Development of a three-layer phoswich alpha–beta–gamma imaging detector

Abstract

a b s t r a c tFor radiation monitoring at the sites of such nuclear power plant accidents as Fukushima Daiichi, radiation detectors are needed not only for gamma photons but also for alpha and beta particles because some nuclear fission products emit beta particles and gamma photons and some nuclear fuels contain plutonium that emits alpha particles. In some applications, imaging detectors are required to detect the distribution of plutonium particles that emit alpha particles and radiocesium in foods that emits beta particles and gamma photons. To solve these requirements, we developed an imaging detector that can measure the distribution of alpha and beta particles as well as gamma photons. The imaging detector consists of three-layer scintillators optically coupled to each other and to a position sensitive photomultiplier tube (PSPMT). The first layer, which is made of a thin plastic scintillator (decay time: $ 5 ns), detects alpha particles. The second layer, which is made of a thin Gd 2 SiO 5 (GSO) scintillator with 1.5 mol% Ce (decay time: 35 ns), detects beta particles. The third layer made of a thin GSO scintillator with 0.4 mol% Ce (decay time: 70 ns) detects gamma photons. Using pulse shape discrimination, the images of these layers can be separated. The position information is calculated by the Anger principle from 8 Â 8 anode signals from the PSPMT. The images for the alpha and beta particles and the gamma photons are individually formed by the pulse shape discriminations for each layer. We detected alpha particle images in the first layer and beta particle images in the second layer. Gamma photon images were detected in the second and third layers. The spatial resolution for the alpha and beta particles was $ 1.25 mm FWHM and less than 2 mm FWHM for the gamma photons. We conclude that our developed alpha-beta-gamma imaging detector is promising for imaging applications not only for the environmental monitoring of radionuclides but also for medical and molecular imaging.

Mapping 238U decay chain equilibrium state in thin sections of geo-materials by digital autoradiography and microprobe analysis

“…The determination of the mobility and localization of 238 U, 235 U and 232 Th decay chains radionuclides is essential for various environmental issues such as actinide migration in subsurface geo-materials (soils, sediments etc), nuclear waste storage and related waste management and health issues (Morishita et al, 2014;Wertheim et al, 2010;Yamamoto and Ishibashi, 2015). Mine tailings generated by uranium extraction contain daughter elements of the 238 U disintegration chain.…”

A novel method for efficiently measuring the non-proportionality of scintillators between light output and alpha particle energies from 1.8 MeV to 5.2 MeV

“…As the alpha particle energy decreased, the light output per unit energy (MeV) decreased, as depicted in figure 9(b) to figure 12(b) and listed in table 3. Plastic scintillator, which is at times used for alpha particle detection and spectroscopy [23][24][25], exhibited the highest degree of non-proportionality. Lack of awareness regarding the non-proportionality of scintillators in relation to alpha particle energies could pose risks in terms of accuracy in alpha radionuclide determinations or energy estimation.…”

A beta-gamma position-sensitive detector based on rod plastic scintillators and artificial neural networks

“…Radiation monitoring in beta-gamma mixed radiation fields is important in different situations including nuclear accidents [1]- [3], radioxenon activity measurement for detecting forbidden nuclear tests [4]- [6], dosimetery purposes [7,8], radiation therapy [9]- [11], imaging applications [3,12], radionuclide spectroscopy [13]- [19] and astronomy [20].…”