Thu 16th Mar
St David’s Day Lecture / Darlith Dydd Gŵyl Dewi
The Large Hadron Collider: a marvel of technology / Y Gwrthdarydd Hadron Mawr: rhyfeddod technolegol
Prof/Yr Athro Lyn Evans (CERN)
Lyn Evans on the Large Hadron Collider
On 16 March Prof. Lyn Evans, former project director of the Large Hadron Collider (LHC) in CERN gave the 2017 St David’s Day Lecture to a large audience in Swansea University.
Lyn began by giving us a crash course in the very smallest things in our universe, elementary particles, and the largest – the Big Bang at the birth of the universe 13.8bn years ago, and what followed. The work of the LHR unites the two, since it aims to recreate the moments immediately after the Big Bang and to observe the particles at play during those moments.
Some elementary particles, like quarks, leptons and photons, are present and observable today, as the building blocks of more complex entities, like protons and neutrons. Each has a characteristic mass, charge and spin. Others, though, like bosons, charm and muons, are no longer with us, but are known to have existed in the universe’s earliest phase. It is these particles that have been the LHC’s main quarry. Some of them have been shy creatures, hard to track down. One, the Higgs boson, was finally cornered in a well-publicised discovery in 2012. Other mysteries the LHC has investigated include anti-matter and its asymmetry (each elementary particle has a twin with opposite properties, the twins annihilating each other when they meet, but with a release of photons), cosmic microwave background (CMB), gravity, and dark matter/dark energy. The latter two must exist, to explain the fact that the expansion of the universe is gathering speed rather than slowing down. Between them dark matter and dark energy are estimated to comprise as much of 96% of all matter. But almost nothing is yet known about either of them.
It’s hard for the lay person to comprehend the scale and ambition of the LHC, the world’s largest particle collider and largest single machine. The ring of the Collider, lying under the French/Swiss border near Geneva, is 23k in diameter. 7,000km of cables were needed to create the superconducting magnetic coils that surround the ring. Protons are speeded along two parallel separate circuits, in opposite directions, until they collide. The different particles emitted by the crash are recorded by a series of huge detectors. The CMS and Atlas detectors each have over 3,000 scientists worldwide working on their results. Initial planning for the LHC began in 1983 and the Higgs boson was discovered 29 years later – an indication of the long timescales of the project. Lyn Evans has been a key figure throughout.
CERN was established in 1954 as part of post-WW2 reconstruction to advance nuclear research cooperatively across Europe and to achieve results that would be impossible by countries working individually. The LHC is its largest project, and initial planning is already under way for its successor. Swansea University has played its part in supplying scientists and ideas for to CERN: Lyn mentioned the talented Eifionydd Jones, who died in 1990. CERN has organised training sessions for teachers in Swansea as a means of exciting school children and interesting them in careers in physics.