Hatsuo Yamazaki

Determination of Electron Energy Distribution Function of Plasmas by Digital Processing from Langmuir Probe Characteristic

Electron energy distribution functions of plasmas were calculated by digital processing from Langmuir probe characteristics. The method used is based on the least squares priciple for fitting the experimental data to a polynomial curve, and performs the differential operation by a convolution of data with weighting functions. The computer program developed in accordance with this method was applied to the probe characteristics of positive column plasmas. The results were compared with the Maxwellian and Druyvesteyn distribution functions.

Fast-neutron-induced tracks in cellulose nitrate

The paper discusses the efficiency of formation of through-etched holes in LR-115 cellulose nitrate irradiated by fast neutrons from a 252Cf source and an Am-Be source. The relation between etch-through time and ranges of charged particles produced by neutrons is obtained. From the experimental results, the threshold energies of charged particles and neutrons for the formation of the holes are derived. It is shown that the efficiency is strongly dependent on etching conditions and detector thickness, as reported by other authors.

Effect of Twinning Caused by Thermal Annealing on Etched Tracks in Synthetic Quartz

Synthetic quartz crystal –x-, y- and z-cut plates– irradiated with fission fragments were heated to temperatures above 573°C and cooled to room temperature before etching in 65% NaOH. The crystals displayed twinning caused by the heating. The openings of etched tracks in twinned areas showed differences in shape in the x-cut plates and in orientation for the y- and z-cut plates (no differences in shape). The bulk etching rates of the twinned areas were also different for twins on the x-cut plates, but were the same for the y- and z-cut plates.

Quick measurement and digital data handling for Langmuir probes

A quick measurement and data processing system for Langmuir probes was developed based on a digital technique. This system enabled us to avoid the effect of probe contamination and plasma-state variations on probe characteristics. For noise reduction, the system had an averaging function by digital accumulation of data from multiple scanning. A set of personal computer programs which automatically determine the electron temperature and density from probe-characteristic data was also developed. The system was applied to a negative glow plasma, and the plasma parameters were successfully determined.

Etched-hole formation in LR-115 cellulose nitrate detector irradiated with fast neutrons

Abstract This paper deals with the neutron detection sensitivity of LR-115 cellulose nitrate by counting the etched holes of α-tracks produced by the ( n , α) reactions of the constituent nuclei of the cellulose nitrate. A formula for the etched-hole formation efficiency is derived, and applied to obtain the efficiency for each of the ( n , α) reactions of 14 N, 16 O and 12 C by using an experimental expression relating the track-to-bulk etch-rate ratio to the residual range of the α-particle. From the efficiencies obtained, and the reaction cross sections, the neutron detection sensitivity is evaluated against neutron energy up to 11 MeV, and compared with the experimental values in the energy region between 2.2 and 5 MeV; the agreement is fairly good in the region.

Plasma Temperature Profile in the Boundary Layers of an MHD Channel

The space-dependent plasma temperature in the boundary layer within the channel of an oil combustion MHD generator with externally-applied magnetic field installed at Hokkaido University was measured by a newly devised method using a light-polarization line-reversal technique. The measurement was performed at four hundred positions across the boundary layer during a period of 0.4 ms. The spatial distribution of temperature thus obtained indicated the 1/7- or 1/8-th power of temperature.

Isolation and inversion transformers for nanosecond pulses

In the transmission‐line approach to the design of transformers, a harmful mode of signal propagation that inevitably appears outside the transmission line has to be taken into account. The effect of this mode upon the output signal was studied theoretically and experimentally using a simplified model. With respect to the use of ferrite beads for suppressing the effect of this mode, a simple rule was derived for their effective use. According to the result obtained, isolation and inversion transformers were made for a test. The result of the test is given.

Measurements of Flow Velocity and Temperature Profile in A Propane-Oxygen Combustion MHD Channel

In a propane-oxygen combustion MHD channel, experimental measurements were made of the plasma flow velocity by means of a cross-correlation function analysis and of the boundary-layer temperature-profile by a newly-devised light-polarization line-reversal method. The following results were obtained: the velocity decreased gradually, the temperature profile of the boundary layer varied appreciably as the magnitude of the externally applied magnetic field increased, and the temperature increased from Joule heating, making the boundary layer profile steeper.