Browse - Journal of Vacuum Science & Technology Archives 1964-1982

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S. P. Wolsky, T. R. Piwkowski, and G. Wallis

J. Vac. Sci. Technol. 2, 97 (1965); http://dx.doi.org/10.1116/1.1492410 (7 pages) | Cited 7 times

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Germanium films were sputtered onto fused quartz and self-substrates in a low-pressure thermionically supported discharge. Reflection electron diffraction and x-ray examination showed that over comparable temperature ranges the orientation of sputtered germanium films on fused quartz differed from that of evaporated films. Epitaxy was obesrved on self-substrates at 150 °C. Electrical characteristics of evaporated and sputtered films were strikingly similar despite wide variation in substrate material and temperature and in deposition rates.

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81.15.Cd	Deposition by sputtering
73.61.Cw	Elemental semiconductors
68.55.-a	Thin film structure and morphology

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Ionization Gauge Calibration System Using a Porous Plug and Orifice

Charles L. Owens

J. Vac. Sci. Technol. 2, 104 (1965); http://dx.doi.org/10.1116/1.1492411 (5 pages) | Cited 3 times

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A calibration facility in which reproducible pressures are conveniently generated for ionization gauge calibration is described. The method uses two conductances in series, both operating in the molecular flow region, to produce low pressures at the test gauge. These low pressures are referenced to higher pressures whose measurement can been accomplished by convenient methods. The test pressure is proportional to the ratio of the two conductances. By using a porous material and a thin plate orifice, the reference pressure is reduced by a factor of approximately one million. A convenient feature of the system is the fact that once the ratio of the conductances has been determined, it can be used for many gases. Experimental results obtained using this method over the range from 10⁻³ to 10⁻⁹ Torr are presented.

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07.30.Dz

Vacuum gauges

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Determination of Thermal Accommodation of Translational Energy of Vapors at a Glass Surface

J. A. Morrison and Y. Tuzi

J. Vac. Sci. Technol. 2, 109 (1965); http://dx.doi.org/10.1116/1.1492412 (4 pages) | Cited 1 time

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A new method has been developed for the determination of translational thermal accommodation coefficients, α_t, of vapors interacting with solid surfaces and has been used to measure α_t for bromine, iodine, benzene, naphthalene, n-hexane, and ethylacetate on Pyrex glass in the temperature region 195 ° to 465 °K. The values obtained (0.55, 0.64, 0.37, 0.37, 0.47, and 0.46, respectively) have a probable accuracy of ±0.06 or better and are only slightly temperature-dependent.

The method, which can be easily adapted for the study of interactions with surfaces other than glass, requires the measurement of the mean velocity of molecules leaving the solid surface. This is accomplished by passing a selected beam of the molecules through the sensitive volume of an ion gauge. The only restriction on the method is that the pressure of the vapor at the temperature of the wall of the gauge should be very low (e.g., 10⁻¹² Torr).

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34.35.+a	Interactions of atoms and molecules with surfaces
68.08.-p	Liquid-solid interfaces
68.43.-h	Chemisorption/physisorption: adsorbates on surfaces
07.30.-t	Vacuum apparatus

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A Mass Spectrometric Study of the Outgassing of Some Elastomers and Plastics

R. S. Barton and R. P. Govier

J. Vac. Sci. Technol. 2, 113 (1965); http://dx.doi.org/10.1116/1.1492413 (10 pages) | Cited 2 times

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Information on the outgassing properties of a number of plastic materials has been obtained by the use of a bakeable mass spectrometer. This was fitted with vacuum locks to avoid affecting the residual gas compositions by introduction of the sample. Each material was examined after, (1) it had been pumped for an acceptable pumpdown time, (2) it had been baked in vacuo at its maximum permissible temperature, (3) re-exposure to the laboratory atmosphere followed by the same period of pumping as originally adopted. The majority of the materials examined showed water to be the main component of outgassing. In general, bakeout in vacuo produced a permanent reduction in hydrocarbon evolution, but after re-exposure to laboratory air the rate of water vapor evolution was comparable with that originally observed.

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07.30.Bx

Degasification, residual gas

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Vacuum Design Problems of High Current Electron Storage Rings

G. E. Fischer and R. A. Mack

J. Vac. Sci. Technol. 2, 123 (1965); http://dx.doi.org/10.1116/1.1492414 (8 pages) | Cited 3 times

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A vacuum of the order of 10⁻⁹ Torr is required in the chamber of a proposed 180-ft-diam, 3-BeV, electron-positron storage ring in order to permit beam lifetimes of many hours and to reduce background interaction rates. This pressure must be maintained in the presence of 500 kW of synchrotron radiation with a critical wavelength of 3.2 Å. The rate of radiation-induced gas evolution is investigated. The process is believed to take place via a two-step mechanism—photoelectric emission followed by electron desorption. Experimental results of various investigators are described. A combination ion-getter and titanium sublimation pumping system with total pumping speed of one half million liters per second is proposed to deal wish the problem.

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29.20.db	Storage rings and colliders
07.30.-t	Vacuum apparatus

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Vacuum Problems of Electron and Positron Storage Rings

M. Bernardini and L. Malter

J. Vac. Sci. Technol. 2, 130 (1965); http://dx.doi.org/10.1116/1.1492415 (12 pages) | Cited 2 times

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The problem of gas evolution in electron-positron storage rings due to synchrotron radiation was explored. The spectral distribution of the radiation was first computed. From this and from data on quantum efficiency it was possible to determine an upper limit to the resultant photoemission from the ring walls. Measurements of the desorption efficiency from stainless steel 304 then made possible a determination of the maximum gas load which could be expected as a result of the synchrotron radiation.

This treatment was applied to a planned storage ring to be built at Frascati. From this it appeared that with modest processing the ring walls could be put into a condition such that the gas evolution would have completely acceptable values. The effects of wall temperature and of processing in hydrogen and oxygen upon the desorption efficiency were determined. On the basis of the results obtained it is concluded that optimum results would be obtained by the use of materials which are gas-free and on which tightly bound layers are formed from the ambient atmosphere.

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29.20.db	Storage rings and colliders
07.30.-t	Vacuum apparatus

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Ultrahigh Vacuum for Storage Rings for 28-GeV Protons

E. Fischer

J. Vac. Sci. Technol. 2, 142 (1965); http://dx.doi.org/10.1116/1.1492416 (7 pages) | Cited 2 times

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The Study Group on New Accelerators at CERN has worked out a proposal to add a pair of intersecting storage rings to the existing 28-GeV proton synchrotron. Accelerated protons injected into both rings would circulate in opposite directions and could collide in eight regions where the rings intersect. The working principle, general layout, and expected performance figures of the proposed research facility are given. The average residual gas pressure in the system must be 10⁻⁹ torr in order to have a useful lifetime of about 12 h. In the colliding beam areas even a pressure of 10⁻¹⁰ to 10⁻¹¹ Torr is very desirable in order to keep the back-ground from residual gas scattering low enough for the observation of p-p scattering. The basic concept of the ultrahigh-vacuum system for the intersecting storage rings is described. Experimental studies on the main vacuum problems have been started.

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29.20.db	Storage rings and colliders
07.30.-t	Vacuum apparatus

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The Stanford Two-Mile Linear Electron Accelerator

R. B. Neal

J. Vac. Sci. Technol. 2, 149 (1965); http://dx.doi.org/10.1116/1.1492417 (11 pages) | Cited 2 times

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A two-mile linear accelerator under construction at Stanford University will, upon completion in 1966, accelerate electrons to energies of 20 BeV for purposes of physics research. The accelerator consists of an evacuated disk-loaded waveguide through which an electromagnetic wave at 2856 Mc∕sec propagates at the velocity of light. Electrons, injected at one end, are accelerated by the traveling wave along the axis of the structure, gaining energy in the process. Radio-frequency power is supplied by 240 klystron amplifiers each producing 24 MW peak and 22 MW average at 360 pulses∕sec and 2.5-μsec pulse length. The accelerator and the waveguides are evacuated to 10⁻⁷ Torr by 120- to 500-liters∕sec ion getter pumps connected to an 8-in. longitudinal manifold in an upper gallery. Vacuum “finger” manifolds extend transversely at 80-ft intervals to the lower accelerator housing. All-metal seals are used throughout the vacuum system.

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