LIGO Document T1700485-v1

LLO X beamtube leakage

Document #:
LIGO-T1700485-v1
Document type:
T - Technical notes
Other Versions:
Abstract:
Using newly commissioned RGA instruments, we've confirmed that, in addition to a previously known leak through the LGV11 stem at the X end, there exists another leak of approximately 5e-6 Tl/s somewhere near the middle of the X arm.

Significantly, however, an argon bag test appears to rule out midpoint valve LGV8 stem failure as the source; it is not the same mechanism as seen on the Y arm (or on LGV11). The planned sarcophagus fabrication project, based on the assumption that LGV8 was failing in the same way as LGV7 did, should be put on hold. A new testing campaign is evidently needed to locate and stop this new leak.

Also significantly, the new data suggest that our prior hypothesis that the LGV11 leak had accelerated dramatically between 2013 and 2015 may have been mistaken. It now seems more likely that the larger mid-arm leak first appeared in that interval, affecting the 2015 total pressure accumulation, and we just assigned the increase to GV11 without considering the possibility of an unrelated new source.

We hope to find the new leak is a simple ConFlat or annulus piping problem. If not, we confront the daunting prospect of bagging and gassing the X arm, as we did most of the Y in 2013 and 2014.

Files in Document:
  • pdf (LLO_Xtube_prelim_T1700485-v1.pdf, 779.0 kB)
Notes and Changes:
initial draft
Referenced by:

DCC Version 3.5.2, contact DCC Help