Radiation Effects in Swept-Synthetic Quartz

In this paper we report the results of a radiation testing program on swept-synthetic quartz resonators and materials. Thirteen resonators representing eight bars of Z-growth, swept-synthetic quartz were tested for transient frequency drifts and accumulated frequency offset. When the drift due to the temperature change induced by a radiation pulse equilibrates, a relatively permanent frequency offset which changes with dose is observed. Typical frequency changes are found to be approximately +2 pp 108 for doses of a few kilorads to about 5 × 104 rads and -1 pp 107 after 2 × 105 rads. Crystals cut from the same bar exhibit frequency shifts which differ by about 1 pp 108 for a given dose, but crystals from different bars differ by larger amounts for a given dose. Changes observed in a resonator irradiated in a mixed gamma-neutron environment to 175 kilorads and 3 × 1014 n/cm2 cannot be accounted for by ionization-induced changes alone. Positive frequency shifts, linear in neutron fluence, are observed. Electron spin resonance and transient and steady-state optical absorption measurements were performed on pieces of the parent material in an attempt to correlate the observed frequency changes with defect properties. Two radiation-induced electron spin resonance centers were observed, one of which appears to anneal at the same temperature as the frequency shift due to ionizing radiation. Predictions of frequency shifts with accuracies of approximately 1 pp 107 can be made from measurements of a piece of a bar.