X-Ray Responsivities of Direct-Scintillator-Deposited Charge-Coupled Device

摘要

We report a new photon-counting detector for 0.1-100 keV X-rays. It consists of an X-ray charge-coupled device (CCD) and a scintillator. The scintillator is directly deposited on the backside of the X-ray CCD. Low energy X-rays below 10 keV can be directly detected by the CCD. The majority of hard X-rays above 10 keV passes through the CCD but can be absorbed in the scintillator, generating visible photons there. Since CCDs have moderate detection efficiency for visible light, visible light can be absorbed by the same CCD. We developed a method of direct deposition of CsI(Tl) forming a needlelike structure on the CCD and succeeded in fabricating the CsI(Tl) deposited CCD (SD-CCD). We investigated the spectral capabilities of our device with ~(109)Cd and ~(241)Am. We found that the lateral spread of visible light emitted from needlelike CsI(Tl) was so large that the pulse height of pixels was not significant compared with the noise level. We then operated the SD-CCD in the on-chip binning mode and investigated its spectral capabilities. The energy resolution of the SD-CCD was 52 ± 1% and 42 ± 2% at 22.1 and 59.5 keV, respectively.