An Improved Pneumatic Frequency Control for Superconducting Cavities

The ATLAS (Argonne Tandem Linear Accelerator System) superconducting cavities use a pneumatic system to maintain the cavity eigenfrequency at the master oscillator frequency [1]. The present pneumatic slow tuner has a limitation in the tuning slew rates. For some resonators, the frequency slew rate is as low as 30 Hz/sec. The total tuning range for ATLAS cavities varies from 60 kHz to as high as 450 kHz depending on the cavity type. With the present system, if a cavity is at the extreme end of its tuning range, it may take an unacceptable length of time to reach the master oscillator frequency. We have designed a new slow tuner system that increases the frequency slew rates by a factor of three hundred. This improved system is directly applicable for use on RIA (Rare Isotope Accelerator) cavities. This paper discusses the design of the system and the results of a prototype test.