The use of diamond as material for X-ray detector is subject of investigation and practice in radiotherapy, space and material science and technology. This paper presents the results of application of Monte Carlo method for simulation of photon transport through diamond detector. The aim is restitution and demonstrating of numerical technique for characterization of electrical properties for different detector conditions and configurations. Monte Carlo code was adopted to determine the energy deposited and dose distribution in the structure of diamond detector. Our results show that the use of numerical simulations may be of essential help in design of diamond detector systems.
Tracking detectors to be used in the future high-luminosity particle physics experiments have to be simultaneously radiation hard and cost efficient. Magnetic Czochralski silicon wafers can be grown with sufficiently high resistivity (several kΩ cm) and well-controlled high oxygen concentration. Significant research and development activity aiming to develop particle detectors made of high resistivity magnetic Czochralski silicon has been ongoing during the past decade. Beam test results presented in this paper show that n-type magnetic Czochralski silicon strip detectors can be operated with acceptable signal-to-noise ratio at least up to a 1 MeV neutron equivalent (n_{eq}) fluence of 1×10^{15} cm^{-2}. The improved radiation hardness, compared to more commonly used float zone silicon, can be explained by the more beneficial electric field distribution inside the detector bulk. We have demonstrated a S/N of >10 for full-size strip detectors attached to readout electronics at a fluence of 1×10^{15} n_{eq}/cm^2. These findings are supporting our transient current technique measurements.
A prototype 64-channel detector module, comprising a silicon strip detector with strip pitch of 100μm and 64-channel ASIC RX64, was tested with the X-Pert Philips MPD diffractometer. Basic parameters of the detector module, energy resolution, and detection efficiency, were evaluated as a function of the counting rate. Energy resolution of 1.1 keV FWHM for photon rate up to 1×10^7 photon/s per 1 cm of the active width of the detector was demonstrated. The prototype detector, when applied in a diffractometer utilizing Bragg-Brentano focusing principle, allows to increase the counting rate by about 2 orders of magnitude with respect to a single counter. Exemplary diffraction patterns of polycrystalline samples of Si and SiO_2 (quartz peak cluster) are presented.
PbWO₄ crystal-Hamamatsu S8148 avalanche photodiode (APD) assembly has been used in the barrel section of the CMS electromagnetic calorimeter. The shot noise of the photodiode is one of the important parameters for the energy resolution of the crystal-APD system. The major source of this noise is the statistical variations in the rate at which primary charge carriers are generated and recombine. Thus, the shot noise varies with position of the primary charge carriers generated in photodiode. In this work, the shot noise properties of the Hamamatsu S8148 APD structure and zinc sulfide-silicon (ZnS-Si) isotype heterojunction APD structure have been compared for the PbWO₄ photons. Calculations were made with a Single Particle Monte Carlo simulation technique.
Axial PET is a novel PET concept based on axially oriented crystals. The axial orientation of the scintillating elements mitigates the uncertainty in the determination of the depth of interaction and provides a scalable and flexible design than can be adapted to different imaging scenarios. Two Axial PET modules have been fully assembled and characterized at CERN with both point-like and extended sources. The capability of Axial PET to break the trade-off between sensitivity and spatial resolution was successfully demonstrated.
Lead iodide has been recognized as a promising material for room temperature radiation detectors. It has a wide band-gap (∼ 2.3 eV), high atomic numbers (82, 53) and it is environmentally very stable compared to mercuric iodide. Electrical and optical properties of lead iodide grown crystals purified under the influence of selected rare earth elements have been investigated. Photo-luminescence and capacitance-voltage measurements have been performed using different rare earth elements.
Biological applications of ion beams have recently become a new important research field using single ion hit facilities to study individual living cells and their response to the hit of a counted number of ions. One motivation is the search for a better understanding of the fundamental processes taking place in cells and organs as a result of irradiation. Another comes from the increasing interest in using high energy protons and heavy ions as a modality for radiotherapy of deep seated tumours. In the view of treatment efficiency, study of cell culture behaviour under controlled radiation experiments, and in different chemical environments at single ion hit facilities, is a first step towards a better understanding of the processes. Tomographic techniques are applicable to situations where you need information of the inside of an object but do not want to section it into thin slices or cannot do it. Using focused MeV ion beams for tomography restricts the sample size to the order of 10-100 μm, depending of the initial energy. On the other hand, the ability to focus at a sub-micrometer level makes ion beams well suited for analyses of small sized objects as cells, spores, etc. The scanning transmission ion microscopy mode of tomography gives the mass density and corresponding morphological structure of holes and pores. It can then be used to correct the results from the other mode, particle induced X-ray emission tomography. Here is discussed a porosity analysis of bentonite clay that is planned to form an important buffer zone around canisters filled with spent nuclear reactor fuel waste deposited 500 m underground in Sweden.
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