J. Kissel

As I'd seen charge continue to accumulate on the test masses (see LHO aLOG 28881), and we haven't been able to commission regular bias flipping since before ER9 (see LHO aLOGs 28362, 28152), I'd turned OFF the bias on the ETM ESDs last week Thursday (Aug 04) while we have HAM6 vented and the gate values are closed. 

After measuring charge today, this has had a noticeable effect on the accumulated charge, in that the majority of both test mass' quadrants show less accumulated charge. This may mean that leaving the bias OFF is just as effective at charge reduction as flipping the bias. 

I've left the BIAS OFF again after these measurements, to try to squeeze out as much more dissipation as I can.

However, I still highly recommend commissioning the ability to flip the bias sign, once we have the IFO back and stable.