The concentrations of native defects in In1-xGaxP(x_??_0.9) mixed crystals are calculated thermodynamically by assuming the presence of charged and neutral vacancies (VIII-, Vp+ VIIIx and Vpx) and anti-site defects (IIIp2-, PIII2+). The total number of the native defects decreases and non-stoichiometry is improved significantly with increasing InP mole fraction. It is important to note that a good quality binary compound can thus, be grown from a suitable ternary solution.
A very small dc current amplifier with a rise time of 40μs at 40 pA is made by using a negative feedback resistance of 1010 ohms. In order to improve the response characteristics of the very small dc current amplifier, the high feedback resistors are made by evaporating stannic oxide on the fine glass fiber which is 50μm in diameter and 5mm in length and they are mounted inside cylindrical metal tubes of 4mm inner diameter to reduce both the distributed capacitance and the stray parallel capacitance of the amplifier. Noise characteristics of the amplifier are studied by use of an equivalent circuit involving noise generators. From a numerical analysis and a measurement of spectra, it is shown that the increase of noise spectra with high speed responses depends on the input-equivalent voltage noise of the amplifier.
The Doppler frequency shift of an optical wave can be made, not only by moving media, but by a moving boundary separating two media at rest. The moving interface can be produced by a travelling step-function electric or magnetic field applied to a nonlinear material, for example. This paper describes the experimental Doppler frequency shift of a He-Ne laser by the moving boundary, which is produced in nitrobenzene (C6H5NO2) by a high voltage pulse transmitted along a strip line in a liquid cell. The frequency of the transmitted light to the end of the cell is shifted by about 15 MHz. The shifted frequency of the reflected light by the boundary has not, however, been observed yet, because the variation of the refractive index of the medium is too little. The results of this paper show that a large amount of the laser frequency shift will be expected, if the medium with a large Kerr constant is discovered in the near future.
A multiwire air ionization chamber with a multiplexer readout circuit used as a profile monitor for electron linac beam measurements is described. The chamber has 16 anode wires of 0.07mmφ and 4 dummy wires. The wire spacing 0.375±0.02mm determines the spatial resolution of the profile measurements. Charges delivered from each anode wire are accumulated in an associated capacitor during a measuring time. The capacitor voltage resulting from the accumulated charges is read out with a combination of a multiplexer and a buffer amplifier with a reset switch. It is shown that this system can be successfully used for profile measurements of a picosecond pulsed electron beam of a 35 MeV linac.
A measurement of the current distribution of micro-focused electron and ion beams is described. The measurement is carried out by a knife-edge method, and the signal to noise ratio is improved by using a rock-in amplifier to detect the first derivative of beam current signal. The use of a rock-in amplifier introduces a new error, but the error can be reduced by slowing down the scanning speed of the beam. Strictly speaking, the measured distribution by a knife-edge method is not the current density distribution of the beam but the current distribution integrated for orthogonal direction of the beam scanning. Correction of a measured result for the current density distribution was attempted, but the result was unsatisfactory because of the various errors. However, the distribution directly obtained by the knife-edge method can usually be regard as an approximate current density distribution of the focused beam.
An inversion technique was developed which detemines the size distribution of tenuous scatterers from the forward scattering pattern. This technique is applicable for 1, 2, and 3 dimensional diffractions and scatterings. It does not require matrix-inversion or presumptive knowledge of functional forms of the size distribution, and it can take advantage of other techniques in spectral analysis such as the Fast Fourier Transform and digital filtering techniques. The relationship between the sampling of the scattering pattern and the estimated size distribution was clarified both in the frequency and the bandwidth. The convergence and stability in inversion were examined by adding random noise to the scattering patterns. Typical error for 10% noise was within a few % in the estimation of Gaussian distribution using 1024 points FFT. The advantage of this technique over the conventional methods was demonstrated.