[Gary T, Danny S, Matt H, Stuart A, Norna R]

During the close-out work of the BSC9 chamber (see LHO aLOG entry 13085) we were able to further investigate the source of the excess noise that had previously been observed on the ETMX (QUAD) L2 (PUM) UL channel (see LHO aLOG entry 13047).

Previously, I had swapped field cables at the Satellite Box between ETMX L1 and L2 stages running to the chamber. This indicated that the noise was downstream, i.e. with the field cables themselves or in-chamber. We repeated this test, but this time swapping field cables at the air side of the vacuum flange. Further measurements then eliminated the field cables and confirmed the issue resided in-chamber.

Gary inspected and re-seated the in-chamber connectors from the vacuum flange to the OSEM, but this offered no improvement. Finally, the L2 UL AOSEM (s/n #270) was removed and a spare unit connected up in it's place, but again, unfortunately this offered no improvement.

This indicates that the excess noise is most likely a in-vacuum harness problem, which would be invasive to attempt to replace. Therefore, it was decided to generate an integration issue and proceed with the close-out of the chamber, with the excess sensor noise on this channel.