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CERN | Geneva | Switzerland

View Blog | Read Bio

The hidden face of CERN

Most people associate CERN with the Large Hadron Collider (LHC). But lesser known although extremely diversified research activities are also ongoing at CERN.

About a thousand physicists are working on experiments ranging from antimatter studies to cancer therapy, cloud formation and radioisotope production.

Already in 2011, the ALPHA experiment made the headlines when they managed to trap antihydrogen atoms for more than fifteen minutes. Antiparticles and particles are produced in equal amounts in high energy accelerators. But since we live in a world made of matter, it is no small feat to prevent antiparticles from annihilating with particles of matter and vanishing. Usually, a magnetic “bottle” is used as the trap  This is a space confined by strong magnetic fields and operated in a high vacuum to keep antimatter from encountering any matter. First hurdle: one has to combine an antiproton with an antielectron (called “positron”) at low temperature to form antihydrogen atoms that are sluggish enough to be able to trap them (less than 0.5 K or -272.5 0C).

Nevertheless, having improved their antihydrogen production techniques in 2011, the goal of the ALPHA, ASACUSA, and ATRAP experiments is now to see if these antiatoms have the same properties as their counterpart of matter, the same spectroscopy for example. A new experiment AEgIS will come online this year with the long-term goal of measuring the gravitational constant g with antihydrogen to see if it is the same g as matter experiences.

Meanwhile, the CLOUD experiment is attempting to solve a long-standing enigma: how do aerosol particles form in the atmosphere? All cloud droplets form on aerosols — tiny solid or liquid particles suspended in the air – but how these aerosols form or “nucleate” remains a mystery. To find out, a chamber with a carefully controlled temperature is used to introduce traces of various chemical vapours into an initially “pure” atmosphere. Surprise: ammonia and sulphuric acid, the two airborne chemicals thought to be responsible for all aerosol formation, can account for only one tenth to one thousandth of the rate observed in nature. The goal for 2012 is clear: identify the missing elements and pursue studies on the influence of cosmic rays (simulated using a pion beam) on the aerosol formation rate.

Lots of developments are happening in hadron therapy, a cutting-edge cancer therapy technique where protons and other light ions are used instead of X-rays photons as in conventional radiotherapy treatment. The challenge is to destroy cancer cells without affecting the neighbouring healthy tissue. Contrary to X-rays, protons and other ions deposit nearly all their energy at a specific point near the end of their path instead of all along their path. This means one can bring large amounts of energy exactly where needed without causing damage along the way.

Energy deposited by different particles as they penetrate matter such as human tissue. Protons and carbon ions deposit most of their energy at a specific depth, whereas photons used in conventional X-rays tend to leave energy all along their path, damaging healthy tissue.

CERN acted as a catalyst in the formation of the European Network for Research in Light-Ion Hadron Therapy (ENLIGHT) in 2002 , which was established to coordinate European efforts in radiation therapy using light-ion beams. During the 1990s a group at CERN developed designs for a hadron therapy accelerator in the Proton Ion Medical Machine Study(PIMMS). This basic work has been incorporated into several of the subsequent designs. CERN is currently supporting the MedAustron therapy project in Austria and is also planning to exploit its accelerator technology and expertise in developing a second generation design for hadron therapy.

The ACE experiment has also tested the idea of using beams of antiprotons for hadron therapy, with the added advantage of blasting more malignant cells because of the amount of energy released when the antiquarks of the antiproton annihilate with the quarks of protons or neutrons from one of the cancer cells. This work is nearly completed and will be finished this year.

Much is also ongoing at the ISOLDE facility, which uses protons from a small CERN accelerator (the Proton Synchroton Booster) to produce “exotic” nuclei from most chemical elements by adding protons to stable nuclei. The radioisotopes are then used by more than 50 experiments to study nuclear structure, nuclear astrophysics, fundamental symmetries, atomic and condensed-matter physics, and for applications in life sciences. Some scientists pursue research using neutron beams from the n_TOF facility in the hope of transforming long-lived radioactive waste from nuclear power plants into shorter-lived or stable, non-radioactive elements.

Others at the CAST and OSQAR experiments are hot on the tail of “axions”, “paraphotons” and “chameleons”, some of the many hypothetical and rather exotic particles proposed by theorists to explain the nature of dark matter. For the past decade, these experimentalists have been adding new tricks to their experiments every few years to test new hypotheses and axions of heavier masses. More ideas keep these experiments’ “dance-cards” full all the time.

As millions of individuals have heard, CERN also supplies a neutrino beam to several experiments at the Gran Sasso Laboratory in Italy, including OPERA where puzzling results on muon neutrinos apparently travelling faster than the speed of light were reported last year. Two separate experiments at Gran Sasso are now setting up to cross-check this result in the coming months.

Much more is happening but it is impossible to do every one justice in a short overview. These are just a few of the many activities ongoing at CERN besides the LHC programme. All together, they make CERN a place well worth keeping an eye on in 2012, so follow us on Twitter @CERN.

Pauline Gagnon

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