Development and testing of a prototype tuner for the CEBAF upgrade cryomodule

An upgrade cryomodule is being developed for CEBAF at Jefferson Lab. The high-gradient, low-current operation of the superconducting cavities puts stringent requirements on the accuracy of the frequency tuner: a resolution of 1 Hz over a range of 400 kHz. We have developed and tested such a tuner; it consists of a stepper-motor-driven coarse tuner, operating in series with a piezo-actuator-driven fine tuner. Tuner test procedures and results are summarized, including frequency resolution, range, and linearity (i.e. frequency vs. tuner position), as well as microphonic effects resulting from tuner operation.