Speaker
Description
We report on total ionizing dose effects on the X-ray SOI pixel sensor, XRPIX. The XRPIX has been developed as an imaging spectrometer for X-ray astronomical use in space. Front- and back-illuminated (FI and BI) devices were irradiated with hard X-rays from an X-ray tube operated at 30 kV with Molybdenum target. We found that the degradation rate of readout noise performance of the FI device is about three times faster than that of the BI device as a function of radiation dose to the devices. The degradation rates of both devices, however, are almost the same as a function of absorption dose of the buried oxide layer, Dbox. This fact demonstrates that the radiation tolerance of XRPIX devices is governed by Dbox and that the BI type has higher radiation tolerance in our use as a focal plane sensor of an X-ray mirror. The readout noise is stable up to about 1 krad of Dbox, increases by about 10% at 10 krad, and rises up for further irradiation. If we employ an X-ray mirror with a half-power diameter of 10 arcsec and a focal length of 10 m, 10 krad of Dbox, a reasonable threshold of radiation tolerance in this experiment, indicates that XRPIX has a lifetime of more than three years which is typically required as a space-borne sensor.
