Scintillators have been widely applied to the measurement of radiation since early times of nuclear and radiation research. This article overviews the recent technologies in radiation measurements and considers an effective use of scintillators. Prospects for a new scintillator are shown in terms of technological aspect of radiation measurements and applications.
New neutron scintillators have been required to be developed as one of the alternatives to ^3He neutron detectors, which have been standard neutron detectors and recently has supply shortage problem. In this paper, current status of thermal neutron scintillators is described and important and required properties for scintillators as ^3He alternatives are summarized. Additionally, some promising neutron scintillators for ^3He alternatives are reviewed.
Thallium bromide (TlBr) is a compound semiconductor attractive for fabrication of gamma-ray detectors. TlBr exhibits very high photon stopping power originating from its high atomic numbers (Ti: 81, Br: 35) and high density (7.56g/cm^3). Capacitive Frisch grid detectors and pixelated detectors were fabricated from TlBr crystals grown by the traveling molten zone method. The capacitive Frisch grid detectors exhibited an energy resolution of 1.7% FWHM for 662keV gamma-rays at -20℃. An energy resolution of 1.2% FWHM for 662keV was obtained from a pixelated anode of a TlBr detector operating at room temperature.
Crystal scintillators are widely utilized for recent X-ray and gamma-ray space observations onboard satellites or balloon observatories. In this paper, we describe the case of Polarized Gamma-ray Observer (PoGOLite), where Bismuth Germanate (BGO) and Lithium Calcium Aluminum Fluoride (LiCAF) are used together with plastic scintillators. The aim of the PoGOLite mission is to observe polarization from celestial sources in the energy band of 25-80 keV (hard X-rays), to study the magnetic field or scattering geometry around pulsars, accreting black-hole binaries, or active galactic nuclei. Compared with the hard X-ray source signal, the event rate of the background reaches 1000 times higher in the space and stratosphere, and it is very important to reduce/identify the background efficiently. The BGO crystal is an active shield to detect gamma-rays coming from outside the field of view or comic-ray particles. The LiCAF scintillator is used for the monitor of atmospheric neutrons.
Compact and high repetition-rate (>kHz) ultraviolet (UV) giant-pulse lasers are attractive for the next generation SNMS (laser post-ionized sputtered neutral mass spectrometry) imaging system. Toward palm-top size 266 nm UV compact laser, we developed a specially designed passively Q-switched Nd:YAG/Cr^<4+>:YAG microchip laser whose high output peak power of 13 MW enables an efficient wavelength conversion without using any optics before the nonlinear crystals. As a result, we obtain 650μJ, 4.3 MW peak power, 150ps, and 100Hz pulse output at 266nm. The benefit of sub-nanosecond giant pulse based efficient nonlinear interactions has been missed until our demonstration, so we call "Pulse Gap" in the giant-pulse lasers. Further investigations to increase the repetition-rate will be discussed. In this project we research and develop the giant-pulse lasers by using micro solid-state photonics, so to speak "Giant Micro-photonies".
Mechanoluminescence is the phenomenon of luminescence induced by a form of mechanical energy, such as compression, tension, torsion, friction, or mechanical shock. In the second half of 1990, we have revealed that certain materials showed a strong light emission repeatedly in small response to stress applied in elastic region, and then this phenomenon was named elasticoluminescence. The elasticoluminescence material provides an effective tool for a non-destructive inspection method, such as a visualization of internal fatigue crack of pressure vessel, a dynamical stress distribution of inside the structure, and so on. This article gives an outline of the developed elasticoluminescence materials, their luminescence properties, and the typical applications for innovative non-destructive inspection method.