[en] Correlation effects due to the cascade transition of gamma-rays with gates on the relevant peaks have been studied in activity measurement of ⁵⁹Fe using the bi-dimensional coincidence counting method. Extrapolation curves were obtained at three gamma gates of 1099.2 keV, 1291.6 keV, and that covering both photo-peaks by a computer discrimination method. Of these extrapolation curves, only that obtained at (950-1350) keV gamma gate shows a linear variation, but those of two single gamma gates are not linearly varied in the high efficiency region. This non-linearity obtained at the gamma gate of 1099.2 keV photo-peak was caused by the correlation effects due to 1-3 coincidence relation via unobserved 192 keV gamma-ray transitions

[en] High performance photovoltaic infrared detectors for the 8-14μ spectral region have been fabricated with Pbsub(1-x)Snsub(x) Te single crystals by a surface inversion technique. The single crystals were grown in this laboratory, which possesses almost perfect single crystal properties. The hole carrier concentrations of the diodes were around 10¹⁸ to 10¹⁹/cm³, the mobilities were the order of close to 10³ cm²/volt.sec, the quantum efficiencies were as much high as 45 percent, and the detectivities were nearly 10¹¹cm x Hzsup(1/2)/W, which are believed to be sufficient characteristics for application to high performance commercial IR detectors. (author)

[en] Auger electron spectrosopcy has been used in conjunction with argon ion sputtering in a study of the surface segregation and interaction of carbon with zirconium in Nb Zr alloys. The result of depth profiling with argon ion sputtering showed that the carbon coverage on the Nb-Zr alloy surfaces was significantly more than that on the Nb polycrystalline surface. The dominant part of these carbon and oxygen was due to the segregation from the Nb-Zr alloys. The carbon in niobium polycrystalline appears to be in two states, namely graphite and carbon. The segregation of zirconium to the Nb-Zr alloy surfaces occurred at temperature as low as 900 degC with the maximum occurring around 1100 degC. While the maximum depths of zirconum and oxygen segregated from the Nb-Zr alloy at temperature 1100 degC were respectively 5A and 15A. (Author)

[en] We have developed a three-dimensional data-acquisition system with which pulse heights from an array of detectors can be multi-scaled with dwell times as short as 31 ns. The main part of the system consists of three ADCs of SAR (Successive Approximation Register) type, a 32 MHz oscillation clock and DRAM (Dynamic Random Access Memory) of 192 Mbyte capacity. The clock time is determined by count the clock pulse generated by 28 bits synchronous counter. Both the pulse height and the time information are stored at an array of DRAM, of 40-bits width, 12-bits for pulse height and 28-bits for clock time. The technique is particularly suitable for experiments such as both double and triple coincidence distributions are required. Virtues of the method are demonstrated by measuring the activity of ¹⁴C with a 3-PM liquid scintillation counting system. The computer discrimination together with the MCTS (multi-channel time scaling) technique is applied for efficiency variation method in the analysis

[en] Adhesion for various metals Ni-Cu-Ag after friction was measured in high vacuum chamber. Surfaces were examined with Auger-Electron-Spectroscopy in 5x10^-10 torr before and after contact to determine nature of surface changes resulting from adhesive contact. Surfaces were cleaned by standard process and electrical heating for friction and AES studies. Thus, from the experimental results, it should be possible to predict which of two surfaces in contact will undergo attrition. We can see that adhesion depends on elastic moduli, surface energy, heat of sublimation, melting point and cohesive strength. (author)

[en] Radon calibration chamber has been constructed to test and calibrate radon and radon progeny detectors at various environmental conditions and to study the characteristic behavior of radon decay products. The size of main room in the chamber is 3.2 mx3.3 mx2.4 m (25.3 m³) and the total volume of the chamber is 39.1 m³. The maximum concentration of radon in the chamber can be maintained up to 250 kBq m^-3 and temperature and humidity are controlled in the ranges of (10-40) deg. C and (30-80)%, respectively. The equilibrium factor and unattached fraction of radon progeny are determined at the radon concentration of 2 kBq m^-3

[en] We are planning to construct a Compton-suppression system permitting accurate and precise determinations of radioactivity of low-level environmental samples. An annulus guard detector (NaI) and a plug-in detector (NaI) are being used as suppression detectors with an HPGe primary detector. The geometry of the Compton suppression spectrometer was optimized by simulation with PENELOPE for obtaining the highest suppression factor (SF) for a point source. The results of the simulations show that the ultimate value of the suppression factor is 7.87±0.18, obtained when the source is located at 57% of an annuls guard detector. - Highlights: • The suppression factor SF was evaluated by MCS that gave a comprehensive insight into it. • The difficulty of the experiment due to the lack of sufficient single gamma sources is solved by using MCS. • It gives the ultimate value of the suppression factor and SF behaviour in function of energy and position. • At low energies SF does not dependent on the position, contrary to high energies. • The highest SF for the whole energy range is obtained with the source at 57% of the annulus detector

[en] A 4pi *b-*g coincidence system was developed with a high efficiency 4pi proportional counter and two NaI(Tl) scintillation detectors. The absolute disintegration rate of sup(60)Co was calculated by the efficiency extrapolation method based on low energy threshold level variation for *b-channel. The result obtained was 351.10+-095kBq/g at the reference time and the difference from that of National Bureau of Standards in U.S.A. was less than o.7%. (Author)

[en] Surface segregation and interaction of oxygen with Nickel, Niobium and Zirconium were studied using Auger Electron Spectroscopy. The results of the experimentals indicated that, Nickel is corresponds to parabolic oxidation rate, Zirconium is corresponds to cubic oxidation rate and Niobium to linear oxidation rate. Segregation of carbon to the surfaces had occured at temperature as low as 1500degC and segregation of sulfur to the nickel single crystal surfaces had occured at temperature as low as 500degC. It was noted that segregation of sulfur was limited to a few monolayers near the surface. (Author)

[en] Oxidation of polycrystalline molybdenum, niobium and tantalum surfaces has been studied by use of Auger Electron Spectroscopy. The methods used to obtain clean and oxidized transition metals surfaces are discussed together with the changes in the Auger spectra on oxidation. AES process in also described in detail. The clean surfaces were obtained by Argon ion bombardment followed by electrical heating. The AES measurements for polycrystalline samples are in good agreement with earlier work on (100) Mo, (100) Nb and Ta surfaces. In the initial stage of exposure to oxygen chemisorptions were dominant, and the electron beam induced the enhancement of oxygen adsorption. At the heating process oxygen Auger peak-to-peak heights increase until 900K for Nb, 500K for Mo and 800K for Ta. At about 1800 - 1900K oxygen coverages of all samples were practically removed, while the carbon peaks remained as unchanged. It is also revealed that oxygen Auger amplitudes of transition metals are a function of exposure, but not affected by the pressure of oxygen for lower than 10^-8 Torr. (author)