Holding time

Since several months we have experienced problems with the vacuum and the LN$_2$ hold-time, which decreased from 5 to 2-3 days. As part of the work done before the installation of the new detector the outer O-rings of the fill and vent tubes of the LN2 tank were examined and found to be out-of-shape. New O-rings were installed, but this did not solve the problem.