Based on photoconductive and photovoltaic effects of Semiconductors, a variety of infrared detectors such as InSb, GeAu and HgCdTe have been developed and widely used in industrial application, medical examination, weather observation and pollution measurement. To extend spectrum ranges, we are now studying infrared detectors using new materials such as PbSnTe. In this paper, we have reported the outlines of InSb, GeAu and HgCdTe infrared dete-ctors. The problems of the detectors may be summarized into five points, including (1) detector housing, (2) detector element sensitivity, (3) time constant, (4) cooling of element and (5) spectral response. Binary semiconductors, Hg1-xCdxTe and Pb1-xSnxTe, have composition-dependent energy gaps which can be made arbitrarily small according to the proposed band model, The unique structure of the energy bands together with the ease in producing single crystals of excellent homogeneity and good quality have made these alloys particularly useful for long wavelength infrared detectors as well as lasers. As described above, HgCdTe and PbSnTe crystals provide very interesting characteristics and are the most suitable materials for infrared detectors. A great many applications of HgCdTe and PbSnTe detectors may be expected in the near future.
Utilization of LNG Cold is important from the view-point of saving energy since the amount of LNG used will be more increased in the future. So far only a part of the cold is used for an air separation plant and a super freezing warehouse in our country. Studies on other new applications like, for example, crushing of scrapped metals and tires at low temperature are being made by many engineers and some of them have been proved to be technically possible, though economic or other terms are not satisfactory. Therefore it is expected that utilization of LNG cold will go towards wide and large scale combination of such processes as storage, handling and distribution of foods and garbage disposition. This affords profits which are not available if those undertakings are schemed individually.
The influence of oscillating magnetic fields of low frequency on the DC transport current in a twisted multifilamentary conductor has been studied by observing the terminal voltage of the conductor. An analysis of the voltage versus oscillating field characteristics, combined with theoretical considerations, shows that the current distribution among filaments becomes uniform due to the oscillation of the field and an effective resistance appears in the transport current when the amplitude of the oscillating field exceeds certain threshold value. The dependence of the effective resistance on the characteristic parameters of both the oscillating field and the filamented conductor is clarified.
It is important to construct superconducting magnets as cheap as possible. One of the methods to achieve such a purpose is to save the supercondcting material and operate the magnets at a high current density. Therefore it is useful to investigate the requirements for the operation of metastable superconducting magnets which can work at a current higher than the recovery current. Using the theory of flux jump, we introduce a “stable current” below which no flux jump can occur. On a rough approximation, it is given byIs=√A PiheTof(x)/ρ where A: cross-section of the composite conductor. Pi: total perimeter of all the superconducting cores. he: effective heat transfer coefficient to the liquid helium through the stabilizer. To: a characteristic temperature of the superconducting cores. f(x): a characteristic function for the relative core radius x. ρ: effective resistivity of the composite. Then it is shown that superconducting magnets can operate without unexpected normal transitions in the region enclosed by the two curves of Is and Ic. Next, we discuss the characteristics of our saddle shaped superconducting magnet for an one-KW MHD generator. We found that, 1) the magnet does safely operate in the metastable state; 2) the characteristics of the magnet are consistent with our theoretical results.