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519. Microwave studies of ionization phenomena in gaseous discharges. (USA)
Classified abstracts 515-527 18 515. Collision cross sections of hydrogen and other ions or determined by ion cyclotron resonance. (USA) Through determination of the widths of ion cyclotron resonance lines as a function of pressure and electric field strengths, the ion-molecule collision cross sections of H +, H~+, H8 +, He +, A r +, N=+, N +, O2+, O2- and O - were obtained. Agreement with dc mobility data was found. In particular, the minimum in collision frequency for Hz + in Ha at E/P0 = 60 V/cm. torr was confirmed The cross sections for H=+ in Ha are 275 and 68 A,= at low and high E/p respectively. D Wobschall et al, J Chem Phys, 47 (10), 15th Nov 1967, 40914094. 18 516. On the impedance characteristics of stationary high-frequency coil discharge. (USA) For the proper dimensioning of a high-frequency apparatus producing a high-frequency plasma by inductive excitation it is necessary to know the plasma impedance as a quotient of the electric field strength E and the magnetic field strength H at the wall of the discharge vessel. The relation between E and H was experimentally examined, in a stationary ring discharge in hydrogen in the range 0.01 to 0.5 torr. E Geissler, Rep JUL-481-PP, April 1967, 19 pages (Sci Tech Aerosvace Reps, 5 (20), 3708, N67-34324). 18 517. Geometrical and chronological distribution of light emission through a vacuum filter. (USA) Consideration is given to the experimental results of a study concerning the electric discharge between two electrodes in a vacuum. The geometric and chronological distribution of light emitted in the spark gap was recorded by a photographic camera. The time gap separating two images varies from 50 to 100 ns. The hypothesis is confirmed that an anode vapour plays an essential role in the formation of the arc. F Jamet, Rep ISL-T-8/66, April 1966, 19 pages (in French) (Sci Tech Aerospace Reps, 5 (20), 3690, N67-35162). 18 518. Experiments with high current pulsed are. (USA) A pulsed high current arc in hydrogen has been investigated experimentally yielding data on a high temperature dense plasma. The discharge tube, the measurement of plasma conductivity, the arrangement of the appropriate magnetic fields, and the determination of the gas kinetic pressure of the plasma by using piezoelectric sensors, are described. (USSR) S G Aiikhanov et al, Rep NP-16669, 1966, 18 pages (Sci Tech Aerospace Reps, 5 (19), 3514, N67-32965). 18 519. Microwave studies of ionization phenomena in gaseous discharges. (USA) Electron density decay in the afterglow of helium and argon plasmas has been measured using a 3 cm microwave free-space interferometer. Results indicate the dominance of ambipolar diffusion at pressures less than 1 tort whereas electron-ion recombination became significant above this pressure. In contrast with previous work carried out at lower densities and smaller plasma dimensions, the existence of non-thermal electron energies is postulated on the basis of the mobility and recombination parameters measured. M C Sexton, Rep AFOSR-67-1112: AD-652503, March 1967, 23 pages (Sci Tech Aerospace Reps, 5 (19), 3512, N67-32807). 18 520. Some phenomena occurring during the interaction of an electron beam with a magnetoplasma. (USA) A beam of electrons penetrating a neutral gas creates a plasma with which it interacts. It is shown theoretically that oscillations with frequencies just below the upper hybrid frequency will be excited. Oscillations near the upper hybrid frequency were detected experimentally. With increasing density the excited oscillations lead to a turbulent state, characterized by high energy losses of the beam particles. (Germany) W Herrmana, Rep IPP-2/61, April 1967, 46pages (Sci Tech Aerospace Reps, 5 (20), 3706, N67-34166). 18 521. The helical instability of the positive column in crossed fields and in annular plasma configurations. (USA) The helical instability typical of collision dominated plasmas has
been studied in the presence of transverse magnetic fields. In all cases the critical value of the magnetic field is very sensitive to an applied transverse component. A rectilinear transverse component destabilizes the discharge whilst a minimum B configuration has a strong stabilizing effect. A magnetic field with shear will destabilize the plasma if the shear is in the same sense as the incipient helical plasma perturbation, but a shear of the opposite sense stabilizes the plasma. E H Holt and J F Reynolds, Rep NASA-CR-87412; TR-67-4; Aug 1967, 10 pages (Sci Tech Aerospace Reps, 5 (20), 3707, N67-34308). 18 522. Non-equilibrium properties of magnetoplasmas. (USA) A n arc plasma facility is described and its operation discussed. With argon gas fed continuously through a hollow cathode and the resultant ionized gas collimated by a magnetic field in the region between the anode and cathode, the arc has been operated up to a current of 80 amps and Langmuir probe measurements of the electron temperature and density have been made. E H Holt et al, Rep NASA-CR-87430, TR-67-3, July 1967, 20 pages, (Sci Tech Aerospace Reps, 5 (20), 3708, N67-34459). 18 523. Propagation of ion waves in a plasma flow towards a wall. (USA) The propagation of ion-acoustic waves in a weakly ionized bounded plasma is investigated typically with reference to discharge tubes, where there is an equilibrium between volume ionization and surface recombination at the walls. It results that the ion-acoustic waves are strongly absorbed at the plasma boundary, whenever the electrostatic boundary conditions require the formation of a space-charge sheath near the wails. (Italy) A Cavaliere et al, Rep LGI.67-4, March 1967, 44 pages, (Sci Tech Aerospace Reps, 5 (19), 3516, N67-33282). 18 524. Anomalous diffusion of an afterglow-plasma. (USA) The diffusion of a helium plasma produced in a metal chamber is investigated as a function of the magnetic field strength and neutral gas pressure. The magnetic field strength is varied from 200 to 3000 gauss and the neutral gas pressure from 2 × 10-2 to 1 × 10-1 torr. A plasma is produced by a narrow electron beam on the central axis of the vacuum chamber. (Germany) T Dodo, Rep IPP-2/62, May 1967, 24 pages (Sci Tech Aerospace Reps, 5 (20), 3706, N67-34162). 18:63 525. Hollow-cathode arcs; literature survey. (USA) Phenomena connected with hollow cathodes are reviewed. Ideas on the hollow electrodes, magnetic fields, gas streams are followed in their development. (France) C Breton, Rep CEA-BIB-88, March 1967, 28 pages (in French) (Sci Tech Aerospace Reps, 5 (19), 3513, N67-32926). 18 526. Anomalous field electron emission of S i O ~ ÷ C system. (USSR) Field emission from a tungsten tip coated by carbon-doped quartz was investigated. After overheating of the tip or by the action of breakdown, the field emission current rises to anomalous values and this emission is decreased at higher temperatures. Experiments confirmed that hot electrons from the tungsten are tunnelled into the thin film of SiO=q-C which is semi-conducting with very high resistivity and in which the electrical field strengths are of the order of 107 V/cm. Experimental data on the emitted electrons energy distributions indicate the influence of the non-elastic scattering of electrons in the emitting layer. A G Zhdan and M I Elinson, Radiotekh Elektron, 12 (10), Oct 1967, 1788-1793 (in Russian). 18 527. Field electron emission from lithium films on tungsten and rhenium single crystals faces. (USSR) Field emission was experimentally investigated for tungsten and rhenium tips and single crystal faces, during adsorption of lithium. Only for the (110) face of tungsten single crystal and the (1011) rhenium face was a definite minimum of the work function found. The residual atmosphere during measurements was of the order of 10-3 torr. A P Ovehinnlkov and B M Tsarev, Fiz Tverd Tela, 9 (12), Dec 1967, 3512-3515 (in Russian)
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been studied in the presence of transverse magnetic fields. In all cases the critical value of the magnetic field is very sensitive to an applied transverse component. A rectilinear transverse component destabilizes the discharge whilst a minimum B configuration has a strong stabilizing effect. A magnetic field with shear will destabilize the plasma if the shear is in the same sense as the incipient helical plasma perturbation, but a shear of the opposite sense stabilizes the plasma. E H Holt and J F Reynolds, Rep NASA-CR-87412; TR-67-4; Aug 1967, 10 pages (Sci Tech Aerospace Reps, 5 (20), 3707, N67-34308). 18 522. Non-equilibrium properties of magnetoplasmas. (USA) A n arc plasma facility is described and its operation discussed. With argon gas fed continuously through a hollow cathode and the resultant ionized gas collimated by a magnetic field in the region between the anode and cathode, the arc has been operated up to a current of 80 amps and Langmuir probe measurements of the electron temperature and density have been made. E H Holt et al, Rep NASA-CR-87430, TR-67-3, July 1967, 20 pages, (Sci Tech Aerospace Reps, 5 (20), 3708, N67-34459). 18 523. Propagation of ion waves in a plasma flow towards a wall. (USA) The propagation of ion-acoustic waves in a weakly ionized bounded plasma is investigated typically with reference to discharge tubes, where there is an equilibrium between volume ionization and surface recombination at the walls. It results that the ion-acoustic waves are strongly absorbed at the plasma boundary, whenever the electrostatic boundary conditions require the formation of a space-charge sheath near the wails. (Italy) A Cavaliere et al, Rep LGI.67-4, March 1967, 44 pages, (Sci Tech Aerospace Reps, 5 (19), 3516, N67-33282). 18 524. Anomalous diffusion of an afterglow-plasma. (USA) The diffusion of a helium plasma produced in a metal chamber is investigated as a function of the magnetic field strength and neutral gas pressure. The magnetic field strength is varied from 200 to 3000 gauss and the neutral gas pressure from 2 × 10-2 to 1 × 10-1 torr. A plasma is produced by a narrow electron beam on the central axis of the vacuum chamber. (Germany) T Dodo, Rep IPP-2/62, May 1967, 24 pages (Sci Tech Aerospace Reps, 5 (20), 3706, N67-34162). 18:63 525. Hollow-cathode arcs; literature survey. (USA) Phenomena connected with hollow cathodes are reviewed. Ideas on the hollow electrodes, magnetic fields, gas streams are followed in their development. (France) C Breton, Rep CEA-BIB-88, March 1967, 28 pages (in French) (Sci Tech Aerospace Reps, 5 (19), 3513, N67-32926). 18 526. Anomalous field electron emission of S i O ~ ÷ C system. (USSR) Field emission from a tungsten tip coated by carbon-doped quartz was investigated. After overheating of the tip or by the action of breakdown, the field emission current rises to anomalous values and this emission is decreased at higher temperatures. Experiments confirmed that hot electrons from the tungsten are tunnelled into the thin film of SiO=q-C which is semi-conducting with very high resistivity and in which the electrical field strengths are of the order of 107 V/cm. Experimental data on the emitted electrons energy distributions indicate the influence of the non-elastic scattering of electrons in the emitting layer. A G Zhdan and M I Elinson, Radiotekh Elektron, 12 (10), Oct 1967, 1788-1793 (in Russian). 18 527. Field electron emission from lithium films on tungsten and rhenium single crystals faces. (USSR) Field emission was experimentally investigated for tungsten and rhenium tips and single crystal faces, during adsorption of lithium. Only for the (110) face of tungsten single crystal and the (1011) rhenium face was a definite minimum of the work function found. The residual atmosphere during measurements was of the order of 10-3 torr. A P Ovehinnlkov and B M Tsarev, Fiz Tverd Tela, 9 (12), Dec 1967, 3512-3515 (in Russian)
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