Stability of Fast-cycling Dipole for the Sis300 Ring

The superconducting (SC) dipole with 100-mm aperture, 6-T magnetic field amplitude and 1-T/s field ramp rate for the SIS300 accelerator [1], now under development at the GSI, Darmstadt. A higher enough field ramp rate causes large AC losses in the magnet, to ensure stable operating mode it is necessary to provide enough temperature margin. The temperature margin of SC magnet is the difference between the critical and operating temperatures under the worst conditions of the applied magnetic field, temperature, and the transport current. Simultaneous solutions of the non-stationary equations of heat balance both in the coil and in a single-phase helium flow and numerical calculations of heat losses in the SC coil, which cause a coil heating, allow one to simulate transient thermal processes in the magnet during the SIS300 operating cycle. Analyses of temperature operating conditions were made with help of computer simulation for three designs [2] of the SC dipole for the SIS300 ring. These designs have been considered and studied in order to choose optimal design, satisfying both field quality and minimal heat losses in the magnet. Possible ways to increase the temperature margin are discussed.