K. Venkateswara

I did another test to make sure the BRS damping works as expected. The attached pdf shows the results of the test. I disturbed the BRS by walking in its vicinity at t=200 seconds and the amplitude gets rung up. The turn-table starts damping it and it switches off after ~1000s.

DriftMonitor:

The channel H1:ISI-GND_BRS_DRIFTMON monitors the position of the beam-balance mirror pattern on the CCD camera. It was scaled to go roughly from +/-16k counts. But it looks like on the positive side it happens a bit earlier than that, roughly 14.5k counts. The second attachment (DriftMonOlder.png) shows the DriftMon output from August-September. It looks like it had already hit the edge on Sept. 4th. The code still works if the pattern goes over the edge but it can appear noisy if there is a partial pattern, so ideally we want to keep it in the working range.

The current DriftMon position is shown in the third file (DriftMonCurrent.png) after I completed the damper installation. It seems to be trending logarithmically towards -10k which is a bit lower than ideal but still in range. Adjustment of the position are not trivial and there are large drifts after each adjustment which are not always easy to predict, so adjustments should be avoided unless necessary. I will monitor it over time and if needed make further adjustments.