15. New developments in trapless leak detection

Abstract

Summary One of the most important developments in trapless helium leak detection : the counter-flow leak detector is described. The diffusion pump, a major component in any helium leak detector and the heart of the gas-handling system in the counter-flow mass spectrometer leak detector, is discussed then the characteristics of the counter-flow mass spectrometer leak detector are examined, its operation, some of its benefits and limitations, and its distinction from classical leak detectors. A detailed description of the impact of diffusion pump design parameters on the counter-flow detector demonstrates that pumping speed and throughput do not substantially affect the performance of the counter-flow leak detector, while the tolerable forepressure and pressure ratio influence dramatically the sensitivity and the over-all test cycle time. It is demonstrated these two parameters cannot be simultaneously optimized. Thus, a leak detector which has a very high sensitivity will also have a low tolerable forepressure at the diffusion pump and conversely, a leak detector set for a low sensitivity will have a high tolerable forepressure. Finally, some applications are given.