YIG tuners for RF cavities

Tuning of RF accelerator cavities in electron storage rings is needed to maintain accelerating gap voltage under varying beam loading conditions. A type of ferrite tuner based on the stripline configuration has been tested at the National Synchrotron Light Source. The tuner is basically a short-circuited ferrite-loaded transmission line which is inductively coupled to the RF cavity to be tuned. The use of substituted yttrium-iron-garnet (YIG) allows for custom tailoring the saturation magnetization to the specific application and thus minimizing the bias field requirement. The design goal for the tuner was to achieve a tuning range of 50 kHz. Linear tunability of 78 kHz was demonstrated, exceeding the goals set for the tuner. Results of testing the YIG tuner are presented