3D position sensing on UltraPeRL CdZnTe detectors
Experimental results of depth and lateral position sensing on UltraPeRL pixellated CdZnTe detectors using signal ratios are presented. Each detector employs one CdZnTe crystal of 20 mm times 20 mm times 5 mm with 8 times 8 pixel electrodes fabricated on the anode surface. The anode pixel pitch is 2.4 mm. The signal ratios are calculated using the signals induced on the collecting pixel and the eight neighboring pixels. The signal on each collecting pixel is then corrected for depth of interaction using the signal ratios. We obtained 7.6%, 4.2% and 2.5% FWHM energy resolution at 122 keV, 356 keV and 662 keV, respectively.
Charge-sensitive front-end electronics with operational amplifiers for CdZnTe detectors
Cadmium zinc telluride (CdZnTe, CZT) radiation detectors are suitable for a variety of applications, due to their high spatial resolution and spectroscopic energy performance at room temperature. However, state-of-the-art detector systems require high-performance readout electronics. Though an application-specific integrated circuit (ASIC) is an adequate solution for the readout, requirements of high dynamic range and high throughput are not available in any commercial circuit. Consequently, the present study develops the analog front-end electronics with operational amplifiers for an 8×8 pixelated CZT detector. For this purpose, we modeled an electrical equivalent circuit of the CZT detector with the associated charge-sensitive amplifier (CSA). Based on a detailed network analysis, the circuit design is completed by numerical values for various features such as ballistic deficit, charge-to-voltage gain, rise time, and noise level. A verification of the performance is carried out by synthetic detector signals and a pixel detector. The experimental results with the pixel detector assembly and a 22Na radioactive source emphasize the depth dependence of the measured energy. After pulse processing with depth correction based on the fit of the weighting potential, the energy resolution is 2.2% (FWHM) for the 511 keV photopeak.
Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing
Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.