Long-lived radon daughters are a critical background source in experiments searching for low-energy rare events. Originating from radon in ambient air, radioactive polonium, bismuth and lead isotopes plate-out on materials that are later employed in the experiment. In this paper, we examine cleaning procedures for their capability to remove radon daughters from PTFE surfaces, a material often used in liquid xenon TPCs. We found a large difference between the removal efficiency obtained for the decay chains of 222Rn and 220Rn, respectively. This indicates that the plate-out mechanism has an effect on the cleaning success. While the long-lived 222Rn daughters could be reduced by a factor of ~2, the removal of 220Rn daughters was up to 10 times more efficient depending on the treatment. Furthermore, the impact of a nitric acid based PTFE cleaning on the liquid xenon purity is investigated in a small-scale liquid xenon TPC.
@article{arxiv.2009.08828,
title = {Radon daughter removal from PTFE surfaces and its application in liquid xenon detectors},
author = {S. Bruenner and D. Cichon and G. Eurin and P. Herrero Gómez and F. Jörg and T. Marrodán Undagoitia and H. Simgen and N. Rupp},
journal= {arXiv preprint arXiv:2009.08828},
year = {2021}
}