Perin, R 1996 1996 Ducimetière, L Faure, P Jansson, U Riege, H Schlaug, M Schröder, G Vossenberg, Eugène B 1996 1996 CERN, the European Laboratory for Particle Physics, has started construction of the Large Hadron Collider (LHC), a superconducting accelerator that will collide protons at a center of mass energy of 14 TeV from the year 2005 onwards. The kicker magnet pulse generators of the LHC beam extraction system require fast high power switches. One possible type is the pseudospark switch (PSS) which has several advantages for this application. A PSS fulfilling most of the requirements has been developed in the past years. Two outstanding problems, prefiring at high operating voltages and sudden current interruptions (quenching) at low voltage could be solved recently. Prefiring can be avoided for this special application by conditioning the switch at two times the nominal voltage after each power pulse. Quenching can be suppressed by choosing an appropriate electrode geometry and by mixing Krypton to the D2 gas atmosphere. One remaining problem, related to the required large dynamic voltage range (1.7 kV to 30 kV) is under active investigation: steps in forward voltage during conduction, occurring at low operation voltage at irregular time instants and causing a pulse to pulse jitter of the peak current. This paper presents results of electrical measurements concerning prefiring and quenching and explains how these problems have been solved. Furthermore the plans to cure the forward voltage step problem will be discussed. Paul, C Russenschuck, Stephan Preis, K 1996 1996 The program package ROXIE has been developed at CERN for the design and optimization of the coil geometries for the superconducting magnets for the Large Hadron Collider, LHC. It has recently been extended, in a close collaboration with the University of Graz, to the calculation of iron induced effects applying a reduced vector potential formulation. The method allows accurate computation of the multipole errors in the magnets and allows the distinction between the effects resulting from the coil geometry and the yoke geometry. Brunet, J C Jacquemod, A 1996 1996 The Large Hadron Collider (LHC) project will be the next major high energy physics facility at CERN. Superconducting magnets operating at a magnetic field of 8.4 Tesla in a superfluid helium bath at 1.8 K are required to guide the high energy beams of protons on their trajectory. As part of the magnet qualification tests, magnetic measurements are made using a special device where demountable seals are required. The seals must be leak tight to vacuum and must be able to resist for short periods to pressure bursts up to 20 bar during resistive transitions (quench). Two types of seals have been qualified. Maximum leak rates were in the range 6.10-10 to 1.10-9 mbar.l.s-1, in the worst conditions (20 bar, superfluid helium at 1.8 K). Herleb, U Riege, H 1996 1996 The method of space-charge neutralization of heavy ion beams with electron beam pulses generated with electron guns incorporating ferroelectric cathodes has been experimentally investigated. Several experiments are described, the results of which prove that the intensity of selected ion beam parts with defined charge states generated in a laser ion source may be increased by one order of magnitude. For elevated charge states the intensity amplification is more significant than for low charge states. For $Al^(7+)$ ions from an aluminium target a charge enhancement by a factor of 4 has been achieved by electron beam focusing. Herleb, U Riege, H 1996 1996 A technique for ion beam space-charge neutralization with pulsed electron beams is described. The intensity of multiply-charged ions produced with a laser ion source can be enhanced or decreased separately with electron beam trains of MHz repetition rate. These are generated with ferroelectric cathodes, which are pulsed in synchronization with the laser ion source. The pulsed electron beams guide the ion beam in a similar way to the alternating gradient focusing of charged particle beams in circular accelerators such as synchrotrons. This new neutralization technology overcomes the Langmuir Child space-charge limit and may in future allow ion beam currents to be transported with intensities by orders of magnitude higher than those which can be accelerated today in a single vacuum tube. Lebrun, P 1996 1996 CERN is presently operating a large distributed 4.5 K helium cryogenic system (48 kW@4.5 K equivalent) for cooling the superconducting acceleration cavities of the 26.7 km circumference LEP2 lepton collider. This also constitutes the first part of the 1.8 K cryogenic system (about 150 kW@4.5 K equivalent) for the future Large Hadron Collider (LHC), the high-field superconducting magnets of which will operate in superfluid helium. We briefly describe the main features of each system, and review the progress of their development, construction and operation. Lebrun, P Tavian, L Claudet, G 1996 1996 CERN, the European Laboratory for Particle Physics, is working towards the construction of the Large Hadron Collider (LHC), a high-energy, high-luminosity particle accelerator and collider [1] of 26.7 km circumference, due to start producing frontier physics, by bringing into collision intense proton and ion beams with centre-of-mass energies in the TeV-per-constituent range, at the beginning of the next century. The key technology for achieving this ambitious scientific goal at economically acceptable cost is the use of high-field superconducting magnets using Nb-Ti conductor operating in superfluid helium [2]. To maintain the some 25 km of bending and focusing magnets at their operating temperature of 1.9 K, the LHC cryogenic system will have to produce an unprecedented total refrigeration capacity of about 20 kW at 1.8 K, in eight cryogenic plants distributed around the machine circumference [3]. This has requested the undertaking of an industrial development programme, in the form of a collaboration between CERN and CEA, France, for investigating specific machinery, i.e. very-low pressure cryogenic heat exchangers, volumetric and hydrodynamic compressors, as well as practical and efficient thermodynamic cycles. We report on the aims lines of action and present progress of this ongoing programme. Benda, V Sergo, V Vuillierme, B 1996 1996 Testing superconducting magnets for the Large Hadron Collider (LHC) in superfluid helium requires large-capacity refrigeration at 1.8K. At CERN, this is provided by a combination of a cold compressor and a set of warm vacuum pumps capable of handling up to 18g/s at 1 kPa suction pressure. The cold helium vapour, after the cold compressor, is warmed up from about 5K to ambient temperature in a 32 kW electrical heater. The device is designed to operate reliably at flow rates varying from 1 to 18g/s, inlet pressure of 1 kPa to 3 kPa, with pressure drop 100 Pa. Design and construction of the heater, completely realised at CERN, are presented, as well as measured performance. Some technological problems are discussed.