Pulsed Bias Voltage Shutdown to Suppress the Polarization Effect for a CdTe Radiation Detector

Pulsed bias shutdown operation, in which the bias voltage supply is periodically shut down for a certain time, is suitable for suppressing the polarization effect in a CdTe radiation detector. The duration of the bias voltage shutdown should be short to decrease the dead time and ensure the continuity of the measurement; however, the polarization effect may not be suppressed if the duration is too short. Therefore, we investigated bias voltage shutdown durations and intervals that stabilize the detector performance. A stacked type detector consisting of four 1-mm-thick CdTe diodes was used. At 35degC, the energy resolution for the 511 keV photopeak of the ²² Na source saturates at around 30 min after the measurement start and then does not change up to 300 min when the bias voltage is shut down for 10 ms every 5 min. Similarly at 60^degC, the energy resolution for the 511 keV photopeak is unchanged for 300 min when the bias voltage is shut down for 10 ms every 10 s.