Y. Li, R. Trubic, Y. He and N.B. Mistry

Laboratories of Nuclear Studies, Cornell University, Ithaca, NY 14853

As a compact, clean and passive pumping method, non-evaporable getters (NEGs) have been increasingly employed in many ultra-high and extreme-high vacuum applications. NEGs with large pumping capacity and relatively low activation temperature have been extensively used in large particle storage rings UHV system for distributed linear pumping. The need for adequate total adsorption capacity before reactivation requires a high pumping capacity in a small space. In this paper, we report pumping characteristics of two types of titanium-based NEG pumps.

The first NEG pump cartridge is made by stacking 50 sintered titanium-vanadium blades (provided by SAES Getters, as ST185) on a stainless steel tube, and are activated by a removable heater cartridge inserted into the tube. This NEG cartridge will be referred as the ST185 pump hereinafter. The ST185 cartridge is mounted on a 2-3/4" ConFlat flange via welding the stainless tube to the flange. The room temperature pumping speeds for CO and N₂ are measured as a function of sorbed gas quantities at various activation temperatures and activation duration. The study shows that there is a threshold of activation at a temperature of about 340^oC and that optimal pumping speed and pumping capacity can be achieved with activation for 30 minutes at 550^oC. The performance of the ST185 cartridge is also measured as a function of the NEG blade spacing to optimize the cartridge design. Linear pumping speeds of 2200 liter/sec^.m and 1300 liter/sec^.m can be achieved for CO and N₂, respectively. The low activation temperature of the ST185 NEG and the compact, scaleable design make the ST185 cartridge particularly attractive for situations with tight space and with components sensitive to high temperature.

The pumping performance of a flanged Ti-based NEG pump, supplied by Toriy Microwave Technologies, Moscow, Russia, was also evaluated with the same setup. This pump will be referred to as the Toriy pump hereinafter. The Toriy pump is a very compact pump, measuring 3.38" in diameter and 5" in height. The pump is activated by direct resistive heating the NEG elements up to 700^oC. The room temperature pumping speeds and pumping capacities for CO and N₂ are measured as a function of sorbed gas quantities at various activation powers and activation durations. One of the very attractive feature of the Toriy pump is its quick activation. Our tests show that pumping speeds of 100 l/s and 60 l/s can be achieved for CO and N₂, respectively, in less than 2 minutes activation at a heating power of 130 watts.