Speaker
Description
The LUX-ZEPLIN (LZ) Ti cryostat, despite having record low levels of many reported radioactive contaminants, shows a surprisingly high level of radon emanation. Possible explanations include ineffective acid etching of surface contamination, significant surface contamination added after the etching, or surprisingly high diffusion of radon in Ti. Measurements to determine the cause and help ensure low radon emanation from Ti in the future will be discussed. Upper limits on radon diffusion through Ti are determined using a setup with Ti foil. Radon emanation is being measured using cleaned Ti from the same batch as used for the LZ cryostat, and from additional Ti discs both before and after acid etching, with multiple measurements providing information on the fraction of radon emanation due to recoils vs. diffusion.