Abstract-The Muon Ionization Cooling Experiment (MICE) spectrometer solenoid magnets will be the first magnets to be installed within the MICE cooling channel. The spectrometer magnets are the largest magnets in both mass and surface area within the MICE cooling channel. Like all of the other magnets in MICE, the spectrometer solenoids are kept cold using 1.5 W (at 4.2 K) pulse tube coolers. The MICE spectrometer solenoid is quite possibly the largest magnet that has been cooled using small coolers. Two spectrometer magnets have been built and tested. This report discusses the results of current and cooler tests of both magnets.

Abstract-This paper describes how a passive quench protection system can be applied to long superconducting solenoid magnets. When a solenoid coil is long compared to its thickness, the magnet quench process will be dominated by the time needed for quench propagation along the magnet length. Quench-back will permit a long magnet to quench more rapidly in a passive way. Quenchback from a conductive (low resistivity) mandrel is essential for spreading the quench along the length of a magnet. The mandrel must be inductively coupled to the magnet circuit that is being quenched. Current induced in the mandrel by di/dt in the magnet produces heat in the mandrel, which in turn causes the superconducting coil wound on the mandrel to quench. Sub-division is often employed to reduce the voltages to ground within the coil. This paper explores when it is possible for quench-back to be employed for passive quench protection. The role of sub-division of the coil is discussed for long magnets. Index Terms-Magnet Quench-back, Coil Sub-division. INTRODUCTION uench-back is a widely used passive quench protection method that enhances the rate of propagation of the normal zone by using a coupled secondary circuit. As quenching proceeds, the secondary will heat up. If it is in good thermal contact with the magnet winding, it will initiate further quenching-effectively increasing quench propagation velocity and therefore reducing the hot spot temperature. It is particularly effective in a situation where the normal zone hits boundaries rather early in the quenching process and thereafter spreads very slowly in the other dimension [1][2][3].Sub-division provides an alternative path for some of the current by connecting shunt resistors across sections of the magnet, and the shunt resistor can absorb some of the stored energy in the coil. So the hot spot temperature of the coil can This paper describes a passive quench protection system that may be applied to a long superconducting solenoid with sub-division. The role of quench-back in the quench protection of such a solenoid is discussed. I. PASSIVE QUENCH PROTECTION OF A LONG SOLENOID A. Long Solenoid ParametersThe solenoid discussed in this paper is a spectrometer magnet used in the MICE project, shown in Fig. 1 [5]. This magnet consists of two match coils M1 and M2 and three-coil spectrometer section (E1, C, and E2). M1 and M2 are used to match the spectrometer section with the MICE cooling channel. The three-coil section produces a uniform magnetic field (±0.3 percent) within a region that is 1000 mm long and 300 mm in diameter. The uniform field section contains a fiveplane scintillating fiber detector for muon beam emittance analysis. The magnet has an Nb-Ti superconductor with a copper to superconductor ratio of four. The insulated conductor dimensions are 1.65 by 1.00 mm. All five coils are wound on a single 6061-T6-aluminum mandrel. The cryostat consists of 4.2 K helium vessel, an 80 K thermal shield, cold mass supports for 500 kN and a 300 K vacuum vessel. The spectrometer se...

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Abstract. This author and other authors have written papers concerning the cost of refrigeration as a function of the refrigeration delivered. These papers have included small coolers as well. The lowest temperature range from 3.8 K to 4.7 K (the liquid helium temperature range) is covered using coolers that have two stages. The use of magnets and power equipment that use MgB 2 conductors and HTS conductors have spurred the development of coolers that work well temperature ranges from 15 K to 30 K (hydrogen temperature applications), HTS conductors like BSSCO and YBCO for the range fro 35 to 50 K and HTS devices from 65 K to 80 K (applications in the liquid nitrogen temperature range). This paper will present some cost data for a number of commercial two-stage and single-stage coolers. This data will be fitted to allow one to estimate the cost of coolers as a function of refrigeration for temperatures of 4.2 K, 20 K, 40 K and 77 K. The efficiency of a large number of coolers over a range of temperatures is also discussed.

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