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530. Video-control equipment for scanning electron microprobe machines. (USSR)
Classified abstracts
527-537
stellarator is investigated under conditions of external injection. It is shown that the amount of impurity ions in the trapped plasma can be considerably reduced by pulse modulation of the maintaining magnetic field of the injector-divertor arrangement. N S Atamanov et al, Zh T&h Fiz, 42 (4), April 1972, 886-888 (in Russian).
33. GENERAL
PHYSICS AND ELECTRONICS
33 527. Formation of narrow molecular beams by cylindrical canals. (USSR) A second approximation of the variation method is applied to the problem of determining the probability of passage of molecules through a cylindrical canal, distribution of density of molecule collisions with the surface of a capillary and the angular distribution of molecule flow from canal into vacuum. I G Neudacbin et al, Zh T&h Fiz, 42 (S), May 1972, 1069-1072 (in Russian). 33 528. Using an electron microscope for checking field electron emitters
and probes. (USSR) An electron microscope attachment is described whereby the radius of curvature, the conical angle, and microgeometry of points may be checked on field emitters and probes used for investigating the electrical parameters of semiconductors. Yu B Boystov et al, Prib Tekh Eksper, No 2, March-April 1972, 245246 (in Russian).
33 529. Temperature dependence of electron attachment at low energies for
poly-atomic molecules. (USA) The cross sections for attachment of low-energy (co.2 eV) electrons to SFB, CCL,, CFC13, CH2Br2, CH31, CHC13, CF3Br and CH3Br molecules were determined as a function of target gas temperature from 300 to 1200°K. For SF,, the total cross section for negative ion production is independent of gas temperature. In contrast to SFB, the total cross sections for negative ion production in some halogenated hydrocarbons are found to be strongly temperature dependent. The background pressure in the vacuum system was about 5 x 10F9 torr and the RPD method was used. D Spence and G T Scbu’z, J Chem Phys, 58 (5), 1 March 1973, 1800-1803.
33
Video-control equipment for scanning electron microprobe machines. (USSR) A video-control equipment for contact-less testing of the results of machining materials by electron probe in vacuum, is described. The sample surface can be imaged in secondary or absorbed electrons and characteristic x-radiation. B E Mashyanov et al, Prib Tekh Eksper, No 2, March-April 1972,253 530.
(in Russian). 33 531. Utilization of Si and Ge films with anomalously high photovoltage
for recording x-radiation. (USSR) The effect of x-radiation on the value of photovoltage in Si and Ge films with anomalously high photovoltage is investigated at room temperature in vacuum of 10e6 torr and in air. The possibility of using these films for recording low intensity x-rays, both in vacuum and in air, is demonstrated. U A Arifov and N Abdullaev. Prib Tekh Ekmer. __ No 2. March-Azwil 1972, 210-212 (in Russian). ’ 33
532. Experimental chamber with open emission electron microscopes.
(USSR) A stainless steel experimental chamber with three open emission electron microscopes is described which enables properties of field emitters of various materials and also adsorption processes in combination with the flash-filament method to be investigated. The chamber also contains an internal heater and a window. For measurement of total and partial pressures an ionization tube and a mass spectrometer are placed inside the chamber. Two variants of evacuation systems for the chamber are given. The first consists of a diffusion pump with liquid nitrogen trap and a sputter-ion pump. After S-h degassing of the whole chamber at 400°C an ultimate vacuum of 1 x 10e9 torr is reached. For investigation of sorption processes
the application of an orbitron ion pump, permitting an ultimate pressure of 2 x lO_“’ torr, is recommended. Yu S Lobachev et al, Prib Tekh Eksper, No 2, March-April 1972,203205 (in Russian). 33 533. LEED study of the surface preparation of bubble domain materials.
(Germany) Yttrium orthoferrite samples were examined in a LEED/Auger system at a pressure of 1Om8torr. It is shown that after polishing, a low temperature orthophosphoric acid etch substantially reduces the domain wall coercivity of orthoferrite slices, the reduction being associated with the removal of an amorphous layer present after the final polish. The low temperature etching treatment avoids the difficulties normally encountered with a high temperature polish. (England) P D Augustus et al, Phys Stat Sol (a), 10 (l), March 1972, Kl-K3. 33 534. A new method of investigating electron structure in metal surfaces with the aid of positron annihiition. (Germany) A method is presented for the investigation of momentum distribution of gamma-quantum annihilation from the metal surfaces. The method uses the interaction between positronium atoms and surface atoms. Possible mechanisms of this interaction are discussed and the conditions under which the method may be applied are delined. A samples and an “Na source with activity of 5 mCi are placed in a vacuum chamber, evacuated to 1O-5 torr by a zeolite pump. The method was used for the investigation of the momentum distribution of photon annihilation from the surface of polycrystalline iron and aluminium, and single-crystal molybdenum. Characteristics of the electron density distribution at the metal surface can be obtained using this method. (USSR) I Ya Dekhtyar and V I Silantev, Phys Stut Sol (a), 10 (2), April 1972, 657-666. 535. Cathode unit. (USSR)
33
A new cathode unit designed to minimize the stresses caused by the welding of different types of materials is proposed. The unit comprises a cathode body made of a nickel alloy, together with a ceramic insulator, a spiral-woven heater, and two nickel pistons. Only that part of the cathode body projecting from the holder (one third of the total length) is made continuous; the rest is provided with stressrelieving gaps. The emitting surface is very accurately positioned by means of ceramic projections attached to the insulator. By virtue of these and other arrangements the weakening of the holder during heat treatment is reduced to an absolute minimum. A G Tabanakov and N A Iofis, USSR Patent No 321868, appl9th June 1967, publd 31st Jan 1972. 536. A cold cathode. (USSR)
33
A cold cathode of the sandwich type (Al-ZnS-SiO-Al or Au) is described. A hetero-junction is formed by a ZnS film 50&2OOOA thick and an SiO film 50&1000 A thick. The substantial film thickness prevents the tunneling of electrons from the substrate to the upper metal film. The source of electrons lies in the semiconductor (ZnS). The potential barrier at the ZnS-SiO junction is low, so that two.bands with different electron concentrations are created in the SiO; on the side of the upper metal film there is a narrow dielectric layer giving a high contact barrier with the metal. The current penetration factor of this system is N 0.1. E I Taborko et al, USSR Patent No 285721, appl 25th June 1969, publd 23rd Fe6 1972. 33 537. Two-electrode tube for generation of nanosecond pulses of x-
radiation. (USSR) A sealed glass two-electrode pulse x-ray tube with a field emission cathode is described. Tantalum of tungsten foil, lo-20 pm thick, serves as an anode. The cathode is made of tantalum foil, 10-20 pm thick, rolled in a cylinder. The edge of the foil serving as field emitter is not subjected to additional treatment. The pressure in the tube is in the range of low5 to 10u7 torr. On supplying voltage pulses with a leading edge of 1 nanosecond and amplitude of 120-150 kV the tube generates x-ray pulses of 10 ns duration. The dose is equal to 25 mr per impulse at voltage of 120 kV at a distance of 5 cm from the anode. The life of the x-ray tube is greater than lo6 operations. N V Belkin and E/G V Aleksandrovich, Prib Tekh Eksper, No 2, March-April 1972, 196-197 (in Russian).
527-537
stellarator is investigated under conditions of external injection. It is shown that the amount of impurity ions in the trapped plasma can be considerably reduced by pulse modulation of the maintaining magnetic field of the injector-divertor arrangement. N S Atamanov et al, Zh T&h Fiz, 42 (4), April 1972, 886-888 (in Russian).
33. GENERAL
PHYSICS AND ELECTRONICS
33 527. Formation of narrow molecular beams by cylindrical canals. (USSR) A second approximation of the variation method is applied to the problem of determining the probability of passage of molecules through a cylindrical canal, distribution of density of molecule collisions with the surface of a capillary and the angular distribution of molecule flow from canal into vacuum. I G Neudacbin et al, Zh T&h Fiz, 42 (S), May 1972, 1069-1072 (in Russian). 33 528. Using an electron microscope for checking field electron emitters
and probes. (USSR) An electron microscope attachment is described whereby the radius of curvature, the conical angle, and microgeometry of points may be checked on field emitters and probes used for investigating the electrical parameters of semiconductors. Yu B Boystov et al, Prib Tekh Eksper, No 2, March-April 1972, 245246 (in Russian).
33 529. Temperature dependence of electron attachment at low energies for
poly-atomic molecules. (USA) The cross sections for attachment of low-energy (co.2 eV) electrons to SFB, CCL,, CFC13, CH2Br2, CH31, CHC13, CF3Br and CH3Br molecules were determined as a function of target gas temperature from 300 to 1200°K. For SF,, the total cross section for negative ion production is independent of gas temperature. In contrast to SFB, the total cross sections for negative ion production in some halogenated hydrocarbons are found to be strongly temperature dependent. The background pressure in the vacuum system was about 5 x 10F9 torr and the RPD method was used. D Spence and G T Scbu’z, J Chem Phys, 58 (5), 1 March 1973, 1800-1803.
33
Video-control equipment for scanning electron microprobe machines. (USSR) A video-control equipment for contact-less testing of the results of machining materials by electron probe in vacuum, is described. The sample surface can be imaged in secondary or absorbed electrons and characteristic x-radiation. B E Mashyanov et al, Prib Tekh Eksper, No 2, March-April 1972,253 530.
(in Russian). 33 531. Utilization of Si and Ge films with anomalously high photovoltage
for recording x-radiation. (USSR) The effect of x-radiation on the value of photovoltage in Si and Ge films with anomalously high photovoltage is investigated at room temperature in vacuum of 10e6 torr and in air. The possibility of using these films for recording low intensity x-rays, both in vacuum and in air, is demonstrated. U A Arifov and N Abdullaev. Prib Tekh Ekmer. __ No 2. March-Azwil 1972, 210-212 (in Russian). ’ 33
532. Experimental chamber with open emission electron microscopes.
(USSR) A stainless steel experimental chamber with three open emission electron microscopes is described which enables properties of field emitters of various materials and also adsorption processes in combination with the flash-filament method to be investigated. The chamber also contains an internal heater and a window. For measurement of total and partial pressures an ionization tube and a mass spectrometer are placed inside the chamber. Two variants of evacuation systems for the chamber are given. The first consists of a diffusion pump with liquid nitrogen trap and a sputter-ion pump. After S-h degassing of the whole chamber at 400°C an ultimate vacuum of 1 x 10e9 torr is reached. For investigation of sorption processes
the application of an orbitron ion pump, permitting an ultimate pressure of 2 x lO_“’ torr, is recommended. Yu S Lobachev et al, Prib Tekh Eksper, No 2, March-April 1972,203205 (in Russian). 33 533. LEED study of the surface preparation of bubble domain materials.
(Germany) Yttrium orthoferrite samples were examined in a LEED/Auger system at a pressure of 1Om8torr. It is shown that after polishing, a low temperature orthophosphoric acid etch substantially reduces the domain wall coercivity of orthoferrite slices, the reduction being associated with the removal of an amorphous layer present after the final polish. The low temperature etching treatment avoids the difficulties normally encountered with a high temperature polish. (England) P D Augustus et al, Phys Stat Sol (a), 10 (l), March 1972, Kl-K3. 33 534. A new method of investigating electron structure in metal surfaces with the aid of positron annihiition. (Germany) A method is presented for the investigation of momentum distribution of gamma-quantum annihilation from the metal surfaces. The method uses the interaction between positronium atoms and surface atoms. Possible mechanisms of this interaction are discussed and the conditions under which the method may be applied are delined. A samples and an “Na source with activity of 5 mCi are placed in a vacuum chamber, evacuated to 1O-5 torr by a zeolite pump. The method was used for the investigation of the momentum distribution of photon annihilation from the surface of polycrystalline iron and aluminium, and single-crystal molybdenum. Characteristics of the electron density distribution at the metal surface can be obtained using this method. (USSR) I Ya Dekhtyar and V I Silantev, Phys Stut Sol (a), 10 (2), April 1972, 657-666. 535. Cathode unit. (USSR)
33
A new cathode unit designed to minimize the stresses caused by the welding of different types of materials is proposed. The unit comprises a cathode body made of a nickel alloy, together with a ceramic insulator, a spiral-woven heater, and two nickel pistons. Only that part of the cathode body projecting from the holder (one third of the total length) is made continuous; the rest is provided with stressrelieving gaps. The emitting surface is very accurately positioned by means of ceramic projections attached to the insulator. By virtue of these and other arrangements the weakening of the holder during heat treatment is reduced to an absolute minimum. A G Tabanakov and N A Iofis, USSR Patent No 321868, appl9th June 1967, publd 31st Jan 1972. 536. A cold cathode. (USSR)
33
A cold cathode of the sandwich type (Al-ZnS-SiO-Al or Au) is described. A hetero-junction is formed by a ZnS film 50&2OOOA thick and an SiO film 50&1000 A thick. The substantial film thickness prevents the tunneling of electrons from the substrate to the upper metal film. The source of electrons lies in the semiconductor (ZnS). The potential barrier at the ZnS-SiO junction is low, so that two.bands with different electron concentrations are created in the SiO; on the side of the upper metal film there is a narrow dielectric layer giving a high contact barrier with the metal. The current penetration factor of this system is N 0.1. E I Taborko et al, USSR Patent No 285721, appl 25th June 1969, publd 23rd Fe6 1972. 33 537. Two-electrode tube for generation of nanosecond pulses of x-
radiation. (USSR) A sealed glass two-electrode pulse x-ray tube with a field emission cathode is described. Tantalum of tungsten foil, lo-20 pm thick, serves as an anode. The cathode is made of tantalum foil, 10-20 pm thick, rolled in a cylinder. The edge of the foil serving as field emitter is not subjected to additional treatment. The pressure in the tube is in the range of low5 to 10u7 torr. On supplying voltage pulses with a leading edge of 1 nanosecond and amplitude of 120-150 kV the tube generates x-ray pulses of 10 ns duration. The dose is equal to 25 mr per impulse at voltage of 120 kV at a distance of 5 cm from the anode. The life of the x-ray tube is greater than lo6 operations. N V Belkin and E/G V Aleksandrovich, Prib Tekh Eksper, No 2, March-April 1972, 196-197 (in Russian).