Effect and control of the dee to dee coupling capacitances

The effect of the capacitances between the dees of a cyclotron is negligible or stabilizing if the dees are operating in 0- or π-mode, respectively. The effect becomes critical in compact three sectors Superconducting Cyclotrons where the dees are operating in modes different from the 0- or π-mode (120 degrees difference in phase). In this paper we present a compensating system design, which can compensate completely this effect without a strong influence on the RF cavity characteristics. The phase difference between the current in the coupler and the current oscillating in the cavity is, as we show in ch.1, the fundamental criteria for a decision on utilizing a compensating system. In ch.2 we present how the system in principle works and in ch.3 we show how one can calculate the main parameters, followed by indications how to optimize the compensating system. In ch.4 we give some practical hints how to use the system and to avoid too elaborated calculations. (author)