Kyle, Gerardo

7/31/2012 

With the leak detector backing a 50l/sec turbo which was pumping the HAM5 HAM6 annulus and the Vertex Volume being pumped by the Vertex MTP (@ 3.4 x 10-7 torr), we sprayed (~5sec bursts of audible flow) at each of the test ports of the HAM6 side of the HAM5/HAM6 septum.  No response.  Next, we moved the leak detector over to back the Vertex MTP such that 100% of the exhaust was being sampled and, at some point, noticed that the helium background had risen (from the ~ 2 x 10-9 torr*l/sec when backing annulus turbo) to 6.5 x 10-9 torr*L/sec


8/1/2012

The indicated helium background of the leak detector was 6.5 x 10-9 torr*L/sec when we left yesterday.  It remained unchanged today.  This value falls off rapidly as the 10" gate valve at the MTP inlet is closed and is behaving as if it is a real signal sourced on the VE side of the 10" gate valve.  Any helium introduced via cross talk to a leaking metal joint yesterday would not remain unchanged for this many hours of 2000 l/sec MTP pumping.  It is much more likely to be a reservoir permeated through the annulus viton from the previous days spraying  -> Today we vented, then pumped, then vented, then pumped, then vented then pumped the HAM6 and HAM5 annulus space over the course of the afternoon in hopes that this might expedite the removal of helium permeated into the annulus viton.  We observed during the initial annulus vent that the helium signal increased slightly while the annulus was vented.  

With the helium background too high for acceptance testing of new conflat or feed-through joints we decided to eliminated any gross leaks existing on HAM5 and HAM6.  All conflat joints and electrical feed-throughs were sprayed with 10 second blasts of audible flow.  The helium background rose slowly and steadily from 6.5 x 10-9 torr*l/sec to 1.3 x 10-8 torr*l/sec over the 1 hour period we were testing