W. Li et al., A modeling method to calibrate the interaction depth in 3-D position sensitive CdZnTe gamma-ray spectrometers, IEEE NUCL S, 47(3), 2000, pp. 890-894
The gamma ray interaction depth in 3-D position sensitive CdZnTe detectors
is currently determined by the pulse height ratio of the cathode signal to
the anode pixel signal (C/A ratio). In experiments with our 3-D CdZnTe dete
ctors, the photopeak area as a function of the CIA ratio deviates from the
expected exponential attenuation with depth. This indicates that the C/A ra
tio is not proportional to the true interaction depth. This paper proposes
a method to calibrate the measured C/A ratio to the interaction depth by mo
deling the signals from the cathode and anode pixels. Knowing the detector'
s mobility-lifetime products of the electrons and holes from measurements,
the expected pulse heights of the signals from the cathode and anode pixels
can be calculated for different interaction depths. The relationship betwe
en the C/A ratios and the interaction depths can then be determined and use
d as the calibration. The calculation for our 3-D CdZnTe detectors shows th
at an 8% error in depth determination is incurred without the calibration.