Pumping of methane by an ionization assisted Zr/Al getter pump
The pumping of methane by an ionization assisted Zr/Al getter pump has been investigated. This pump consists of 12 pieces of ring getters. A spiral shape W filament is located within the ring getters. A bias voltage is applied across the filament and the getter itself. The experiments have shown that (1) when the bias voltage is turned off, the pumping speed of the getter pump for methane increases exponentially with the filament temperature; (2) when the filament temperature is held constant, its pumping speed varies directly with the ionization electron current; (3) when the filament temperature is 2063/sup 0/C and the electron current is 57 mA, the pumping speed of the Zr/Al getter pump is 475 ml/s, and the specific speed is 16.8 ml/s cm/sup 2/; and (4) an activation energy and critical temperature measured for methane molecules decomposition are, respectively, 47.4 kcal/mol and about 1700/sup 0/C. Analysis of the results indicates that methane is pumped by an ionization assisted Zr/Al getter pump not because of the adsorption and the diffusion of methane molecules directly, but because methane molecules are decomposed as C and H/sub 2/ through a catalysis of the hot W filament, carbon is adsorbed on the surface of the W filament, and is diffused into the interior of the W lattice. H/sub 2/ is immediately absorbed by the Zr/Al getters. Besides, electron impact with CH/sub 4/ would result in the additional decomposition and ionization, then the effect of electron bombardment enhances methane pumping by the Zr/Al getters.
- Research Organization:
- Institute of Electronics, Academia Sinica, Beijing, People's Republic of China
- OSTI ID:
- 6423889
- Journal Information:
- J. Vac. Sci. Technol., A; (United States), Journal Name: J. Vac. Sci. Technol., A; (United States) Vol. 5:4; ISSN JVTAD
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360104* -- Metals & Alloys-- Physical Properties
ADSORPTION
ALKANES
ALLOYS
ALUMINIUM ALLOYS
CARBON
CATALYSIS
DIFFUSION
ELEMENTS
EQUIPMENT
GETTERING
GETTERS
HYDROCARBONS
HYDROGEN
LABORATORY EQUIPMENT
METHANE
NONMETALS
ORGANIC COMPOUNDS
PUMPING
PUMPS
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES
VACUUM PUMPS
ZIRCONIUM ALLOYS