A historical aspect of development of radiation detectors in Japan for the last four decades is described. The main part of the description consists of a history of detectors used in the field of nuclear physics and atomic energy relations and that in the field of cosmic ray physics and high energy physics. In the former, a historical aspect on G-M counter, scintillation counter, semiconductor detector and solid state dosimeter and, in the latter, that on radiation detectors developed with experimental studies in the fields are given.
The history of the study of iron cored electromagnet since 1850 is briefly described. Iron cored electromagnets are classified into two types, one is the narrow range type which is designed to produce high field possible in a narrow space and the other is the wide range type which produces a homogeneous field in a wide space. On the narrow range type, present understanding of the physics as to why it can produce higher field than that corresponding the saturation magnetization is described. On the wide range type, a method is described to supress the variation of relative distribution by coil current and also its hysteresis effect is mentioned. Also present status of coil electromagnets is briefly explained.
Semiconductor single crystal manufacturing equipments can be said as precise machine which requires both of high chemical purity and high physical perfection. And its required value in purity extends to 99.9999999999% or 99.99999999% exceeding 99.9999%; the common value in chemistry. The perfection means that crystals have only one dislocation per 1cm2 or non. To satisfy these items, the crucible for growing must be selected carefully; and in some cases, it is necessary to produce crystals in vacuum. Second important point is to check the temperature and its distribution in crucible and establish the temperature stability and optimum distribution to lower the fluctuation of constitution and the generation of thermal stress. Third, vapor pressure control is needed to restrain the variation of constitution. The reason why ordinary compound semiconductor has been non-stichiometric crystal in many cases is that the method mentioned above was not perfect. From these point, the main semiconductor single crystal manufacturing equipments are mentioned.
An instantaneous display of topographic images with a resolution of 20_??_30, tam was made by a TV system with an X-ray sensing PbO-vidicon camera tube. Diffracted intensities necessary for the display were obtained with an X-ray generator which was operated at 60 kV and 0.5A for a focus size of 0.5×10mm with Cu-Cr (1%) alloy- and Mo-rotating targets. For transmission topography, two regions with a width of 1mm each on a specimen crystal are seen on a picture monitor with Ka1 and Ka2 radiation. By moving both the crystal and TV camera and storing the Kai images consecutively in an image storage tube, a Lang topograph with an area of 13×9mm is synthesized for 3_??_10 sec. This storage improves image quality, and the signal-to-noise ratio of _??_10 is obtained for individual dislocation images in Si crystals. The capability of the system is demonstrated by some applications for the in situ observation of dislocation motion and melt-growth process of Si crystals.
Technological and engineering problems of a tokamak device are surveyed. The history of a tokamak device is presented and the importance of attaining a good vacuum condition and problems concerning the production of high magnetic fields are pointed out. Some pro-blems on future large tokamaks are also pointed out.