共查询到20条相似文献,搜索用时 9 毫秒
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《低温学》2017
The helium vessel of the superconducting cyclotron (SCC) at the Variable Energy Cyclotron centre (VECC), Kolkata shows a gradual loss of insulation vacuum from 10−7 mbar to 10−4 mbar with increasing coil current in the magnet. The insulation vacuum restores back to its initial value with the withdrawal of current. The origin of such behavior has been thought to be related to the electromagnetic stress in the magnet. The electromagnetic stress distribution in the median plane of the helium vessel was studied to figure out the possible location of the helium leak. The stress field from the possible location was transferred to a simplified 2D model with different leak geometries to study the changes in conductance with coil current. The leak rate calculated from the changes in the leak geometry was compared with the leak rate calculated from the experimental insulation vacuum degradation behavior to estimate the initial leak shape and size. 相似文献
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《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1987,257(2):71-76
We present the results of cryogenic tests on a superconducting half-wave resonator for the acceleration of heavy ions. The resonator was built out of OFHC copper and electroplated with 1.5 μm of Pb without chemical polish of the Pb surface. Measured properties include a low level Q of 4 × 108 and a power dissipation of 6 W at 4 MV/m giving an energy gain of 1 MV per unit change to a particle of velocity 0.16 c. 相似文献
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M.A. Hilal 《低温学》1979,19(7):415-420
A general method for optimizing ideal Claude cycles with multiple expansion engines is presented for two types of engine arrangements. In one case, the inlet temperature of one engine is equal to the outlet temperature of another engine. In the second case, inlet and outlet temperatures of adjacent engines are independent of each other, the more general case which is sometimes used in practice. The optimizing technique is especially adapted to superconductive systems in which some of the helium vapour is used to cool electrical leads and mechanical support systems. The helium fraction to be returned to the refrigerator-liquefier vs the fraction to be used for other purposes is conventionally entered as a parameter which becomes part of the optimization technique. 相似文献
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A versatile cryogenic test bed, based on circulating cryogenic helium gas, has been designed, fabricated, and installed at the Florida State University Center for Advanced Power Systems (FSU-CAPS). The test bed is being used to understand the benefits of integrating the cryogenic systems of multiple superconducting power devices. The helium circulation system operates with four sets of cryocooler and heat exchanger combinations. The maximum operating pressure of the system is 2.1 MPa. The efficacy of helium circulation systems in cooling superconducting power devices is evaluated using a 30-m-long simulated superconducting cable in a flexible cryostat. Experiments were conducted at various mass flow rates and a variety of heat load profiles. A 1-D thermal model was developed to understand the effect of the gas flow parameters on the thermal gradients along the cable. Experimental results are in close agreement with the results from the thermal model. 相似文献
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The feasibility of 50 μm thick diaphragms with a metallic film heater integrated on a quartz disc and working up to 500 °C has been demonstrated. The diaphragms have been realized with the coupling of abrasive jet machining and mechanical polishing techniques. The metallic film has been obtained by means of a sequence of e-gun evaporation and electrochemical growth steps. No degradation of the adhesion characteristics was registered. Electrical properties were retained without electro-migration even for working conditions of 50 h at 500 °C. Aim of the device is the application in quartz molecular sieves thermally/electrically modulated, basically for helium leak detection. 相似文献
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M. Morpurgo 《低温学》1979,19(7):411-414
A large superconducting dipole cooled by forced circulation of two-phase helium is described. Details are given of the magnet design and construction. A short discussion of some cryogenic problems are presented together with the first results of the dipole's operation. 相似文献
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Simple helium dewars have been constructed using gas-cooled radiation shields and multi layer aluminized plastic insulation. They will retain one litre of liquid for up to 40 hours The shields may be made mostly non-conducting so the dewar can be used with ultrasensitive superconducting magnetometers. For most other applications thin sheet metal such as copper or aluminium is suitable for the shields. 相似文献
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We have developed a resistance thermometry system for the acquisition, control and monitoring of temperature in large-scale cryogenic applications. The resistance of the sensor is converted to a voltage using a self-balancing AC bridge circuit featuring square-wave excitation currents down to 1 nA. The system is easily scalable and includes intelligent features to treat special situations such as magnet quenches different from normal operation. 相似文献
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This paper presents an ultra low noise instrumentation based on cryogenic electronic integrated circuits (ASICs: Application Specific Integrated Circuits). We have designed successively two ASICs in standard BiCMOS SiGe 0.35 μm technology that have proved to be operating at cryogenic temperatures. The main functions of these circuits are the readout and the multiplexing of TES/SQUID arrays. We report the cryogenic operation of a first ASIC version dedicated to the readout of a 2 × 4 pixel demonstrator array. We particularly emphasize on the development and the test phases of an ultra low white noise (0.2 nV/sqrtHz) cryogenic amplifier designed with two multiplexed inputs. The cryogenic SiGe amplifier coupled to a SQUID in a FLL operating at 4.2 K is also presented. We finally report on the development of a second version of this circuit to readout a 3 × 8 detectors array with improved noise performances and upgraded functionalities. 相似文献
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《低温学》2013
Experimental and numerical studies have been conducted with the aim of modeling pressure rises which occur in the helium, during quenches of the 11.7-T superconducting magnet named Iseult. Iseult is based on a double-pancake winding internally cooled by superfluid helium channels opening into a pressurized He II bath at 1.8 K. A scale mock-up has been built of 10 copper equivalent pancake slices and 7 helium channels per pancake. The heat produced by a quench of the Iseult magnet is simulated by electrical heaters put inside each copper plate. Cryogenic pressure and temperature sensors have been fitted in the helium channels and in the bath. Bath pressure measurements are given for various heating powers, various numbers of heated plates and various bath volumes. Comparisons with a simple numerical model permit to identify the main physical mechanisms which drive the pressure rise during a quench. 相似文献
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Forced-cooled superconductors are viewed as a promising alternative in the development of high field superconducting magnets for future fusion devices. The high current density cable superconductor is protected against thermal instabilities by forcing (single phase) supercritical helium through the cable.The cryogenic cooling system for a forced-cooled superconducting magnet works as a refrigerator and a reciculator at the same time. The paper discusses the conceptual design of the cooling systems for forced-cooled superconducting magnets with the overall objective of reducing the refrigeration costs. The general conclusion of this article is that economic cooling systems must employ efficient cold pump recirculators in which the large flow demanded by the forced-cooled superconducting magnet is confined to the cold end of the refrigerating column. If the liquid helium pump efficiency is less than 40%, systems employing elevated temperature compressors are more economic. 相似文献
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E. Gregory 《低温学》1982,22(5):203-212
The February 1971 edition of this journal carried a ten page article by the author and his colleagues reviewing the then ‘state of the art’ in multifilamentary superconducting composites.1 At the time we attempted to cover in a fairly comprehensive manner the first decade of development of these materials since the construction of the first high field superconducting magnet.2 Now more than another decade of development has passed and obviously the field can no longer be reviewed comprehensively in the same few pages. This article will attempt to give a brief overview of these materials from the point of view of one engaged in their development and supply for large applications. Hopefully, the references to books,3,4 review articles,5,6 and the proceedings of the various conferences7–11 will serve as a source of further information for those who require more details. 相似文献