1、Lessons Learned Entry: 0542Lesson Info:a71 Lesson Number: 0542a71 Lesson Date: 1996-04-01a71 Submitting Organization: LARCa71 Submitted by: Ruth M. AmundsenSubject: Use of RGA Quadrupole Mass Spectrometer for Leak Detection Description of Driving Event: On the MIDAS project, leak detection for the v
2、acuum chamber was done both by helium “sniffing“ using the RGA, and also by checking the N2 to O2 ratio to see if there was a steady air leak present. In one case, this ratio did not indicate a leak, because the cryopump was preferentially pumping oxygen.Lesson(s) Learned: It is possible to not have
3、 a 5:1 ratio of N2 to O2 in a vacuum chamber that has a steady leak, when there is a cryopump running that will preferentially pump the O2.Recommendation(s): When using gas ratios based on a quadrupole mass spectrometer (RGA) to tell you if you have a leak (i.e., looking for 5:1 ratio between N2 and
4、 O2), make sure you do not have a pump running that is pumping one gas preferentially (such as an ion pump or cryopump).Evidence of Recurrence Control Effectiveness: When using gas ratios based on a quadrupole mass spectrometer (RGA) to tell you if you have a leak (i.e., looking for 5:1 ratio betwee
5、n N2 and O2), make sure you do not have a pump running that is pumping one gas preferentially (such as an ion pump or cryopump).Documents Related to Lesson: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N/AMission Directorate(s): N/AAdditional Key
6、Phrase(s): a71 Hardwarea71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 1997-05-05a71 Approval Name: Elijah C. Kenta71 Approval Organization: 421a71 Approval Phone Number: 757-864-3345Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
