Around the Laboratories

Curt Ekstrom at the frozen hydrogen pellet target system at Uppsala's CELSIUS ring.

should significantly reduce overall beam at a rate of about 7 thousand dead-time. pellets per second travelling at 60 HERA's 96 ns bunch crossing time metres per second. is only a factor of four away from that The pellets are formed by breaking planned for CERN's LHC proton up a liquid hydrogen jet into droplets collider. The level-1 pipelined trigger at the temperature and pressure has some 2.2 microseconds for its where solid, liquid, and vapour decision, and was previously fed coexist in equilibrium and injecting directly into an on-line software these droplets tnto a vacuum. trigger. The central trigger system Mesons are produced when the 1360 has been supplemented with an MeV CELSIUS proton beam collides intermediate level-2 trigger which with the frozen pellets. presently has two parts, one The new solenoid provides the exploiting preselected topological magnetic field for momentum aspects of the events, and the other measurements of the emerging consisting of several parallel neural charged particles. It is made in a networks, each optimized for a split coil configuration with 40 mm specific class of reactions. separation between the two windings The upgraded detector will be in a allowing the stream of frozen good position to exploit the improved hydrogen pellets to pass. Each and extended possibilities The WASA detector is being as­ winding consists of four layers of provided by HERA. sembled at the The Svedberg Labo­ superconducting wire wound on the ratory's CELSIUS (Cooling with inside of an aluminium bobbin. The From Graham Thompson, Queen ELectrons and Storing of Ions from total coil thickness is 9 mm, or 0.18 Mary Westfield College, London the Uppsala Synchrocyclotron) radiation lengths, with a length and storage ring. About 70 researchers diameter about 50 cm and cold mass from Germany, Japan, Poland, of 20 kg. The central magnetic flux Russia and Sweden are involved. density is 1.3 Tesla at a current of The magnets of the CELSIUS ring have an illustrious history, starting life UPPSALA in the classic muon anomalous magnetic moment experiment at Pelting pellets CERN in the 1970s before being used in pioneering cooling studies collaboration between Sweden's and finally being shipped to Uppsala A Uppsala University and the in 1983. Japanese KEK laboratory came to WASA will use a novel target fruition in August when a thin walled system developed at Uppsala with superconducting solenoid magnet support from the Wallenberg was delivered to Uppsala's The Foundation. The new target Svedberg Laboratory. achieves high luminosity by replacing The solenoid is a vital part of the a traditional gas jet with a stream of Wide Angle Shower Apparatus, solid pellets - 0.03 mm-diameter WASA, which will make precision micro-spheres of frozen hydrogen, measurements of unstable mesons injected vertically into the proton (neutral pions and etas). It was developed with support from the Japanese Ministry of Education, The new superconducting solenoid for the The Monbusho, and the Nippon Kokan Svedberg Laboratory's WASA detector shortly Company. after its arrival in Uppsala in August.

20 CERN Courier, October 1996 U COMJNq TO WORk ON AN EXpERilVIENT AT CERN

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CERN Courier, October 1996 21 People and things

875 A. The interaction between braic symbols has been a privileged ICTP medals protons and pellets was tested for the tool for a full generation of physicists". first time in April. Further tests are Instituted in 1985, the Dirac Medals under way to optimize the system for The prestigious Dirac Prize of the are awarded annually for contri­ WASA experiments, scheduled to International Centre for Theoretical butions to and start in the autumn of 1998. Physics (ICTP, Trieste, ) is mathematics, the announcement awarded this year to Tullio Regge traditionally being made on P.A.M. (Politecnico di Torino) and Martin us Dime's birthday - 8 August. The Dirac Veltman (University of Michigan). Medals are not awarded to Nobel Prize Tullio Regge is honoured "for or Wolf Foundation Prize winners. crucial contributions in theoretical and mathematical physics starting with his seminal investigation of the Adolf Minten retires asymptotic behaviour of potential scattering processes through the This summer marked the formal analytic continuation of the angular retirement from CERN of Adolf momentum to the complex plane. Minten. A member of Wolfgang This technique has found many Paul's low energy but highly prolific applications in the study of differen­ group at Bonn in the 1950s, he joined tial equations while in the physics of CERN in 1962. After a sabbatical at Books received the Strong Interactions, the so-called SLAC during the momentous years Regge trajectories have helped in the of electron scattering experiments in classification of particles and 1966-67 he returned to CERN, where Thermal Field Theory, by Michel Le resonances by grouping together he was a pioneer of large electronic Bellac, Cambridge University Press, entities with different spin. The so- detectors, becoming leader, with ISBN 0 521 46040 9 (hbk) £45 called Regge behaviour was, and still Georges Charpak, of the Split Field is, an important ingredient in the Magnet group at the Intersecting This treatise in the series of construction of String theories. In Storage Rings. In 1976 he became Cambridge Monographs on addition, Regge is also known for the dynamic and popular leader of Mathematical Physics covers thermal having introduced the first the newly formed Experimental effects in relativistic thermal field discretisation of space-time with a Physics Facilities (EF) Division, theory, looking into the implications simple Einstein dynamics (the so- remaining until 1984. After a second of quantum chromodynamics for called ) and for its stay at SLAC he joined the Aleph collisions of high energy nuclear formulation of supergravity theories collaboration at LEP in 1987. beams, and for astrophysics and in the geometric language of differen­ cosmology. tial forms". Martinus Veltman is honoured "for Ron Newport retires his pioneering investigations on the Doing Physics - How Physicists Take renormalizability of gauge theories Recently retired is Ron Newport, Hold of the World, by Martin H. and consequently, his analysis of the Head of the UK Daresbury Krieger, Indiana University Press, sensitivity of radiative corrections to Laboratory. Graduating from ISBN 0 253 33123 4 (hbk) 0 253 both the mass differences in fermion Liverpool in 1955, he began a long 20701 0 (pbk) doublets and the Higgs particle career in bubble chamber work at mass. These calculations provided CERN, the UK Rutherford Laboratory A useful explanation of the way the basic prediction in the search for and at Berkeley. In the preparations physicists do physics and try to make the top quark mass. Towards this for the experimental programme at sense of the world. With key physics goal, Veltman was one of the first to CERN's SPS proton synchrotron, he arguments not always as transparent use the computer in Feynman dia­ led the design of the rapid cycling as they could be, such a primer gram calculations. His software bubble chamber at the heart of the provides a useful bridge. package for manipulations of alge­ big European Hybrid Spectrometer.

22 CERN Courier, October 1996