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AdV-ISC (Automatic Alignment)
flaminio - 10:41 Monday 30 January 2023 (58623) Print this report
Drift in dark fringe power

The night between Saturday and Sunday there was a drift of the power on the dark fringe by about 15% (see Figure).

This took place over a period of 12 hours starting from one hour after the lock, so after the initial transient.

At the same time there is a drift of the LSC_SRCL_B1p signal (demodulation of the SRCL line in B1p_DC) i.e. the signal that measures how well the signal recycling cavity is locked on the top of the dark fringe.

At the same time there is a change in the alignment of the input beam wrt to the arm cavities seen by the B4 quadrants and a motion of the 56 MHz sidebands wrt to theĀ  carrier seen by the B4 phase camera.

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sorrentino - 23:56 Monday 30 January 2023 (58632) Print this report

Including the reading of thermistors on NI and WI mirror coils. It seems that the slow transient on all figures of merit, including the B4 6 MHz wavefront sensor, depend on the temperature of ITMs.

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ruggi - 11:19 Tuesday 31 January 2023 (58637) Print this report

12 hours of lock on Jan 19th. Arm alignment strategy was different (B4 quadrant in loop). All the other drifts were not too different.

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