Chemical gettering at high pressures

Summary form only given. Conventional gettering involves the scavenging of gases in a chamber after the pressure has been first lowered with at least a mechanical pump. Once gettering is complete, as in a vacuum tube; the amount of desorbed gas which would require follow-on pumping is not normally significant. The same is not true for a variety of systems of current interest to the plasma community. The impracticality of connecting an external pump to a fielded system caused us to research the feasibility of gettering at high pressures. It was found that the pressure of carbon dioxide in a closed chamber can be dramatically reduced by letting it react with a mixture of sodium hydroxide and magnesium perchlorate. By distributing the solid reactants throughout a porous substrate to maintain an uncorrupted large surface area, it was found that the chamber pressure in a container of volume 20 filters could be reduced from 1000 mTorr to 100 mTorr a dozen times, with the pumping time in each case being only about two minutes.