A New Multi-Electrode Evaporator for Refractory Metals and Its Application to Getter Pumps

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Abstract
The design and operating characteristics of a new multielectrode evaporator are described. To examine the operation of this evaporator, deposition rates for Ta, Nb and Mo were measured by a quartz-crystal thickness monitor placed 135 mm from the source. The values obtained are as follows: Ta, 73 Å/min at 400 W; Nb, 29 Å/min at 200 W; Mo, 75 Å/min at 160 W. The gettering properties of deposited Ta were studied in an ultra-high vacuum system. The ultimate pressure below 8×10-9 Pa was obtained by using Ta films deposited onto liquid nitrogen cooled walls. The significance of reducing gas evolution from getter films is emphasized.