Showing papers in "Vacuum in 1974"

TL;DR: In this article, the four lowest autoionizing levels in helium have been studied near their thresholds for excitation by electron impact, and features in the spectra of electrons ejected from these states were seen to shift to steadily higher energies as the impact energy was lowered to within a few electron volts above threshold.

TL;DR: Secondary ion mass spectrometry (SIMS) can be used to investigate the composition of solids in the following way: by means of an ion bombardment (energy 3-15 keV) the sample is sputtered away.

TL;DR: In this article, a saddle field ion source with its axis of symmetry coincident with the center of the ion beam is described, and a typical energy distribution curve for argon at 6 kV at 2 × 10−4 torr, the beam energy is 0.85 of the anode potential and the half width is about 250 V.

TL;DR: In this article, the results of a series of experiments aimed at producing cleaner surfaces in vacuum chambers are presented. But the results are only from the empirical point of view with the emphasis on practical implications for machines where the surfaces of the vacuum system are subjected to ion bombardment.

TL;DR: In this paper, the authors used solvent cleaning and high temperature treatment in vacuo and gas discharge cleaning to obtain a clean vacuum chamber surface with low gas desorption under ion bombardment.

TL;DR: The AEI IM20 ion probe and MS702R mass spectrometer form a composite instrument incorporating both techniques; the design and different operating modes are described in this paper, where a primary ion beam diameter as low as 2 μm can be obtained under favourable circumstances; the minimum detectable concentration of a typical element is derived as a function of this diameter.

TL;DR: In this article, low energy helium ions have been injected into 304 stainless steel, polycrystalline nickel foil and single crystal nickel targets and the gas evolution rate monitored during post-bombardment annealing.

TL;DR: The various problems arising in the quantitative application of resonance theory to dissociative attachment are reviewed, with particular attention to the problem of a unique definition for the resonant state.

TL;DR: A review of the epitaxial growth of metals in high and ultra-high vacuum leading to single-crystal films is presented in this paper, where conditions for obtaining such films are described and tabulated for two groups of substrates: (i) metals, Si, Ge (strong interfacial bonding) and (ii) alkali halides and MgO cleavage faces (weak interfacial binding).

TL;DR: In this article, the transition radiation at the anode of a high voltage vacuum device using a low-light telescope has enabled the positions of the emission sites on the cathode to be determined accurately and showed the way in which emitters are destroyed and sometimes produced at a breakdown.

TL;DR: In this article, a new technique for the fabrication and resharpening of field emitters is described, which employs an ion gun and uses methods analogous to those used to produce thin foils for the transmission electron microscope.

TL;DR: In this article, metal surfaces have been bombarded with deuterons in the energy range 5 − 35 keV and mass spectra of the gases desorbed observed, the principal gases released are hydrogen and carbon monoxide.

TL;DR: When low energy (100 eV to a few keV) ions interact with a target surface several secondary emission processes occur, each of which may be studied to give information on the nature of the bombarded material as discussed by the authors.

TL;DR: In this article, the authors measured the pumping speed of BA-gauges using W (thoriated Ir) filaments and found it to be 0.28 (0.12) litres/s for H2, 1.5 ( 0.5) litres /s for O2, and no pumping speed could be detected for CO.

TL;DR: In this article, a molecular beam detector based on a mass spectrometer is used to measure backstreaming phenomena in high vacuum systems, which are not due to mere evaporation but to molecular scattering within the baffle.

TL;DR: In this paper, the authors investigated the electron (n e ), negative ion (n − ) and positive ion ( n + ) densities produced by electron attachment in oxygen at low pressure (10 − 3 torr), and the factors limiting the achievement of very low electron density β = n e n + ).

TL;DR: In this article, an electron beam excited fluorescence technique was used to make simultaneous measurements of rotational and translational accommodation of nitrogen on nickel, silver, gold and stainless steel solid surfaces.

TL;DR: In this article, the evaporation of polymer films is described by a simple theory, which indicates clearly that electronic rate measurement gives no correct result due to the mechanism, and the theory is illustrated with experimenal results made on PTFE.

TL;DR: In this paper, the authors used a rotating substrate and a rotating shutter situated between the source and the substrate, the axis of rotation of the shutter being displaced from the line joining the center of rotation on the substrate and the centre of the source.

TL;DR: In a drift tube mass spectrometer, the following reactions have been studied: CO3− + 2CO2→CO3−CO2 + CO2 k ≤ 10−33 cm6 s−1CO3+ + CO→CO2+ CO2 + e k = 5 ± 1·0 × 10−13 cm3 s− 1CO3 − + H2→products k Gas temperatures up to 523 K had no observable effect on ion molecule reactions.

TL;DR: In this paper, mass spectra are given of the gas atmospheres in an r.f. getter sputtering plant when depositing tantalum, and it is shown that gettering reduces the gaseous impurities.

TL;DR: In this article, the design and working characteristics of vapour pumping groups have been discussed and the various elements (valves, trap, baffle, pump etc) incorporated in a single structure.

TL;DR: In this article, a unified treatment of formal mathematical relationships for thermal desorption from an energetically homogeneous surface is given for a wide class of heating regimes, and the processing of experimental data is discussed.

TL;DR: In this paper, a restricted review is made of recent measurements on negative ion/molecule reactions under swarm conditions only processes where the detachment of an electron plays a part are considered.

TL;DR: In this article, the performance of the oscillating electron electrostatic ion source has been improved by incorporating a small chimney into the ion exit aperture to reduce the field distortion at the aperture.

TL;DR: In this article, the characteristics of a small quadrupole mass spectrometer are described in detail and the requirements of an analytical instrument for use in high and ultra high vacuum systems have been met.

TL;DR: In this paper, the effects of dose, dose rate and implant temperature on post-bombardment gas evolution rate spectra have been investigated and a model for low energy helium trapping is suggested which is consistent with previously observed dose dependent trapping probability and explains almost total inhibition of gas trapping observed at implant temperatures in excess of 450°C.

TL;DR: In this paper, the reemission of deuterium from molybdenum during 7 keV D + bombardment at 77 K has been measured and this data compared with 20 keVD + bombardment, showing an increase in the number of peaks at lower temperatures as the incident ion dose is increased.

TL;DR: In this article, the authors describe results obtained on sampling both positive and negative ions from flames, and illustrate the problems common to, and differences between, positive or negative ion sampling.