| Abstract: | The stability of the bak rate of Helium test leaks For the sensitivity calibration of Helium leak detectors, test leaks with known Helium throughput are used. Widespread is the type of test leak with internal gas reservoir from which the gas is delivered by permeation through a wall. In case of constant temperature, one expects a constant gas throughput except for a gradual minor decrease due to gas loss (typically ?1% per year). This behavior is in fact found for test leaks with quartz wall. In contrast, substatial scattering is observed for test leaks with plastic wall which is not yet understood. In the paper also reaction times of the leak rate on changes of temperature and reservoir pressure are reported for test leaks with quartz and plastic wall. |
