Development of High Pressure Ultrapure Water Rinsing

Superconducting niobium rf cavities have suffered and are still suffering from field emission loading at high electric surface fields caused by artificial contamination of the sensitive rf surfaces. Field emission will degrade the Q-value of sc cavities and limit the achievable gradients. Reduction or elimination of this contamination will result in improved cavity performance and a great deal of effort has been invested in improving cleaning and assembly procedures. One method, which has been pursued at Jlab after the initial reporting of its benefits [1] is high pressure ultrapure water rinsing (HPR), during which the interior cavity surfaces are repeatedly sprayed with ultra pure water of up to ~ 100 bar.[2]. This method turned out to be very beneficial and is being used presently by all laboratories involved in SRF technology as a final step in the surface preparation of sc cavities.

[1] Ph. Bernard et al.;Proc. 3 rd European Part.Acc.Conf., Berlin, Germany (1992), p. 1269