living cells in vitro. The energy released, by the annihilation between the injected antiprotons and the protons of the atomic nuclei, will then destroy the cells. The goal is to be able to destroy cancerous tumors by projecting antiprotons into them, a method which would be more advantageous than other particle beam therapies because it is less damaging to healthy tissue. The first results are promising, but medical applications are not expected for about ten years.
ALPHA and ATRAP: the aim of these experiments is to study the differences in properties between matter and antimatter. To do this, antihydrogen atoms (composed of an antiproton and a positron) are created and their characteristics are then compared to those of ordinary hydrogen atoms.
ASACUSA: This experiment has the same goal as the previous two, but with a different method. Rather than using antihydrogen atoms, the physicists at ASACUSA will produce much more exotic configurations, such as antiprotonic helium, that is to say helium atoms of which one of the electrons has been replaced. by an antiproton! (reminder: the antiproton has a negative electric charge, like the electron). The advantage of these configurations is that they are easier to produce and have a longer lifespan than antihydrogen.
AEgIS: an experiment whose main goal is to verify whether the effects of gravity on antimatter are identical (or not) to those exerted on matter. Several hypotheses are considered, including the possibility that for antimatter the effect of gravity is reversed.
C ERN A ction S olar T telescope (Telescope for solar axions CERN). An instrument for detecting hypotheticalaxionsfrom thesun.
Axions are particles that are suspected of being part of dark matter, and which would also explain the origin of the small differences observed between matter and antimatter, hence the interest in researching their existence. The principle of operation of CAST is to position a powerful magnetic field in the path of these particles, within correctly oriented vacuum tubes, which should have the effect of transforming them into X-rays.when they cross it. It is this X-ray radiation, more easily detectable than the axions themselves, which is intended to be recorded. If the axions exist, it is likely that they are present in the center of our star, it is for this reason that CAST is a telescope which is pointed in the direction of the Sun thanks to a mobile platform.
Note that this experiment reuses a certain number of already existing components: a prototype of a superconducting dipole magnet which was used for the design of the LHC, a cryogenic cooling device which was used for the DELPHI experiment of the large electron-positron collider (LEP), and an X-ray focusing system from a space program. Combining techniques from astronomy and particle physics, CAST is also the only experiment not to use a beam produced by accelerators, but it nevertheless benefits from the skills acquired by CERN.
C osmics L eaving OR tdoor D roplets (Cosmic rays producing outer droplets)
CLOUD (in) is planned for qu’exerceraient investigate a possible influence the cosmic rays on the formation of clouds. Indeed, these charged particles coming from space would be able to produce new aerosols affecting the thickness of the cloud cover. Satellite measurements allow us to suspect a correlation between the thickness of clouds and the intensity of cosmic rays. However, variations of a few percent in cloud cover can have a definite influence on the climate and the thermal balance of our planet.
CLOUD, still in the preparatory phase with a prototype detector, will consist of a fog chamber and a “reaction chamber” in which the pressure and temperature conditions of any region of the atmosphere can be reconstituted, and which will be subjected to a particle flux produced by the PS simulating cosmic rays. Multiple devices will monitor and analyze the contents of these chambers. This is the first time that a particle accelerator has been used for the study of the atmosphere and climate. This experience could “significantly alter our understanding of clouds and climate”.
CO mmon M uon and P roton A pparatus for S tructure and S pectroscopy
This versatile experiment consists of exploring the structure of hadrons (of which the proton and neutron, constituents of matter of which we are made), and therefore the links between gluons and the quarks that compose them, are part. For this it uses protons accelerated by the SPS. The various objectives are among others:
study the origin of nucleon spin, in particular the role played by gluons. To do this, muons are created (unstable particles, comparable to the electron but more massive) which are projected onto a “polarized target”;
detection of glue balls, hypothetical particles made up only of gluons;
determination of the hierarchy of the different types of hadrons, by creation and then use of a pion beam.
C LIC T is F acility 3. A test site where CERN is already preparing after the LHC, as part of the Compact Linear Collider (CLIC) project.
The goal is to develop a next-generation accelerator, the CLIC, which will make it possible to deepen the discoveries made by the LHC, but for a cost and installation dimensions which would remain relatively reasonable. The goal is to achieve an energy comparable to that obtained at the LHC, but this time with electron / positron collisions (instead of protons / protons collisions), which will open up new perspectives.
The operating principle of the future CLIC is based on a two-beam system, which should make it possible to produce higher acceleration fields than the previous accelerators, ie of the order of 100 to 150 MV / m. The main beam will be accelerated by radiofrequency power, which will be produced by a parallel beam of electrons at lower energy but with high intensity. It is the deceleration of this “drive beam” which will supply the energy used for the acceleration of the main beam. We could compare this principle to that of an electric transformerwhich would produce a high voltage electric current from a lower voltage current, but at the cost of a drop in intensity.
DI meson R elativistic A tomic C omplex (Relativistic atomic complex of di-mesons). This experiment aims to better understand thestrong interactionthat bindsquarkstogether, thus constitutinghadrons. More precisely, it is a question of testing the behavior of this force over “great” distances and at low energy.
For this, DIRAC studies the decay of pionic atoms (or pioniums, that is to say unstable assemblies of positive and negative pions), or of “” atoms (each made up of a pion and of a kaon of opposite charges, also unstable). The lifespan of these exotic assemblies, produced thanks to the proton beam of the PS, is “measured to a level of precision never reached before”.
I sotope S eparator O n L ine OF tector (the on-line isotope separator (in))
Called an “alchemical factory”, ISOLDE is a facility that allows the production and study of a large number of unstable isotopes, some of which have a half-life of only a few milliseconds. These isotopes are produced by impact of protons, coming from the PS injector, on targets of various compositions (from helium to radium). They are separated by mass, then accelerated so that they can then be studied. Many of these experiments use a gamma ray detector called a “ Miniball ”.
ISOLDE thus seeks to explore the structure of the atomic nucleus essentially, but also has other objectives in biology, astrophysics, and other fields of physics (atomics, solid state, fundamental physics).
An ISOLDE team observed an abnormal heat effect (AHE) during an electrolysis experiment with a palladium electrode, known since 1989, and exposes it during a seminar.
“The Neutron Factory”. Using protons from the PS, this equipment is intended to produce neutrons with high intensity fluxes and a wide range of energies. The so-called “neutron time-of-flight” installation allows a precise study of the processes in which these particles are involved. The results obtained are of interest to various research projects where neutron fluxes play a role: nuclear astrophysics (in particular concerning stellar evolution and supernovas); destruction of radioactive waste; or the treatment of tumors by particle beams.
Since its inauguration, CERN has used several accelerators, some of which have been dismantled to accommodate others that are more efficient or better suited to current research. These accelerators are:
Linac1, CERN’s first linear accelerator, commissioned in 1959 and replaced by Linac3 in 1993;
a 600 MeV synchrocyclotron (SC), which was in service from 1957 to 1991. It had an electromagnet consisting of two coils 7.2 meters in diameter and weighing 60 tons each;
CESAR, an “electron storage and accumulation ring”, completed in 1963 and dismantled in 1968. The commissioning of CESAR was difficult, but it made it possible to acquire useful know-how for the development of future CERN colliders;
the Intersecting Storage Rings (ISR), built from 1966 to 1971 and in service until 1984. They were the very first proton collider, which was also the first particle accelerator to use superconducting magnets (from November 1980), then the first to produce collisions between protons and antiprotons (in April 1981);
the Large Electron Positron (LEP), in service from 1989 to 2000 to be replaced by the LHC. LEP was in its day CERN’s largest accelerator, colliding electrons and positrons;
the Low Energy Antiproton Ring (LEAR), commissioned in 1982, which allowed the first atoms of antimatter to be assembled in 1995. It was shut down in 1996 to be transformed into a LEIR (Low Energy Ion Ring) intended to supply the LHC with heavy ions.
C ern N eutrinos to G ran S asso (Neutrinos from CERN to Gran Sasso).
This installation consists of producing a beam of neutrinos which is directed to a laboratory located in Italy and 732 kilometers away. To do this, protons accelerated by the SPS are sent to a graphite target. The resulting collisions produce unstable particles called pions and kaons, which are focused, by a magnetic device, into a kilometer-long vacuum tunnel where they will decay. These decays in turn generated muonsand, above all, neutrinos. A shield and then the rock beyond the end of the tunnel absorb all particles (muons, non-decayed pions and kaons, or protons that have passed through the target) other than neutrinos, which are thus the only ones to continue their route. The assembly is oriented in such a way that the resulting neutrino beam is directed to an Italian laboratory located in the Gran Sasso, where it will be analyzed by instruments built for this purpose.
The aim of all this is to study the phenomenon of oscillation of neutrinos.: Indeed, there are three types (called flavors) of neutrinos, and it is now accepted that these particles “oscillate” between these three flavors, transforming from one to the other. CNGS allows the study of these oscillations because the neutrinos produced are exclusively of muonic flavor, while at the level of the Gran Sasso, and after a journey of 732 km inside the Earth, some will have been transformed into others. flavors, which can be recorded. The first neutrino beams were emitted in the summer of 2006. Given the low interactivity of neutrinos and the scarcity of their oscillations, years of experimentation and data collection will be necessary. InMay 2010was observed the first event corresponding to the oscillation of one of the neutrinos produced by CNGS. This facility was shut down in December 2012 after six years of service. The CERN tunnels used for the CNGS will now be used to host the AWAKE experiment (Advanced WAKefield Experiment) supplied with protons by the SPS, it should start operating at the end of 2016.
Environmental protection at CERN
Environmental monitoring at CERN is carried out on the one hand by the HSE unit (Health & Safety and Environmental protection) and on the other hand by two external bodies: the Federal Office of Public Health (Switzerland) and the ‘ Institute for radiation Protection and nuclear safety (France). The FOPH has launched a CERN zero point monitoring program which aims to obtain a reference point of the radiological situation around CERN before the Large Hadron Collider put into service.