Improvement of Hydrogen Pumping Characteristics of Penning Discharge Getter-Ion Pumps

Pumping hydrogen with Penning discharge getter-ion pumps at the flow rates normally encountered with accelerators employing hydrogen ion sources presents problems that do not appear when these pumps are employed on systems where the only gas load is that arising from surface degassing and residual leakage. These problems are,-1) thermal instability resulting from reemission of absorbed hydrogen, and 2) deformation of the titanium cathodes with hydrogen absorption. This report outlines the pertinent considerations involved in modification of the design of the pumping elements of a standard 500 l/s pump (air rating), 1) to increase by a factor of about 10 the hydrogen gas load the pump can handle without danger of thermal instability, and 2) to virtually eliminate titanium deformation. Hydrogen gas loads of up to 5 atm cm3/min can now be accomodated with a 500 l/s pump. While service life expectancy was previously limited to 2000-3000 hours by anode-cathode short circuit, it is presently limited by the ultimate hydrogen absorption capacity of the titanium. It is anticipated that life expectancies of up to 25000 hours can be realized with the 500 l/s pump at a hydrogen flow rate of 1 atm cm3/min.