摘要 :
Upgrades presently being planned for high-energy hadron colliders require magnet performance beyond the capabilities of$ NbTi$superconducting wire. Recent improvements in the performance of$ Nb_3 Sn$material and in the capability ...
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Upgrades presently being planned for high-energy hadron colliders require magnet performance beyond the capabilities of$ NbTi$superconducting wire. Recent improvements in the performance of$ Nb_3 Sn$material and in the capability to use it in practical magnets make it the logical choice for the next generation of accelerator magnets. We discuss recent results of R&D programs, some remaining issues and possible solutions. Recent progress in understanding and in technical details of design and assembly have made$ Nb_3 Sn$magnets easier to fabricate and more reliable in performance.
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An important part of FAIR (Facility for Antiproton and Ion Research), being developed at GSI, Darmstadt, Germany, is the fast-ramping heavy ion synchrotron SIS 300. The main elements of the SIS 300 magnetic system are 6 T, 2.6 m l...
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An important part of FAIR (Facility for Antiproton and Ion Research), being developed at GSI, Darmstadt, Germany, is the fast-ramping heavy ion synchrotron SIS 300. The main elements of the SIS 300 magnetic system are 6 T, 2.6 m long superconducting dipoles, to guide charged particle beams on a path with a 50 m curvature radius. A model superconducting dipole, manufactured for the UNK project, was chosen to study the influence of bending on the magnet characteristics. The straight collared coil of this model magnet was tested, then bent with a 50 m curvature radius, and then retested. The main measured and calculated characteristics of the coil for both tests are presented. Test results showed similar characteristics, both in training and in ramp rate dependence, as well as in field quality of the straight and bent coils. There is a good agreement between measured and calculated results of the completed study.
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MECO, the muon-to-electron conversion experiment, requires a total of 96 superconducting solenoids designed for construction by industry and assembly into 4 separate cryostats following completion of final design. The magnet syste...
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MECO, the muon-to-electron conversion experiment, requires a total of 96 superconducting solenoids designed for construction by industry and assembly into 4 separate cryostats following completion of final design. The magnet system has a 12$times$26 m installation footprint. The objective of the tolerances and uncertainties sensitivity studies was to demonstrate the feasibility of building a MECO magnet system around the conceptual design that meets the performance requirements in the presence of expected material property variances, realistic manufacturing tolerances, and manufacturing and design uncertainties. The study also presents a method for minimizing manufacturing costs by setting adequate tolerances and using the most appropriate manufacturing and assembly procedures. Monte-Carlo magnetic modeling was used to introduce field errors from various possible deviations of the structure from the nominal design, and correlate them with the field performance. The conclusion from the study is that the design is robust. Field requirements are met in the presence of material property uncertainties and modest machining and assembly tolerances. This implies that the project may be able to accept field quality risk and ask the fabricator to accept only the responsibility for placing the coils with correct turn counts in their warm positions at reasonable tolerances.
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Within the framework of the European Fusion Programme (EFDA) a design activity has been started in late 2004 by the EFDA Close Support Unit at Garching (FRG) to design a 12.5 T superconducting dipole magnet. The final goal of this...
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Within the framework of the European Fusion Programme (EFDA) a design activity has been started in late 2004 by the EFDA Close Support Unit at Garching (FRG) to design a 12.5 T superconducting dipole magnet. The final goal of this activity is to define a “minimum cost” and “minimum risk” dipole to be built within the next 3 years by European industries. The newly built magnet shall be hosted in one of the existing cryogenic laboratories in the EU to test, in particular, the full size conductor samples that shall be produced during the ITER magnets procurement. As a result of this study—carried out in cooperation with several European laboratories—different concepts have been analyzed and optimized. All designs are based on the use of high current density$ Nb_3 Sn$strands ($ j_ csim2000 A/mm^2$at 12 T/4.2 K). It is assumed that these strands can be cabled either as Cable In Conduit Conductors (CICC) or as Rutherford-type Cables (RC) and then wound as planar racetrack, non-planar (saddle) or$costheta$coils. The aim of this paper is to provide an overview of this study activity with particular emphasis to the optimization steps followed in the design of each magnet concept. Four different types are described: a planar CICC/RC-based coil, a saddle CICC-based coil and a$costheta$RC-based coil. Each design is described together with the salient optimization steps that include electromagnetic, structure mechanic and thermo-hydraulic analyses as well as different manufacturing constraints.
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The authors present a model for calculating the levitation force, magnetic stiffness and damping for a superconductor in the presence of the magnetic field of a permanent magnet. Bulk and thin film shapes are chosen for the superc...
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The authors present a model for calculating the levitation force, magnetic stiffness and damping for a superconductor in the presence of the magnetic field of a permanent magnet. Bulk and thin film shapes are chosen for the superconductor. They compare the results for both and conclude that, in general, the thin film shape enhances the magnitude of the force while maintaining a good stability and without increasing the losses associated with small displacements.
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The evolution of physics with colliding beams has required ever increasing volumes of magnet field around the interaction points for effective particle detection. This has been the main driver for the development of detector magne...
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The evolution of physics with colliding beams has required ever increasing volumes of magnet field around the interaction points for effective particle detection. This has been the main driver for the development of detector magnet system over the past 25 years. This paper traces the evolution of detector magnet technology through the engineering solutions developed to meet the increased scale and field strength. The paper will address major aspects of detector magnet engineering from design and analysis to conductor and magnet fabrication technology. Advances in conductor design for stability, fabrication and protection will be described. The paper will evaluate the techniques developed to achieve high transparency, efficient cooling (direct vs. indirect) and magnetic force transfer. The current state of the art at both large (CMS and ATLAS) scale and small scale (BESS) will be reviewed. Future requirements for detector magnets will be reviewed.
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Recent progress in$ Nb_3 Sn$superconductor technology provides the base for increasing magnet field in accelerator magnets up to 15–16 T. The work on such magnets based on both block-type and shell-type coils are in progress at F...
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Recent progress in$ Nb_3 Sn$superconductor technology provides the base for increasing magnet field in accelerator magnets up to 15–16 T. The work on such magnets based on both block-type and shell-type coils are in progress at Fermilab, LBNL and elsewhere. One of the novel approaches to the design of this magnet is to split the magnet winding into two separate dipole windings powered in series or separately. Each winding generates a homogeneous magnetic field in the magnet aperture. The paper presents conceptual magnetic and mechanical designs of 15 T double dipole magnets and discusses several scenarios of magnet powering. The inner dipole winding is based on the 2-layer$ Nb_3 Sn$coils previously developed and tested at Fermilab. The outer dipole winding is made of sub-sized$ Nb_3 Sn$cable and has about two times higher current density. Both windings have the shell-type configuration. For the different powering scenarios the results of calculation of the field quality, coil magnetization effects, and the stress analysis are presented.
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In the frame of ITER program a prototype superconducting magnet for 170 GHz Gyrotrons was designed, manufactured and tested. The operating field (7.17 T in the center of 219 mm cold bore and 8.1 T at the winding) corresponds to a ...
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In the frame of ITER program a prototype superconducting magnet for 170 GHz Gyrotrons was designed, manufactured and tested. The operating field (7.17 T in the center of 219 mm cold bore and 8.1 T at the winding) corresponds to a current of 183.5 A. In the final version of the magnet design the operating field was reached without any training. A specific field distribution along the axis was required with sharp decrease from both sides along the axis. Due to large axial forces a special support structure was used. The subcoils were wound from both$ Nb_3 Sn$and NbTi multifilamentary graded wires. For quench protection the subcoils were shunted with 16 resistive shunts. A quench transformer type energy extraction system was also implemented in the magnet design. During the tests mechanical disturbances in the subcoils and support structure were observed.
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Levitation of bulk Y-Ba-Cu-O superconductors could successfully be controlled using a Bi-Sr-Ca-Cu-O superconducting electromagnet. It was found that stable levitation without tilting was obtained only when the sample trapped a cer...
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Levitation of bulk Y-Ba-Cu-O superconductors could successfully be controlled using a Bi-Sr-Ca-Cu-O superconducting electromagnet. It was found that stable levitation without tilting was obtained only when the sample trapped a certain amount of field, the minimum of which depended on the external field and the sample dimensions. We also employed a novel analysis method for levitation based on the total energy balance, which is much simpler than the force method and could be applied to the understanding of general levitation behavior. Numerical analyzes thus developed suggested that stable levitation of superconductors with large dimensions can only be achieved when the induced currents can flow with three dimensional freedom.
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A Neutron spin-echo spectrometer (NSE) of the next generation will be build for the Spallation Neutron Source (SNS) in Oak Ridge, USA. A NSE spectrometer measures tiny velocity changes of the neutrons encoded by the neutrons spin ...
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A Neutron spin-echo spectrometer (NSE) of the next generation will be build for the Spallation Neutron Source (SNS) in Oak Ridge, USA. A NSE spectrometer measures tiny velocity changes of the neutrons encoded by the neutrons spin clock at a sample while the Neutron spin precesses in large magnetic fields following Bloch''s equation. This instrument will be the best of its class both with respect to resolution and dynamic range. In order to reach this ambitious goal, a large magnetic precision field integral before and after the sample is required which directly scales linearly with the resolution of the instrument. Therefore superconducting technology will be used to allow for a higher magnetic field integral. Here, we present the first basic design of the solenoids which has been developed in a joint project study by J脺lich Research Center (FZJ) and Babcock Noell GmbH (BNG). The solenoids will generate an integrated magnetic flux density of 1.8 Tm. To reduce the fringe field, active shielding is foreseen. To minimize vibrations modern pulse-tube cryocoolers cool the NbTi windings below Tc. A special feature of the magnet system is the position measurement with an accuracy in the order of micrometers for the windings in the cryostat during operation. This information is required for the adjustment of so called Fresnel coils outside the cryostat. Together with the setup of these correction elements, a field integral homogeneity better than $10^{-6}$ for different Neutron paths through one of the solenoids will be achieved. In addition special care has been taken in the selection procedure for the SC strands. This is necessary for the minimization of its hysteresis values and subsequently for full determination and control of the magnetic field with an accuracy of about $10^{-5}$ .
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