The In/CdTe/Au p-n junction-diode X/γ-ray detectors, formed by frontside laser irradiation doping, were studied using IV characteristics, measured at different temperatures, and spectra of 241Am, 57Cs, and 137Cs isotopes, obtained in a wide bias range V = 60-380 V. A key feature of the technology was low-temperature ( ~90 ºC) vacuum annealing of polished in a Br-methanol solution detector-grade (111) oriented p-like CdTe crystals prior to the deposition of an In dopant film and formation of electrodes. After laser-induced doping of a layer near the In/CdTe interface and deposition of an Au electrode (ohmic contact), the In/CdTe/Au structures showed high rectification. The I-V measurements and calculations revealed that the dominant charge transport mechanism at low reverse bias was generation-recombination in the space charge region. It was noteworthy that the reverse current linearly increased at higher V ≥ 50 V when the depletion region extended over the entire crystal thickness. A sharp increase in I at higher V, that was inherent in diode structures (I ~ V n , n < 1), was not observed that evidenced a perfect ohmic contact, i.e. no injection of minority carriers from the Au/CdTe contact occurred. The detectors formed on the preliminary annealed CdTe crystals showed high energy resolution ((FWHM = 0.99 %@662keV at V = 300 V). Furthermore, high spectroscopic characteristics (detection efficiency, energy resolution, true energy position of the 662 keV peak) were observed (with a deviation < 20 %) at V =150-400V.
The electrical and spectroscopic properties of the CdTe-based p-n junction-diode X/γ-ray detectors have been studied by the measurements of I-V characteristics and emission spectra of 137Cs, 57Co, and 241Am radioisotopes. The In/CdTe/Au diodes were fabricated by the frontside laser irradiation doping technique. Detector-grade p-like CdTe(111) crystals, pre-coated with an In dopant (electrode) film, were irradiated with nanosecond KrF laser pulses in distilled water. Laser stimulated solid-phase doping was attributed to generation and propagation of stress and shock waves, barodiffusion of In dopant atoms into the thin CdTe surface region and thus, creation of high concentration donors. The second contact (quasi-ohmic) was formed on the opposite (Cd-terminated) crystal side by vacuum evaporation of Au. In addition, some diodes were created on CdTe crystals, which were preliminary annealed in vacuum prior to deposition of metal films. The I-V characteristics of the In/CdTe/Au p-n junction diodes evidenced that the reverse dark current in the initial part was described by the Sah-Noyce-Shockley theory. Creation of the favorable conditions for efficient collection of photogenerated charge carriers, decrease in the reverse dark current in the In/CdTe/Au detectors ensured obtaining the high-energy resolution spectra. Based on the electric field dependence of the 137Cs isotope spectrum, it was established that the applied bias V = 800 V was the optimal for the diodes formed on preliminary annealed CdTe crystals which ensured the energy resolution FWHM = 0.62 % at the 662 keV line
The paper deals with a problem of insufficient productivity of existing computer means for large image processing, which do not meet modern requirements posed by resource-intensive computing tasks of laser beam profiling. The research concentrated on one of the profiling problems, namely, real-time processing of spot images of the laser beam profile. Development of a theory of parallel-hierarchic transformation allowed to produce models for high-performance parallel-hierarchical processes, as well as algorithms and software for their implementation based on the GPU-oriented architecture using GPGPU technologies. The analyzed performance of suggested computerized tools for processing and classification of laser beam profile images allows to perform real-time processing of dynamic images of various sizes.
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