[en] The release of the trapped electrons generated by gamma-ray irradiation was investigated by the observation of the TSC spectra of PTFE filled with CeO₂ powder. The material used for this experiment was commercial PTFE powder with reagent grade CeO₂ powder as the filler. The gamma-irradiation was carried out with Co-60 gamma-ray. The TSC spectra of PTFE samples were measured at temperature from about 20 degree to 200 degree C. The variation of the observed TSC spectra with CeO₂ content is considered to reflect the behaviour of the molecular motion in these regions of PTFE. The increase in crystallinity occurred as a result of the radiation-induced scission of main chains. The effect of radiation on PTFE was greatly accelerated by the presence of oxygen. The charge traps in the amorphous region of PTFE seem to decrease with the decrease in the amorphous region of PTFE. If the releasing current of trapped charges in the temperature range from 150 degree to 200 degree C in this experiment is ascribed to the trapped charges in the amorphous region of PTFE, the TSC current of varying amount might decrease with increasing total dose and CeO₂ content. (Kato, T.)

[en] For investigating property changes of ceramics by radiation to study radiation resistance and modification, changes of dielectric loss tangent at ultra low frequency region (0.1 to 100 Hz) and microwave region (0.1 to 10 GHz) were examined by irradiating ⁶⁰Co γ-ray to alumina ceramics. As a result, it was found that the dielectric loss tangent in ultra low frequency had nearly same slope in graph of irradiated sample as that of non-irradiated one, and showed to decrease with decline of test frequency even in non-irradiated alumina ceramics. And, it was also found that in the alumina ceramics irradiated 300 KGy of γ-ray, the test dielectric loss tangent increased in a wide range in comparison with that of non-irradiated one. On next, as a result of measuring the dielectric properties at microwave frequency ranges from 0.1 to 10 GHz, it was found that radiation effect was rarely found and the alumina ceramics was a very stable material as well as testing at frequency ranges from 100 Hz to 15 MHz. (G.K.)

[en] This paper reports on the variation of the thermally released current (TSC) spectra of polytetrafluoroethylene (PTFE) samples irradiated by Co-60 gamma-ray owing to the sample density and the temperature of the samples during irradiation. The material used for this experiment was commercial PTFE powder, which was pressed so as to form circular plates. Irradiation was carried out, using Co-60 gamma-ray. Immediately after the irradiation, the TSC spectra of these samples were measured from about 20 degree to 200 degree C. The observed spectra suggests that almost all charges held in the charge traps generated by the gamma-irradiation below 20 degree C were rapidly released in the vicinity of the 19 degree C transition of PTFE. In the peaks of the TSC curves for the gamma-irradiated PTFE samples, the amplitude increased with decreasing density. (Kato, T.)

[en] CL is a luminous phenomenon caused by that the accelerating electrons irradiated to the materials. CL method is one of the estimation method of physical properties using luminescence caused the positive hole pair generated by excited electron beam in the micro field. CL can be observed by a combination of the scanning electron microscope (SEM) and the photo detector. The excitation origins, the concentrator system, the detector system, the image processing system, the electrical signal detector system and the cooling parts were explained in detail. The evaluation method, one of the estimation method of materials in the micro-field, can be applied to the distribution of crystal defect in semiconductor, its functional analysis, the photo device of semiconductor hetero film, the studies of luminescent materials, oxides, ceramics and organic materials, for example, organism. For the example of measurement and analysis, the evaluation of micro field (GaAs crystal, dislocation of Si crystal), wide gap materials (diamond film) and depth analysis are explained. (S.Y.)

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No abstract available

[en] The surface potential, surface charge density and thermally stimulated current of the FEP films which were changed to electrets by irradiating 170 keV electron beam were measured, and the relationship among their measured values was investigated. As the result, it was known that the mean value of surface potential was proportional to surface charge density. Besides, according to the results of measurement of surface charge density and thermally stimulated current, also positive charges seemed to exist in the samples irradiated with electron beam. The measurements of surface potential, surface charge density and thermally stimulated current are reported. There are the FEP film surfaces irradiated with electron beam on which potential distributed largely changing from positive to negative, and on which only negative potential distributed with relatively small change. Thermally stimulated current is due to the polarization in samples and the relaxation phenomena of trapped charges. As FEP is assumed to be without polarity, the latter cause is conceivable, and also positive charges seemed to exist. (K.I.)

[en] Polytetrafluoroethylene(PTFE) films were modified by radiation-induced grafting of styrene. Preirradiation method and simultaneous irradiation method were applied. With the preirradiation method, the degree of grafting increased with dose and reaction time. But, with the simultaneous irradiation method, it decreased at higher dose. With the both methods, tensile strength decreased with dose and increased with the degree of grafting, and elongation decreased with dose and the degree of grafting. But, with the simultaneous irradiation method, elongation increased remarkably at the dose between 5 and 10 kGy. When the modified samples and the unmodified sample were irradiated in air to 10 kGy, the tensile strengths of the former were about 50 % higher than that of the latter. (author)

[en] Solid dielectrics such as non-browning glass, which is used as a radiation-shielding window glass, are electrically polarized by irradiation with ⁶⁰Co γ-rays. Then, a thermally stimulated current (TSC) due to the release of the trapped charge in the irradiated non-browning glass has been observed. In this paper, the temperature dependence of TSC for the non-browning glass irradiated with ⁶⁰Co γ-rays are presented. The TSC were investigated with an open-circuit TSC measurement technique without dc conduction currents at the temperature range from room temperature to 200degC. The negative and positive peaks were observed. They were observed at 52degC and 82degC. The origins of these peaks are explained by the formation of electrical polarization in space and the existences of secondary electrons in the glass and injected electrons from outside. We concluded that the charge trap sites are spatially distributed over the whole samples. (author)

[en] For the purpose of electret formation from Teflon FEP (Florinated ethylene-propylene copolymer), FEP samples (130 μm, 190 μm, 250 μm, in thick) were irradiated with a 170 keV electron-beam at room temperature in N₂ gas flow. To modify the electron range, the 170 keV electron beam was slowed down with some layers of FEP film absorbers on the incident surface of each sample. After irradiation, these irradiated FEP samples were stored in short-circuit in air. And then, surface voltage, surface charge density and short-, open-circuit TSC of each sample were measured. These experimental results are as follows. 1) Distribution of charge density on the electret surface is not homogeneous over a surface. 2) The surface charge density is low on the FEP samples irradiated by fully penetrating electron-beam. 3) The accumulated charges in the electron-beam irradiated FEP samples were observed to become unstable at about 40degC, 85degC and 170degC in TSC spectra. 4) The activation energies of trapped electrons were found to change due to thermal treatment after irradiation. 5) The activation energies of trapped electrons released by thermal treatment of less than 90degC in the FEP samples irradiated by fully penetrating electron-beam were found to be quite as low as those of free electrons. (author)