Temperature dependence and long term behaviour of capillary-type helium reference leaks with gas reservoir

Abstract

Built-in reference leaks for modern automated leak detectors are required to have a small temperature dependence. Capillary-type leaks are known to have a rather small temperature coefficient but are not well accepted because they are said to be clogged easily. Measurements are presented which show that the temperature dependency is not only due to a change in conductance but that a small diffusion term contributes appreciably to it. A big number of capillary-type reference leaks have been manufactured in the past years without problems of clogging when operated in a leak-detector or routinely used in the laboratory.