Experience with a pulsed gas flow technique for calibrating vacuum gauges

Chubb, JN; Gowland, L.

doi:10.1016/0042-207x(67)91786-1

Cited by 10 publications

(5 citation statements)

References 3 publications

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“…If the rate of desorption and the sticking coefficient are uniform over the condensing surface there will be no net transport of gas in the system, and the incidence rates of molecules across all boundaries and on all surfaces will be identical. The average rate of desorption, in molecules cm-2 s-1, may then be related to the gas density ng observed in any defined region of uniform temperature Tg (Chubb and Gowland 1967) by the equation Vd=$yng?Oo( Tg/273*15)'/2…”

Section: Experimental Techniques Of Performance Assessmentmentioning

confidence: 99%

Condensation pumping of hydrogen and deuterium on to liquid-helium-cooled surfaces

Chubb¹,

Gowland²,

Pollard³

1968

J. Phys. D: Appl. Phys.

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The condensation of hydrogen and deuterium on to liquid-helium-cooled surfaces is being studied for high-efficiency contamination-free pumping applications in plasma physics experiments. The present experimental studies show that the sticking coefficient of hydrogen and deuterium at room temperature increases during initial coverage of a liquid-helium-cooled condensing surface from around 0·5 at about 1013 molecules cm−2 to between 0·7 and 0·95 at 1016 molecules cm−2, and then remains essentially independent of further coverage. The sticking coefficient tends to increase with increasing gas incidence rate, but is only susceptible to surface temperature at the higher end of the range 2·1-3·7°K for very low gas inflow rates. During initial coverage of the condensing surface the desorption rate of gas molecules increases with surface coverage and reaches a steady value for coverages of about 3 × 1016 molecules cm−2. This desorption rate does not decrease as rapidly with surface temperature as expected from published hydrogen and deuterium vapour-pressure curves. Experiments show that this is due to thermal-radiation desorption effects. The application of condensation pumping in practice to maintain gas densities below about 5 × 108 molecules cm−3 (about 10 ntorr) thus requires some restriction of the thermal-radiation loading at the condensing surface.

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Section: Experimental Techniques Of Performance Assessmentmentioning

confidence: 99%

Condensation pumping of hydrogen and deuterium on to liquid-helium-cooled surfaces

Chubb¹,

Gowland²,

Pollard³

1968

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

show abstract

Section: Experimental Techniques Of Performance Assessmentmentioning

confidence: 99%

“…where Iis the electron emission current and S the sensitivity in units of cm3 molecule-1 (Chubb and Gowland 1967). When additional gas is introduced into the vacuum chamber to allow measurement of the pumping performance, the free molecular flow of gas molecules from the point of introduction to the condensing surface will give rise to some non-uniformity in the impact density distribution of molecules around the surfaces of the vacuum chamber.…”

Section: Experimental Techniques Of Performance Assessmentmentioning

confidence: 99%

“…To allow variations of the sticking coefficient and the desorption rate to be studied during progressive coverage of a condensing surface a special gas flow system was developed which allowed a known gas flow rate to the chamber to be switched on and off with a short time constant (Chubb and Gowland 1967). This system provided gas incidence rates at the condensing surface down to about 1 x 1012 molecules cm-2 s-1 with total impurity levels usually below 1 % .…”

Section: Experimental Techniques Of Performance Assessmentmentioning

confidence: 99%

“…In this illustration the 10 s gas flow pulses were separated by 10 s intervals of no gas flow. As the vacuum chamber in figure 1 could be valved-off from its pumps the switching facility of the gas flow system could be used to generate known gas densities in the chamber for calibration of the ion gauges and mass spectrometers used in assessing pumping performance (Chubb and Gowland 1967). A gas flow rate of 3 x 1014 molecules s-1 could be injected into the 60 1. volume of the chamber for times down to about 0-5 s to provide calibrating gas densities down to about 3 x lo9 molecules cm-3 (equivalent to about 100 ntorr).…”

Section: Experimental Techniques Of Performance Assessmentmentioning

confidence: 99%

See 2 more Smart Citations

Vertical Coherence Measurements of Ambient Noise in Shallow Water off the East Coast of Korea

Cho¹,

Choi²

2011

Jpn. J. Appl. Phys.

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The condensation of hydrogen and deuterium on to liquid-helium-cooled surfaces is being studied for high-efficiency contamination-free pumping applications in plasma physics experiments.The present experimental studies show that the sticking coefficient of hydrogen and deuterium at room temperature increases during initial coverage of a liquid-heliumcooled condensing surface from around 0.5 at about 1013 molecules cm-2 to between 0.7 and 0.95 at 1016 molecules cm-2, and then remains essentially independent of further coverage. The sticking coefficient tends to increase with increasing gas incidence rate, but is only susceptible to surface temperature at the higher end of the range 2.1-3.7"~ for very low gas inflow rates.During initial coverage of the condensing surface the desorption rate of gas molecules increases with surface coverage and reaches a steady value for coverages of about 3 x 1016 molecules cm-2. This desorption rate does not decrease as rapidly with surface temperature as expected from published hydrogen and deuterium vapourpressure curves. Experiments show that this is due to thermal-radiation desorption effects. The application of condensation pumping in practice to maintain gas densities below about 5 x 108 molecules cm-3 (about 10 ntorr) thus requires some restriction of the thermal-radiation loading at the condensing surface.

show abstract

Development of master instruments for measuring total and partial pressures in high and ultrahigh vacuum regions

Gulyaev¹,

Eryukhin²

1971

Meas Tech

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Experience with a pulsed gas flow technique for calibrating vacuum gauges

Cited by 10 publications

References 3 publications

Condensation pumping of hydrogen and deuterium on to liquid-helium-cooled surfaces

Condensation pumping of hydrogen and deuterium on to liquid-helium-cooled surfaces

Vertical Coherence Measurements of Ambient Noise in Shallow Water off the East Coast of Korea

Development of master instruments for measuring total and partial pressures in high and ultrahigh vacuum regions

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