Recent progresses on studies of charge collection process in Ge (Li) detectors and problems in their manufacturing are described. Topics such as radiation damage of Ge (Li) detectors, well-type Ge (Li) detectors, double-diode Compton suppression gamma-ray spectrometers, and CdTe detectors are also reviewed.
A mechanical velocity selector for molecular beams has been constructed and tested. It is similar to that reported by Hostettler and Bernstein, except that slits are cut obliquely. Therefore, Miller and Kusch's treatment originally given for cylinder type velocity selector with spiral grooves can be applied here to problems of velocity resolution and transmission. The selector has a high resolution (3.96%) and a very high transmission (47.6%). The transmitted velocity was 1500m/sec at the highest rotor speed used (25000rpm). A potassium beam has been velocity analyzed and found to be in good agreement with the calculated distribution.
The energy distribution of transmitted secondary electrons from thin porous KCl films was measured by an ac-retarding field method. Half width of energy distribution curve was about 10-30eV. Surface potential could be obtained from the peak position of this energy distribution curve. Secondary yield was also measured simultaneously as a function of primary electron energy and collector voltage. Secondary yield of these films increases intensely with surface potential. Field enhanced secondary electron emission mechanism of thin porous KCl films was discussed taking into account the energy distribution of transmitted secondary electrons.
Accuracy of calibration of platinum resistance thermometers against vapour pressure of 20°K equilibrium hydrogen has been examined with a comparison cryostat made of a copper block enclosed in an atmosphere of helium and immersed in liquid hydrogen. After being condensed in a glass bulb filled with Nd2O3 powder as a catalyser and circulated for complete contact with the catalyser, sample hydrogen is introduced to the vapour pressure measuring system. This procedure is proved to be satisfactory for producing equilibrium condition for ortho-para composition of hydrogen. About 30 calibrations obtaind for each of two platinum thermometers in a range from 760 to 840 mmHg of pressure shows that the reproducibility of the point is ±0.27 mdeg in terms of standard deviation.
Modulation transfer function of photographic materials is known to be valuable for expressing their optical characteristics. This report presents an application of a Fraunhofer diffraction spectrometer for determining the modulation transfer function of photographic color films. Squarewave light intensity distribution of low contrast was applied to photographic color films through gratings of the Grayson type by contact printing; after development, the photographic image was nalyzed by means of a Fraunhofer diffraction spectrometer. The modulation transfer functions were determined for two elementary layers (yellow and magenta) of photographic color film. The modulation transfer functions obtained by this method were somewhat different from that obtained by the sine-wave exposure method. This difference can be explained by adjacency effect and certain other factors.
The relation between the infinite order Born approximation and the usual dynamical treatment in the electron diffraction theory is discussed. The infinite order Born approximation is found to be equivalent to the dynamical theory, so long as the crystal potential has the periodicity of the lattice. It is thus seen that recent theories in LEED (low energy electron diffraction) in which the absorption effect is neglected are nothing but the well-known dynamical theory and not treatments characteristic to LEED. Therefore the interesting features which have so far been considered to be peculiar to LEED are not necessarily restricted to the low energy region.
Nanosecond light pulsers have been developed which are simple to construct and use. The lamps are of gaseous discharge type operated in relaxation mode. The characteristics of discharges of such gases as nitrogen and hydrogen are measured in the pressure range from 1 to 20kg/cm2. It is observed that the pulse brightness as well as the half height pulse width increases with pressure and gap width. The satisfactory maintenance to obtain intense, stable pulses is bound to be a pressure of about 5kg/cm2 which results in minimum stray capacitance for lamps with 0.1mm gap width. The lamp filled with nitrogen yields light pulses with half-width of 2 nsec or less under the condition mentioned above.
Solute atoms in dilute alloys were observed by the field-ion microscope after field-evaporation at various temperatures. Strong bright spots believed to arise from solute atoms appeared in herium ion image. The cause of these bright spots should be attributable to the fact that the field evaporation energy is modified by the contribution of the polarization energy due to the redistribution of surface charge and by a change in binding energy and that the field ionization probability increases on such polarized atoms.