Quench analysis of a superconducting magnet for RISP 28 GHz ECR ion source

This paper presents quench analysis of a superconducting magnet system for 28 GHz electron cyclotron resonance (ECR) ion source. The magnet system consists of a hexapole coil and four solenoid coils located outside of the hexapole one. All coils were wound with NbTi wire and impregnated by epoxy. To analyze the characteristic of superconducting coil when the quench occurs, a numerical code was developed. The analysis procedures are as follows. First, normal zone propagation (NZP) velocity which is as a function of magnetic field was calculated. Second, a fraction of the winding volume was obtained by transient analysis, considering longitudinal and transverse NZP velocities. Third, a generated resistance and temperature rising over time were simulated. Lastly, current trace of the coil was calculated. The current trace calculated by simulation well agrees with the test result. Also the result of hot-spot temperature is reasonable. Since simulated hot-spot temperature and experimental result are 60.32 K and 63 K when the operating current is 169 A. The normal zone resistances are also identical for 1.13 s which is the convergence time of simulation. The final resistances are about 10.2 Ω and 11.23 Ω. Therefore it is expected that the analysis code can be used to estimate the characteristic of superconducting magnet when the quench occurs.