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5393. Improved source of cold plasma electrons and negative ions
Classified abstracts 5393-5403 than 25 MeV FWHM at 10 -9 A, with high stability and reproducibility. Design and operating details are given. (Italy) R Grisenti and A Zecce, Rev Sci Instrum, 53 (1), 1982, 9-13. 36 5393. Improved source of cold plasma electrons and negative ions. (USA) A cold electron plasma has been produced, with a greater latitude in neutral pressure and plasma density than previously, by drifting plasma through an improved magnetic cusp cage. The motion across this cage has been characterized as a two-step process. First, the plasma between the cusps cools offas it loses contact with the primary ionizing electrons which are confined at the cusps and, second, the cold plasma electrons experience a VB x B drift across the cage barrier magnetic field. Large ambipolar fields are also seen across the region. A two-component, positive ion (Ar + )-negative ion (SF~-) plasma was created with the ratio of electron density (he) to positive ion density in+) continuously variable from lO-3
surfaces are discussed and the uses of these interactions are briefly mentioned. I W Drummond, Vacuum, 31 (10-12), 1981, 579-588. 36 5398, Further aspects ofsputial separation ofmoleculesina molecular beam by iohomogeneous electrostatic fields. (GB) A further study has been made of a ring-type electrostatic focuser for molecular beams in respect of the degree of spatial separation of molecules with either the internal or external electric field. The external electric field of the ring focuser is calculated and is shown to have a very similar magnitude, and spatial extent to that of the already known internal field. State selection of that part of a molecular beam which sheaths the ring focuser, as well as that part within but deflected away from the beam axis, are shown experimentally to form intense annular rings of state selected molecules, concentric with the central core of focused molecules. Similar experimental results are also obtained with focusers of different geometries. A new method of molecular beam spectrometer signal enhancement based on these observations is proposed. D H H AI-Amiedy et al, J Phys D: Appl Phys, 15 (2), 1982, 193-196. 36 5399. Low energy electron beam relaxation in gases in uniform electric fields. (GB) The problem of low energy electron beam relaxation in a gas between two parallel plates is extended to include accelerating or retarding electric fields. The problem is solved by two different methods, assuming that the elastic scattering is isotropic and neglecting the energy losses in elastic collisions. The first method is based on solution of the equations of moments of the electron velocity distribution function. The second uses a novel Monte-Carlo simulation scheme, which allows us to find various moments of the distribution function without the simplifying assumptions of the first method. The calculated current to the plates and the calculated density distribution between the plates obtained by the two methods are in good agreement. (Israel) L. Friedland et al, J Phys D: Appl Phys, 15 (2), 1981, 251-262. 36 5400. An electron cyclotron maser for nanosecond megawatt pulses. (GB) An electron cyclotron maser with an output power of 1 MW in the X-band has been constructed. The device uses a relativistic electron beam with a radial electron density distribution similar to Gaussian, not annular as usual. The non-adiabatic perturbation of the magnetic guide field is produced by a single iron ring of 57 mm axial length. Measurements are reported of reproducibility, peak power and frequency-spectrum as a function of electron energy and magnetic field strength. The results presented are interpreted as far as possible using existing theories. (West Germany) H E Frank et al, J Phys D: Appl Phys, 15 (1), 1982, 41-49. 36 5401. An injection system for CHEER. (Canada) The injection system for CHEER must provide 34 bunches of 10xl electrons. We describe here a system consisting of a linear accelerator, accumulator-buncher ring, and a booster ring which can inject such bunches at 2 GeV into the main CHEER ring in an acceptably short time. K W Edwards et aL Con J Phys, 59 ill), 1981, 1797-1802. 36 5402. Convenient fast pulsed molecular beam valve. (USA) We describe a fast electromagnetic valve for generation of a pulsed supersonic molecular beam. The valve produces 70 #s pulses with typical intensities in the neighbourhood of I x 1022 molecules sr - t s - t at frequencies to 35 Hz. It is triggered by a low voltage-low current pulsed power supply which activates externally-mounted coils, minimizing problems of heat dissipation and electrical and magnetic interference. It also features a corrosion resistant gas reservoir isolated from the driving mechanism by a stainless steel bellows. Thomas E Adams et al, Rev Sci lnstrum, 52 (10), 1981, 1469-1472.
37. VACUUM INSTRUMENTATION FOR SURFACE STUDIES 37 5403. Transmission electron microscopy investigation of silkide formation on slightly oxidized silicon substrates. (USA) The formation of PtSi and Pd2Si on chemically cleaned and on slightly oxidized Si substrates had been investigated by TEM with cross-sectional specimens. The oxide has been found to influence the silieide-Si interface 773
surfaces are discussed and the uses of these interactions are briefly mentioned. I W Drummond, Vacuum, 31 (10-12), 1981, 579-588. 36 5398, Further aspects ofsputial separation ofmoleculesina molecular beam by iohomogeneous electrostatic fields. (GB) A further study has been made of a ring-type electrostatic focuser for molecular beams in respect of the degree of spatial separation of molecules with either the internal or external electric field. The external electric field of the ring focuser is calculated and is shown to have a very similar magnitude, and spatial extent to that of the already known internal field. State selection of that part of a molecular beam which sheaths the ring focuser, as well as that part within but deflected away from the beam axis, are shown experimentally to form intense annular rings of state selected molecules, concentric with the central core of focused molecules. Similar experimental results are also obtained with focusers of different geometries. A new method of molecular beam spectrometer signal enhancement based on these observations is proposed. D H H AI-Amiedy et al, J Phys D: Appl Phys, 15 (2), 1982, 193-196. 36 5399. Low energy electron beam relaxation in gases in uniform electric fields. (GB) The problem of low energy electron beam relaxation in a gas between two parallel plates is extended to include accelerating or retarding electric fields. The problem is solved by two different methods, assuming that the elastic scattering is isotropic and neglecting the energy losses in elastic collisions. The first method is based on solution of the equations of moments of the electron velocity distribution function. The second uses a novel Monte-Carlo simulation scheme, which allows us to find various moments of the distribution function without the simplifying assumptions of the first method. The calculated current to the plates and the calculated density distribution between the plates obtained by the two methods are in good agreement. (Israel) L. Friedland et al, J Phys D: Appl Phys, 15 (2), 1981, 251-262. 36 5400. An electron cyclotron maser for nanosecond megawatt pulses. (GB) An electron cyclotron maser with an output power of 1 MW in the X-band has been constructed. The device uses a relativistic electron beam with a radial electron density distribution similar to Gaussian, not annular as usual. The non-adiabatic perturbation of the magnetic guide field is produced by a single iron ring of 57 mm axial length. Measurements are reported of reproducibility, peak power and frequency-spectrum as a function of electron energy and magnetic field strength. The results presented are interpreted as far as possible using existing theories. (West Germany) H E Frank et al, J Phys D: Appl Phys, 15 (1), 1982, 41-49. 36 5401. An injection system for CHEER. (Canada) The injection system for CHEER must provide 34 bunches of 10xl electrons. We describe here a system consisting of a linear accelerator, accumulator-buncher ring, and a booster ring which can inject such bunches at 2 GeV into the main CHEER ring in an acceptably short time. K W Edwards et aL Con J Phys, 59 ill), 1981, 1797-1802. 36 5402. Convenient fast pulsed molecular beam valve. (USA) We describe a fast electromagnetic valve for generation of a pulsed supersonic molecular beam. The valve produces 70 #s pulses with typical intensities in the neighbourhood of I x 1022 molecules sr - t s - t at frequencies to 35 Hz. It is triggered by a low voltage-low current pulsed power supply which activates externally-mounted coils, minimizing problems of heat dissipation and electrical and magnetic interference. It also features a corrosion resistant gas reservoir isolated from the driving mechanism by a stainless steel bellows. Thomas E Adams et al, Rev Sci lnstrum, 52 (10), 1981, 1469-1472.
37. VACUUM INSTRUMENTATION FOR SURFACE STUDIES 37 5403. Transmission electron microscopy investigation of silkide formation on slightly oxidized silicon substrates. (USA) The formation of PtSi and Pd2Si on chemically cleaned and on slightly oxidized Si substrates had been investigated by TEM with cross-sectional specimens. The oxide has been found to influence the silieide-Si interface 773