The SC prepares for ISOLDE
The 600 MeV synchrocyclotron began a long shutdown on 8 May, which will extend to mid-July. During this time major modifications will be carried out as part of a programme to improve the capacity of the machine and its associated facilities. One of the main items of work planned for the shutdown is the construction of a new underground tunnel to take the external proton beam line to the ISOLDE (lsotope Separator On-line Development) project. This tunnel has to be constructed underground to keep external radiation levels down. It also frees the existing proton room for experiments involving less intense beams.
• Compiled from CERN News p90.
News from abroad
Six sites have emerged from the second stage of the selection process for the American-proposed 200 GeV accelerator. They are: Ann Arbor, Michigan; Brookhaven; Denver, Colorado; Sierra foothills, California; Madison, Wisconsin; and Weston, Chicago. A site at South Barrington, a suburb of Chicago, was also listed as an alternative to the Weston site, but was withdrawn after local pressure. One of the contentions against having the accelerator at South Barrington was that the influx of scientists would "disturb the moral fiber of the community"! Four commissioners of the US Atomic Energy Commission will make the final decision which is expected within a few months.
Villigen
The Swiss Parliament has approved the construction of a 500 MeV isochronous cyclotron at Villigen. The site of the new accelerator Laboratory is across the River Aare from the Federal Institute of Reactor Research at Würenlingen, north-west of Zürich. The project has been under consideration since 1961. It involves a two-stage acceleration process – a 70 MeV cyclotron injecting into the 500 MeV machine, which uses eight spiral ridge magnets and four accelerating cavities. External proton beams of 50 to 100 _mu_A will be available. The total cost of the accelerator is estimated at about 90 million Swiss francs.
Research will cover nucleon–nucleon interactions with emphasis on the use of polarized beams; meson studies with _pi_ and _mu_ meson beams; nuclear-structure research; radiation-damage studies, and also research into the biological use of meson beams.
Brookhaven
A large-scale experiment, planned by scientists from the Brookhaven Laboratory, to investigate the solar neutrino flux, is expected to be in operation very soon. The experiment uses as its detector a tank containing 3.8 _times_ 105 litres of perchloroethylene in which neutrino interactions produce the radioisotope argon-37 from chlorine-37. It is located in a mine in South Dakota 1470 m deep. About five solar-neutrino events per day are expected to be recorded in the detector.
• Compiled from News from Abroad pp93–94.
Compiler's Note
The 1960s were golden years for particle physics, with new machines, ground-breaking experiments and giant leaps in quantum theory all setting the scene for the emergence of the Standard Model of particle physics in the early 1970s.
Ever since the first experiments in October 1967, ISOLDE has played a pioneering role in exploring nuclear structure in terms of masses and β-decay. ISOLDE's observations of nuclear beta-decay, mediated by the weak interaction, form part of on-going tests of the Standard Model, while studies of neutron-saturated nuclei are contributing to a full understanding of rapid neutron capture (the r-process) in core-collapse supernovae, which creates approximately half of the nuclei in the universe that are heavier than iron.
In the US, Weston was chosen as the site for the 200 GeV accelerator and became home to Fermilab, which now runs the Tevatron, the world's highest-energy machine until the LHC comes on air. The lab has several famous firsts to its credit: the bottom quark in 1977, the top quark in 1995, and direct observation of the tau neutrino in 2000. However, "moral fiber" perturbation theory has not been proven!
The Villigen cyclotron, at what is now the Paul Scherrer Institute, had its first extracted proton beam in January 1974. Today PSI boasts a widely diverse research programme, ranging from health to energy, with studies in radiation medicine, reactor physics, nuclear-waste management and condensed matter, to mention but a few.
The nascent Brookhaven experiment went on to give us the "solar neutrino problem" when, during 30 years of operation, it revealed the famous short-fall in the number of electron-neutrinos reaching Earth and inspired a series of follow-on experiments. Finally, in 2002, the Sudbury Neutrino Observatory in Canada provided direct evidence that 2/3 of the Sun's neutrinos "oscillate" to another type before reaching Earth (CERN Courier May 2007 p24). While this accounted for the disappearance of electron-neutrinos from the solar-neutrino flux, such oscillations can happen only if neutrinos have mass, however small. In this way the solar-neutrino experiments provided important evidence for massive neutrinos and some of the first physics beyond the realm of the Standard Model.