RF parameter and field stability requirements for the Cornell ERL prototype

Cornell University, in collaboration with Jefferson Laboratory, has proposed the construction of a prototype energy-recovery linac (ERL) to study the energy recovery concept with high current, low emittance beams. The ERL will require the operation of superconducting cavities in two extreme regimes. In the injector a multi-mA beam is accelerated to several MeV energy. The resulting high beam loading in the superconducting cavities requires a strong coupling of the fundamental mode coupler and a high power transfer. The dominating sources of field perturbation in the injector cavities are beam transients and beam current fluctuations. In the main linac the decelerated recirculated beam cancels the beam loading of the accelerated beam. Accordingly these cavities are operated at a high external quality factor to minimize the RF power requirements. Microphonic cavity detuning and path length fluctuations significantly increase the RF power demands. In this paper an overview of the prototype RF system is given and the RF power demands and field stability requirements are discussed in detail.