Yoneichi Hosono

Fast neutron detector using PIN-type silicon photodiode

Abstract A new fast neutron detector has been developed using a PIN-type windowless photodiode with a polyethylene radiator of 45 μm thickness and a low noise charge sensitive preamplifier for the photodiode. The detection efficiency was 7.8 × 10−5 for fast neutrons and the detector was sensitive to neutrons with an energy higher than 1.2 MeV. Additionally the thickness of the depletion layer in the photodiode can be estimated using the saturated range of recoil proton pulses. A charge sensitive preamplifier with lower noise is described for the photodiode radiation detection systems. The input stage of this preamplifier consists of four FETs. The equivalent noise charge was obtained as 1.1 × 10−16 C (FWHM) when connected to the photodiode. It can be concluded that this new system can be successfully used as a simple fast neutron detector.

Radiation distribution sensor with optical fibers for high radiation fields

Radiation distribution sensors with their feasibilities have been described in earlier works. However, due to large radiation induced transmission losses in optical fibers, especially in the visible wavelength region, it has been difficult to apply these techniques to high radiation fields. In this study, we proposed a new concept of optical fiber based radiation distribution measurements with near infrared (IR) emission. Near IR scintillators were attached to the ends of optical fibers, where the fibers were bundled and connected to an N-MOS line sensor or a cooled CCD camera. From the measurements of each area density, the radiation levels at the positions of the scintillators can be known. The linearity between the gamma dose rate at each scintillator and the registered counts has been examined. For correcting the radiation induced loss effects, we applied the Optical Time Domain Reflectometry technique to measure the loss distribution and from the results, a possibility for correction of the loss effe...

Multi-Faraday-cup-type beam profile monitoring system for a dual-beam irradiation facility

Abstract A multi-Faraday-cup-type ion beam profile monitor (BPM) with simplified readout circuit for use in dual-beam irradiation experiments is described.

Spatial Distribution Measurement of Ions Surrounding an Alpha Source using a New Micro-ionization Chamber

Recently, a new alpha radioactivity measurement technique was proposed, which directly measures ions surrounding alpha radioactivity. In order to implement this technique, a better understanding of ions behavior is required. We have developed a micro-ionization chamber with multi-channel charge-integrating ASICs (Application Specific Integrated Circuit). In this study, we will introduce the design of the micro-ionization chamber and show first results from ion measurements using an 241 Am alpha source. When we increase the electric field, the spatial distribution of ions exhibited two different components. Simulation calculations were also performed to account for these components.

Development of Proton Detection System with Thin Ruby Scintillator Insensitive to Neutrons and Gamma Rays for Neutron Lifetime Measurement

A proton detector for lifetime measurement of neutrons using a thin ruby scintillator which can be used under an environment of neutrons and γ-rays has been developed. The detector is almost insensitive to neutrons and γ-rays. This was confirmed by setting the detector adjacent to the ultra-cold neutron (UCN) facility installed in Kyoto University Reactor. When a single proton was injected into the scintillator, many scintillation signals were observed. The number of scintillation signals decreases with decreasing proton energy. Although the output signals generated by the scintillation and by the dark currents of a photomultiplier have approximately the same pulse heights, the proton can be detected by counting the signals within the time width corresponding to the decay time of scintillation. This neutron lifetime measurement system can be applied to the detection of particles other than protons.

Bunch-Shape Monitor for a Picosecond Single-Bunch Beam of a 35 MeV Electron Linear Accelerator

A non-interactive-type bunch-shape and beam intensity monitor for a 35 MeV electron linear accelerator (linac) has been developed. The monitor consists of an electric SMA-type connector and an Al pipe of 50 mm inner diameter. Test measurements of the present monitor have been made under the conditions of the accelerated charges of lower than 27 nC/pulse and the pulse width ranging from 6 to 30 ps (Full Width at Half Maximum). The results show that the present monitor is applicable to bunch-shape measurement of the picosecond single-bunch beam. The monitor output is also found to be proportional to the beam intensity of more than 0.05 nC/pulse.

Experiment on Deflection of High-Speed Plastic Pellets Using Curved Guide Tubes

High-speed plastic pellets for plasma diagnostics have been transported using guide tubes curved at 90°. The ratio of the output velocity to the input one has depended on the roughness of the inner surface of the curved tube, but not on the curvature of the tube. The pellets are transported through the curved guide tube without being broken and without a significant reduction in speed. The output velocities required for plasma diagnostics have been obtained. The experimental results show that the pellets do not pass through the curved tube by means of sliding, but via repeated reflections.

Radiation distribution measurements with optical fibers in high radiation fields

Radiation distribution sensors with their feasibilities have been described in earlier works. However, due to large radiation induced transmission losses in optical fibers, especially in the visible wavelength region, it has been difficult to apply these techniques to high radiation fields. In this study, we proposed a new concept of optical fiber based radiation distribution measurements with near infrared (IR) emission. Near IR scintillators were attached to the ends of optical fibers, where the fibers were bundled and connected to a N-MOS line sensor or a cooled CCD camera. From the measurements of each area density, the radiation levels at the positions of the scintillators can be known. The linearity between the gamma dose rate at each scintillator and the registered counts has been examined. In case of continuous monitoring in high radiation fields, radiation induced losses affect the measurements. We applied the Optical Time Domain Reflectometry technique to measure the loss distribution and from the results, a possibility for correction of the loss effect has been demonstrated. The applicable dose rate range was evaluated to be from 0.1 Gy/h to 10/sup 3/ Gy/h. This system can be a promising tool as a flexible dose rate distribution monitor in radiation facilities like nuclear plants and accelerator facilities.

Characteristics of 16-Channel ASIC Preamplifier Board for Microstrip Gas Chamber and Animal PET

A 16-channel ASIC preamplifier board has been designed for microstrip gas chamber (MSGC) and animal position emission tomography (PET) detectors. The highly integrated ASIC chips can be used for individual readouts from a large number of channels to improve the spatial resolution and counting rate. The preamplifier board was tested to have a low optimum equivalent noise charge (ENC) of ~ 1400 e− FWHM at a shaping time of 0.1 μs. The output voltage to input charge gain is 0.96 V/pC, and the nonlinearity is ~ 2:0% over a range of −500 fC to 1000 fC in input charge. The rise time (10%–90%) with no input capacitor is about 54 ns. The power consumption of this preamplifier board is ~ 100 mW. The preamplifier board has been used to read out a 3 × 3 cm MSGC plate and an optimum FWHM energy resolution of 19.1% (5.9 keV peak of Fe-55) was obtained.

A small-volume and low-background digital anticoincidence beta counting system for C-14 dating using a gas counter combined with tiled CdTe wall detectors

A low-background anticoincidence beta counting system was developed by combining an internal gas proportional counter with CdTe detectors to decrease the volume of the anticoincidence gas counter. According to performances of CdTe detectors, digital signal processing was incorporated and a small-volume and low-background digital anticoincidence beta counting system was developed for C-14 dating.