Temperature dependence of radiation damage and its annealing in silicon detectors

Silicon detectors at future collider facilities such as the Superconducting Super Collider (SSC) will be exposed to large fluences of both neutral and charged particles, resulting in considerable bulk radiation damage. In order to reduce the increase in leakage current associated with that damage, the proposed operating temperature of the silicon detectors in the SSC Solenoidal Detector Collaboration (SDC) experiment is 0 degrees C. In order to explore any potential complications of operating detectors at 0 degrees C, two sets of detectors were irradiated. One set was kept close to 0 degrees C during the exposure and annealing period, while the other was maintained at room temperature throughout ( approximately 27 degrees C during the exposure, and approximately 23 degrees C during the annealing period). The full depletion voltage and leakage current of the detectors during the irradiation period and over the subsequent annealing period were monitored. It is concluded that detectors will have to be operated at 0 degrees C, and, once damaged, be maintained at 0 degrees C in order to keep their operating voltage at a reasonable value (<<160 V). Turning off the bias voltage when the detectors are not in use seems to provide an extra margin of safety.<
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