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Radiation Detection and Measurement
Published in Alan Owens, Semiconductor Radiation Detectors, 2019
Detectors detect radiation by recording energy deposition in their active components. For most detectors, this energy deposition is in the form of ionization produced in the detection medium (which may be solid, liquid or gas) by charged particles. The choice of which detection medium to use depends to a large extent on what the detector will be used for. For example, in a tracking detector one wishes to detect the presence of a particle without affecting its trajectory, so the medium will be chosen to minimize energy loss and particle scattering (thus, low density). Conversely, if one wishes to measure the total energy deposition by calorimetry or spectroscopy, the absorber will be chosen to maximize energy loss, for example, by high density or high atomic number. Energy is then converted into an electrical signal, either directly or indirectly. In direct energy conversion, the incident radiation produces charge in the detector which is directly proportional to the energy absorbed and is collected by an electrode system. For example, in a gas counter the radiation ionizes the atoms/molecules of the gas and the resulting charge is collected by electrodes. Similarly, in a semiconductor detector, the ionization produced by the radiation will create electron-hole pairs that are swept towards the electrodes by an electric field. In indirect conversion, incident radiation excites atomic or molecular states that decay by the emission of light, as in the case of scintillation detectors. This light is then converted into an electrical signal using a photosensitive sensor, such as a photomultiplier tube.
Silicon Radiation Sensors
Published in Cinzia Da Vià, Gian-Franco Dalla Betta, Sherwood Parker, Radiation Sensors with Three-Dimensional Electrodes, 2019
Cinzia Da Vià, Gian-Franco Dalla Betta, Sherwood Parker
Simply put, a semiconductor can be described as a solid-state ionization chamber, with an operating principle that is similar to a gaseous detector. When traversing a semiconductor detector, an impinging particle releases energy that creates electron-hole pairs along its path; in the presence of an electric field, electrons and holes are separated and start drifting, inducing a signal on the electrodes. However, in comparison to the gaseous counterpart, radiation absorption is higher in semiconductors because their density is larger. Moreover, because the ionization energy is rather low (just 3.6 eV), semiconductor detectors are characterized by an excellent intrinsic energy resolution. Other important advantages of semiconductors are their fast time response, a linearity of performance over a wide range, good stability, low noise, and the possibility of adjusting the effective detection volume by changing the junction depletion bias voltage. (This topic will be explained in more detail shortly.) With respect to gaseous detectors, semiconductor ones can be fabricated with a wide variety of geometries, yielding an excellent spatial resolution and with a very compact size, although this latter characteristic can sometimes be a limitation for some applications.
Application Specific Integrated Circuits for Direct X-Ray and Gamma-Ray Conversion in Security Applications
Published in Choi Jung Han, Iniewski Krzysztof, High-Speed and Lower Power Technologies, 2018
Krzysztof Iniewski, Chris Siu, Adam Grosser
When a photon is absorbed within the semiconductor detector, electron-hole pairs are usually generated over an extremely small volume and then drift in opposite directions in an externally applied electric field or bias. These moving charges, particularly the electrons, are sensed by a small electrode, which provides not only the energy of the absorbed photon, but also the position of the interaction site.
A Fluorous Phosphate for the Effective Extraction of LnIII from Nitrate Media: Comparison with A Conventional Organic Phosphate
Published in Solvent Extraction and Ion Exchange, 2021
Yuki Ueda, Kei Kikuchi, Kohei Tokunaga, Tsuyoshi Sugita, Noboru Aoyagi, Kazuya Tanaka, Hiroyuki Okamura
Europium L3-edge EXAFS spectra were collected at beamline BL-12C at Photon Factory, KEK (Tsukuba, Japan), with a Si(111) double-crystal monochromator and two mirrors. The energy was calibrated by assigning the first peak maxima of a Eu(NO3)3 pellet, a value of 6.980 keV. The EXAFS spectra of the reference compounds were collected in transmission mode. In contrast, the experimental samples were measured in fluorescence mode using a 19-element germanium semiconductor detector placed at 90° relative to the incident beam. In fluorescence mode, the samples were positioned at 45° to the incident beam. Multiple scans were performed to verify any radiation damage-induced changes to the oxidation state of Eu in the samples; no appreciable change was observed in every spectrum obtained. The measurements were carried out at room temperature.
Basic consideration of a nuclear power monitoring system using neutron-induced prompt gamma rays
Published in Journal of Nuclear Science and Technology, 2020
Koichi Okada, Atsushi Fushimi, Shun Sekimoto, Tsutomu Ohtsuki
The peak appearing in an energy spectrum may be buried among Compton scattering components of higher energy gamma rays. The peak Compton ratio depends on the gamma-ray energy, the kind of detector and detector size. For example, the peak Compton ratio of a high-purity germanium semiconductor detector (HPGe) with a relative efficiency of 10% to 160% for gamma rays below 10 MeV is 40:1 to 110:1 for each energy [15]. Thus, we surveyed gamma rays which have an intensity exceeding 1/10, which included margins, of the total intensity of higher energy gamma rays from the same metal. The gamma ray peaks meeting this condition (condition b) are able to be detected without being buried in Compton scattering released by the same metal. We determined that the lower limit energy of the monitoring gamma rays was 6 MeV. Thus, the number of gamma rays with energy more than 6 MeV emitted by any one metal was limited to 10 (condition c) in order to identify the gamma ray peaks because too many gamma-ray emissions make identification of the gamma rays derived from other metals difficult. For the case to use the escape peaks for identification of the gamma rays, the number of gamma rays with energy of more than 5 MeV emitted by any one metal was limited to 15 (condition d). In fact, for the prompt gamma rays, energies less than 6 MeV are dominant.
A review of efforts for volume reduction of contaminated soil in the ten years after the accident at the Fukushima Daiichi Nuclear Power Plant
Published in Journal of Nuclear Science and Technology, 2022
Shinya Yamasaki, Satoshi Utsunomiya
Funakawa et al. also conducted a size separation experiment on soil (9,200–12,500 Bq kg−1) collected from the Fukushima Prefecture (Date City, Fukushima City, and Minami-Souma City) [49]. The samples were collected using a 9.5 mm sieve to remove large particles and plants. Soil (10 kg) of water (10 kg) were then placed in a container and then stirred for primary washing at 40 rpm for 1 min to produce a slurry. The floating plants were removed from the slurry using a 500 µm-mesh stainless steel sieve. The suspension was then separated into primary washed soil and wash water via wet classification at the point corresponding to 75 µm. The washed soil was further placed in an agitator for secondary treatment with water, Cs adsorbent (zeolite), and iron balls at 40 rpm for 1 min. Water was then added to the slurry, and the slurry was separated using a 75 µm mesh sieve to produce secondary washed soil and secondary effluent samples. The secondary washed soil was separated into five fractions via stainless steel sieves. The radioactivity of each fraction was measured by gamma-ray spectrometry using a germanium semiconductor detector. The Cs activity per unit mass in the secondary washed soil was reduced to 1,100–3,300 Bq kg−1. The Cs removal rate by the separation was 73%–90%, and no significant difference was observed among the soil samples. The Cs activity per unit mass increased with the decrease in particle size. The Cs activity per unit mass of clay and silt fractions was 2.8–7.9 times higher than that of the fraction (75–125 µm). For soils with a 30% clay and silt fraction, more than 50 wt% of the soil can be reduced via size separation.