The a to Z of Accelerators

present explanation for this behav The long timescale needed to terparts. But superconductivity iour is that superconductivity exists produce acceptable conductors of above 77K provides a powerful in many discrete regions within niobium-tin (10-12 years) following stimulant to solve the technological the sample but only weak coupling its discovery in 1962 inevitably problems of dealing with brittle exists between these regions. This comes to mind in assessing the materials. The next few months weak coupling is strongly dimin potential timeîscales for developing could give us many more surprises ished by an external field. Electro high field magnets with the new in an area where none were sus magnetic and structural character materials. These new oxides, like pected only a few months ago. izations of these compounds are niobium-tin and the other A15 The discovery of Bednorz and proceeding furiously and we may compounds are inherently brittle Muller has given a profound new soon expect to know whether this and this is bound to affect their stimulus to superconductivity and percolative nature of the supercon application in magnets, just as the last discovery has surely not ductivity is inherent in the material large scale construction of niobium- yet been made. or results from the way present tin magnets has lagged behind samples are being prepared. their ductile niobium-titanium coun The A to Z of accelerators With great skill, the organizers physics but this information was 1965. The attendance of over of the 1987 Particle Accelerator surpassed in volume by reports 1100 was another reflection of Conference arranged a vast pro from the many other areas where the wealth of activity in the field. gramme to run through nearly 700 accelerators now play a key role. papers from Session A to Session Synchrotron light sources are The debate on the big machines Z. They took in en route the latest now illuminating the world in al on construction and plans for the most thirty Laboratories. Free elec high energy machines for particle tron lasers are confirming their Since the hot topic appeared in promise for the creation of un Session Z, not many people left US Superconducting Super Collider Central dreamed of fluxes of electromag the Conference early. In the wake Design Group leader Maury Tigner — aiming at the highest possible energies. netic radiation. 'Star wars' ma chines are now openly discussed. Reports on other actual or potential applications in medicine, food pro cessing, fusion, etc., underlined how the seemingly esoteric tech nology developed for the study of particles has continued to ripple into everyday life. (Already many people sit in front of a particle ac celerator for several hours every evening!) The Conference was held in Washington from 16-19 March and was the 12th in the North American series which began in Giorgio Brianti — pushing for a hadron collider in the tunnel now being completed at CERN for the LEP electron-positron collider. ^ CERN Courier, May 1987 7 Leon Lederman — international collaboration on future accelerators. of President Reagan's endorsement 1989. Congressional hearings for of the Superconducting Super Col budget authorization were immi lider and of the CERN Committee nent at the time of the Conference. of Council's promotion of the Large Tigner quoted Abdus Salam on Hadron Collider, there was no hid the importance of aiming at the ing the potential overlap between highest possible energy and re the two projects. It would clearly peated the statement that partici not make sense to build two sim pation from other countries could ilar machines of such size and cost be envisaged with the machine (unless perhaps the lower energy ultimately open to qualified scien machine could be completed much tists from all countries. faster or one machine had signifi While the Conference was in cant capabilities inaccessible to progress, a meeting of the Amer the other). ican Physical Society in New York Maury Tigner, who leads the was in ecstasies about the newly Central Design Group on the SSC, discovered high temperature super gave the first talk, followed by conductors (see page 3). Tigner Giorgio Brianti, deeply involved in brilliantly fielded a question about LEP is not in operation (and the the LHC work at CERN. Accom the possible impact of these new CERN machines are busy with anti- panying both proposals are invita materials on the magnet design protons) and would not necessarily tions to other world regions to join for the SSC. As known at present, interfere with completion of LEP in the construction and exploitation their current densities are a factor to its 100 GeV per beam design of the huge machines. Leon Leder of 1000 down on those needed energy. The estimated earliest man had a more delicate task than for the SSC; mechanical properties, timescale for LHC is 1995. The he could reasonably have antici feasibility of volume production, CERN Committee of Council (see pated when he accepted the title production costs are all unknown. April issue, page 1) has proposed of The status and outlook for in From past experience, moving scientific and technical cooperation ternational collaboration on future from this situation to the demand with non-Member States. accelerators' for the concluding ing environment of storage ring Lederman recalled the history talk. magnets is likely to take a very of the moves towards greater in Tigner outlined the main para long time. ternational collaboration since the meters of the SSC — 20 TeV per Brianti cited the LHC parameters World Laboratory/Very Big Accel beam, luminosity of 1033, six inter — about 8 TeV per beam, luminos erator (VBA) was first discussed action regions, 6.6 T magnets, ity of over 1033, magnet fields up in 1975. Following the formation 85 km circumference, $ 4.4 billion to 10 T in 'two-in-one' magnets, of the International Committee for cost (R and D, machine, detectors, located over the electron-positron Future Accelerators (ICFA) a year computers), 8 Vi year construction ring in the 27 km circumference later, which initially had the VBA time. Preparations are going well LEP tunnel now being completed as a potential mission, at every and, in particular, the dipole bend at CERN. point in time one or other region ing magnets, which are the most The attractions of the LHC stem was, to use Pief Panofsky's costly of the technical compo from its much lower cost because phrase, 'pregnant with a new ma nents, are comfortably exceeding of the existing tunnel and injectors, chine'. What has happened in the design specification in the recent and from the unique physics poten intervening years has followed the prototypes which have been tial of proton-proton, proton-elec 'leapfrog model' rather than full tested. tron, and even ion collisions. The collaboration. ICFA has had to Beginning in April, the site se final touches are now being made content itself with promoting inter lection procedure is scheduled to to the conceptual design and a national collaboration in exploita filter out a small set of favoured cost estimate will be detailed at tion of machines and in developing sites by July 1988. The final the same time. accelerator technology. choice is planned for end 1988 so Construction could proceed dur An alternative route has emerged that digging could begin early ing the six months per year when in recent years and has become 8 CERN Courier, May 1987 Installation work for the LEP electron-positron collider at CERN is well underway. This shows the pit to house the L3 experiment, with the tunnel opening in the background. At the Washington meeting Gunther Plass described LEP progress. (Photo CERN 446.3.87) known as the HERA model since it has been crucial to the building of that electron-proton collider at DESY. It involves the core of the responsibilities and costs remaining with the host country but with very extensive bilateral agreements for machine component construction and financing worked out for other countries. Lederman recognized that the SSC proposal itself, when it first emerged, 'was a blow to hopes of a World Laboratory'. (In fact at that time it caused considerable dismay in ICFA since it was pro moted without prior consultation or consensus amongst the different regions. The latest LHC proposal has been promoted in the same way.) Lederman concluded with his personal thoughts on the present situation. He is concerned about the adequacy of the LHC to cope with the needs of all regions, par ticularly when constrained by LEP X/;:; exploitation in the same tunnel. The SSC is likely to be at least double the cost but for double the energy (the European contention is that the interesting energy region example, the tiny beam spot size Gunther Plass talked about the would be reached at LHC). at the crossing point has been other Z°, and eventually W, facto A strong case can be made for relaxed to 2.8 compared to 1.6 ry-LEP at CERN. The first ele going in either the SSC or LHC microns, the pulse rate is reduced ments of the injection system have direction. Both regions are pro to 120 rather than 180 Hz, initial all reached or exceeded specifica moting their candidate with con energy is likely to be 47 GeV and tion and the next stage will occur viction, just as they have always so on). in July when electrons go into the done in the past. There are some problems in the SPS; the first transfer to LEP will damping rings causing bunch be a year later. LEP operation is lengthening which will require at scheduled for mid-89 and comple The present front-line machines tention to the vacuum chamber tion of the machine to its full and the pulsed magnets.

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