| The muon ionization cooling experiment (MICE) will be a demonstration of muon cooling in a configuration of superconducting solenoids and absorbers that may be useful for a neutrino factory or moun collider. The MICE cooling channel consists of alternating three absorber focus coil modules (AFC) and two RF coupling coil modules (RFCC). The RFCC module comprises a superconducting coupling solenoid magnet mounted around four conventional conducting 201.25MHz closed RF cavities bounding by thin beryllium windows. The function of the coupling magnet is to produce enough magnetic field up to 2.6T on the magnet centerline to keep the beam within the iris of the thin RF cavity windows. MICE coupling magnet is a single superconducting solenoid magnet, with an inner diameter of 1.5m and a peak magnetic field of 7.4T. The thesis researches several key technical issues in the superconducting magnet design including cold mass support, AC losses, magnet thermal stability and HTS leads protection. The results are helpful for the long-term stable operation and failure protection of the coupling magnet, which have important engineering value.1) The cold mass support is the key component of a superconducting magnet. A self-centered double-band cold mass support system is designed in detail for MICE superconducting coupling magnet. A 1-D theory analysis model is built to compare and analyze the influences of cold and warm shipment schemes on the support performances and structure, and the warm shipment scheme is adopted. The parameters of pre-tension and tension in the cold mass support bands are analyzed during warm shipment, cooling down and charge. The structure and major dimensions of cold mass support assembly are introduced in detail. And the effects of support materials and ratio between 60K~300K band and 4.2K~60K band on the cold mass support capacity are discussed also.2) A series of numerical model are built based on the general finite element software. The detailed numerical simulations on the cold mass support system assemblies are carried out using ANSYS. A 3-D integral analysis model for the whole cold mass support system is built, and the self-centered characteristics for the support system are verified using the model. The tension in each support assembly, the displacement of the magnet center and the co-axial departure of magnet axis in different modes, such as warm, cold and charge are obtained. A 3-D thermal and structure FE model are built for the support assembly. The temperature profile and the heat leak along the support assembly are obtained, which is coincident well with the 1-D theory analyzed results. The contact analysis technology is applied on the stress simulation on the support assembly, which is close to the real contact condition between support band and support cylinder. The von-Mises stress distribution on the major components, such as support bands, thermal intercept, rod end and pins are obtained in detail. The strength of the cold mass support assembly is verified, and the results are used to determine the final dimensions of the support structure.3) The electrical characteristics of coupling magnet are analyzed based on the reduce-state method and the principle of L-R circuit. The critical current density of MICE superconductor under different temperature and magnetic field are predicted using reduced-state method and the basis parameters for the coupling magnet such as the maximum operation current and temperature margin are obtained. Various charge and discharge schemes for the coupling magnet are compared, and the optical charge and discharge schemes are obtained according to the present power supply. The rapid discharge circuit is designed, and the thermal dynamic analysis for the diode cooling during rapid discharge is discussed also.4) The analysis of the AC losses and their influence on the thermal stability of superconducting magnet indirectly cooled by helium are carried out using FE software combined the developed program. The thesis provides the methods to keep the thermal stability of the MICE coupling magnet. The primary calculation of the AC losses for the coupling magnet shows that the hysteric AC loss and the eddy current loss in mandrel are the major souses of AC losses. During charge, discharge and rapid discharge, the liquid helium around the coil can be vaporized to utilize the latent heat to keep the thermal stability of the coupling magnet. So certain volume of liquid helium should be kept in the cooling system. The transient temperature distributions in coupling magnet during charge, discharge and rapid discharge are numerical simulated using the FE software together with the developed program. The results show that the coupling magnet can be rapid discharged safely with maximum temperature rise of 0.42K. At last, the protection of HTS leads in failure modes such as power off or fault of small coolers is discussed. A new HTS lead protection method utilizing the sensible heat of vaporized helium gas during rapid discharge is provided to protect the HTS leads. A small coiled heat exchanger attached on the first stage of small cooler is designed and analyzed.
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