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414. A compact high-power nitrogen laser
Classified abstracts 407-418 16 407. Photoelectric work function and Auger electron spectroscopy of
5.59 atomic per cent Si-Fe alloy (100) single crystals. (Germany) The relation of the work function to the imouritv concentration on the surface of 5.59 atomic per cent Si-Fe (iO0) single crystals was investigated using photoelectric Fowler isotherm method combined with Auger electron spectroscopy. The stainless steel experimental chamber was evacuated by oil diffusion pumps to a final pressure of 2 x low9 torr. The four-grid LEED system was used for Auger electron spectroscopy measurements. It is shown that the work function depends only slightly on the phosphorus concentration, though in this sample phosphorus was the predominant impurity after annealing and carbon after ion bombardment. (Japan) K Ueda and R Shimizu, Phys Sfat Sol (a),18 (l), 1973, 329-336. 16 408. Electron irradiation hardening of copper and copper alloys at 78 and 300°K. (Germany) Electron irradiation hardening of Cu, Cu-Ni, Cu-Si and Cu-Ge single crystals was measured at 78 and 300°K. Electron irradiations were cariied out at 1.8 and 2 MeV using a Van de Graaff accelerator with maximum current density of about 10 pA/cmZ. It is concluded that the hardening after 78°K irradiation is due to interstitial tetragonality. After 300°K irradiation, an extraordinarily large hardening rate per point defect introduced is observed. Although the mechanism of this hardening is not understood in detail it is attributed to interstitial clusters. (Japan) K Kamada et al, Phys Stat Sol (a),18 (l), 1973, 377-386. 16 409. F-centre profiles associated with electronic stopping power in LiF bombarded with high energy ions. (Germany) F-centre profiles associated with electronic stopping power are investigated in LiF crystals irradiated with 56 MeV alpha-particles and 28 MeV deuterons in vacuum of 10m5 torr. (France) A Perez et al, Phys Stat Sol (a), 18 (l), 1973, 189-195. 17. THERMODYNAMICS 17 410. Kinetics of thermal decomposition of TM,. (USA) The thermal decomposition rate of TiH, over the temperature range 250-500°C (523-773°K) in a continuouslv numoed vacuum svstem was found to be much’ slower than predi%d fr>m diffusion model calculations. The rate was insensitive to the presence of oxygen in the environment and on the specimen surface; however, small amounts of residual hydrogen in the chamber decreased the rate considerably. The rate controlling process appears to be the reaction between hydrogen atoms to form gaseous molecules on the surface. When specimens were decomposed in flowing helium, the rate was slower than in vacuum, indicating that diffusion of hydrogen through a gaseous boundary layer on the surface can control the rate when a second gas is present. C W Schoenfelder and J H Swisher, J Vuc Sci Techd, 10 (5), 1973, 862-870. 18. GASEOUS
ELECTRONICS
18 411. CO laser gas temperature. (USA) The gas translational temperature of a slowly flowing, liquid nitrogen cooled, directly excited CO laser has been determined by rather simple means. The evaporation rate of the liquid nitrogen from the insulated cooling jacket about the laser discharge was measured and used to calculate the laser gas temperature. J D Barry and J E Brandelic, Appl Opt, 12 (12), 1973, 2809-2810. 18 412. Decomposition of N20 in a glow discharge. (GB) A time-of-flight mass spectrometer has been used to examine the dissociation of nitrous oxide in a glow discharge. The dissociation arises from the direct electron impact reactions e + N20 + N2 + 0 + e and e + N,O + N + NO + e. The overall dissociation coefficient was found to be 7.3 x 10-I’ cm* for 2.2 torr N20 (E/p N 30 V cm-’ torr-‘) and to increase by nearly an order of magnitude when the N,O is mixed with argon. The discharge product NO significantly alters the discharge conditions and is itself considerably dissociated. J M Austin and A L S Smith, J Phys D: Appl Phys, 6 (18), 1973, 22362241. 222
18 413. Time-resolved electron energy distribution measurements in highcurrent discharges. (GB) A sampling technique withipulsed probe bias is described which enables time-resolved electron energy distribution measurements to be made in higher-current discharges (- 300 mA cm-‘) in which the probe would normally become incandescent. The method enables the probe temperature to be significantly reduced, eliminating errors due to large variations of the probe surface workfunction and thermal emission. The method is illustrated with measurements made in a neon discharge operating above the Pupp limit. S W Rayment and N D Twiddy, J Phys D: Appl Phys, 6 (18), 1973, 2242-2249. 18 414. A compact high-power nitrogen laser. (GB) A compact high-power nitrogen laser has been devised using commercially available ceramic capacitors. An output power of 1 MW with a 7 ns pulse width is obtained for an active length of 50 cm when it is operated at 18 kV. The dependence of the laser light output on the configuration of the ceramic capacitors has been studied experimentally as a function of the nitrogen gas pressure. (Japan) I Nagata and Y Kimura, JPhys E: Scknt Znstrum, 6 (12), 1973, 11931195. 18 415. Electron beam and dense plasma focus interaction heating experiments. (USA) Several attempts to transiently heat a dense plasma discharge using intense electron beams at voltages of 280 to 300 keV and 3.6 MeV are discussed. The results, although requiring further confirmation, suggest a positive interaction and indicate that low v/r beams are required for injection into the plasma focus column. J W Mather et al, J Appl Phys, 44 (ll), 1973, 49134919. 18 416. Radial neutral gas temperature and density pro&s in low-pressure argon discharges. (USA) In this paper we describe the direct measurement of the neutral gas density and the determination of the neutral temperature profiles in a low-pressure weakly ionized argon discharge. The measurements were made using a single-wavelength coupled cavity laser interferometer to study the neutral density variations in the afterglow of a crowbarred dc (steady-state) discharge. The temporal and radial variations of the neutral gas density in the afterglow were used to infer the dc steady-state gas density and temperature profiles, assuming an ideal gas. It is shown that the profiles are strongly current and pressure dependent and that the axial depletion of neutrals can be as high as 25-30x. Long neutral relaxation times (2-3 ms) were encountered in order to reach thermal equilibrium in the afterglow for the pressures and currents studied (l-10 torr, 5&350 mA). Radial profiles of the neutral gas density for a fixed pressure and current are in agreement with the hypothesis that neutral heating is caused primarily by collisions with the electron gas, resulting in a convective flow of the hot neutrals radially outward towards the cooler walls. J G Eden and B E Cherrington, J Appl Phys, 44 (1 l), 1973,492@4926. 18 417. Optical diagnostics of an ECRH plasma (USA) Line ratios and absolute intensities of helium singlet and triplet states are used to determine the electron temperature and number density of an electron cyclotron resonance heated (ECRH) plasma. Excitation rates and line ratios are calculated using the best available crosssection information. An averaging technique based on absolute intersities is used to determine the temperature. This technique permits an experimental calibration of the line ratios. In particular, the ratio of the 4713-A intensity to the 4921-A intensity is found to be strongly dependent on electron and neutral atom number densities. The ratio of the intensities of the 5048- and 4713-A lines is also studied. These results show that the helium line ratios can be used to obtain accurate information on the temperature and number density of an ECRH plasma. B J Easthmd et al, J Appl Phys, 44 (1 l), 1973, 4930--4935. 18 418. Interaction of a relativistic electron beam with a turbulent Plasma. (USA) The interaction of a relativistic electron beam (v/r N 2) with the turbulent phase of a Z discharge is examined. An enchancement in
5.59 atomic per cent Si-Fe alloy (100) single crystals. (Germany) The relation of the work function to the imouritv concentration on the surface of 5.59 atomic per cent Si-Fe (iO0) single crystals was investigated using photoelectric Fowler isotherm method combined with Auger electron spectroscopy. The stainless steel experimental chamber was evacuated by oil diffusion pumps to a final pressure of 2 x low9 torr. The four-grid LEED system was used for Auger electron spectroscopy measurements. It is shown that the work function depends only slightly on the phosphorus concentration, though in this sample phosphorus was the predominant impurity after annealing and carbon after ion bombardment. (Japan) K Ueda and R Shimizu, Phys Sfat Sol (a),18 (l), 1973, 329-336. 16 408. Electron irradiation hardening of copper and copper alloys at 78 and 300°K. (Germany) Electron irradiation hardening of Cu, Cu-Ni, Cu-Si and Cu-Ge single crystals was measured at 78 and 300°K. Electron irradiations were cariied out at 1.8 and 2 MeV using a Van de Graaff accelerator with maximum current density of about 10 pA/cmZ. It is concluded that the hardening after 78°K irradiation is due to interstitial tetragonality. After 300°K irradiation, an extraordinarily large hardening rate per point defect introduced is observed. Although the mechanism of this hardening is not understood in detail it is attributed to interstitial clusters. (Japan) K Kamada et al, Phys Stat Sol (a),18 (l), 1973, 377-386. 16 409. F-centre profiles associated with electronic stopping power in LiF bombarded with high energy ions. (Germany) F-centre profiles associated with electronic stopping power are investigated in LiF crystals irradiated with 56 MeV alpha-particles and 28 MeV deuterons in vacuum of 10m5 torr. (France) A Perez et al, Phys Stat Sol (a), 18 (l), 1973, 189-195. 17. THERMODYNAMICS 17 410. Kinetics of thermal decomposition of TM,. (USA) The thermal decomposition rate of TiH, over the temperature range 250-500°C (523-773°K) in a continuouslv numoed vacuum svstem was found to be much’ slower than predi%d fr>m diffusion model calculations. The rate was insensitive to the presence of oxygen in the environment and on the specimen surface; however, small amounts of residual hydrogen in the chamber decreased the rate considerably. The rate controlling process appears to be the reaction between hydrogen atoms to form gaseous molecules on the surface. When specimens were decomposed in flowing helium, the rate was slower than in vacuum, indicating that diffusion of hydrogen through a gaseous boundary layer on the surface can control the rate when a second gas is present. C W Schoenfelder and J H Swisher, J Vuc Sci Techd, 10 (5), 1973, 862-870. 18. GASEOUS
ELECTRONICS
18 411. CO laser gas temperature. (USA) The gas translational temperature of a slowly flowing, liquid nitrogen cooled, directly excited CO laser has been determined by rather simple means. The evaporation rate of the liquid nitrogen from the insulated cooling jacket about the laser discharge was measured and used to calculate the laser gas temperature. J D Barry and J E Brandelic, Appl Opt, 12 (12), 1973, 2809-2810. 18 412. Decomposition of N20 in a glow discharge. (GB) A time-of-flight mass spectrometer has been used to examine the dissociation of nitrous oxide in a glow discharge. The dissociation arises from the direct electron impact reactions e + N20 + N2 + 0 + e and e + N,O + N + NO + e. The overall dissociation coefficient was found to be 7.3 x 10-I’ cm* for 2.2 torr N20 (E/p N 30 V cm-’ torr-‘) and to increase by nearly an order of magnitude when the N,O is mixed with argon. The discharge product NO significantly alters the discharge conditions and is itself considerably dissociated. J M Austin and A L S Smith, J Phys D: Appl Phys, 6 (18), 1973, 22362241. 222
18 413. Time-resolved electron energy distribution measurements in highcurrent discharges. (GB) A sampling technique withipulsed probe bias is described which enables time-resolved electron energy distribution measurements to be made in higher-current discharges (- 300 mA cm-‘) in which the probe would normally become incandescent. The method enables the probe temperature to be significantly reduced, eliminating errors due to large variations of the probe surface workfunction and thermal emission. The method is illustrated with measurements made in a neon discharge operating above the Pupp limit. S W Rayment and N D Twiddy, J Phys D: Appl Phys, 6 (18), 1973, 2242-2249. 18 414. A compact high-power nitrogen laser. (GB) A compact high-power nitrogen laser has been devised using commercially available ceramic capacitors. An output power of 1 MW with a 7 ns pulse width is obtained for an active length of 50 cm when it is operated at 18 kV. The dependence of the laser light output on the configuration of the ceramic capacitors has been studied experimentally as a function of the nitrogen gas pressure. (Japan) I Nagata and Y Kimura, JPhys E: Scknt Znstrum, 6 (12), 1973, 11931195. 18 415. Electron beam and dense plasma focus interaction heating experiments. (USA) Several attempts to transiently heat a dense plasma discharge using intense electron beams at voltages of 280 to 300 keV and 3.6 MeV are discussed. The results, although requiring further confirmation, suggest a positive interaction and indicate that low v/r beams are required for injection into the plasma focus column. J W Mather et al, J Appl Phys, 44 (ll), 1973, 49134919. 18 416. Radial neutral gas temperature and density pro&s in low-pressure argon discharges. (USA) In this paper we describe the direct measurement of the neutral gas density and the determination of the neutral temperature profiles in a low-pressure weakly ionized argon discharge. The measurements were made using a single-wavelength coupled cavity laser interferometer to study the neutral density variations in the afterglow of a crowbarred dc (steady-state) discharge. The temporal and radial variations of the neutral gas density in the afterglow were used to infer the dc steady-state gas density and temperature profiles, assuming an ideal gas. It is shown that the profiles are strongly current and pressure dependent and that the axial depletion of neutrals can be as high as 25-30x. Long neutral relaxation times (2-3 ms) were encountered in order to reach thermal equilibrium in the afterglow for the pressures and currents studied (l-10 torr, 5&350 mA). Radial profiles of the neutral gas density for a fixed pressure and current are in agreement with the hypothesis that neutral heating is caused primarily by collisions with the electron gas, resulting in a convective flow of the hot neutrals radially outward towards the cooler walls. J G Eden and B E Cherrington, J Appl Phys, 44 (1 l), 1973,492@4926. 18 417. Optical diagnostics of an ECRH plasma (USA) Line ratios and absolute intensities of helium singlet and triplet states are used to determine the electron temperature and number density of an electron cyclotron resonance heated (ECRH) plasma. Excitation rates and line ratios are calculated using the best available crosssection information. An averaging technique based on absolute intersities is used to determine the temperature. This technique permits an experimental calibration of the line ratios. In particular, the ratio of the 4713-A intensity to the 4921-A intensity is found to be strongly dependent on electron and neutral atom number densities. The ratio of the intensities of the 5048- and 4713-A lines is also studied. These results show that the helium line ratios can be used to obtain accurate information on the temperature and number density of an ECRH plasma. B J Easthmd et al, J Appl Phys, 44 (1 l), 1973, 4930--4935. 18 418. Interaction of a relativistic electron beam with a turbulent Plasma. (USA) The interaction of a relativistic electron beam (v/r N 2) with the turbulent phase of a Z discharge is examined. An enchancement in