Ponderomotive oscillations in a superconducting helical resonator

The onset of ponderomotive oscillation, a radiation pressure driven mechanical oscillation, at 120 Hz was observed at low field strengths in a superconducting 130 MEz helical resonator suitable for use in a heavy ion accelerator. Thresholds were observed over a wide range of parameters such as RF Q's from 105 to 108 and mechanical Q's from 8 x 103 to 2 x 105. A typical minimum threshold value was 10-8 joule of RF energy in the resonator. A theory is presented which quantitatively explains all the threshold data. Hethods of damping ponderomotive oscillations are discussed.