Summary:

On Thursday Mar 24th, we made an attempt to fully wire-brush and sample inside iLIGO HAM12 (aLIGO HAM11).  We were partly successful in that 2/3 of the chamber is now wire brushed, and we believe the procedure outlined in T1000725 will form the baseline for cleaning fully the H2 diagonal envelope, and later, L1 and H1 volumes. However in the process we erroneously made use of a screw-type air/oil compressor which may have contaminated some interior surfaces of the chamber.  FTIRs were taken and are due back Thu Mar 31. They will inform of a solution for how to proceed with this chamber.

Some details:

Setting out to wire brush the iHAM12 interior, we defined a matrix for interior surfaces of the chamber and began wire brushing the roof.  This work is ergonomically taxing, requiring sufficient person-power in-chamber, and short shifts of about 5 minutes each, particularly when overhead.  The original (clean) compressor supplying the pneumatic tool was found to decay in air-pressure, inducing delays while the compressor regenerated, so we opted to acquire another, larger capacity unit. This second compressor (Atlas Copco XAS 185) is a screw compressor in which the pump unit employs oil in the screws and then separates it out, and cannot be employed for our clean in-chamber work.  Running the pneumatic tool with the new compressor for 20-30min yielded a failure of the tool (not unexpected as that tool had integrated ~1hr worth of activity). When inspected, oil mist contamination was noted in the tool, the operation was shut down, FTIR samples were taken of both the areas that were brushed with the clean compressor, and the two areas (approx 4 square feet each) that were cleaned with the dirty compressor.  We have ceased operations on iHAM12 and will do no more tests until any further mitigation steps are decided upon; additional assays may be required.  Hoses and garb from Thursday's cleaning operation are quarantined, as are the vacuum.

More details and pictures in a follow-up alog.