This paper deals with the resolving power of anthracene single crystal for electrons of monochromatic energy. As the electrons, internal conversion electrons emitted from cesium-137 and mercury-203 are used. Electrons impinging on the crystal are collimated by aluminum collimator, 8mm in diameter and 5mm in thickness. The crystal is the one that was used in a previous work (T. WATANABE: J. App. Phy., Japan, 28, 377, (1959)), and its side faces being now covered with filter paper to reflect the light produced in the crystal. The use of collimator and reflector is found to improve the energy resolution. To see the effect of gamma-rays on pulse height distribution curve, an acrylic resin plate, served as the absorber of beta-rays and electrons, is inserted between the source and the crystal. On the assumption that about 30% of light produced in the crystal falls on the photocathode of photomultiplier tube, energy resolution calculated by using E. Breitenberger's equation agrees with that obtained by experiment, but if 100% of light is assumed to fall on the cathode, calculated value is 14% against 14% in the case of 30% efficacy of light, on cesium-137 source.
A method is devised to obtain gamm-rays of Compton single scattering effectively monochromatized in gradated energies. A scatterer in a form of a strip is bent circularly in curvature of a circle on which a gammarays source, a detector and the scatterer are placed. The gamma-rays that are scattered at all the points of the scatterer and reach the detector are of the same angle of scattering because of the circular configuration, thus attaining effective focusing of monochromatic scattered gamma-rays. Gamma-rays of differently gradated energies are obtained by shifting the detector to different positions on the circumference. To obtain intense and well qualified rays, considerations are given to scatterer material, stray radiation and geometry of the configuration. From some results with a cesium-137 source and an iron scatterer of 1.6mm in thickness, intensity of the obtained rays is proportional to the mass of the scatterer up to 60 grams or more. Because of Compton multiple scattering in the scatterer, the monochromatic nature becomes worse when a large scatterer is used, but when compared with a block scatterer of the same mass, even at the mass of several 100 grams, the quality of the obtained rays is considerably better with the circular scatterer than with the block scatterer. The energy shift of the obtained rays by a slight deviation of the scatterer from the prescribed geometry is negligible except in the neighbourhood of the source and the detector.
A neutron sensitive ion chamber, electrically compensated for γ rays, has been devised to measure correctly the neutron flux in nuclear reactors. After some experiments, electrical compensation has been confirmed to be superior to mechanical one. A chamber of this type, filled with nitrogen at 1 atm, has a sensitivity of 1.0×10-14 amp per unit thermal flux with linearity covering 107 range of neutron flux which corresponds to current range of 7×10-11 amp._??_7×10-4 amp. This type of neutron chamber turned out to be practical, and is now being used in Toshiba Training Reactor (TTR-1) at Kawasaki.
The analytical method of finding the kind of element and the amount of dose by the use of radiation spectrum patterns is well known to be convenient, for it needs no complicated chemical processes. The apparatus used for these purposes, the pulse height analyzer, is in two types, single-channel pulse height analyzer and multi-channel pulse height analyzer. The latter is made up of a scintillation detector, a linear amplifier, an A-D converter, a digital computer, a readout circuit, a power supply, and some other circuits. In using this apparatus for gamma-ray energy measurement, principle of its operation, construction and characteristics of its component parts should be well acquainted with, for its performance is much involved in comparison with that of single-channel pulse height analyzer. In the course of years, 1956-1959, transistorization of 100-channel and 400-channel pulse height analyzers was carried out and their respective parts were studied with the results that the analyzers have good linearity within 1% of deviation for radiation energy, stability within 1%/day of fluctuation, and dead time of (28+0.5N)μsec. Particulars of these analyzers are given in this paper.