Title: Design of Racetrack Coils for High Field Dipole Magnets - eScholarship
Abstract: LBNL#45139 SC-MAG 702 Design of Racetrack Coils for High-Field Dipole Magnets G. Sabbi, S. Caspi, S.A. Gourlay, R. Hafalia, A. Jackson, A. Lietzke, A.D. McInturff, R.M. Scanlan Ab.'Jtract- The magnet group at LBNL is currently in the process of developing high-field accelerator magnets for use in future colliders. One of the primary challenges is to provide a design which is cost-effective and simple to manufacture, at the same time result- ing in good training performance and field quality ad- equate for accelerator operation. Recent studies have focused on a racetrack geometry that has the virtues of simplicity and conductor compatibility. The results have been applied to the design of a series of prototype high-field magnets based on Nb3Sn conductor. Coil Modules Iron Yoke Keys 1. INTRODUCTION Iron Pole A program to develop high-field accelerator magnets for future colliders is underway at several U.S. laboratories. After completion of the 13.5 T cos-8 dipole D-20 [1], the LBNL magnet group has started to investigate a recently proposed common coil configuration for two-aperture Shell Fig. 1. RD-3 cross-section. dipoles, using racetrack coils shared between both mag- net apertures [2J [3J. The first test involved a 6 T short model (RD-2) built using ITER-type Nb,Sn conductor. The magnet reached short sample field with no training in a variety of configurations [4J. The following magnet in this series (RD-3) uses high-performance Nb 3 Sn con- ductor with critical current density above 2 kA/mm 2 at 12 T, 4.2 K, and is designed to reach 14 T [5J. The coil structure is composed of two outer modules and one in- ner module. The two outer modules have been pre-tested in back-to-back configuration (RT-l) and have achieved a field of 12 T [6J. The complete structure is now assembled and testing is underway. Present experiments are focused on basic structural is- II. DESIGN REQUIREMENTS Fig. 1 shows a cross-section of the RD-3 dipole. The magnet has three major components. The first compo- nent comprises 3 coil modules wound around iron cores (islands). For each module, vertical pre-load is provided by face plates (skins) welded to side rails. The second component is the iron yoke, which serves as a flux return. The third component is the outer aluminum shell, which provides support against the large horizontal forces . The yoke is split between an inner pad and an external struc- ture. Keys are inserted in the resulting gap using a Pres- surized Bladder System (PBS) to reach the desired pre- stress at room temperature [7J. Two bore pieces, each one providing a 10 mm clear aperture, are inserted between sues and the development of fabrication techniques for the new configuration. Goal for the next phase of the program is to achieve field quality suitable for operation in high-energy colliders while retaining the highest level of simplicity and efficiency. This paper presents a list of requirements for the experimental program, and describes . a series of prototype magnets which are being designed to satisfy these requirements. Manuscript received September 18, 2000. Authors are with Lawrence Berkeley National Laboratory, One Cy- clotron Road, Berkeley, CA 94720. Work supported by the U.S. Department of Energy. the coils. The first requirement for the next phase of the magnet program is to increase the clear bore diameter from 10 mm to 40 mm. It should be noted that significant cost sav- ings can be realized by decreasing the magnet aperture of future colliders to lower values than in present machines . The racetrack configuration is particularly well suited to fabrication of small-aperture dipoles. Preliminary studies indicate that a racetrack magnet with coil to coil spac- ing of 20 mm can be fabricated, using 0.7 mm strand, with all harmonics well within one unit within a circle of 14 mm diameter (2/3 of the coil to coil spacing) [8J. How- ever, it is first necessary to demonstrate that a high-field
Publication Year: 2011
Publication Date: 2011-04-20
Language: en
Type: article
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