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5145. Calculation and observation of thermal electrostatic noise in solar wind plasma
(~la~ified abstracts 5139-5148 33 5139: ~Computer studies on radiation of uxially~cbanncled electrons. (USA) Within the framework of classical mechanics, the radiation gmitted by a~ial..ehanneled electrons has been studied by computer simulation. The pattern of a spiral motion of an electron channeled along the major axis is found to depend strongly on the entrance condition of the electron at the crystal surface~ The profile of the calculated intensity spectrum shows a good agreement with that of the experimental spectrum. (Japan) ¥ Yamamura and, Y H 'Ohtsukk Rad Effects, 56 (1/2}, 1981. !-8. 33 5140. Effect of ion current in the,eolllsionless theory of floating ae probe m ~ e m e n t s . (USA) Previous treatment of the theory of floating ac probes has considered only the electron current voltage dependence. In. this paper the effect of including the Voltage dependence of the ion current is examined, and equations are derived which allow the use of the calculations by Laframboisc of the ion current to cylindrical probes having arbitrary ratios of probe diameter to Debye length. The error in electron temperature' measurements introduced by neglecting the ion current variation, and the range of usefulness of the technique, is discussed. For example, in the normally expected range of floating potential, a measurement of the electron temperature could be in error by as much as ~ 13~0 if the voltage dependence of ion current is ignored. Earl R Mosberg, Jr, Reo Sci lnstrum, 52 {8), 1981, 1182-1186. 33 5141. Channeling analysis of MBE InAlAs/InGaAs interfaces. (USA) In this paper we discuss how the Rutherford backscattering/channeling techniques may be used to study the interfaces between InA1AsflnGaAs epitaxial layers. D V Morgan et al, J Vac Sci Technol, 19" (3), 1981, 596-598. 34. ELECTRONICS TECHNOLOGY
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34 5142. Developments and trends in vacuum metrology. (France) In roc~nt years vacuum metrology has developed into a well established part of the programme of many national standards laboratories. This review covers the various aspects of vacuum metrology needed to establish a proper national measurement system. Starting with a review of the most recent work on vacuum standards this paper then discusses the performance of commercially available gauges and of gauges specially designed for use as secondary standards, such as the spinning rotor gauge and the JHP ionization gauge. Details will be given of recent intercomparisons of vacuum standards such as that organized in the European Community which used JHP gauges and showed that the standards of France, Germany, Italy and Britain are in agreement to _ 2.4 % over the range 8.10 -s Pa to 8.10 -2 Pa. Finally the use of comparison methods for the calibration of gauges in industry will be discussed. g F Poulter, Le Vide, 207, 1981, 521-531. 34 5143. Beam-intensity fluctuations in atmospheric turbulence. (USA) An expression is derived for the intensity correlation function of a partially coherent beam wave of arbitrary size ~nd focus propagating through weak atmospheric turbulence. Because the derivation employs the quadratic structure function IQSF) approximation, it describes only long-term beam-wander effects. Calculated covariance results agree wall with measured data and substantiate the importance of beam-wander effects on focused beam statistics. Illustrative results show the effects of the deviation, size, and phase curvature of the source as well as the strength of turbulence and range. The weak-turbulence formulas are used to calculate strong-turbulence statistics by iterative recalculation of the coherence parameters of the beam in a succession of weakly turbulent path intervals. Successively calculated values of the beam-phase deviation and correlation length effectively provide wave-tilt correlation information that is missing in the original QSF approximation. The iterative solution for the normalized beam-intensity variance saturates and asymptotically approaches unity in a manner predicted by other theories. Calculated eovariance functions also exhibit the initial rapid falloff and subsequent long coherence tail typical of saturated covariance behaviour. Some magnitude discrepancies between calculated results and reported measurements are apparent for strong turbulence conditions. The iteration analysis predicts that logamplitude fluctuations are diminished for increasingly strong turbulence and that saturated conditions arise soely from phase effects, in agreement with Fante's conclusions [R L Fante, Radio Sci, 15, 757 (1980)]. J Carl Leader, J Opt Sue Am, 71 {5), 1981, 542-558.
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34 5144. Effect of the turlmlent atmosphere on the autocovariance function for a speckle field generated by a laser beam with random pointing error. (USA) An analytic formulation for the speckle-intensity autocovariance function generated by a laser beam with random pointing error is developed. The analysis utilizes the extended Huygens-Fresnel principle and includes the effects of atmospheric turbulence on propagation of the misaligned laser beam to a diffuse target and on propagation of the speckle field back to the receiver. The main object of the development is to estimate the effects of deterministic and random pointing errors of the illuminating source on the statistics of the received intensity. In addition, methods for numerical evaluation of the autocovariance function are discussed, and some numerical results are shown, It is found that the autocovariance can be substantially increased above its vacuum value by the atmospheric turbulence. Myung Hun Lee and J Fred Holmes, J Opt Soc Am, 71 (5), 1981,559-565.
34 5145. Calculation and observation of thermal electrostatic noise in solar wind plasma. (GB) Calculations, both approximate algebraic and numerical, have been carried out for the noise due to electrostatic waves incident on a dipole antenna. The noise is calculated both for a thermat equilibrium plasma, and one having several components at different temperatures. The results are compared with measurements from the IMP-6 satellite. In various frequency ranges, the noise power is dominated by Langmuir oscillations, by electron acoustic waves and by ion acoustic waves. The measurements are consistent with all of these, although the ion waves are not definitely observed, due to interference from shot noise. {USA) Paul J Kellogg, Plasma Phys, 23 (81, 1981, 735-751. 34 5146. Variance of intensity for a discrete-spectrum, polychromatic speckle field after propagation through the turbulent atmosphere. (USA) The extended Huygens-Fresnel principle is used to develop formulations for the variance of the received intensity for a discrete-spectrum, polychromatic speckle field after propagation through the turbulent atmosphere. This principle takes into account the effects of the turbulent atmosphere on a polychromatic laser beam as it propagates to "an incoherent target and on the resultant speckle field as it propagates back to the receiver. It is found that the variance of the received intensity can be increased substantially by atmospheric turbulence and that, for the purpose of formulating the variance, under certain conditions the source can be completely characterized by its vacuum speckle contrast ratio. Fred J Holmes and V S Rao Gndimetla, J Opt Soc Am, 71 (10), 1981, 1176-1179.
35. PROCESSING OF MATERIALS 35 5147. Ion beam oxidation. (USA) We describe a new technique for controlled oxide growth using a directed. low-energy ion beam. The technique is evaluated by fabricating Ni-oxideNi and Cr-oxide-Ni tunneling junctions, using oxygen ion beams with energies ranging from 30 to 180 eV. High ion current densities are achieved at these low energies by replacing the conventional dual grid extraction system of the ion source with a single fine mesh grid. Junction resistance decreases with increasing ion energy, and oxidation time dependence shows a characteristic saturation, both consistent with a process of simultaneous oxidation and sputter etching, as in the rf oxidation process. In contrast with rf oxidized junctions, however, ion beam oxidized junctions contain less contamination by backsputtering, and the quantitative nature of ion beam techniques allows greater control over the growth process. J M E Harper et at, J Appl Phys, 52 (6), 1981, 4118-4121. 35 5148. Compounds in the Pd-Si and Pt~Si system obtained by electron bombardment and post-thermal annealing. (USA) Thin Pt, Pd, Si, and P,Si films deposited on Si were reacted by using electron beam pulses of=60 nsec duration in the 0.4-2.4 J cm -2 energy density range. Irradiation of Pd/Si structure produces at the same time PdSi, Pd2Si, PdsSi, and Pd,,Si, while PdSi is the only phase observed starting from the Pd2Si/Si structure. Post-thermal annealing of these layers up to 600°C induces the growth of Pd2Si phase at the expense of the other phases. PdSi seems to be a metastable phase at least up to 600°C. PtSi, Pt2Si, P%Si compounds are formed after irradiation of Pt/Si
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ALTITUDE
PHYSICS AND
34 5142. Developments and trends in vacuum metrology. (France) In roc~nt years vacuum metrology has developed into a well established part of the programme of many national standards laboratories. This review covers the various aspects of vacuum metrology needed to establish a proper national measurement system. Starting with a review of the most recent work on vacuum standards this paper then discusses the performance of commercially available gauges and of gauges specially designed for use as secondary standards, such as the spinning rotor gauge and the JHP ionization gauge. Details will be given of recent intercomparisons of vacuum standards such as that organized in the European Community which used JHP gauges and showed that the standards of France, Germany, Italy and Britain are in agreement to _ 2.4 % over the range 8.10 -s Pa to 8.10 -2 Pa. Finally the use of comparison methods for the calibration of gauges in industry will be discussed. g F Poulter, Le Vide, 207, 1981, 521-531. 34 5143. Beam-intensity fluctuations in atmospheric turbulence. (USA) An expression is derived for the intensity correlation function of a partially coherent beam wave of arbitrary size ~nd focus propagating through weak atmospheric turbulence. Because the derivation employs the quadratic structure function IQSF) approximation, it describes only long-term beam-wander effects. Calculated covariance results agree wall with measured data and substantiate the importance of beam-wander effects on focused beam statistics. Illustrative results show the effects of the deviation, size, and phase curvature of the source as well as the strength of turbulence and range. The weak-turbulence formulas are used to calculate strong-turbulence statistics by iterative recalculation of the coherence parameters of the beam in a succession of weakly turbulent path intervals. Successively calculated values of the beam-phase deviation and correlation length effectively provide wave-tilt correlation information that is missing in the original QSF approximation. The iterative solution for the normalized beam-intensity variance saturates and asymptotically approaches unity in a manner predicted by other theories. Calculated eovariance functions also exhibit the initial rapid falloff and subsequent long coherence tail typical of saturated covariance behaviour. Some magnitude discrepancies between calculated results and reported measurements are apparent for strong turbulence conditions. The iteration analysis predicts that logamplitude fluctuations are diminished for increasingly strong turbulence and that saturated conditions arise soely from phase effects, in agreement with Fante's conclusions [R L Fante, Radio Sci, 15, 757 (1980)]. J Carl Leader, J Opt Sue Am, 71 {5), 1981, 542-558.
450
34 5144. Effect of the turlmlent atmosphere on the autocovariance function for a speckle field generated by a laser beam with random pointing error. (USA) An analytic formulation for the speckle-intensity autocovariance function generated by a laser beam with random pointing error is developed. The analysis utilizes the extended Huygens-Fresnel principle and includes the effects of atmospheric turbulence on propagation of the misaligned laser beam to a diffuse target and on propagation of the speckle field back to the receiver. The main object of the development is to estimate the effects of deterministic and random pointing errors of the illuminating source on the statistics of the received intensity. In addition, methods for numerical evaluation of the autocovariance function are discussed, and some numerical results are shown, It is found that the autocovariance can be substantially increased above its vacuum value by the atmospheric turbulence. Myung Hun Lee and J Fred Holmes, J Opt Soc Am, 71 (5), 1981,559-565.
34 5145. Calculation and observation of thermal electrostatic noise in solar wind plasma. (GB) Calculations, both approximate algebraic and numerical, have been carried out for the noise due to electrostatic waves incident on a dipole antenna. The noise is calculated both for a thermat equilibrium plasma, and one having several components at different temperatures. The results are compared with measurements from the IMP-6 satellite. In various frequency ranges, the noise power is dominated by Langmuir oscillations, by electron acoustic waves and by ion acoustic waves. The measurements are consistent with all of these, although the ion waves are not definitely observed, due to interference from shot noise. {USA) Paul J Kellogg, Plasma Phys, 23 (81, 1981, 735-751. 34 5146. Variance of intensity for a discrete-spectrum, polychromatic speckle field after propagation through the turbulent atmosphere. (USA) The extended Huygens-Fresnel principle is used to develop formulations for the variance of the received intensity for a discrete-spectrum, polychromatic speckle field after propagation through the turbulent atmosphere. This principle takes into account the effects of the turbulent atmosphere on a polychromatic laser beam as it propagates to "an incoherent target and on the resultant speckle field as it propagates back to the receiver. It is found that the variance of the received intensity can be increased substantially by atmospheric turbulence and that, for the purpose of formulating the variance, under certain conditions the source can be completely characterized by its vacuum speckle contrast ratio. Fred J Holmes and V S Rao Gndimetla, J Opt Soc Am, 71 (10), 1981, 1176-1179.
35. PROCESSING OF MATERIALS 35 5147. Ion beam oxidation. (USA) We describe a new technique for controlled oxide growth using a directed. low-energy ion beam. The technique is evaluated by fabricating Ni-oxideNi and Cr-oxide-Ni tunneling junctions, using oxygen ion beams with energies ranging from 30 to 180 eV. High ion current densities are achieved at these low energies by replacing the conventional dual grid extraction system of the ion source with a single fine mesh grid. Junction resistance decreases with increasing ion energy, and oxidation time dependence shows a characteristic saturation, both consistent with a process of simultaneous oxidation and sputter etching, as in the rf oxidation process. In contrast with rf oxidized junctions, however, ion beam oxidized junctions contain less contamination by backsputtering, and the quantitative nature of ion beam techniques allows greater control over the growth process. J M E Harper et at, J Appl Phys, 52 (6), 1981, 4118-4121. 35 5148. Compounds in the Pd-Si and Pt~Si system obtained by electron bombardment and post-thermal annealing. (USA) Thin Pt, Pd, Si, and P,Si films deposited on Si were reacted by using electron beam pulses of=60 nsec duration in the 0.4-2.4 J cm -2 energy density range. Irradiation of Pd/Si structure produces at the same time PdSi, Pd2Si, PdsSi, and Pd,,Si, while PdSi is the only phase observed starting from the Pd2Si/Si structure. Post-thermal annealing of these layers up to 600°C induces the growth of Pd2Si phase at the expense of the other phases. PdSi seems to be a metastable phase at least up to 600°C. PtSi, Pt2Si, P%Si compounds are formed after irradiation of Pt/Si