Masahiro Takebe

A particle energy determination with an imaging plate

Abstract It is shown that the stimulation spectra of Eu 2+ luminescence in BaFBr:Eu 2+ based imaging plates are strongly dependent on the energies of the incident charged particles and the ratios of the luminescences stimulated by two different light wave lengths, e.g. of 600 and 500 nm, indicate simply the energies. This additional feature enables us to determine the incident particle energies by the imaging plate itself, keeping all the high performances of the imaging plate intact.

A novel particle identification with an imaging plate

Abstract We found out that the imaging plate has the feature of particle identification in itself. A set of two stimulation lights, e.g. red and green lights, were found capable of discriminating different types of causes of the latent images, or the types of radiations. Moreover, the discrimination was found to be enhanced with photo-bleaching, i.e. a post-exposure of the imaging plate to the light of a usual fluorescent lamp for a short period of time.

The generalized mobility curve for alkali ions in rare gases: Clustering reactions and mobility curves

The measurements of mobility values for alkali ions in rare gases at room temperature over a wide range of E/N were completed for all 25 combinations. The experimental mobility curves were compared with a generalized mobility curve calculated from a model potential consisting of an inverse 8th power repulsive term and 6th and 4th power attractive terms, which took into account the core size, and potential well depths being determined for all the ion–gas combinations except for the cases of Rb+–He and Cs+–He from the relation between the observed maximum mobility and the ion energy. Experimental generalized mobility curves for alkali ions in rare gases were obtained using these well depths. It was found that all the experimental mobility curves were unified into a single curve using the model potential including the core size. The rate coefficients were measured for backward clustering reaction: Li+Ar–Ar, Li+Kr–Kr, and Li+Xe–Xe, using a drift tube. It was found that the activation energy is roughly half th...

Measurements of mobilities and longitudinal diffusion coefficients for Li+ ions in some molecular gases

The transport coefficients for Li+ ions in some moleculars gases have been measured over a wide range of E/N with a conventional drift tube at temperatures close to 300 K. The zero‐field reduced mobilities are found to be 3.91±0.11, 4.44±0.12, 3.64±0.10, 2.46±0.07, and 3.44±0.10 cm2/V s in N2, O2, CO, CO2, and CH4 gas, respectively, and these values except in O2 gas significantly deviate from the Langevin limit. In N2, CO, and CO2 gas, the resulting mobility curves show clear minima at intermediate E/N, but the depressions in O2 and CH4 gas are slight. The drop of the zero‐field values in N2, CO, and CO2 gas is explained in terms of an effective ion–quadrupole interaction which provides the r−6 attractive behavior. From the mobility calculations with using n−4–6(γ) potential, it is suggested that the depression of the mobility curve is developed by the addition of a sufficient r−6 term and is partly attributed to inelastic collisions as expected even at intermediate E/N. The experimental diffusion data ar...

Identification of Ionizing Radiation with an Imaging Plate Using Two-Wavelength Stimulation Light

Imaging plates are widely used in various fields. However, ordinary reading instruments give no information on the type of radiation. We proposed that radiation type can be identified by stimulation with light of two wavelengths. Recently, we have carried out further investigation and found that the intensity ratio of photostimulated luminescence (PSL) between two wavelengths depends on particle properties. Imaging plates were irradiated with 3.2 MeV protons, 40 kVp X-rays, 200 keV electrons and Co-60, and stimulation spectra were observed for each type of radiation. We compared the PSL intensities at 500 nm with those at 600 nm 18 hrs after irradiation. The PSL intensities at 600 nm normalized by those at 500 nm were observed to decrease in order of irradiation with 3.2 MeV protons, 40 kVp X-rays, 200 keV electrons and Co-60.

Emission characteristics of zeolite A ion source

An easy method to prepare alkali ion emitters has been realized by using the ion‐exchange technique. The thermionic emission characteristics of zeolite A alkali ion sources have been studied. Experimental results indicate that ion transport process within zeolite plays an important role in the emission mechanism.

Mobilities and longitudinal diffusion coefficients for K+ ions in nitrogen and argon

We have constructed a drift tube with a movable ion source and measured the mobilities and longitudinal diffusion coefficients for K+ ions at 303 °K in N2 and at 305 °K in Ar in the pressure range 0.3–5.0 Torr, over the E/N range 4–346 Td in N2 and 3–320 Td in Ar. The zero‐field reduced mobilities for K+ ions in N2 and Ar were determined to be 2.50±0.03 and 2.63±0.03 cm2/V sec, respectively. Both values are in excellent agreement with the values reported by Elford and Milloy. When our data are compared with the values obtained by Thomson et al. in N2 and the values obtained by James et al. in Ar over the entire E/N range, we find that the mean deviations are about 1.7%, independent of gas species and E/N. Our zero‐field reduced mobilities are about 1.2% lower in both cases than the values compiled by Ellis et al. It is concluded that the discrepancy is due to a systematic error and is not caused by clustering reactions. The mean values of NDL over the E/N range 4–7 Td in N2 and 5–10 Td in Ar were found to...

Design of a continuous guard ring and its application to swarm experiments

A new type of drift tube was designed and constructed for the study on the behavior of slow ions in gases. The guard ring, made up only of an aluminous porcelain tube, is different from those of conventional thin or thick types. Thick‐film resistor for microcircuits was coated over the inner surface of the tube. With this guard ring a new swarm experiment was carried out: the drift distance scanning method. Spectra representing the spatial distribution of ions for fixed drift times were obtained. Mobilities and longitudinal diffusion coefficients of K+ ions in oxygen were measured in a trial and compared with the data obtained by a conventional analysis of the arrival time spectra.

Mobilities and longitudinal diffusion coefficients for Li+ ions in Ar, Kr, and Xe at room temperature

The mobility of Li+ ions has been measured in Ar, Kr, and Xe at room temperature over the E/N range 6–218 Td in Ar, 8–216 Td in Kr, and 8–228 Td in Xe using a drift tube without mass spectrometer. The pressures used were 0.3–2.0 Torr for argon and 0.5–2.0 Torr for krypton and xenon. It is found that mobilities can be deduced from arrival time spectra which have been affected by reactions. The zero‐field reduced mobilities are found to be 4.56±0.05 cm2/V s for Ar, 3.65±0.04 cm2/V s for Kr, and 2.77±0.03 cm2/V s for Xe. These mobility values are higher than the Langevin values by 2.3%, 4.9%, and 3.4%, respectively. The longitudinal diffusion coefficients were also measured and compared with values calculated using the generalized Einstein relations and the present mobility data. The experimental values are somewhat higher than the calculations in all cases.

Mobilities of Li+ in Ne and in N2 and Na+ in SF6: Effect of inelastic energy loss

Ion mobility measurements were made for Li+ in Ne and in N2 and Na+ in SF6 using a variable‐temperature drift tube. The measurements were made by two different methods: variable‐E/N method at constant T and variable‐T method at constant E/N, where E, N, and T are the electric field strength, the gas number density, and the gas temperature, respectively. Two datasets were compared at the same effective temperature Teff, as calculated from the Wannier equation. For Li+ in Ne, the two datasets are put on a single curve in the range 150 K<Teff<10 000 K, indicating that the scaling rule holds well. However, for Li+ in N2 and Na+ in SF6 there exists a mobility difference between the two datasets, which is attributed to inelastic energy loss in the variable‐E/N measurement. Using the modified Wannier equation developed by Viehland et al., we determined the inelastic energy loss factor for Na+ in SF6.