engLivran, JMourou, G AParente, CRiddone, GRybkowski, DVeillet, NA Cryogenic Test Set-Up for the Qualification of Pre-Series Test Cells for the LHC Cryogenic Distribution LineAccelerators and Storage RingsLHC-Project-Report-380CERN-LHC-Project-Report-380Three pre-series Test Cells of the LHC Cryogenic Distribution Line (QRL) [1], manufactured by three European industrial companies, will be tested in the year 2000 to qualify the design chosen and verify the thermal and mechanical performances. A dedicated test stand (170 m x 13 m) has been built for extensive testing and performance assessment of the pre-series units in parallel. They will be fed with saturated liquid helium at 4.2 K supplied by a mobile helium dewar. In addition, LN2 cooled helium will be used for cool-down and thermal shielding. For each of the three pre-series units, a set of end boxes has been designed and manufactured at CERN. This paper presents the layout of the cryogenic system for the pre-series units, the calorimetric methods as well as the results of the thermal calculation of the end box test.2000-07-26http://cds.cern.ch/record/449264http://cds.cern.ch/record/449264oai:cds.cern.ch:449264 engChorowski, MKonopka, GRiddone, GHelium Discharge and Dispersion In the LHC Accelerator Tunnel in Case of Cryogenic FailureAccelerators and Storage RingsLHC-Project-Report-381CERN-LHC-Project-Report-381The Large Hadron Collider (LHC), presently under construction at CERN, will contain about 100 tonnes of helium, mostly located in the underground tunnel and caverns [1]. Potential failure modes of the accelerator, which may be followed by helium discharge to the tunnel, have been identified and the corresponding helium flows calculated. The paper presents the analysis of the helium discharge in the worst case of conditions, as well as the corresponding helium dispersion along the tunnel. The variation of oxygen concentration has been calculated and the oxygen deficiency hazard (ODH) analysed. The preventive means of protection, namely location and sizing of safety valves are also discussed.2000-07-26http://cds.cern.ch/record/449265http://cds.cern.ch/record/449265oai:cds.cern.ch:449265 engBarth, KDauvergne, J PDelruelle, NFerlin, GJuillerat, A CPirotte, OCryogenic Facilities at 1.9 K for the Reception of the Superconducting Wires and Cables of the LHC Dipoles MagnetsAccelerators and Storage RingsLHC-Project-Report-382CERN-LHC-Project-Report-382CERN's LHC project has moved to an implementation phase. The fabrication of 1600 high-field superconducting magnets operating at 1.9 K will require about 6400 km of Nb-Ti cables. A cryogenic test facility has therefore been set up in order, on the one hand, to verify the quality of individual wires and, on the other hand, to control the critical current of the assembled cables. The facility is composed of a helium liquefier, a transfer line, a dewar and pumps. The paper describes the fully automatic operation of this installation and the different test cycles applied to these wires and cables.2000-07-26http://cds.cern.ch/record/449266http://cds.cern.ch/record/449266oai:cds.cern.ch:449266 engBarranco-Luque, MTavian, LGaseous Helium storage and management in the cryogenic system for the LHCAccelerators and Storage RingsLHC-Project-Report-383CERN-LHC-Project-Report-383The Large Hadron Collider (LHC) is presently under construction at CERN. Its main components are superconducting magnets which will operate in superfluid helium requiring cryogenics on a length of about 24 km around the machine ring with a total helium inventory of about 100 tonnes. As no permanent liquid helium storage is foreseen and for reasons of investment costs, only half of the total helium content can be stored in gaseous form in medium pressure vessels. During the LHC operation part of these vessels will be used as helium buffer in the case of multiple magnet quenches. This paper describes the storage, distribution and management of the helium, the layout and the connection to the surface and underground equipment of the cryogenic system.2000-07-26http://cds.cern.ch/record/449267http://cds.cern.ch/record/449267oai:cds.cern.ch:449267 engBrunet, J CChâtelain, AJacquemod, AMonteiro, IAn automatic ultrasonic welding process for interconnecting superconducting wires of the CERN Large Hadron Collider (LHC)Accelerators and Storage RingsLHC-Project-Report-384CERN-LHC-Project-Report-384The Large Hadron Collider (LHC), the next research tool for particle physics at CERN, is due to start operation in 2005. The main components of the LHC are the superconducting twin-aperture magnets, operating at a temperature of 1.9 K. A large number of auxiliary superconducting wires have to be interconnected in series to electrically feed, at 600 A, the main dipole and quadrupole corrector magnets. To interconnect these wires, an ultrasonic welding process has been developed and compared to the former soft-soldering technique. An industrial ultrasonic welding machine has been adapted and automated to satisfy the reliability and reproducibility. A high strength mechanical junction between wires has been obtained over the operating range from 293 K to 1.9 K. Results of mechanical and electrical validation tests are presented.2000-07-26http://cds.cern.ch/record/449268http://cds.cern.ch/record/449268oai:cds.cern.ch:449268 engChorowski, MGrzegory, PParente, CRiddone, GExperimental and Mathematical Analysis of Multilayer Insulation below 80 KAccelerators and Storage RingsLHC-Project-Report-385CERN-LHC-Project-Report-385The Large Hadron Collider [1], presently under construction at CERN, will make an extensive use of multilayer insulation system (MLI). The total surface to be insulated will be of about 80000 m2. A mathematical model has been developed to describe the heat flux through MLI from 80 K to 4.2 K. The total heat flux between the layers is the result of three distinct heat transfer modes: radiation, residual gas conduction and solid conduction. The mathematical model enables prediction of MLI behavior with regard to different MLI parameters, such as gas insulation pressure, number of layers and boundary temperatures. The calculated values have been compared to the experimental measurements carried out at CERN. Theoretical and experimental results revealed to be in good agreement, especially for insulation vacuum between 10-5 Pa and 10-3 Pa.2000-07-26http://cds.cern.ch/record/449269http://cds.cern.ch/record/449269oai:cds.cern.ch:449269 engRoussel, PJäger, BTavian, LA Cryogenic Test Station for Subcooling Helium Heat Exchangers for LHCAccelerators and Storage RingsLHC-Project-Report-386CERN-LHC-Project-Report-386The superconducting magnets of the Large Hadron Collider (LHC) will be cooled at 1.9 K by distributed cooling loops where counter-flow heat exchangers will be integrated. To qualify potential suppliers for the 250-units series production, prototypes of various technologies have been selected by CERN and a test station was set up at CEA-Grenoble. This test station, is constituted of a cryostat allowing an easy access to the heat exchanger to be tested as well as very low pressure pumping facilities.2000-07-26http://cds.cern.ch/record/449270http://cds.cern.ch/record/449270oai:cds.cern.ch:449270 engWagner, USolutions for Liquid Nitrogen Pre-Cooling in Helium Refrigeration CyclesAccelerators and Storage RingsLHC-Project-Report-387CERN-LHC-Project-Report-387Pre-cooling of helium by means of liquid nitrogen is the oldest and one of the most common process features used in helium liquefiers and refrigerators. Its two principle tasks are to allow or increase the rate of pure liquefaction, and to permit the initial cool-down of large masses to about 80 K. Several arrangements for the pre-cooling process are possible depending on the desired application. Each arrangement has its proper advantages and drawbacks. The aim of this paper is to review the possible process solutions for liquid nitrogen pre-cooling and their particularities.2000-06-27http://cds.cern.ch/record/449271http://cds.cern.ch/record/449271oai:cds.cern.ch:449271 engBenda, VVullierme, BSchouten, J AExperience with a Pre-Series Superfluid Helium Test Bench for LHC MagnetsAccelerators and Storage RingsLHC-Project-Report-388CERN-LHC-Project-Report-388The Large Hadron Collider (LHC) under construction at CERN is based on the use of high-field superconducting magnets operating in superfluid helium. For the validation of the machine dipoles and quadrupoles, a magnet test plant is under construction requiring 12 so-called Cryogenic Feeder Units (CFU). Based on experience done at CERN, two pre-series CFUs were designed and built by industry and are currently in use prior to final series delivery. This presentation describes the features of a CFU, its typical characteristics and the experience acquired with the first units.2000-07-26http://cds.cern.ch/record/449272http://cds.cern.ch/record/449272oai:cds.cern.ch:449272 engSchmidt, RSonnemann, FModelling of the Quench Process for the Optimisation of the Design and Protection of Superconducting Busbars for the LHCAccelerators and Storage RingsLHC-Project-Report-389CERN-LHC-Project-Report-389The superconducting busbars powering the LHC magnets are highly stabilised with copper to reduce the probability of a quench starting in a busbar and to avoid excessive temperatures after a quench during current discharge. In order to determine the required copper stabilisation and the parameters of the protection system a finite difference program has been developed. The program numerically approximates the heat balance equation and evaluates the temperature profile after a quench as a function of time and space. The approach emphasises the modelling of heat transfer into helium. The evaluation of the temperature includes the entire quench process, i.e., the time for quench detection and the current decay.2000-07-26http://cds.cern.ch/record/449273http://cds.cern.ch/record/449273oai:cds.cern.ch:449273 engClaudet, SLebrun, PTavian, LTowards Cost-To-Performance Optimisation of Large Superfluid Helium Refrigeration SystemsAccelerators and Storage RingsLHC-Project-Report-391CERN-LHC-Project-Report-391The field range of superconducting devices may be extended by lowering their operating temperature, using superfluid helium refrigeration systems which have to deliver working pressures down to 1.6 kPa. The corresponding pressure ratio can be produced by integral cold compression or using a combination of cold compressors in series together with "warm" compressors at room temperature. The optimisation of such a system depends on the number, arrangement and characteristics of cold and warm machines as well as on the operating scenario and turndown capability. The aim of this paper is to compare relative investment and operating costs of different superfluid helium cryogenic systems, with the aim of optimising their cost-to-performance ratio within the constraints of their operating scenario.2000-06-27http://cds.cern.ch/record/449274http://cds.cern.ch/record/449274oai:cds.cern.ch:449274 engClaudet, SGayet, PJäger, BMillet, FRoussel, PTavian, LWagner, USpecification of Eight 2400 W @ 1.8 K Refrigeration Units for the LHCAccelerators and Storage RingsLHC-Project-Report-392CERN-LHC-Project-Report-392The cooling capacity below 2 K for the superconducting magnets in the Large Hadron Collider (LHC), at CERN, will be provided by eight refrigeration units at 1.8 K, each of them coupled to a 4.5 K refrigerator. Taking into account the cryogenic architecture of the LHC and corresponding process design constraints, a reference solution based on a combination of cold centrifugal and warm volumetric compressors was established in 1997. The process and technical requirements expressed in the specification issued in 1998 and the procurement scenario based on pre-series acceptance prior to final series delivery between 2002 and 2004 are presented in this paper.2000-07-26http://cds.cern.ch/record/449275http://cds.cern.ch/record/449275oai:cds.cern.ch:449275 engBremer, JThe Cryogenic System for the ATLAS Liquid Argon DetectorAccelerators and Storage RingsLHC-Project-Report-393CERN-LHC-Project-Report-393The ATLAS experiment will include three argon detectors of unprecedented size. The total liquid argon fill of the three cryostats is 83 m3. Gas bubble formation which is detrimental for the functioning of the detector is avoided by sub-cooling of the liquid argon volume with saturated liquid nitrogen heat exchangers placed in the cryostats. Furthermore, to prevent degradation of the detector performance, the maximum temperature gradient across the total liquid volume must be kept within 0.6 K. Additional severe constraints are imposed by the request of uninterrupted cryogenic operation during several years and by the safe handling of a large amount of argon in a 100 m deep underground area.2000-06-27http://cds.cern.ch/record/449276http://cds.cern.ch/record/449276oai:cds.cern.ch:449276 engCastoldi, MDolizy, FParma, VittorioSkoczen, BlazejTrilhe, PThe Insulation Vacuum Barrier for the Large Hadron Collider (LHC) Magnet CryostatsAccelerators and Storage RingsLHC-Project-Report-394CERN-LHC-Project-Report-394The sectorisation of the insulation vacuum of the LHC magnet cryostats, housing the superconducting magnets, which operate in a 1.9 K superfluid helium bath, is achieved by means of vacuum barriers. Each vacuum barrier is a leak-tight austenitic stainless steel thin-wall structure, mainly composed of large diameter (between 0.6 m and 0.9 m) bellows and concentric corrugated cylinders. It is mounted in the Short Straight Section (SSS) [1], between the magnet helium enclosure and the vacuum vessel. This paper presents the design of the vacuum barrier, concentrating mostly on its expected thermal performance, to fulfil the tight LHC heat in-leak budgets. Pressure and leak test results, confirming the mechanical design of two prototypes manufactured in industry, and the preparation of one of these vacuum barriers for cryogenic testing in an SSS prototype, are also mentioned.2000-07-26http://cds.cern.ch/record/449277http://cds.cern.ch/record/449277oai:cds.cern.ch:449277 engBager, TBalle, CBertrand, GCasas-Cubillos, JGomes, PParente, CRiddone, GSuraci, AInstrumentation, Field Network And Process Automation for the LHC Cryogenic Line TestsAccelerators and Storage RingsLHC-Project-Report-395CERN-LHC-Project-Report-395This paper describes the cryogenic control system and associated instrumentation of the test facility for 3 pre-series units of the LHC Cryogenic Distribution Line. For each unit, the process automation is based on a Programmable Logic Con-troller implementing more than 30 closed control loops and handling alarms, in-terlocks and overall process management. More than 160 sensors and actuators are distributed over 150 m on a Profibus DP/PA network. Parameterization, cali-bration and diagnosis are remotely available through the bus. Considering the diversity, amount and geographical distribution of the instru-mentation involved, this is a representative approach to the cryogenic control system for CERN's next accelerator.2000-07-26http://cds.cern.ch/record/449278http://cds.cern.ch/record/449278oai:cds.cern.ch:449278 engNeumann, HPerinic, GHigh capacity Helium purifier for 14 g/s at 200 barAccelerators and Storage RingsLHC-Project-Report-390CERN-LHC-Project-Report-3902000-07-26http://cds.cern.ch/record/497407http://cds.cern.ch/record/497407oai:cds.cern.ch:497407