New ionization gauge geometries providing stable and reproducible sensitivities
Abstract
A primary cause of inaccuracies in Bayard–Alpert (BA) gauges has been previously identified as the unstable and nonreproducible distribution of electron emission from hot cathodes. Because of uncontrollable variations and instabilities in electron emission density pattern along the length of a hot cathode, the assumptions required to apply the fundamental ionization gauge equation, p=i+/(Si−), are not well satisfied in BA gauges or other ionization gauges employing grids. A new class of ionization gauge geometries is described which avoids these difficulties by closely satisfying the assumptions. New geometries are defined so that regardless of where on the hot cathode an electron is emitted, the electron has the same probability of causing ionization as any other emitted electron. Computer simulated electron and ion trajectories are presented for an optimum simple geometry. Testing of hardware has shown that our computer model is a good predictor of actual electron trajectories. Extensive testing including life testing is being carried out but the limits of performance of this new design have not yet been ascertained. These data indicate it should be possible to duplicate the pressure range of the BA gauge in a simple ionization gauge that is fully compatible with existing gauge controllers and which provides considerably better stability and reproducibilty of gauge sensitivity than does a BA gauge.
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Bills et al. designed a BAG with a semi-circular ribbon cathode in front of a slit of a slightly deformed hemispherical anode grid; all electrons take the same type of path and length and have almost the same energy so that changes of emission will not affect sensitivity.
“To meet these requirements Bills et al. [23] designed an interesting BAG shown in Fig. 3.A semi-circular ribbon as cathode is positioned in front of a slit of slightly deformed hemispherical anode grid.All electrons emitted from this ribbon take the same type of path and therefore length and have almost the same energy so that any changes of emission will not affect the sensitivity.”
From A review on hot cathode ionisation gauges with focus on a suitable design for measurement accuracy and stability (2020) · cites this paper as [23]
Bills et al. stated that the main cause of inaccurate and unstable sensitivities in BAG is the unstable and nonreproducible distribution of electron emission from hot cathodes.
“Bills et al. [23] stated in 1984 that the main cause of inaccurate and unstable sensitivities in BAG is the unstable and nonreproducible distribution of electron emission from hot cathodes.”
From A review on hot cathode ionisation gauges with focus on a suitable design for measurement accuracy and stability (2020) · cites this paper as [23]
The approaches of Bills et al. [23] and Klopfer [29] offer both the possibility of a well-defined electron path and the possibility to separate at least some of the surface effects from volume effects.
“These designs offer both the possibility of a well-defined electron path and the possibility to separate at least some of the surface effects from volume effects.”
From A review on hot cathode ionisation gauges with focus on a suitable design for measurement accuracy and stability (2020) · cites this paper as [23]
Bills et al. defined four requirements for a stable BAG design: all emitted electrons must enter the ionisation space; path length and energy of each electron must be independent of the point of origin on the cathode; the number of transits through the ionisation space must be constant (preferably 1); and the ion collection efficiency must be independent of the point of origin on the cathode.
“To this end, they defined 4 requirements for a design of a stable BAG: a.All emitted electrons must enter the ionisation space b.Path length L (Eq. ( 1)) and energy of each electron must be independent of the point of origin on the cathode c.The number of transits through the ionisation space must be constant (preferably 1) d.The ion collection efficiency must be independent of the point of origin”
From A review on hot cathode ionisation gauges with focus on a suitable design for measurement accuracy and stability (2020) · cites this paper as [23]
In a modified design, Bills et al. proposed an exit slit for the electrons on the opposite side of the ribbon so that electrons hit the outer part of the grid, preventing X-rays from reaching the ion collector directly.
“In a modified design the authors proposed an exit slit for the electrons on the opposite side of the ribbon so that the electrons hit the outer part of the grid.In this way, the X-rays could not reach the ion collector directly.”
From A review on hot cathode ionisation gauges with focus on a suitable design for measurement accuracy and stability (2020) · cites this paper as [23]
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Jousten, K., Boineau, F., Bundaleski, N., Illgen, C., Setina, J., Teodoro, O. M. N. D., Vicar, M., & Wüest, M. (2020) · Vacuum · doi:10.1016/j.vacuum.2020.109545 · Cited by 34 · see citing works
- Authors
- Bills, D. G., Arnold, P. C., Dodgen, S. L., & Van Cleve, C. B.
- Affiliations
- Granville–Phillips Company, Boulder, Colorado 80303
- Venue
- Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films
- Publisher
- American Vacuum Society
- Published
- 1984-04-01
- Volume
- 2
- Issue
- 2
- Pages
- 163-167
- ISSN
- 0734-2101
- 1520-8559
- Cited by
- 11
- References
- 0
- Language
- en
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