CR-39 plastic track detectors have been used to detect energetic charged particles because of its high sensitivity. Recently an atomic force microscope has been applied to visualize very small etch pits on CR-39, so that we can determine the incident position of energetic charged particles at high resolution of < 100 nm. Using this technique, we have developed a new method of high-resolution alpha-autoradiography for the measurements of boron-compound distribution at subcellular scale in boron neutron capture therapy (BNCT). Tumor cells injected by boron-compound were mounted on a CR-39, and irradiated by thermal neutrons and soft X-rays. After etching process in NaOH solution, alpha tracks and transmission X-ray image of the cells as relief on the surface of the CR-39 were observed simultaneously with an AFM. The imaging resolution was about 100 nm. This technique will provide the information on drug delivery of the boron compounds, microdosimetry in BNCT and so on.

  Selective operation of laser doping process and laser ablation process using KrF excimer laser irradiation (wavelength 248nm, pulse duration 20ns) was carried out that is used for fabricating an integrated gamma-ray imaging detector. At high vacuumed condition, laser irradiated surface region is heated up to ablated. At high-pressure condition, ablation is suppressed and impurity on the surface was melt and diffuse into the CdTe substrate.

  We have fabricated an integrated imaging detector using above combination process. The detector showed low leakage current at room temperature and good gamma-ray detection property.

  Cesium bromide is chased as a new photostimulable phosphor material because the atomic number of CsBr is almost the same as that of BaFBr phosphor which is a commercially available phosphor as an imaging plate used for medical diagnoses. The Photostimulated luminescence (PSL) characteristic were studied for new photostimulable CsBr phosphor ceramics doped with luminescent center such as Eu, Sm, Tb, Ce, Gd, Nd, and In. Intense PSL peak at about 450 nm was observed, for the first time, in X-ray irradiated CsBr:Eu phosphor ceramics. The peak wavelength of stimulation spectrum for CsBr:Eu phosphor ceramics was to be about 690 nm. The preparation conditions such as sintering temperature, doping concentration of luminescent center and sintering time for CsBr:Eu phosphor ceramics were optimized. The optical characteristics of CsBr:Eu such as optical absorption spectra, PL emission and its excitation spectra and fading characteristic were determined.

  Thallium bromide chloride (TlBrxCl1-x) has grown mixed crystal of thallium bromide (TlBr) and thallium chloride (TlCl). In this study, TlBrxCl1-x crystals have been grown by the traveling molten zone (TMZ) method from purified materials. Radiation detectors have been fabricated from the grown TlBrxCl1-x crystals and the detector performance has been characterized.

  A multi-grid-type microstrip gas chamber (M-MSGC) is being developed for the new spallation neutron source in Japan. The objective of this study is to develop a new position readout electronics for two-dimensional M-MSGC, which can reduce the number of interconnections through a high-pressured gas vessel by using a new encoding readout scheme based on ASIC technology. In order to test an ASIC based individual readout method, an ASIC chip, which has typically 16 individual input channels, has been designed and fabricated using a ROHM 0.35μm CMOS process and the chip was connected to a developed encoding circuit. The main results of the performance test indicated that the front-end electronics was able to encode 1500 pixels of the input position with 4.4% of position non-linearity. The results of this work confirm that the developed circuit is appropriate for the front-end electronics of two-dimensional M-MSGC.

  We are developing x-ray microcalorimeters using transition edge sensors of iridium/gold (Ir/Au-TES) for high resolution x-ray spectroscopy. TES microcalorimeters can achieve faster response than conventional microcalorimeters by keeping the operating point of TES in the transition region through the use of strong negative electrothermal feedback (ETF). At present, the energy resolution of 9.4 eV (FWHM) was achieved for a 5899 eV Mn K_al line. At a synchrotron X-ray radiation facility, we demonstrated microscopic signal response profile of the device and high-resolution X-ray fluorescence spectroscopy using a small amount of sample.

  As a promising technique for fast neutron imaging with a large sensitive area and high spatial resolution, we propose an organic liquid scintillator system combined with wavelength shifting fiber read-outs. We have made a prototype detector and preliminary experiments measuring the detector response to charged particle (muon) beams and fast neutron beams. Through these experiments, we have verified the detection principle and also confirmed a possibility of pulse shape discrimination between neutron and gamma-ray signals.

  A sputtered neutrals mass spectrometry (SNMS) system with a pulsed laser was developed to analyze neutral-molecules sputtered by ion beam for organic substance surface. The Laser-SNMS is a time-of-flight secondary ion mass spectrometer using 100kV ion irradiation system and Q-sw Nd:YAG laser. Preliminary experiments for phenol resin [-C₆H₄OHCH₂-]_n were performed with the Laser-SNMS system.

  The dark matter (DM) problem is one of the most important subjects in astrophysics and particle physics. The candidate of DM is WIMPs (Weekly Interacting Massive Particles). Our aim is to detect WIMPs with high purity NaI(Tl) scintillator.

In this work, the high purity NaI(Tl) scintillator was developed and measured with this scintillator in low background environment. Sensitivity of this scintillator for DM was reported.

  In a nuclear reactor plant, the neutron monitoring is indispensable in order to find an unusual neutron event which may be the signal of an accident or a damage of the reactor. In this work, the possibility of a neutron monitor by means of an inorganic scintillator was researched. The detection efficiency of NaI(Tl) scintillator and its sensitivity for neutrons have been studied.

  Current scintillating optical fibers for radiation measurement have drawbacks as high intrinsic and radiation-induced loss. In order to overcome these problems, a new optical fiber sensor for multi-point radiation measurements has been proposed with sensing regions in its cladding and in the area outside of the core. A part of the scintillation photons is trapped inside the fiber core and is transmitted to the end. The time of flight technique has been applied to the arrival time difference of the photons which are transmitted to each fiber end. Discrete radiation measurements were possible with a time resolution of 3nsec. Linearity of the measured counts has been demonstrated in a dose rate ranging between 4.2μSv and 44μSv.