Leak detector for spacecraft testing with high accuracy

It is convenient to measure the leak rate of spacecraft when the spacecraft is kept in its container and the increment of tracer gas, mostly noble gases, in the container air is measured as function of time. In order to meet the specification of the new voluminous spacecraft, a leak detector with high accuracy is required. This is made difficult, because of the natural abundance of noble gases in air, which mean a considerable background exists. A leak detector is described which allows the measurement of an increment of the concentration of a few % using reference gas.