High vacuum leak testing with the mass spectrometer

THE DETECTION of small leaks in large all-metal vacuum systems has long been a troublesome manufacturing problem for which there was no satisfactory solution. All of the generally used techniques of leak detection are cumbersome or have serious limitations such as lack of sensitivity, lack of selectivity, poor response, dependence upon vacuum conditions, uncertainty of interpretation of response, or usefulness being restricted to certain materials. Experience with many methods of leak detection on all sizes of apparatus has shown that an ideal leak detector must have the, following characteristics: (a). High sensitivity. The instrument must be able to detect small leaks.