TCAD simulation studies of novel geometries for CZT ring-drift detectors

In this work, technology computer-aided design (TCAD) simulation results of new CZT ring-drift detector geometries are presented. The physics model was developed and validated against the results from an existing device which had been comprehensively characterised at x-ray wavelengths. The model was then applied to new detector geometries and a systematic study of the parameters influencing charge collection performed. A comparison between one- two- and three-ring circle and semi-rectangular (or squircle) geometries is presented. In was found that charge collection with the squircle ring configuration was systematically better than the circular configuration and extends approximately m further from the collecting anode. In addition, a two-ring geometry device is shown to collect charge m and m further from the anode when compared to one- and three- ring geometries, respectively. Based on these results, we derive an optimum configuration which potentially can be multiplied on larger crystals, offering an increased charge collection volume without compromising energy resolution

Vibration characteristics of miniature stirling electric coolers

We present the investigation results of vibration characteristics of miniature stirling electric coolers, which can be used for compact HPGe spectrometers for space applications. Comparative assessment between three Stirling cycle coolers – two Ricor model K508 coolers and one Thales model RM3 cooler were done. In spite of the limited number of the coolers tested, the following conclusions can be made, that there are significant differences in the vibration characteristics between the various types of coolers and between coolers of the same type. To categorize the vibration characteristics of the coolers we carried out our tests by different methods in certified Vibroacoustic laboratory and BSI laboratory. The results obtained in our laboratory follow the same trends and give the same ranking as the test results obtained in the Vibroacoustic laboratory

TCAD simulations of internal amplification in high purity germanium detectors

Simulations of internal amplification processes in high purity germanium (HPGe) detectors for gamma radiation are presented. The Synopsys Sentaurus Technology Computer-Aided Design (TCAD) package was employed to study conditions favourable to charge multiplication within volume of the detector. The physics model was developed, and validated where possible against known results from existing literature. The model was then applied to a new detector and a systematic study of the measurable parameters influencing charge collection and electric field profile was performed. Evidence of the internal amplification in the developed HPGe detector model was demonstrated at 4 kV bias voltage with anode diameter below 100 μm, corresponding to 16 kV/cm electric field and when an additional dopant with concentrations >5×1010cm−3 under the anode implanted. These effects were also simulated and observed in silicon detectors, giving additional confidence in the validity of the findings for germanium, presented in this work

Long-Lasting Current Transient Phenomena in TlBr

The persistent conductivity effects in TlBr were evidenced at the temperatures below about 200 K after the intrinsic light excitation. They were associated with the filling of the trapping states having thermal activation energy of about 0.08-0.12 eV and accompanied by the appearance of the pronounced maximum of the thermally stimulated currents. In this state the enhanced photoconductivity was observed that could be thermally quenched above about 180 K. The quenching is initiated by the emptying of the trapping states having activation energy of 0.63-0.65 eV

Characterisation of the natural gamma-ray background in the underground Callio Lab facility

Abstract Herein, we measured the natural gamma-ray background in a new underground laboratory facility within Pyhäsalmi Mine in Finland at a depth of 1430 m (~4100 m.w.e). The radionuclide compositions of the rocks in the walls along with the shotcrete on the walls were investigated. The specific activities of the natural radionuclides in these materials were calculated. The measured spectra of the natural gamma-ray background and calculated minimal detected activities of several natural and artificial radionuclides are presented