Yoshihide Honda

Calibration of imaging plate for high energy electron spectrometer

A high energy electron spectrometer has been designed and tested using imaging plate (IP). The measurable energy range extends from 1to100MeV or even higher. The IP response in this energy range is calibrated using electrons from L-band and S-band LINAC accelerator at energies 11.5, 30, and 100MeV. The calibration has been extended to 0.2MeV using an existing data and Monte Carlo simulation Electron Gamma Shower code. The calibration results cover the energy from 0.2to100MeV and show almost a constant sensitivity for electrons over 1MeV energy. The temperature fading of the IP shows a 40% reduction after 80min of the data taken at 22.5°C. Since the fading is not significant after this time we set the waiting time to be 80min. The oblique incidence effect has been studied to show that there is a 1∕cosθ relation when the incidence angle is θ.

Dose-rate effects on the bulk etch-rate of CR-39 track detector exposed to low-let radiations

Abstract The effect of gamma-rays and pulsed electrons has been investigated on the bulk etch rate of CR-39 detector at doses up to 100 kGy under various dose-rate between 0.0044 and 35.0 Gy/s. The bulk etch rate increased exponentially with the dose at every examined dose-rates. It was reveled to be strongly depend on the dose-rate: the bulk etch rate was decreased with increasing dose-rate at the same total dose. A primitive model was proposed to explain the dose-rate effect in which oxygen dissolved was assumed to dominate the damage formation process.

Application of the positron annihilation method for evaluation of organic materials for cryogenic use

Abstract The positron annihilation method was used to evaluate the unoccupied spaces in epoxies with the aim of molecular design of epoxies for cryogenic use. The fracture toughness of commercially available epoxies was measured and compared with the lifetime τ 3 . Evaluation by positron annihilation enabled the epoxies to be classified into two types: (1) those whose fracture toughness increases with free volume, and (2) those that do not change much with increasing free volume. The former type was understood to have systems with disordered networks, the latter, to have different crosslinking densities. The discussion suggests that the latter system is preferable for cryogenic use; it was confirmed experimentally.

Interlaboratory comparison of positron annihilation lifetime measurements for synthetic fused silica and polycarbonate

Interlaboratory comparison of positron annihilation lifetime measurements using synthetic fused silica and polycarbonate was conducted with the participation of 12 laboratories. By regulating procedures for the measurement and data analysis the uncertainties of the positron lifetimes obtained at different laboratories were significantly reduced in comparison with those reported in the past.

Effects of low-LET radiations on CR-39 track detector

Abstract The effects of Co-60 gamma-rays and about 25-MeV pulsed electrons have been investigated on CR-39 plastic nuclear track detector. The bulk etch rate was measured as a function of the absorbed dose under three different irradiation conditions; gamma-ray exposure in air at the dose rate of 6 kGy/h, that in vacuum and electron shower in air at 126 kGy/h on average. It was found that the bulk etch rate ( V ) increased nearly exponentially with the dose ( D ); V = V 0 exp( kD ), and the characteristic parameter ( k ) was 35, 9 and 12 MGy −1 , respectively. It is considered that a lack of oxygen in damage formation processes could occur momentarily during a short electron pulse, just similarly to the vacuum effect of reduction in track etch rates in outgassed CR-39 plastic.

Self-amplified spontaneous emission at wavelengths of 20 and 40 μm from single-bunch electron beams

Abstract The high-brightness single-bunch electron beams of a 38-MeV L-band linac have been used for free-electron laser amplifier experiments to investigate self-amplified spontaneous emission at wavelengths of 20 and 40 μm. At a charge of electrons in a bunch of 28 nC and a pulse length of about 30 ps the intensities of radiation measured have been 5 and 100 times those of the incoherent spontaneous emission estimated at wavelengths of 20 and 40 μm, respectively. The characteristics of the radiation are discussed for developing intense pulsed light-sources.

Interlaboratory Comparison of Positron Annihilation Lifetime Measurements

An interlaboratory comparison for positron annihilation lifetime (PAL) measurements for pure nickel and fused silica was performed. Based on the reported positron (for nickel) and positronium (for fused silica) lifetimes, the uncertainties in the PAL measurements were estimated.

Single-bunch and multibunch electron beam generation for FEL experiments with the 38 MeV L-band linear accelerator at ISIR

Abstract The generation of multibunch electron beams used for FEL oscillation experiments with the 38 MeV L-band linear accelerator at The Institute of Scientific and Industrial Research has been studied. Originally, the components of the accelerator system have been optimized for generating a high-brightness single-bunch beam. The operational conditions of the system have been investigated for a multibunch beam. A multibunch beam with a macropulse length of 4 μs has been accelerated at energies of 17 to 19 MeV. The latter part of the pulsed beam with a length of 1.8 μs has an energy spread of 1.8%. The charge per bunch is 2 nC. The beam of this part has been successfully used for oscillation experiments at a wavelength of 32 to 40 μm.

Evaluation of Epoxy Resin by Positron Annihilation for Cryogenic Use

The physical properties of commercially available epoxy resins for cryogenic use have been measured and were compared with the free volume evaluated by positron annihilation. The macroscopic physical properties of epoxy resin were changed by adding the plasticizer or changing the molecular weight between crosslinks. The life time of ortho-positronium were used to evaluate the free volume. The crosslinking density were changed systematically by changing the amount of plasticizer. The lifetime of ortho-positronium were used to evaluate the free volume in the epoxy resins. The different free volume dependence of macroscopic physical properties, such as fracture toughness, were found between the two systems even if the glass transition temperature was almost same. The fracture toughness of the two systems also showed the different crosslinking density dependence at liquid helium temperature. This means that the positron annihilation spectroscopy could be applicable to the molecular design of the glassy polymer epoxy resins for cryogenic use.

Free-electron laser oscillation with a multibunch electron beam of the 38 MeV L-band linear accelerator at ISIR

Abstract Free-electron laser oscillation has been achieved with a multibunch electron beam generated with the 38 MeV L-band linear accelerator at The Institute of Scientific and Industrial Research in Osaka University. The wavelengths of the observed FEL are 32 to 40 μm for energies of the electron beams of 17 to 19 MeV. The macropulse length of the beam is 1.8 μs. The net FEL gain measured at a wavelength of 40 μm is 25%. The tuning range of the length of the optical cavity and the FEL spectra have also been measured. The total output FEL energy of 12 mJ has been obtained in the recent experiments at a wavelength of 40μm. The intracavity peak power of the FEL is estimated to be about 150 MW.