A regenerable filter for liquid argon purification

A filter system for removing electronegative impurities from liquid argon is described. The active components of the filter are adsorbing molecular sieve and activated-copper-coated alumina granules. The system is capable of purifying liquid argon to an oxygen-equivalent impurity concentration of better than 30 parts per trillion, corresponding to an electron drift lifetime of at least 10 ms. Reduction reactions that occur at ∼250∘C allow the filter material to be regenerated in situ through a simple procedure. In the following work we describe the filter design, performance, and regeneration process.