PUMPING CHARACTERISTICS OF A TITANIUM DROPLET GETTER-ION PUMP

Journal Article · Thu Sep 01 04:00:00 EDT 1960 · Brit. J. Appl. Phys.

DOI:https://doi.org/10.1088/0508-3443/11/9/302· OSTI ID:4140906

Holland, L; Laurenson, L

The performance of a 12-in. diameter titanium getterion pump with an evaporated getter area of 3400 cm/sup 2/ was studied. The titanium was evaporated from an electronbombarded molten bead suspended via a frozen zone from a cooled anode. A triode electrode system was used for ionization pumping. The sorption rates of a number of gases were measured in the pressure range 10/sup -4/ to 10/sup -8/ mm of mercury. The pumping speed for nitrogen was enhanced by operating the ionization source during evaporation. The high tension voltage used with the vapor source influenced the form of the titanium bead, and at low voltages ( approximately 800 v) and high-power inputs ( approximately 465 w) large metal droplets were obtained giving the highest evaporation and sorption rates. Sorption rates were greatly increased if a diffusion pump was in operation during gettering, because impurity gases slowly sorbed by the getter- ion pump were more effectively removed. Pumping speeds in liters/sec at 10/sup - 6/ mm of mercury for the getter-ion pump with a diffusion pump (10 liters/sec) in operation and a titanium evaporation rate of 40 mg/min were as follows: oxygen/ sub 2/, 2450; nitrogen/sub 2/, 4500; hydrogen/sub 2/, 1600; air, 600; argon, 2.5; and calor gas, 90. The low pumping speed of air was due to the low sorption rate of the argon component. Hydrocarbon gases were slowly sorbed and when mixed with active gases greatly reduced their pumping speed. The pump-down characteristics of the getter-ion pump were examined and it was found that the ultimate pressure was only slowly regained after exhausting oxygen. The sorption efficiency can be found from the equation: S/sub m/ = alpha S/sub 0/, where S/sub m/ is the measured sorption rate per unit getter area d alpha the sorption coefficient. Values of alpha measured at 10/sup -6/ mm of mercury were as follows: oxygen/ sub 2/, 0.068; nitrogen/sub 2/, 0.12; and hydrogen/sub 2/, 0.012; possible reasons for the low value of alpha for hydrogen are considered. (auth)

• Research Organization: Edwards High Vacuum Ltd., Crawley, Sussex, Eng.
• NSA Number: NSA-14-025596
• OSTI ID: 4140906
• Journal Information: Brit. J. Appl. Phys., Journal Name: Brit. J. Appl. Phys. Vol. Vol: 11
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ADSORPTION
AIR
ANODES
ARGON
CONFIGURATION
COOLING
DIFFUSION
EFFICIENCY
ELECTRIC POTENTIAL
ELECTRODES
ELECTRON BEAMS
ENGINEERING AND EQUIPMENT
EQUATIONS
EVAPORATION
GASES
HYDROCARBONS
HYDROGEN
IMPURITIES
ION SOURCES
IONIZATION
IONS
MEASURED VALUES
MIXING
NITROGEN
OPERATION
OXYGEN
PERFORMANCE
PUMPS
SOLIDIFICATION
TITANIUM
TRAPS
VACUUM
VAPORS
VELOCITY
ZONES