Digital signal processing for CdTe photon-counting X-ray sensor

Abstract

Recently the practical X-ray measurement system is demanded energy distinction function with the high count rate and the high energy resolution used photon-counting X-ray sensor. Photon-counting CdTe semiconductor detectors have a high energy resolution in a low count rate at room temperature. However, the energy resolution is decreased by pile-up phenomenon in a high count rate. It is because that the photon counting sensor was used the signal-processing algorithm that the photon energy was estimated by integration of the output waveform from the CdTe detector. Moreover, the photon counting sensor is required to maintain the property of a high energy resolution even if the pile-up occurred. This paper purposes to maintain the high energy resolution by changing the signal-processing algorithm which derived the digital energy value from the pulse rise height of the output waveform generated the pile-up from the CdTe detector. As a result, the pulse rise time required to estimate the pulse rise size was shorter than 500ns. As the result of calculating energy spectrum by using this data, the FWHM of about 4keV (at 60keV) when the count rate of 3counts/60us in the pulse attenuation constant of 60μs was obtained (the pile-up is occurred in this condition). Furthermore, for confirmation of this signal processing in high count rate condition, we used white X-ray together with Am241 in order to measure energy spectrums in a high count rate. As a result of measurement energy spectrum in a high count rate, the FWHM was about 11keV (at 60keV) when the count rate of 500kcps.This result is indicated the possibility that the photon counting sensor has application for the high count rate imaging without decrease of the high energy resolution.