Numerical treatment of the quenching process in superconducting magnet systems

A computer program for testing coil and protection design of a composed magnet system is presented. Small high field magnets consisting of two uniaxial cylindrical coils of different superconducting materials (eg NbTi and V₃Ga or Nb₃Sn) are considered, each coil may be subdivided into several sections which are protected by parallel resistors. Quench propagation due to thermal conduction and also due to rapid current increase (important in inductively coupled systems) is taken into account by means of solving a one-dimensional thermodiffusion equation. Field and temperature dependence of the critical current for every layer of the coils, is taken into account. The program calculates the time dependence of currents, external and internal voltages, resistances of the sections and of the radial temperature distribution. Calculations are compared with experimental investigations of three different systems, the results agree with experimental values concerning current decay and propagation velocity.