PERM-PUMP: A Power-Free Hydrogen-Extraction Permeation Pump for XHV

Extreme high vacuum (XHV) systems are characterized by very low gas pressure and a small outgassing rate of the system surfaces. The pumping techniques required to reach XHV conditions impede further reduction of the XHV pressure by either re-emitting chemically-stored pumped gas or allowing back streaming of exhaust gas. It will be advantageous to be able to switch to a true gas exhausting pump without any danger of back streaming, after reaching XHV pressures. An XHV-specific passive, power-free pump, capable of permanently removing hydrogen gas from the system via permeation through a palladium membrane, will be constructed. The pump consists of a hydrogen transparent membrane capable of withstanding a differential pressure of several atmospheres differential pressure. The upstream side of the membrane is exposed directly to the vacuum, while downstream is connected to a small exterior volume continuously micro-flushed with inert gas to transport the permeated hydrogen away. The principle milestone in the Phase I was to show that a Pd membrane or foil could successfully be operated in vacuum to transport hydrogen one way, i.e., it pumps. This was accomplished and the foils were shown to be mechanically robust with their pumping action simulated using COMSOL. The overall Phase II program goal is to optimize the Perm-Pump design for maximum pumping speed while improving its robustness against overpressure and contamination, and demonstrate its operation at extreme high vacuum. At the end, a prototype will be ready for demonstration. This pump will extend system pressures into the lower XHV range, without the re-contamination from conventional vacuum pumps that reduces effective pumping speeds. Commercial Applications and Other Benefits: The pumps advantage is that it will operate at the low end of the ultrahigh vacuum (UHV) range and all the XHV range. Those laboratories utilizing XHV can immediately take advantage of it use on existing systems as a direct add on product. Such a major improvement in pumping technology would also spur efforts to improve materials and make XHV systems as common as UHV systems are now. Commercial uses would include semiconductor EUV lithography, MEMS devices, and the aerospace industry as well as science labs.