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5331. Space environment and vacuum properties of spacecraft materials
Classified abstracts 5324-5333 reduced electric field of E/N=60 Td (1 T d = 10- ~ V cm2), attachment was the principal ion production process. (N is the total gas number density.) The reduced attachment coeffÉcients ~I/N measured were small ( < 10-19 cm z) and in excellent agreement with numerical predictions. In ternary mixtures of He:CO2:Nz, positive ion formation described by Townsend's first ionization coefficient,, played a more important role over the same range of E/N. The reduced coefficient for total ion formation, (" + ~I)/N, was measured in 12:4:1 and 8:1 : 1 mixtures and found to be in good agreement with numerical calculations. Electron drift velocities in both the binary and ternary mixtures were determined using a time-offlight technique. O~erall agreement with previous experimental and numerical results was good. (USA) R A Sierra et al, J Phys D Appl Phys, 14 (10), 1981, 1791-1801. 33 5324. Antenna patterns in electron-proton scattering. (Canada) Using the calculations of Peccei and Riickl, numerical results are generated to describe the angular energy distribution in electron-proton scattering. When one-gluon emission is taken into account, an azimuthal asymmetry is observed in the energy distribution about the axis defined by the virtual photon and the incoming hadron. R Migneron and G McKeou, Can J Phys, 59 (11), 1981, 1750-1753. 33 5325. Ion-electrostatic instabilities in curreot-earryiug magnetized plasmas.
33 5329. Operation of a laser-heated thermal diffusion column. (USA) Separation of N160 and NIaO has been measured in a thermal diffusion column heated by resonant absorption of CO laser photons. For the most part, the behaviour of the laser-heated column can be adequately explained as a simple thermal effect, although the separation efficiency at low input powers is higher in the laser-heated column than in a comparable hot-wire experiment. (Israel) F S Klein et al, J Appl Phys, 52 (10), 1981, 6074-6077. 33 5330. Plasma kinetic effects of the addition of oxygen to CO laser discharges. The mechanism responsible for the beneficial effect of oxygen addition to room-temperature sealed-off CO-He-Xe cw gas lasers has been investigated. This has been carried out by observing the changes in gain, electron density, discharge voltage, and positive ion spectrum as 02 is added. It has been established that the gain %(err)is increased both because the electron density r/c is increased, and because the gas heating decreased resulting in access to larger values of %(~m/r/c, but there is no need to postulate a change in the electron energy distribution. Finally, one selfconsistent hypothesis is shown to explain the effect of O2 addition as well as that of xenon and krypton. G A Murray and A L S Smith, d Phys D: Appl Phys, 14 (10), 1981, 1745-1751.
(USA) A fluid analysis of the stability of obliquely propagating ion-electrostatic waves to current flow along the magnetic field in a fully ionized, collisional plasma is presented. The stabilizing or destabilizing effects of frictional force, collisional energy transfer, electron and ion viscosity, electron and ion thermal conductivity, and thermal force are investigated. Simple analytical expressions for the growth rate arising from each dissipative mechanism are derived from ion-cyclotron, cosine ion-acoustic, ionacoustic, and cosine ion-cyclotron waves. Joseph E Willett and Hassan Mehdlau, J Appl Phys, 52 (10), 1981, 6078-6083 33 5326. Stopping power of diamond for low energy electrons. (USA) Theoretical models used to describe the interaction of electrons with the valence band of insulators are discussed, results for the application of these models to calculate stopping power and mean-free-path of low-energy electrons ( < 10 keV) in diamond are presented. The influence of core polarizability, oscillator strength coupling between core and valence electrons, and exchange corrections is included. The contributions to the mean-free path and stopping power from ionization of inner shells have been evaluated from sum-rule-constrained classical binary-collision model. (Taiwan) C J Tung et al, Rad Effects, 59, 1981, 7-11. 33 5327. Theory of electron spin resonance of magnetic ions in metals. (GB) Reviewed at both a relatively elementary and more advanced level is the interpretative theory of the electron spin resonance of magnetic ions in metals. The various theoretical possibilities are illustrated by experimental examples wherever possible. Initially the development is based upon the Bloeh-Hasegawa equations. The relationship of the advanced theory to this more elementary theory is emphasized. Multimagnetic-impurity experiments, the skin depth problem, the analysis of exchange, hyperfine and crystal field parameters, Redfield theory, ionic and virtual bound state models and the Kondo effect, all in relation to E.S.R. in metals, are each covered in some detail. A discussion of some outstanding problems and projections for the future are also included. (Switzerland) S E Barnes, Advances in Physics, 30 (6), 1981, 801-938. 33 5328. A method for measuring fast time evolutions of the plasma potential by means of a simple emissive probe. (GB) A method is presented for obtaining the temporal evolution of the plasma potential, which is assumed to be given by the floating potential of a simple emissive probe. The construction of the probe is also described. The method avoids the slow time response of the usual technique where the floating potential is measured across a high resistance. During each sweep of the probe voltage, the changing of the sign of the probe current, which is sampled at a specific time, gives rise to a negative pulse, driving the pen-lift of an X - Y recorder. Since the real floating potential is measured where the probe current is zero, the disturbance of the plasma is kept as low as possible. (Denmark) S iizuka et al, J Phys E: Sci lnstrum, 14 ill), 1981, 1291-1295. 766
34. ELECTRONICS TECHNOLOGY
AND HIGH ALTITUDE PHYSICS AND
34 5331. Space environment and vacuum properties of spacecraft materials. (GB) This review of the literature of vacuum aspects of space and technology during the last decade has focused on (i) the vacuum environment of spacecraft in orbit and under test and (ii) materials for structures, instrumentation and mechanisms of spacecraft. Earlier knowledge of the parameters of the environment for near-Earth orbits has been consolidated. There have been advances in the understanding of the molecular flow around spacecraft. The outgassing of materials remains an important consideration, so criteria for selection still include low mass loss and low propensity to contaminate critical surfaces. There are now good data for the choice of lubricants, both liquid and solid, for mechanisms intended to operate for several years in space. The techniques for spacecraft testing in space simulation chambers are well established and only relatively small special-purpose chambers are now being built. T J Patrick, Vacuum, 31 (8-9), 1981, 351-357. 34 5332. Temporal and latitudinal 5577/~ airglow variations. (Canada) From 32000 [OI] 5577 A airglow limb observations made between April 1971 and December 1972 from the ISIS-2 satellite, the major temporal and spatial night airglow features have been identified. Two methods of analysis were employed: harmonic fitting and global correlation. Airglow emission rate maxima occurred in mid-October and mid-April at all latitudes. The intensities peaked near 35 ° in the winter and near 25 ° in the summer and showed a symmetry with latitude centred about 5° in the winter hemisphere. The mean intensity at mid-latitudes was 175 R and near the equator was 120 R. From the global correlation analysis it was shown that there are two distinct contributions to the temporal and spatial airglow variations: one is from local production which dominates during the post-solstice period, and the other is from large scale meridional transport which dominates during the post-equinox period. L L Cogger et al, Can J Phys, 59 (10), 1981, 1296-1307. 34 5333. Ozone generation in oxygen by corona discharges in a point-to-plane gap subjected to a chopped DC positive voltage. (GB) It is shown that ozone generation increased when a chopped dc positive voltage, frequency 2.5 kHz, is applied to a point-to-plane gap, compared with production obtained with a dc negative voltage. This method makes it possible to limit the thermal destruction effect and leads to a better repartition into the volume of the production by electron impact and photo-ionization. It is thus possible to reach a concentration of 600 ppm with a yield of 125 ppm W -1 h - L (France) R Peyrous and R-M Millot, J Phys D: Appl Phys, 14 {12), 1981, 2237-2242.
33 5329. Operation of a laser-heated thermal diffusion column. (USA) Separation of N160 and NIaO has been measured in a thermal diffusion column heated by resonant absorption of CO laser photons. For the most part, the behaviour of the laser-heated column can be adequately explained as a simple thermal effect, although the separation efficiency at low input powers is higher in the laser-heated column than in a comparable hot-wire experiment. (Israel) F S Klein et al, J Appl Phys, 52 (10), 1981, 6074-6077. 33 5330. Plasma kinetic effects of the addition of oxygen to CO laser discharges. The mechanism responsible for the beneficial effect of oxygen addition to room-temperature sealed-off CO-He-Xe cw gas lasers has been investigated. This has been carried out by observing the changes in gain, electron density, discharge voltage, and positive ion spectrum as 02 is added. It has been established that the gain %(err)is increased both because the electron density r/c is increased, and because the gas heating decreased resulting in access to larger values of %(~m/r/c, but there is no need to postulate a change in the electron energy distribution. Finally, one selfconsistent hypothesis is shown to explain the effect of O2 addition as well as that of xenon and krypton. G A Murray and A L S Smith, d Phys D: Appl Phys, 14 (10), 1981, 1745-1751.
(USA) A fluid analysis of the stability of obliquely propagating ion-electrostatic waves to current flow along the magnetic field in a fully ionized, collisional plasma is presented. The stabilizing or destabilizing effects of frictional force, collisional energy transfer, electron and ion viscosity, electron and ion thermal conductivity, and thermal force are investigated. Simple analytical expressions for the growth rate arising from each dissipative mechanism are derived from ion-cyclotron, cosine ion-acoustic, ionacoustic, and cosine ion-cyclotron waves. Joseph E Willett and Hassan Mehdlau, J Appl Phys, 52 (10), 1981, 6078-6083 33 5326. Stopping power of diamond for low energy electrons. (USA) Theoretical models used to describe the interaction of electrons with the valence band of insulators are discussed, results for the application of these models to calculate stopping power and mean-free-path of low-energy electrons ( < 10 keV) in diamond are presented. The influence of core polarizability, oscillator strength coupling between core and valence electrons, and exchange corrections is included. The contributions to the mean-free path and stopping power from ionization of inner shells have been evaluated from sum-rule-constrained classical binary-collision model. (Taiwan) C J Tung et al, Rad Effects, 59, 1981, 7-11. 33 5327. Theory of electron spin resonance of magnetic ions in metals. (GB) Reviewed at both a relatively elementary and more advanced level is the interpretative theory of the electron spin resonance of magnetic ions in metals. The various theoretical possibilities are illustrated by experimental examples wherever possible. Initially the development is based upon the Bloeh-Hasegawa equations. The relationship of the advanced theory to this more elementary theory is emphasized. Multimagnetic-impurity experiments, the skin depth problem, the analysis of exchange, hyperfine and crystal field parameters, Redfield theory, ionic and virtual bound state models and the Kondo effect, all in relation to E.S.R. in metals, are each covered in some detail. A discussion of some outstanding problems and projections for the future are also included. (Switzerland) S E Barnes, Advances in Physics, 30 (6), 1981, 801-938. 33 5328. A method for measuring fast time evolutions of the plasma potential by means of a simple emissive probe. (GB) A method is presented for obtaining the temporal evolution of the plasma potential, which is assumed to be given by the floating potential of a simple emissive probe. The construction of the probe is also described. The method avoids the slow time response of the usual technique where the floating potential is measured across a high resistance. During each sweep of the probe voltage, the changing of the sign of the probe current, which is sampled at a specific time, gives rise to a negative pulse, driving the pen-lift of an X - Y recorder. Since the real floating potential is measured where the probe current is zero, the disturbance of the plasma is kept as low as possible. (Denmark) S iizuka et al, J Phys E: Sci lnstrum, 14 ill), 1981, 1291-1295. 766
34. ELECTRONICS TECHNOLOGY
AND HIGH ALTITUDE PHYSICS AND
34 5331. Space environment and vacuum properties of spacecraft materials. (GB) This review of the literature of vacuum aspects of space and technology during the last decade has focused on (i) the vacuum environment of spacecraft in orbit and under test and (ii) materials for structures, instrumentation and mechanisms of spacecraft. Earlier knowledge of the parameters of the environment for near-Earth orbits has been consolidated. There have been advances in the understanding of the molecular flow around spacecraft. The outgassing of materials remains an important consideration, so criteria for selection still include low mass loss and low propensity to contaminate critical surfaces. There are now good data for the choice of lubricants, both liquid and solid, for mechanisms intended to operate for several years in space. The techniques for spacecraft testing in space simulation chambers are well established and only relatively small special-purpose chambers are now being built. T J Patrick, Vacuum, 31 (8-9), 1981, 351-357. 34 5332. Temporal and latitudinal 5577/~ airglow variations. (Canada) From 32000 [OI] 5577 A airglow limb observations made between April 1971 and December 1972 from the ISIS-2 satellite, the major temporal and spatial night airglow features have been identified. Two methods of analysis were employed: harmonic fitting and global correlation. Airglow emission rate maxima occurred in mid-October and mid-April at all latitudes. The intensities peaked near 35 ° in the winter and near 25 ° in the summer and showed a symmetry with latitude centred about 5° in the winter hemisphere. The mean intensity at mid-latitudes was 175 R and near the equator was 120 R. From the global correlation analysis it was shown that there are two distinct contributions to the temporal and spatial airglow variations: one is from local production which dominates during the post-solstice period, and the other is from large scale meridional transport which dominates during the post-equinox period. L L Cogger et al, Can J Phys, 59 (10), 1981, 1296-1307. 34 5333. Ozone generation in oxygen by corona discharges in a point-to-plane gap subjected to a chopped DC positive voltage. (GB) It is shown that ozone generation increased when a chopped dc positive voltage, frequency 2.5 kHz, is applied to a point-to-plane gap, compared with production obtained with a dc negative voltage. This method makes it possible to limit the thermal destruction effect and leads to a better repartition into the volume of the production by electron impact and photo-ionization. It is thus possible to reach a concentration of 600 ppm with a yield of 125 ppm W -1 h - L (France) R Peyrous and R-M Millot, J Phys D: Appl Phys, 14 {12), 1981, 2237-2242.