AVS 49th International Symposium
    Vacuum Technology Wednesday Sessions
       Session VT-WeA

Paper VT-WeA9
An Ultra-sensitive Leak Detection and Calibration System

Wednesday, November 6, 2002, 4:40 pm, Room C-104

Session: Vacuum Measurements, Components, and Control
Presenter: Liangzhen Cha, Tsinghua University, P.R. China
Authors: Ping Chen, Tsinghua University, P.R. China
Xu Chen, Tsinghua University, P.R. China
Q. Jin, Tsinghua University, P.R. China
Liangzhen Cha, Tsinghua University, P.R. China
Correspondent: Click to Email
Although the minimum detectable leak rates can be as low as 10@super -12@Pa*m@super 3@/s for most commercial dry leak detectors, but demands on lower and reliable detection limit are challenging for highly reliable vacuum devices. To meet these demands, an ultra-sensitive leak detection and calibration system is developed. In order to improve the dynamic leak detection limit, it is necessary to decrease the background noise of the vacuum system. An all-metal ultra high vacuum system consisted of a turbo-molecular pump, an ion pump, a dry roughing pump and an UHV comparative Quadrupole Mass Spectrometer is developed with a minimum working pressure of 10@super -7@Pa. The leak detection limit can still be improved if the undesirable background gas is pumped out by a getter pump during the accumulation process. By using a 10@super -7@Pa*m@super 3@/s molecular flow platinum wire-glass reference leak@footnote 1@with an adjustable device to change the inlet trace gas pressure and (or) concentration, a range of leak rate more than 6 orders of magnitude can be directly calibrated without extrapolation. Experimental result shows that Helium leak rate lower than 10@super -14@Pa*m@super 3@/s has been detected and calibrated reliably by this system. @FootnoteText@ @footnote 1@Liangzhen Cha, Theoretical and experimental studies of a platinum wire-glass standard leak, Vacuum,Vol 41,PP:1860-1862(1990).