•X* Mid-September, two joined sections of twenty cells operated excellently, A Q value of 2.2x109 was achieved (four times higher than is needed) with a magnetic field of 360 gauss. This corresponds to a def/ection field of 2.4 MV/m. proving much more difficult than experiment with a 100 kJ store is concentric rings in the same plane, inltially expected. There will be two now under way. The aims are to learn 2960 m in circumference, built with cryostats (both now under test) each the behaviour of high current, high superconducting magnets capable of with a cavity built up of five sections. voltage Systems in cryogénie environ- 4 T. Eight intersection régions will be The tests on individual sections yield- ments so as to be able to design the incorporated where a luminosity up ed excellent results (see February large Systems which will be needed to 1033 per cm2 per s is anticipated issue 1974) but when two sections in a fusion reactor. with 10 A stored in each ring. are joined together the same perform• Finally, there is basic research into ISABELLE recently had renewed ance is not yet reached. the phenomenon of superconductivity. support from the Subpanel on New It is not clear whether the problem This involves the investigation of new Facilities set up by the High Energ* is due to the additional length or to superconducting materials and of Physics Advisory Panel (HEPAP) an unsatisfactory joint between the sputtered thin films, and the study of which reports to the USA Energy two sections. Réfrigération is by the properties of the known materials. Research and Development Adminis• superfluid hélium which has excellent Topics of the research include the tration. The Subpanel was chaired properties as far as heat conduction détermination of the local flux distri• by F. Low and has re-examined the and spécifie heat are concerned. It bution in hard superconductors, flux recommendations of the Subpanel of does, however, also find leaks much flow experiments, the behaviour of 1974 chaired by V.F. Weisskopf (see more readily and the cooling System superconductors under pressure, their July issue, 1974), in the light of the has to be carefully built to avoid leaks. mechanical properties at cryogénie dramatic developments which have In compensation for thèse problems températures and the effect of radia• occurred in high energy physics during there are other aspects of super• tion (in particular, the effect of neutron the past year. The Low Subpanel conducting r.f. separators which are fluxes such as would be experienced retained the three major recommenda• trivial by comparison with their con- around a fusion reactor). By means tions of the Weisskopf Subpanel — ventional équivalents. For example, of a 'decorating' technique, informa• they give first priority to the construc• the electrical Systems have to cope tion about the static flux distribution tion of the Berkeley/Stanford 15 GeV with only 1 kW of d.c. power com• and its dynamic behaviour is obtained. électron-positron storage ring project, parée! with mégawatts of pulsed The technique involves evaporating PEP, urging an immédiate start; they power. ferromagnetic material, in an inert recommend a start on ISABELLE in It is hoped to have the separators (hélium) atmosphère, which is de- 1976 which is a much more positivp at CERN by the end of 1976 but there posited on superconductor at régions position than the Subpanel felt abL_ remain several problems to overcome where the flux pénétrâtes the surface. to adopt a year ago; they support the before this pioneering project meets FermiLab programme of research and its spécification. development aiming at énergies of The application of superconductivity 1000 GeV and above. in fusion devices, such as a Tokamak, BROOKHAVEN The Low Subpanel urged that is also being studied. The work is ISABELLE Summer Brookhaven double the research and being done in association with the Study development effort applied to the Max Planck Institute for Plasma superconducting magnets and cryo• Physics at Garching and in collabora• From 14-25 July over a hundred high génie Systems for the ISABELLE pro• tion with the other two GESSS energy physicists and accelerator phy- ject. An ISABELLE Division has been Laboratories. Fusion reactors, in addi• sicists gathered at Brookhaven to set up within the Accelerator Depart• tion to the magnetic confinement coils, examine again the project for the ment with H. Hahn as Division Head require large energy storage and construction of the 200 GeV Inter- and J. Spiro as Deputy Head. They transfer Systems with puise cycle secting Storage Accelerator, ISA• will be looking harder at ways of times comparable to those of a syn- BELLE. The proposed machine will cutting costs on the project, again chrotron. Storage and transfer Systems take protons from the existing 33 GeV following a recommendation of the are being developed at Karlsruhe and Alternating Gradient Synchrotron and Low Subpanel. the first small experiments have been accelerate and store them at énergies The ISABELLE Summer Study took carried out on two 15 kJ super• up to 200 GeV for very high energy place in an atmosphère of great conducting storage coils linked to a colliding beam experiments. The de• enthusiasm reflecting the excitement superconducting switch. A second sign, up-dated in June, involves two pervading the whole world of high 272 Brookhaven making full use of the 'T-shirt' to 2. Members of the team of S. Ting, who get their message across — discovered the new particle at Brookhaven at the same time as the Berkeley/Stanford team, 1. During the ISABELLE Summer Study, the project their selected name for the 3.1 GeV Chairman of the Organizing Committee, particle. M. Barton, Chairman of the Accelerator A. Pevsner (right), presented an ISABELLE Department, also sported a J-shirt when shirt to W. Wallenmayer of the ERDA Washington addressing the ISABELLE Summer Study saying office — money from Washington for the "We have had a tradition at Brookhaven of very 200 GeV storage rings would be welcome. good relations with the user community; we provide them with protons and they provide us with T-shirts'. energy physics at the moment to which a machine like ISABELLE would certainly contribute greatly. No major changes to the existing project design emerged from the Summer Study but the spécifications of a number of components could be made sharper as a resuit of the discussions. For example, récent observations at the CERN ISR and PS concerning longitudinal instabilities have consi• dérable impact on the ISABELLE in• jection conditions and vacuum System. It has been shown that the stability criteria normally applied to unbunched beams can be relevant to bunched beams in which an instability can grow quickly before the particle feels the effect of being in a bunch. The instabilities can happen at microwave frequencies. Landau damping, due to the différent révolution frequencies of the individual protons, inhibits thèse instabilities from growing, but in a large circumference machine where the aperture has not increased cor- respondingly, the damping does not act as much. For ISABELLE it seems necessary to inject with the highest beam intensity possible from the AGS, to do some bunch predilution before injection, and to présent the beam with as smooth a vacuum pipe as possible to travel in around the rings. The working group considering the superconducting magnets recom- mended an ail out effort during the coming year to build several full-scale bending magnets and a focusing quadrupole. One such magnet, 4.25 m long, was built in a hurry in May/June in an attempt to have it operational prior to the meeting of the Low Sub• panel. The coils for the magnet were made in only six days. This pace seems to have been a little too fast for the magnet performance is not high. Considérable training was expe- rienced. The first quench occurred at 3 T and peak fields later climbed to 3.59 T. The problems concerned the 273 leads (which can be easily improved), the picture related to variations in a appears on the film as whiter and the slow speed at which a quench small thickness of the object. blacker lines alongside one another. propagated (which can be cured by Scattering radioscopy is in its The use of this phenomenon for replacing some stainless steel inert infancy and we reported last month radiography has been pursued by turns by copper) and a mismatch in the preliminary experiments at CERN. D. West and A.C. Sherwood at the expansion coefficients between Microy It uses nuclear scattering of the pro• Harwell 160 MeV synchro-cyclotron post pièces and the rest of the coil tons and the remarkable abilities of and at the 7 GeV proton synchrotron, (which can be cured by using other drift chambers to trace particle tra- Nimrod, at the Rutherford Laboratory. material). Nevertheless, the field qua- jectories very precisely so that a three The experiments showed that the lity of the magnet was good. dimensional picture of the nuclear edges are picked out almost regard- The magnet is being rebuilt with locations in the object can be extracted less of the thickness of the objectsv the improvements mentioned above. from the computer. The width of the light and dark bands Tests have continued with the latest The third technique is the outcome dépends on the distance to the film, in the 1 m long séries of pulsed super• of some puzzling observations which the proton energy and the density and conducting magnets, ISA IV (see were made when higher energy proton thickness of the object. The magni• January issue) to study the relation- beams became available in the 1950s.