In this review the ion implantation which is a very important technique to realize GaAs integrated circuits will be discussed. The results reported so far on implantation in GaAs will be summarized in a table. Emphasis will be placed on the authors' results which include the evaluation of semi-insulating substrates, annealing process after implantation and practical application of implantation to GaAs ICs. It will be presented that during post annealing the behavior of heavily doped Cr in the substrate exerts serious influences on the electrical characteristics of implanted GaAs layers. Selective Si implantation directly into the substrate is introduced to fabricate two types of planar GaAs ICs with GaAs MESFETs and MOSFETs, respectively. Some anticipations on the future of GaAs ICs with ion implantation techniques will be presented at the end ofthis review.
A Xe IV laser was excited by the discharge of a long square currentpulse with a duration of about 100 μs. Visible laser emissions were observed tostudy the effects of discharge current and gas pressures on output waveforms. The Xe IV laser can be operated in the long pulse mode with a duration of about 40μs up to a xenon pressure of 0.1mmHg. This value of xenon pressure is about 3 times as large as the previously reported data by short pulsed excitation. Itcan also have a double pulsed output at low filling pressures. The first pulseisa short one with a duration of a few microseconds, while the second one is longand several tens of microseconds in duration. It is suggested that the double or long pulsed oscillation of Xe IV laser would be very useful for the excitation of a dye laser, especially when mode-locked operation is desired.
An automated biological cell sorting system (A.B.C.S.) which is based on laser light scattering by a single biological cell has been designed and constructed for various clinical applications. The principal part of the system consists of rapid cell flow, forward laser light scattering, signal processing anddisplay, and cell sorting portions. Using the A. B. C. S. size distributions ofseveral groups of small polymer spheres were measured and then were separated according to their size in order to investigate systematically the optimal operating condition of the system. The particle separation was performed at a rate of 4000/s with a separation efficiency of about 70%. Various biological cells such as red blood cells and lymphocytes were analyzed and successfully separated employing the A. B. C. S. From the results, several morphological infor-mations about the cells were obtained. One of the results is that human peripheral lymphocyte has a different size distribution from that of human tonsillar lymphocyte.
The effects of spatial brightness enhancements (Mach's band, Craik-O'Brien effect, simultaneous contrast effect) were measured by using the psychophysical methods of the increment threshold and brightness matching. The incrementthreshold increased as it approaches the edge, but the brightness enhancements of broad area, such as Craik-O'Brien effect and simultaneous contrast effect werehardly detectable by this method. On the other hand, brightness matching was seen to be fairly well associated with a change in the apparent brightness enhancements. In the experiments by dichoptic stimulus, edge enhancements were hardly detectable by the increment threshold method and there was practically no difference in the results from the brightness matching method under monoptic viewing. From these results, it is inferred that there are two mechanisms for brightness enhancements, namely narrow enhancement from edge element and broad spread enhancement.
In order to study the correlation of the brightness enhancement nearthe edge transition and the effect of the broad area, experiments were carried out on the effect of simultaneous masking of the edge and the change of the threshold contrast for the low spatial frequencies by masking the suprathreshold grating having the high spatial frequencies. The results suggest that the contrast thresholds of low frequency components rose with masking by the high contrast pattern of high frequency components. A model is assumed in which the spatial brightness enhancements are the result of the interactions of four kinds of spatial brightness signals in the visual system, that is, outputs of ‘ narrow receptive fields’, ‘broad receptive fields’, ‘differential detectors’ and ‘gradient detectors’. The model based on these four signals are discussed.
Frequency differences between two CO2 laser lines are measured by using harmonics of an X-band microwave generated in a W-Ni point contact diode. The diode can generate harmonics up to the 12th of the Xband frequency and therefore the frequency difference from 8.2 to 148.8 GHz can bemeasured with only one klystron. The measured frequency difference between P(18)-P(20) is 53 548.940±0.028 MHz and that between P(20)-P(22) is 54283.218± 0.052 MHz. These values agree well with the values measured at NBS.
The thermoset plastic CR-39 found by Cartwright, Shirk and Price is introduced. CR-39 has a unique sensitivity and high resolution in the recording of nuclear tracks. It is presented that CR-39 can record the tracks of all natural aparticles and relativistic nuclei heavier than carbon. Characteristics of CR-39 are investigated and its applications to detection of aparticles and heavyprimary cosmic ray particles are discussed. The possibility of the automatic measurement of tracks in CR-39 is emphasized.
Nuclear fusion research is one of the very interesting subject of applied physics not only from the side of plasma physics but also from the component developments and related problems under fusion reactor environment such as vacuum wall, superconductive coil, surface phenomena, bulk radiation damage, etc. These problems must be defined through conceptual designs of fusion reactor of four generation, namely, physical and engineering feasibility, reactor with energy pay back and compatibility with environment. The constructions of large fusion devices are also one of the subject of applied physics, which correspond tothe method of experimental physics to assemble device and to do reasonable experiment.
The current state of art of medical ultrasonotomography is briefly reviewed. The ultrasonic characteristics of living tissues are briefly summarizedand the instrumentation for B-mode imaging is described with an emphasis on electronic scanning system. The other ultrasonic imaging systems such as ultrasonic computerized tomography and ultrasonic holography are also briefly described andthe inherent problems of these systems are pointed out. Towards the future goal, discussion is presented on the possibility of solving general “inverse problem”, that is, estimating spatial distribution of all ultrasonic parameters inside the body from the observation outside.