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. Such conditions are essential for longevity of photoemitters in accelerator injectors and particle and hydrocarbon-free environments, in, for example, production of multi-layer x-ray mirrors for semiconductor lithography. The pumping techniques required to reach XHV conditions (e.g., sputter-ion, cascaded turbomolecular, and non-evaporable getter pumps) impede further reduction of the XHV pressure by either re-emitting chemically-stored pumped gas (sputter-ion and getter) or allowing backstreaming of exhaust gas (turbomolecular). It would be advantageous to be able to switch to a true gas exhausting pump without any danger of backstreaming, 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 proposed 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. Commercial Applications and Other Benefits: Because the principal residual gas present in XHV is hydrogen, this pump will extend system pressures into the lower XHV range, without the re-contamination from conventional vacuum pumps that reduces effective pumping speeds. The advantage of our product is that it will deliver improved pumping in existing systems that 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 for employment in, e.g., free-electron lasers, particle injectors, and storage rings. Another application is to reduce the residual hydrogen induced traps in semiconductor component encapsulations by using a miniature version of the pump to reduce the enclosure hydrogen.