Coull, L Denz, R Hagedorn, Dietrich High Current Diffusion Type Diodes at Cryogenic Temperatures for the LHC Superconducting Magnet Protection Adv. Cryog. Eng., A 371-378 43 High-current by-pass diodes are required for the protection of the superconducting magnets for the Large Hadron Collider LHC at CERN . These diodes are at liquid helium tem-perature and will be exposed to irradiation. With the re-location of the by-pass diodes for the main dipoles underneath the iron yoke and of those for the quadrupoles at the bottom of the cryostat the new estimations for the irradiation dose amounts to about 30 Gy and a neutron fluence of about 1.5 x 1011 n/cm2 for the dipole di-odes and about 100 Gy and5 x 1011 n/cm2 for the quadrupole diodes during 10 years. These relatively low doses may allow the use of diffusion type diodes in-stead of epitaxial diodes. The electrical characteristics of several diodes were measured at temperatures in the range between 1.8K and 300K. Diffu-sion type diodes from three manufacturers were submitted to high current endurance tests in liquid helium. Electrical characteristics and temperatures were measured versus time and showed acceptable results. First irradiation tests show that modified diffusion diodes can be used at least for the dipole by-pass. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-131; http://cds.cern.ch/record/333076/files/lhc-project-report-131.pdf; http://cds.cern.ch/record/333076/files/lhc-project-report-131.ps.gz;

Imported from Invenio. Millet, F Roussel, P Tavian, L Wagner, U A Possible 1.8 K Refrigeration Cycle for the Large Hadron Collider Adv. Cryog. Eng., A 387-393 43 The Large Hadron Collider (LHC) under construction at the European Laboratory for Particle Physics, CERN, will make use of superconducting magnets operating below 2.0 K. This requires, for each of the eight future cryogenic installations, an isothermal cooling capacity of up to 2.4 kW obtained by vaporisation of helium II at 1.6 kPa and 1.8 K. The process design for this cooling duty has to satisfy several demands. It has to be adapted to four already existing as well as to four new refrigerators. It must cover a dynamic range of one to three, and it must to allow continuous pump-down from 4.5 K to 1.8 K. A possible solution, as presented in this paper, includes a combination of cold centrifugal and warm volumetric compressors. It is characterised by a low thermal load on the refrigerator, and a large range of adaptability to different operation modes. The expected power factor for 1.8 K cooling is given, and the proposed control strategy is explained. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-140; http://cds.cern.ch/record/336204/files/lhc-project-report-140.pdf; http://cds.cern.ch/record/336204/files/lhc-project-report-140.ps.gz;

Imported from Invenio. Brunet, J C Parma, Vittorio Peón-Hernández, G Poncet, Alain Rohmig, P Skoczen, Blazej Williams, L R Design of the second series 15 m LHC prototype dipole magnet cryostats Adv. Cryog. Eng., A 435-441 43 A first series of six LHC 10 m long prototype dipole magnets and cryostats have been manufactured in European Industry and the assembled cryo-magnets tested singly and connected in series in a test string at CERN between March 1994 and December 1996. During the same period, an evolution in the requirements for LHC cryogenics distribution has lead the project management to adopt a separate cryo-distribution line running parallel to the LHC machine1. The former standard LHC half-cell, made up of a short straight section unit and four 10 m dipoles, has been discarded and replaced with one composed of a short straight section unit and three 15 m dipoles. The new 15 m LHC dipole magnet cryostats are described. These units house the dipole magnet cold mass standing on three low heat in-leak support columns, and enclosed within an actively cooled radiation screen operating at 4.5-20 K and an actively cooled thermal shield operating at 50-75 K. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-133; http://cds.cern.ch/record/333078/files/lhc-project-report-133.pdf; http://cds.cern.ch/record/333078/files/lhc-project-report-133.ps.gz;

Imported from Invenio. Chorowski, M Erdt, W K Lebrun, P Riddone, G Serio, L Tavian, L Wagner, U Van Weelderen, R A Simplified Cryogenic Distribution Scheme for the Large Hadron Collider Adv. Cryog. Eng., A 395-402 43 The Large Hadron Collider (LHC), currently under construction at CERN, will make use of superconducting magnets operating in superfluid helium below 2 K. The reference cryogenic distribution scheme was based, in each 3.3 km sector served by a cryogenic plant, on a separate cryogenic distribution line which feeds elementary cooling loops corresponding to the length of a half-cell (53 m). In order to decrease the number of active components, cryogenic modules and jumper connections between distribution line and magnet strings a simplified cryogenic scheme is now implemented, based on cooling loops corresponding to the length of a full-cell (107 m) and compatible with the LHC requirements. Performance and redundancy limitations are discussed with respect to the previous scheme and balanced against potential cost savings. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-143; http://cds.cern.ch/record/336314/files/lhc-project-report-143.pdf; http://cds.cern.ch/record/336314/files/lhc-project-report-143.ps.gz;

Imported from Invenio. Lebrun, P Serio, L Tavian, L Van Weelderen, R Cooling Strings of Superconducting Devices below 2 K: the Helium II Bayonet Heat Exchanger Adv. Cryog. Eng., A 419-426 43 High-energy particle accelerators and colliders contain long strings of superconducting devices - acceleration RF cavities and magnets - operating at high field, which may require cooling in helium II below 2 K. In order to maintain adequate operating conditions, the applied or generated heat loads must be extracted and transported with minimum temperature difference. Conventional cooling schemes based on conductive or convective heat transport in pressurized helium II very soon reach their intrinsic limits of thermal impedance over extended lengths. We present the concept of helium II bayonet heat exchanger, which has been developed at CERN for the magnet cooling scheme of the Large Hadron Collider (LHC), and describe its specific advantages as a slim, quasi-isothermal heat sink. Experimental results obtained on several test set-ups, and a prototype magnet string have permitted to validate its performance and sizing rules, for transporting linear heat loads in the W.m-1 range over distances of several tens of meters. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-144; http://cds.cern.ch/record/336315/files/lhc-project-report-144.pdf; http://cds.cern.ch/record/336315/files/lhc-project-report-144.ps.gz;

Imported from Invenio. Chorowski, M Hilbert, B Serio, L Tavian, L Wagner, U Van Weelderen, R Helium Recovery in the LHC Cryogenic System following Magnet Resistive Transitions Adv. Cryog. Eng., A 467-474 43 A resistive transition (quench) of the Large Hadron Collider magnets provokes the expulsion of helium from the magnet cryostats to the helium recovery system. A high-volume, vacuum-insulated recovery line connected to several uninsulated medium-pressure gas storage tanks, forms the main constituents of the system. Besides a dedicated hardware configuration, helium recovery also implies specific procedures that should follow a quench, in order to conserve the discharged helium and possibly make use of its refrigeration capability. The amount of energy transferred after a quench from the magnets to the helium leaving the cold mass has been estimated on the basis of experimental data. Based on these data, the helium thermodynamic state in the recovery system is calculated using a lumped parameter approach. The LHC magnet quenches are classified ina parametric way from their cryogenic consequences and procedures that should follow the quench are proposed. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-145; http://cds.cern.ch/record/336316/files/lhc-project-report-145.pdf; http://cds.cern.ch/record/336316/files/lhc-project-report-145.ps.gz;

Imported from Invenio. Rousset, B Gauthier, A Grimaud, L Van Weelderen, R Latest Developments on HeII Co-Current Two-Phase Flow Studies Adv. Cryog. Eng., B 1441-1448 43 Large scale experiments were performed at CEA Grenoble with the support of CERN to simulate and understand the HeII cooling circuit of the LHC. This paper describes the latest results obtained in HeII co-current two-phase flow configuration. First we summarize thermal and hydraulic behaviour of flows obtained in a 40 mm I.D., 86 m long tube inclined at 1.4% which resembles closely the LHC heat exchanger tube. For low vapour velocities, the flow pattern is found to be stratified. A model based on this observation has been developed which fits very well the measured pressure losses. However the wetted surface predicted by the model underestimates the measured one, notably for high vapour velocities. In that case, liquid droplets entrainment takes place. Droplets landing on the tube wall increase the wetted surface. Thus we infer that for higher vapour velocities, the stratified two-phase flow model should not be applied anymore. In order to validate the range of availability of the model, and begin to draw a flow pattern map, a 20 mm I.D. horizontal test sector was built and experiments were performed. First results are presented here, including the observation of the stratified-annular flow transition. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-150; http://cds.cern.ch/record/339987/files/lhc-project-report-150.pdf; http://cds.cern.ch/record/339987/files/lhc-project-report-150.ps.gz;

Imported from Invenio. Verweij, A P The Consequence of Self-field and Non-uniform Current Distribution on Short Sample Tests of Superconducting Cables Electrical measurements on samples of superconducting cables are usually performed in order to determine the critical current $I_c$ and the n-value, assuming that the voltage U at the transition from the superconducting to the normal state follows the power law, U\sim($I/I_c$)$^n$. An accurate measurement of $I_c$ and n demands, first of all, good control of temperature and field, and precise measurement of current and voltage. The critical current and n-value of a cable are influenced by the self-field of the cable, an effect that has to be known in order to compare the electrical characteristics of the cable with those of the strands from which it is made. The effect of the self-field is dealt with taking into account the orientation and magnitude of the applied field and the n-value of the strands. An important source of inaccuracy is related to the distribution of the currents among the strands. Non-uniform distributions, mainly caused by non-equal resistances of the connections between the strands of the cable and the current leads, can easily result in a misinterpretation of the measured critical current and n-value by 5% and 50% respectively. In this paper this effect is explained in detail, taking also into account the influence of the current ramp-rate (during a voltage-current measurement), the sample length, the contact resistance between the strands and the placement of the voltage taps. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-151; http://cds.cern.ch/record/340485/files/lhc-project-report-151.pdf; http://cds.cern.ch/record/340485/files/lhc-project-report-151.ps.gz;

Imported from Invenio. Verweij, A P Review on Boundary-Induced Coupling Currents Boundary-Induced Coupling Currents (BICCs) are generated in multistrand superconducting cables during a field sweep if a) the field sweep and/or b) the electrical contacts between the strands of the cable vary along the cable. Typical parts in a coil which cause large BICCs are the connections between two cables in or outside a coil and the coil ends of racetrack magnets. In the first part of the paper several approaches for describing and calculating BICCs are reviewed. Attention is paid on the steady-state as well as the time dependent solutions. In the second part of the paper the consequences of BICCs on the behaviour of magnets are discussed. These are additional field variations along the magnet length, additional coupling losses and a non-uniform distribution of coupling losses and current among the strands, resulting in a reduced stability. Several effects are illustrated by means of measurements on model dipole magnets. It is shown how the additive effect of all the BICCs in a coil is rather unpredictable so that similar coils can have rather different BICC related behaviour. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-152; http://cds.cern.ch/record/340486/files/lhc-project-report-152.pdf; http://cds.cern.ch/record/340486/files/lhc-project-report-152.ps.gz;

Imported from Invenio. Junquera, T Amand, J F Thermeau, J P Casas-Cubillos, J Neutron Irradiation Tests of Calibrated Cryogenic Sensors at Low Temperatures Adv. Cryog. Eng., A 765-772 43 This paper presents the advancement of a program being carried out in view of selecting the cryogenic temperature sensors to be used in the LHC accelerator. About 10,000 sensors will be installed around the 26.6 km LHC ring, and most of them will be exposed to high radiation doses during the accelerator lifetime. The following thermometric sensors : carbon resistors, thin films, and platinum resistors, have been exposed to high neutron fluences (>10$^15$ n/cm$^2$) at the ISN (Grenoble, France) Cryogenic Irradiation Test Facility. A cryostat is placed in a shielded irradiation vault where a 20 MeV deuteron beam hits a Be target, resulting in a well collimated and intense neutron beam. The cryostat, the on-line acquisition system, the temperature references and the main characteristics of the irradiation facility are described. The main interest of this set-up is its ability to monitor online the evolution of the sensors by comparing its readout with temperature references that are in principle insensitive to the neutron radiation (i.e. Argon gas bulbs when working at about 84 K, and below 4.5 K, either helium gas bulbs or the saturation pressure of the superfluid helium bath). The resistance shifts of the different sensors at liquid helium temperatures are presented. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-153; http://cds.cern.ch/record/340487/files/lhc-project-report-153.pdf; http://cds.cern.ch/record/340487/files/lhc-project-report-153.ps.gz;

Imported from Invenio. Balle, C Casas-Cubillos, J Thermeau, J P Cryogenic Thermometer Calibration Facility at CERN Adv. Cryog. Eng., A 741-748 43 A cryogenic thermometer calibration facility has been designed and is being commissioned in preparation for the very stringent requirements on the temperature control of the LHC superconducting magnets. The temperature is traceable in the 1.5 to 30 K range to standards maintained in a national metrological laboratory by using a set of Rhodium-Iron temperature sensors of metrological quality. The calibration facility is designed for calibrating simultaneously 60 industrial cryogenic thermometers in the 1.5 K to 300 K temperature range, a thermometer being a device that includes both a temperature sensor and the wires heat-intercept. The thermometers can be calibrated in good and degraded vacuum or immersed in the surrounding fluid and at different Joule self-heating conditions that match those imposed by signal conditioners used in large cryogenic machinery. The calibration facility can be operated in an automatic mode and all the control and safety routines are handled by a Programmable Logic Controller (PLC). LabVIEW is used both as the PLC operator interface and for configuring and reading the thermometric data sampled by the higher accuracy laboratory equipment. The isothermal support onto which the thermometers are mounted is thermally anchored through the wiring to a helium bath. The calibration procedure begins once the temperature of the support is stabilized. Measured data is presented and it is possible to infer that the absolute accuracy that can be obtained is better than ± 5 mK for the full temperature range. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-157; http://cds.cern.ch/record/340497/files/lhc-project-report-157.pdf; http://cds.cern.ch/record/340497/files/lhc-project-report-157.ps.gz;

Imported from Invenio. Decker, L Kündig, A Löhlein, K Purtschert, W Ziegler, B L Lebrun, P Tavian, L Brunovsky, I Tucek, L Operational Experience with a Cryogenic Axial-Centrifugal Compressor Adv. Cryog. Eng., A 637-641 43 The Large Hadron Collider (LHC), presently under construction at CERN, requires large refrigeration capacity at 1.8 K. Compression of gaseous helium at cryogenic temperatures is therefore inevitable. Together with subcontractors, Linde Kryotechnik has developed a prototype machine. This unit is based on a cryogenic axial-centrifugal compressor, running on ceramic ball bearings and driven by a variable-frequency electrical motor operating at ambient temperature. Integrated in a test facility for superconducting magnets the machine has been commissioned without major problems and successfully gone through the acceptance test in autumn 1995. Subsequent steps were initiated to improve efficiency of this prototype. This paper describes operating experience gained so far and reports on measured performance prior to and after constructional modifications. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-161; http://cds.cern.ch/record/340506/files/lhc-project-report-161.pdf; http://cds.cern.ch/record/340506/files/lhc-project-report-161.ps.gz;

Imported from Invenio. Cameron, W Dambre, P Kurtyka, T Parma, Vittorio Renaglia, T Rifflet, J M Rohmig, P Skoczen, Blazej Tortschanoff, Theodor Trilhe, P Védrine, P Vincent, D The New Superfluid Helium Cryostats for the Short Straight Sections of the CERN Large Hadron Collider (LHC) Adv. Cryog. Eng., A 411-418 43 The lattice of the CERN Large Hadron Collider (LHC) contains 364 Short Straight Section (SSS) units, one in every 53 m long half-cell. An SSS consists of three major assemblies: the standard cryostat section, the cryogenic service module, and the jumper connection. The standard cryostat section of an SSS contains the twin aperture high-gradient superconducting quadrupole and two pairs of superconducting corrector magnets, operating in pressurized helium II at 1.9 K. Components for isolating cryostat insulation vacuum, and the cryogenic supply lines, have to be foreseen. Special emphasis is given to the design changes of the SSS following adoption of an external cryogenic supply line (QRL). A jumper connection connects the SSS to the QRL, linking all the cryogenic tubes necessary for the local full-cell cooling loop [at every second SSS]. The jumper is connected to one end of the standard cryostat section via the cryogenic service module, which also houses beam diagnostics, current feedthroughs, and instrumentation capillaries. The conceptual design fulfilling the tight requirements of magnet alignment precision and cryogenic performance are described. Construction details, aimed at minimizing costs of series manufacturing and assembly, while ensuring the high quality of this complex accelerator component, are given. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-162; http://cds.cern.ch/record/344977/files/lhc-project-report-162.pdf; http://cds.cern.ch/record/344977/files/lhc-project-report-162.ps.gz;

Imported from Invenio. Mathieu, M Parma, Vittorio Renaglia, T Rohmig, P Williams, L R 293 K - 1.9 K supporting systems for the Large Hadron Collider (LHC) cryo-magnets Adv. Cryog. Eng., A 427-434 43 The LHC machine will incorporate some 2000 main ring super-conducting magnets cooled at 1.9 K by super-fluid pressurized helium, mainly 15m-long dipoles with their cryostats and 6m-long quadrupoles housed in the Short Straight Section (SSS) units. This paper presents the design of the support system of the LHC arc cryo-magnets between 1.9 K at the cold mass and 293 K at the cryostat vacuum vessel. The stringent positioning precision for magnet alignment and the high thermal performance for cryogenic efficiency are the main conflicting requirements, which have lead to a trade-off design. The systems retained for LHC are based on column-type supports positioned in the vertical plane of the magnets inside the cryostats. An ad-hoc design has been achieved both for cryo-dipoles and SSS. Each column is composed of a main tubular thin-walled structure in composite material (glass-fibre/epoxy resin, for its low thermal conductivity properties), interfaced to both magnet and cryostat via stainless steel flanges. The thermal performance of the support is improved by intercepting part of the conduction heat at two intermediate temperature levels (one at 50-75 K and the other at 4.5-20 K). These intercepts, on the composite column, are thermally connected to the helium gas cooled thermal shield and radiation screen of the cryo-magnet. An overview of the design requirements is given, together with an appreciation of the system design. Particular attention is dedicated to the support system of the SSS where the positioning precision of the quadrupole magnet is the most critical. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-163; http://cds.cern.ch/record/347116/files/lhc-project-report-163.pdf; http://cds.cern.ch/record/347116/files/lhc-project-report-163.ps.gz;

Imported from Invenio. Bonneton, M Tavian, L Gistau-Baguer, Guy M Turcat, F Viennot, P A High Reliability Gas-driven Helium Cryogenic Centrifugal Compressor Adv. Cryog. Eng., A 643-649 43 A helium cryogenic compressor was developed and tested in real conditions in 1996. The achieved objective was to compress 0.018 kg/s Helium at 4 K @ 1000 Pa (10 mbar) up to 3000 Pa (30 mbar). This project was an opportunity to develop and test an interesting new concept in view of future needs. The main features of this new specific technology are described. Particular attention is paid to the gas bearing supported rotor and to the pneumatic driver. Trade off between existing technologies and the present work are presented with special stress on the bearing system and the driver. The advantages are discussed, essentially focused on life time and high reliability without maintenance as well as non pollution characteristic. Practical operational modes are also described together with the experimental performances of the compressor. The article concludes with a brief outlook of future work. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-164; http://cds.cern.ch/record/344978/files/lhc-project-report-164.pdf; http://cds.cern.ch/record/344978/files/lhc-project-report-164.ps.gz;

Imported from Invenio. Bottura, L Schneider, M Walckiers, L Wolf, R Cable Magnetization Effects in the LHC Main Dipole Magnets Adv. Cryog. Eng., A 451-458 43 Several short (1 m) and long (10 m) dipole models have been tested within the scope of the on-going R&D programme for LHC at CERN. We report here the results of measurements of field quality in these dipoles, focussing on the contribution of cable magnetization. We show that the results obtained over a significant (> 10) number of magnets at 1.8 and 4.2 K are in reasonable agreement with calculati ons of the dependence of allowed harmonics on field. The calculations are based on the Bean model of filament magnetization and assume an approximate Jc(B) dependence, calibrated against low field mea surements of strand magnetization. The field quality measurements at low field also correlate satisfactorily to measurements of cable critical current at high field and geometric filament diameter. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-169; http://cds.cern.ch/record/350135/files/lhc-project-report-169.pdf; http://cds.cern.ch/record/350135/files/lhc-project-report-169.ps.gz;

Imported from Invenio. Ferlin, G Jenninger, B Rieubland, Jean Michel Precise wide range heatmeters for 1.5 K up to 80 K Adv. Cryog. Eng., A 811-818 43 Two heatmeters were designed at CERN for applications below 20 K with the option to work also at temperatures up to 80 K. The new calibration principle and design permits the construction of wide rang e heatmeters with precision in the range of milliwatts. The calibration function takes into account the temperature dependence of the thermal conductivity of the heatmeter material. The heat flow meas urement is, therefore, independent of the base temperature, i.e. it is also independent on the temperature drop across thermal contact between heatmeter and the cold source. The simple calibration fun ction makes the heatmeter a user-friendly portable diagnostic device. It is possible to quantify parasitic heat flow without a previous calibration, or to calibrate the heatmeter during a measurement with a specimen. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-171; http://cds.cern.ch/record/353208/files/lhc-project-report-171.pdf; http://cds.cern.ch/record/353208/files/lhc-project-report-171.ps.gz;

Imported from Invenio. Gayet, P Kaiser, D Winkler, G Beam Effects on the Cryogenic System of LEP2 Adv. Cryog. Eng., A 131-137 43 The LEP collider was operated during 1996 for the first time with superconducting cavities at the four interaction points. During operation for physics it was observed that the dissipated heat in the cavities is not only a function of the acceleration gradient, but depends also on beam characteristics such as intensity, bunch length and beam current. These beam effects had not been foreseen in the original heat budget of the LEP cryogenic system. The observations indicating the beam effect and its origin are presented. The available capacity of the refrigerators demonstrates that cryogenics might become a limiting factor for the performance of the LEP collider. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-97-007; http://cds.cern.ch/record/337371/files/lhc-97-007.pdf; http://cds.cern.ch/record/337371/files/lhc-97-007.ps.gz;

Imported from Invenio. Chorowski, M Hilbert, B Serio, L Van Weelderen, R Thermohydraulics of Resistive Transitions of the LHC Prototype Magnet String: Theoretical Modeling and Experimental Results Adv. Cryog. Eng., A 459-466 43 In preparation for the Large Hadron Collider (LHC) project, a 40 m-long prototype superconducting magnet string, representing a half-cell of the machine lattice, has been built and operated. The superconducting magnets which comprise this string normally operate in a pressurized static bath of superfluid helium at a pressure of 1 bar and at a temperature of 1.9 K. At 13.1 kA they have about 15.3 MJ of stored magnetic energy. A series of tests was performed to assess the thermohydraulics of resistive transitions (quenches) of the string of magnets. These measurements provide the necessary foundation for describing of the observed pressure rise as the combination of two processes, each acting on a different time scale. The measurements are presented and an explanatory model description of the events is given. eng 1998

http://preprints.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=LHC-PROJECT-REPORT-146; http://cds.cern.ch/record/336186/files/lhc-project-report-146.pdf; http://cds.cern.ch/record/336186/files/lhc-project-report-146.ps.gz;

Imported from Invenio.