Quench Protection System of Superconducting Quadrupole Magnet: Simulation and Experimental Studies

Abstract

The main motivation behind this thesis is to design an efficient quench protection system (QPS)for the superconducting quadruple magnet system under development at IUAC. A detailed the magneto-static simulations have been done for the quadruple magnet using OPERA-3D software to analyse the field profile and the magnet bore, fringe field and peak field in the conductor of the magnet system. Quench simulation with different QPS circuit configurations using OPERA-QUENCH code for a single NbTi coil and a quadrupole singlet is one of the major objectives of the thesis. One of the configurations of the protection circuit for single NbTi coil has been tested at 4.2K in a test rig. Single superconducting quadrupole coil is simulated in QUENCH package with adiabatic boundary condition for same circuit operated at current of 80A and 100A, it results in linear increment of final maximum temperature and resistance of coil after quenching. Depending on the protection circuit such as only resistor, back-to-back diode and back-to-back diode with resistor across the coil. The final temperature varies in between 38 to 47 K. The purpose of the heater power to initiate the quench in the magnet analysed and experimentally validated from the single coil experiment in LHe cryostat. The effect of dumping resistors of 0.91 and 2.5 ? results into the decrement in original time constant (t_C=1.5 s) to decay the remaining current from 1 s and 0.667 s respectively is characterized. Simulation study is extended to superconducting quadruple singlet with many combinations of circuits and gets an idea about mutual coupling between the coils during quench. A helium cryostat has been designed for testing of the QPS of the superconducting quadrupole doublet structure (QDS). And optimized it mechanically for minimum heat load of 21.4 W.