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Nov 1964

Volume 1, Issue 2, pp. 35-68


Initiation of Electrical Breakdown in Ultrahigh Vacuum

D. Alpert, D. A. Lee, E. M. Lyman, and H. E. Tomaschke

J. Vac. Sci. Technol. 1, 35 (1964); http://dx.doi.org/10.1116/1.1491722 (16 pages) | Cited 92 times

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Existing theories for the initiation of electrical breakdown are reviewed, together with the experimental observations on which they are based. Experiments here described have extended the available data on electrical breakdown between broad area electrodes under ultra-high-vacuum conditions. The results, together with those of several other experimenters, are interpreted on the basis of a single picture which explains and relates the phenomena of predischarge currents and the initiation of breakdown. Based on field emission from sharp submicroscopic points, this picture predicts breakdown when the local electric field at the cathode reaches a critical value. The local field, which for broad area electrodes may be much larger than the average field, is deduced from observations of field emission prior to breakdown. When properly analyzed, data for tungsten electrodes from this research and several others indicate a value for the electrical field at breakdown which is independent of gap spacing or geometrical configuration for voltages up to 250 kV. The critical breakdown field for tungsten is 6.5×107 V∕cm. The above picture also gives physical insight into other phenomena associated with electrical breakdown.
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52.80.Vp Discharge in vacuum

Vacuum Vapor Deposition of Plutonium onto Aluminum

D. L. Coffey and P. A. Tucker

J. Vac. Sci. Technol. 1, 51 (1964); http://dx.doi.org/10.1116/1.1491723 (3 pages)

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A technique was developed for depositing plutonium-239 coatings up to 100 μ thick on aluminum sheet. The deposition system was an electron beam vacuum evaporator. Of several crucible materials evaluated, tantalum–0.1% tungsten was the most satisfactory material for containing the plutonium vapor source. The essential feature of the deposition process was a controlled sequence of substrate temperatures and evaporation rates. The average experimental rates of evaporation of plutonium agreed well with theoretical values, but wetting of the crucible resulted in scattering of the data. The aluminum–plutonium bond area was examined metallographically to determine the factors which influenced the adherence of the deposit. Insufficient reaction as well as excessive reaction between the substrate and the coating resulted in poor adherence.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Bx Metals, semimetals, and alloys

Orbitron Pump of 30-cm Diameter

Joseph C. Maliakal, Peter J. Limon, Eldon E. Arden, and R. G. Herb

J. Vac. Sci. Technol. 1, 54 (1964); http://dx.doi.org/10.1116/1.1491724 (8 pages) | Cited 6 times

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An Orbitron pump of 30-cm diameter was constructed and performance was studied as parameters were varied. The pump arrangement chosen gave pumping speed values of 105 liters∕sec for argon, 4500 liters∕sec for air, 6000 liters∕sec for nitrogen, and 9000 liters∕sec for hydrogen.
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07.30.Cy Vacuum pumps

A Bakeable Thermistor Vacuum Gauge

R. W. Roberts, P. E. McElligott, and G. Jernakoff

J. Vac. Sci. Technol. 1, 62 (1964); http://dx.doi.org/10.1116/1.1491725 (3 pages) | Cited 5 times

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A thermistor detector for measuring pressures in the range 10−4 to 1 Torr is described. This gauge operates at constant temperature (∼ 100 °C), has a small volume, and presents an innocuous surface to the vacuum system. This gauge is very stable, maintains its calibrations after a 450 °C bakeout, and is suited for use in ultrahigh-vacuum systems. Operating characteristics are described.
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07.30.Dz Vacuum gauges

Attainment of Pressures below 10−11 Torr after Bake at 250 °C

J. R. Young and F. P. Hession

J. Vac. Sci. Technol. 1, 65 (1964); http://dx.doi.org/10.1116/1.1491726 (2 pages) | Cited 1 time

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Abstract Unavailable
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07.30.Bx Degasification, residual gas

Avoiding Erroneous Submicron Pressure Readings: A Refrigerated McLeod

Erhard W. Rothe

J. Vac. Sci. Technol. 1, 66 (1964); http://dx.doi.org/10.1116/1.1491727 (3 pages) | Cited 17 times

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Abstract Unavailable
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07.30.Dz Vacuum gauges
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