The goal of the shift was to tune the SR RH by increasing its power and monitoring the DCP.
Last night there was a successful LN3 (started at 21.03 UTC) which confirmed the ITF’s workability, after the step back of the ETM RHs’ powers (63445), in the TCS configuration which is summarized in the two following tables.
CO2 powers:
|
| Reference | CH [W] | INNER DAS [W] | OUTER DAS [W] |
|---|---|---|---|---|
| W | on the ITF | 0.047 | 0 | 1.27 |
| on the pickoff | 0.291 | 0 | 0.208 | |
| N | on the ITF | 0.116 | 0.340 | 3.68 |
| on the pickoff | 0.715 | 0.055 | 0.60 |
RHs powers:
| NE RH [W] | WE RH [W] | SR RH [W] |
| 4.7 | 6.3 | 7 |
The cavities’ power remained stable at approximately 485 mW, with the sidebands showing an increasing trend, particularly the 56 MHz. Meanwhile, the contrast defect was decreasing and the BNS range was oscillating around 54 Mpc. The USB and LSB of 56 MHz on B4 were still separated, albeit to a lesser extent than in previous locks. The main ITF signals of this lock are shown in Fig. 1.
After that lock, there were various unlocks due to the high gain of the DIFFp TY. Consequently, this morning Maddalena reduced the gain by 50%.
At 8.44 UTC ITF locked at LN2.
At 09.15 UTC: SR RH increase up to 9 W (26.23 V)
At 9.37 UTC: ITF unlocked and it was difficult to relock again. There were several unlocks before reaching DC READOUT, as already happened on Sunday (63398).
In agreement with the commissioning coordinator, the idea was to decrease the SR RH power in order to scan a different WP in the opposite direction, since the ITF did't work properly after the power increase up to 9 W. At 13.50 UTC we manually unlocked the ITF in order to start the Fast Response for the SR RH.
Thus, at 13.51 UTC we decreased the SR RH power from 9 W (26.23 V) to 4 W (17.48 V).
The effect of this action will be evaluated in the afternoon shift.
