Higgs:The invention and discovery of the 'God Particle' by Higgs- The Invention & Discovery of the God Particle (epub)

Author:Higgs- The Invention & Discovery of the God Particle (epub)
Language: eng
Format: epub
Publisher: OUP Oxford
Published: 2012-08-16T04:00:00+00:00

____________

One possible solution had emerged in the late 1960s. It was possible – in principle – to turn an accelerator into a hadron collider by creating beams of protons and anti-protons that circulate around an accelerator ring in opposite directions. The beams could then be brought into head-on collision. A proton–proton collider required two intersecting rings, with protons in each ring travelling in opposite directions, but proton–anti-proton collisions could be engineered in a single ring. And it would be possible to achieve collision energies equal to twice the highest accelerator energies.

But this was no straightforward matter. Anti-protons are produced by colliding high-energy protons with stationary targets (such as copper). A million such collisions are required to produce a single anti-proton. Worse still, the anti-protons are produced with a broad range of energies, too broad to be accommodated in a storage ring. Only a small fraction of the anti-protons so produced would ‘fit’ in the ring, greatly reducing both the intensity of the anti-proton beam and the beam luminosity, a measure of the number of collisions that the beam can produce.

To make a beam of anti-protons sufficiently luminous for successful proton–anti-proton collider experiments would require that the anti-proton energies be somehow ‘gathered’ and concentrated around the desired beam energy.

Fortunately, Dutch physicist Simon van der Meer had figured out how to do precisely this. Van der Meer had graduated in engineering from the Delft University of Technology in 1952. He had worked for the Philips electronics company in the Netherlands for a few years before joining CERN in 1956. At CERN he became an accelerator theorist, primarily concerned with the practical application of theoretical principles to the design and operation of particle accelerators and colliders.

Van der Meer had performed some speculative experiments using the ISR in 1968 but did not publish an internal report on his findings until four years later. The reason for his tardiness was simple: the physics he was pursuing seemed vaguely mad. In his report he wrote: ‘The idea seemed too far-fetched at the time to justify publication.’4

His 1968 experiments had hinted that it might indeed be possible to concentrate anti-protons with an initial spread of energies to the much narrower energy range needed to fit in a storage ring. The technique involved using ‘pick-up’ electrodes to sense anti-protons with energies that strayed from the desired beam energy and sending a signal to a ‘kicker’ electrode on the other side of the ring to nudge these particles back into line. The signals passed from pick-up to kicker electrodes are like a shepherd’s whistled instructions to a sheep dog. On receiving the instructions, the dog barks the stray sheep back into line, and allows the flock to be neatly escorted into the pen.

Van der Meer called the technique ‘stochastic cooling’. The word stochastic simply means ‘random’, and the cooling refers not to the temperature of the beam but to the random motions and the energy spread of the particles contained within it. By repeating the process many millions of times, the beam would gradually converge on the desired beam energy.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.