MA cavities for J-PARC with controlled Q-value by external inductor

The original J-PARC RCS cavity design used cut-cores to control the Q-value. Adjusting the distance between the C-shaped core parts the optimum Q=2 is reached. Because of problems related to the cut-core surfaces, the "hybrid cavity" was introduced, using tanks with uncut cores (Q=0.6) in parallel to tanks with cut-cores with a wider gap (Q=4), resulting in total Q=2. Although this was successfully tested, the manufacturing procedure for cut-cores involves more steps than for uncut cores. To reduce risks for long-term operation, the RCS cavities are loaded with uncut cores for day-1 operation. In the following, we describe how we establish Q=2 with parallel inductors.