Switzerland is home to one of the most exciting scientific
establishments in the world, and on Friday 16 August 2013, twenty-nine ladies
and one husband, members of ZIWA’s Off the Wall group, made this destination
another voyage of discovery for the Zürich-based group. Travelling by first
class train for the three-hour journey to Geneva, the ladies discussed their
expectations and previous knowledge – more excitement than scientific
expertise. This was soon to change on our arrival by tram at the CERN HQ in
Meyrin outside Geneva.
Scientific background
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| What we were about to discover |
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| CERN's worldwide users |
First we were treated to an illuminating introduction from
experimental physicist Marc Goulette, who gave a PowerPoint presentation of the
history and function of the establishment. CERN, or the
Conseil Europeen pour
la Recherche Nucleaire, was founded in 1954, has currently 20 member states and
comprises a multi-site international laboratory for experiments in particle
physics. The headquarters is located near the French border in Switzerland, and
the tunnel occupied by the
Large Hadron Collider lies almost 100 metres
underground and extends over 140 km. There are over 11,000 scientists and
engineers working at CERN, which is financed and used by 110 countries. Its
budget is CHF1.2 billion per annum, the equivalent of one cup of coffee per
person, according to Marc.
The purpose of the research is to understand the nature of
matter and the origins of the universe. Scientists collaborate in the analysis
of data gathered during the process of particle collision. As well as PhD
students, the centre hosts scientists from universities, hospitals, engineering
and industry who all have a stake in the institution. The first particle
collider, the LEP, was built in 1989 and by 1995 was able to uncover more
understanding of anti-matter. Construction of the current Large Hadron Collider
system began in 1999. The most recent experiment, the PS201, was set up in
2008 when the LHC started operating. In July 2012, the Higgs Boson particle,
postulated 49 years earlier, was detected, and its properties have since then
been examined. This particle is believed to have originated just after the
universe was created with the Big Bang.
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| A major discovery in July 2012 - the Higgs Boson |
The
Large Hadron Collider is the world’s largest particle
accelerator and consists of a 27 kilometre tunnel with a ring of
superconducting magnets which focus the particle beam as it whizzes round the
tunnel. Particle collisions are created in 4 different locations deep under the
ground in Switzerland and France. The collisions cause different particles to
be released, and the surrounding detector tubes enable different types of
particle to be sensed and analysed. Such particles include quarks, leptons,
bosons, gluons, muons and fermions. There are a number of projects taking place
at the moment, but the collider is not in operation today while it is being updated, and the data collected
over the past years is now being analysed.
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| Into the underground realm of the LHC |
Over the border
After this quick introduction to this complex topic, we were
taken by bus over the border into France, to see the Large Hadron Collider. At
the centre at Cessy, we split into three groups to learn about the geography
and physics of the different installations. We first saw a life-size image of a
cross-section of the Compact Muon Solenoid (CMS) which focusses the proton
beams. The huge magnetic tube is located 90 metres below the earth in hard
rock, and operates at a temperature of -269 degrees C, close to absolute zero.
The solenoid consists of different layers which detect different types of
particle by means of magnetic superconductors and leaded silicon crystals. At
the push of a button, the source protons or lead ions start to fly round the
ring in opposite directions. Collisions are induced at four different spots
under the ground over periods of 15 hours, and the detectors run constantly. The
scientists then try to recreate the pattern of interactions in order to
understand the phenomena taking place.
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| The cross-section of the solenoid |
100 metres underground
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| Each section detects different phenomena |
After waiting patiently for our turn, we passed through the
airlock door and took the lift down to the rocky interior. As the LHC was not
in operation, we were able to see more of its cross-section. Engineers used
bicycles to travel along the tunnel during construction, and a mountaineer is
employed to fix faults on the huge surface of the solenoid. But any small
faults inside the collider cannot be fixed. If a small electrical fire should
break out, the charge is directed safely to the earth’s surface, and a quench
system operates in case of a major incident – thankfully very rare.
After this fascinating glimpse into the realm of state-of-the-art
nuclear physics deep in the French and Swiss countryside, we retraced our steps
back to base and returned by tram and train to Zürich. Thanks to Katrin Gygax
and to the CERN scientists and guides for making this unforgettable day
possible.
Julia Newton. 19 August 2013.
