Hey there, Alpha here, and today I’m going
to talk about a recent visit to some facilities
at CERN. Located in the beautiful city of
Geneva, by the Swiss-French border, CERN employs
over 12,000 researchers in an attempt to figure
out what happened in the first trillionth
of a second after the Big Bang. After World
War 2, CERN was formed in Geneva with the
aim of continuing the growth of world-class
science without letting political tensions
between its 23 member states get in the way
of that. And of course, CERN is known for
its Large Hadron Collider. Electrons from
a Hydrogen bottle are first removed by passing
an electric discharge through the atoms, leaving
just the protons behind. Roughly 300 trillion
protons are used in the beam and I was surprised
to learn that Lead tungstate is sometimes
used instead of the protons, resulting in
‘showers’ of new particles when protons
or electrons interact with their heavy nuclei.
The beam is then accelerated 4 times through
vacuum tubes of increasing circumference,
with the use of superconducting electromagnets,
so that when the particles finally reach the
Compact Muon Solenoid, or CMS, they have a
velocity extremely close to the speed of light.
The CMS is used to validate theories and is
kept underground, due to the severe radiation
risks. The workers actually have to use the
lift back up in the case of an evacuation
as climbing up about 100m of stairs would
take too long. This machine checks the radiation
dose, and if it is too high, showers must
be taken to be sterilised. There is even an
automated safety program for the detector,
which connects internationally so that the
facility can be controlled from miles away.
The CMS is about 15m high and 20m long, with
a mass of 14,000 tonnes. This huge mass means
that compressed air must be used to move it,
essentially turning the CMS into a giant hovercraft.
Inside it, there is a tracker which tracks
the trajectories of the collisions, filtering
the noise of other particles by backtracking
the trajectory, as the collision does not
occur in a vacuum. Up to 64 PB of data were
analysed from 2009 to 2013, which is amazing
considering that the data from only 1 out
of every 6 million collisions is kept. Readings
take 2 nanoseconds and collisions occur every
25 nanoseconds. As the data is kept strictly
confidential, the metadata is used for comparisons
with ATLAS. I found out that the researchers
work for universities, and CERN is just the
facility, so the international LHC Computing
Grid is used to analyse data. Using the trajectories
of particles, alongside magnets to check for
particles versus antiparticles, the charges
and velocities of the particles can be found
– charge, velocity and the magnitude of
the magnetic field are all proportional to
the force. These factors, coupled with energy,
allow for the deduction of particles. Many
unique detectors make up the CMS as it was
put together in parts. This allows for the
different detectors to spot a diversity of
particles. Unfortunately, neutrinos are famously
hard to detect and there may be missing energy,
due to the production of neutrinos or other
undetected particles. Both the strong and
electromagnetic forces can be detected, but
not the weak force. I was also told that inside
the chamber, liquid helium is used as it is
the most suitable substance for the optimum
temperature of 1.9 K. This does pose
a risk, especially due to the rapid expansion
of the gas, so special equipment must be worn
when in the chamber. Some particles are able
to escape the chamber, particularly muons,
which have a high penetrating power, so much
so that hundreds of metres of artificially
grown crystals cannot stop the muons. These
crystals are used, however, to stop electrons
instead.
In talking to my tour guide, I discovered
that working in this specific area of physics can be
difficult due to the slow rate of progress.
It can often take decades for a theory to
be validated, for example, with the Higgs
boson, but I believe that this is something
that can easily apply to many different fields
of science in general. Progress takes time.
Just take Geneva for example. So much progress
has come from this small city: the Geneva
conventions for human rights, the formation
of the International Committee of the Red
Cross, the formation of the League of Nations,
building the European HQ of the UN, and the
creation of the largest international science
experiment over the globe. This just goes
to show that when countries work together
in an international effort, great things can
be done, amazing organisations can be created,
and progress can be made. Progress will be
made.
Thanks for watching! See you in the next one.
