Some aspects involving the use of CdTe for finding end-point energies in diagnostic radiology

We have considered the use of CdTe detectors and commercially available spectroscopy systems for the determination of the end-point energies of diagnostic X-ray devices. A simple technique based upon filtered spectra and simple fitting procedures was used to deduce end-point energies. We observed some unexpected detector-related effects such as significant shifts in the energy calibration at high count rates. When CdTe detectors operate at high counting rates drifts in the DC level, associated with collection rates of the positive charge (holes) can yield a corresponding shift in the spectrum towards lower energies. Only for relatively low counting rates and long detection periods, in excess of 10 min, can end-point energies be obtained with CdTe that reach levels of precision found in recent protocols. High rates also decrease energy resolution and lower the accuracy of recalibrations using characteristic X-rays from the target.