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Two pad sensors of high-flux CdZnTe grown by Redlen Technologies with different anode metallization (platinum and titanium-gold) were characterized under direct X-ray beam in P07 beamline at Petra III, during 40-bunch mode operation. A Transient Current Technique (TCT) readout setup from the University of Hamburg [1] was used, with a homemade Bias-T, a Femto 40 dB 2GHz amplifier and a Tektronix MSO 4104 5GS/s oscilloscope. The transient signal was collected per bunch, using the revolution bunch clock from the storage ring as a trigger. It was possible to observe the transient current signals for each bunch, as illustrated in Figure 1.
The 87 keV beam was defined by slits to 100x100 µm, and the area of the pad sensors was scanned with 200 µm steps for four different attenuations of the beam, with estimated fluxes of 3e+08 photons/second to 1e+09 photons/second. The results show that the full charge was collected by the sensors before 50 ns in most positions. The sensors’ areas show a homogeneous charge collection efficiency. In regions associated with defect vicinities, a longer charge collection time up to 180 ns was observed, indicating delayed charge transport; some regions indicated also an excess of charge (as shown in Figure 2), which can be associated with Excess Leakage Current effects [2]. The different observed pulse shapes further indicate differences in the internal electric field of the sensors, provoked by the different anode electrodes.
[1] J. Becker, PhD thesis, Universität Hamburg (2010).
[2] B.D. Cline et al., JINST 20 (2025), P10021