The hidden face of CERN
Most people associate CERN with
Hadron Collider (LHC).
But lesser known although extremely diversified research
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
antihydrogenatoms 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
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
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
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.
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