How goes ISABELLE?

Recent aerial view of ISABELLE construction at Brookhaven. The ring tunnel and half the experimental halls are in place. The injection links with the existing Alternating Gradient Synchrotron are also ready to receive .

(Photo Brookhaven) well as are involved in the work. The aim is to achieve colliding beams by 1986. Plans for the Collider Detector Fa­ cility, CDF, for -antiproton physics aim to have a usable detec­ tor ready to observe the first colli­ sions. Assembly should start in the B-0 hall next year. Design and use of the detector have been greatly sim­ plified by the decision to build an overpass for the Main Ring so that only the Energy Saver vacuum tube will pass through the CDF. The ex­ periment now involves some hundred physicists from about fif­ teen research centres including some in Japan and who are con­ tributing greatly to detector compo­ nents. For example, the supercon­ ducting coil is being built in Japan; an excellent design has emerged pro­ viding a 1.5 T field with a thickness of less than one radiation length. Letters of intent for an experiment to use a second colliding beam area (in the D-0 position) have been called There cannot be many people in the around a 'warm bore' vacuum cham­ for by 1 November and proposals are high energy physics community un­ ber and constructed inside a cold required by 1 February next year. aware that the ISABELLE project to laminated iron. The yoke is im The possible hall volume is about build 400 GeV proton storage rings mersed in a cryostat and force- 750 m3 and the detector it accom­ at Brookhaven has been in trouble for cooled by supercritical helium at a modates must be easily removable. several years. The design incorpo­ maximum temperature of 3.8 K. The Two proposals to use the D-0 area rates two rings of 5 T superconduct­ dipoles are 4.75 m long. A major are already under consideration. One ing magnets and, until late last year, contributor to the problems involves a large lead glass array. The the fabrication of these dipoles to the was the initial choice to use braid for other involves the construction of an required quality was proving an in­ the superconducting coils. Since the ring to observe electron- tractable problem. change to cable in 1981, perfor­ proton collisions. This year a long range planning mance has improved. The flat cable After all the frustrations of recent report on the high energy physics has 23 multifilamentary twisted su­ years with the development of programme for the USA concluded perconducting wires of the type de­ pulsed superconducting dipoles, it is that, unless there is additional fund­ veloped at Rutherford and Fermilab. very satisfying to see the world's ing for the programme, it is difficult Another factor in the improved per­ first superconducting synchrotron to see how the ISABELLE project, as formance seems to be the introduc­ coming together. Its operation within at present conceived, can continue. tion of a layer of teflon in addition to the next year will be another demon­ This has frustratingly come at a time the kapton insulation between the stration of Fermilab's innovative when the magnet problems seem to inner and outer coils providing a low work in accelerator design and con­ be convincingly overcome and when friction slip plane. struction. new management is reinjecting en­ After the success of the first full thusiasm and confidence. size revamped magnet in November The dipole design consists of two of last year, it was decided to com­ layers of superconducting coil plete six by the end of March 1982.

318 CERN Courier, October 1982 Yoke of the first 5 foot 'two in one' magnet built to test the idea of incorporating the two ISABELLE rings in one magnet structure. The magnet operated as expected and a full length version is now being built. The aim is to trim back ISABELLE costs in case of funding shortfalls in funding the US high energy physics programme.

(Photo Brookhaven)

helium refrigerator) and r.f. accelera­ tion systems are well advanced. Only the controls system has not yet received much attention. Though the technical aspects of the project are now in very much bet­ ter shape, there is still concern for the future of ISABELLE. This is be­ cause of doubt about the funding lev­ el for high energy physics which is likely to be obtained from the US government during the remaining years foreseen for construction of the machine. An examination of this situation was a major task of the 'Subpanel on long range planning' set up by HEPAP (High Energy Phy­ sics Advisory Panel) and chaired by George Trilling. Its report, presented earlier this year and usually referred to simply as the 'Trilling report', is now taken by the Department of En­ ergy as its bible in determining use of high energy physics money. The Trilling report recognized that the US programme needs a new fa­ This was successfully done and in tion is slower in supercritical helium; cility, providing front-line physics tests in a bath of liquid helium at 4.5 nevertheless, at the time of writing, and supporting a large number of '< they all surpassed 5 T before their all attempts to burn out a magnet users, to be in action by the end of iflrst quench, and exhibited very little because of inadequate propagation this decade. At present ISABELLE is subsequent training. The magnets (so as to find where the limits are) that facility. It would be unique in were also tested at lower tempera­ have failed. allowing high energy hadron experi­ tures under forced cooling con­ The next major aim of the dipole ments with high intensity (luminosi­ ditions and reached fields of 6 T programme is to install and operate a ties of some 1033 per cm2 per s). which put them ahead of all other full fully equipped cell of the magnet lat­ Nevertheless completion of ISA­ size dipoles in terms of peak field tice (six dipoles and two quadru­ BELLE, as at present conceived, will performance. A first quadrupole has ples) in the ISABELLE tunnel by require a further $500 million (in fis­ also been built and operated suc­ March of next year. Meanwhile the cal year 1982 dollars). The report cessfully. magnet assembly and testing facili­ maintains that to provide this mon­ Investigations of field quality were ties are being extended so that they ey, while also sustaining viable pro­ initially carried out on shorter 5 foot will be able to cope with the produc­ grammes at the other USA Labor­ magnets. Progress is good and the 5 tion of a thousand magnets within atories, and allowing completion of foot series is being concluded while five years. Fermilab and SLAC projects, re­ quality studies are moving to the full The civil engineering work for the quires an annual USA high energy size magnets. Previous troublesome project is not far from completion. physics budget rising to $440 million eddy current effects have also gone The ring tunnel and the injection tun­ in 1984 or 1985. If the present level away. Two features remain to be nels are ready, three of the six exper­ of $395 million cannot be increased, mastered — the trim coils to be in­ imental halls are built (inside angle the report regretfully recommends corporated into the dipole and an hall, major facility hall and narrow termination of the ISABELLE pro­ understanding of the mechanisms of angle hall). The cryogenic systems ject. quench propagation. The propaga­ (including the building of the largest To complete a significant new fa-

CERN Courier, October 1982 319 cility by the end of the decade would is more serious and the machine lat­ magnet ISABELLE and would use require construction beginning in tice is more difficult. Nevertheless, beam from the very successful 1985. There is therefore not much the potential saving on the magnet Brookhaven tandem Van de Graaff time to review the various possibili­ system may be as high as 20 per boosted in energy by an intermediate ties. At Brookhaven the aims are first cent and the idea is being pursued. cyclotron. In any of these scenarios a to demonstrate the viability of the Construction of a full length 'two in ring of superconducting magnets magnet system so as to confirm that one' magnet was authorized in July. would find its way into the ISABELLE ISABELLE can be built. At the same The decision as to whether to adopt tunnel. time, ways of cutting magnet cost the approach will be needed by Despite these uncertainties there are being investigated. March of next year. A second mag­ is no doubt that the Brookhaver One of these is what is known as net cost saving idea is to build a qua- team has found fresh enthusiasm the 'two in one' magnet where two drupole and dipole into the same since the success of the new magnet of the present coil configurations sit cryostat, eliminating quadrupoles, as design. They have also been helped side by side in a single double aper­ separate units. This could save over by the fresh stimulus of the appoint­ ture iron yoke. The machine would 10 per cent of the magnet system ment of Nick Samios as Laboratory then have a single ring of double costs. Director. Samios has an ability to magnets rather than two separate To be ready for alternatives to identify the silver linings in all situ­ rings. This would cut the number of ISABELLE, two working groups ations and makes it difficult to re­ yokes to be built by two and also have been set up to look at an elec­ member the existence of the cloud. halve the number of cryostats. A 5 tron-proton option (chaired by Kjell The whole world-wide high energy foot model was rapidly put together Johnsen) and a heavy ion collider physics community is certainly be­ and performed well in line with ex­ option (chaired by Mark Barton). The hind him in hoping that the full unique pectations. There are obvious con­ e-p option is required to allow exten­ abilities of ISABELLE will be real­ about magnetic and mechani­ sion to p-p at a later stage. The heavy ized. cal asymmetries, quench protection ion option is conceived as a missing

Cornell: CESR and beyond

The electron- tor doing gamma spectroscopy in cles in each bunch and possibly CESR, at Cornell is now operating the machine's North area. avoid the vernier filling scheme (see regularly with a luminosity of over It is believed that the luminosity April 1976 issue, page 129) present­ 1031 per cm2 per s (400 inverse na- can be pushed higher by a factor of ly necessary to build up positron nobarns) and, thanks to the money two or three. Machine physics exper­ bunch intensity. There are also ideas saved by operating the magnet of the iments have reduced the mini-beta on having more than one bunch per CLEO detector with a superconduct­ from 3 cm to 2 cm with further beam using electrostatic separa­ ing coil, the number of hours avail­ increase in luminosity but the CLEO tors. able for physics is not restricted. The magnet was not in operation and the The CLEO detector will probably research remains concentrated existing magnet compensation run in its present configuration for around the upsilon resonances scheme cannot cope. There are another year after which the inner (operating the storage ring at just schemes for going to micro-beta by detector is likely to be modified to over 5 GeV per beam). After skim­ installing new quadrupoles at the in­ give better particle identification, for ming the cream in this energy region, teraction region, though these would example by installing a time projec­ where CESR had unique access with probably limit peak energy to 6 GeV. tion chamber or some other energy good luminosity, extracting further A new injector for the Linac, using loss measurement system. The physics is more difficult but there the triode gun developed at SLAC, CUSB detector may also replace its remain several years of good work in will soon be in operation and should sodium iodide modules by the better front of CLEO and the CUSB detec­ make it possible to put more parti­ BGO material to improve resolution.

320 CERN Courier, October 1982