The goal was to compare the sensitivity with SR aligned and SR misaligned, with the frequency noise at a low level in both cases.
In LN3 an offset on BS TX of 1e-3 was again successful at improving the BNS range by a few Mpc and reducing the I quadrature of the SSFS coupling. In LN2, the I quadrature of the SSFS coupling was not affected by BS alignment, so we could reduce only the Q quadrature.
Figure 1 compares the final spectra between SR aligned and misaligned. The final SR aligned spectrum may actually not be the best, as something was progressively getting worse as visible on Figure 2.
Figure 2 shows the trend data during the different steps we did in LN2. B1s has been progressively getting worse since 16:10 UTC, until it crossed the safety threshold and triggered the unlock.
We had two lock acquisitions. One acquistion failed once at the CARM NULL 1F/3F transition, and was successful at the second attempt. The other failed in ACQUIRE LOW NOISE 2and was successful at the second attempt.
Details of the shift:
14:02 BS TX set to 1e-3 with 360s long ramp
14:13 UTC (10 min) SR misaligned reference time
14:24 SR TY set to 305 (Hz) with 1200s long ramp
during the SR TY transient adjusting MICH SET in steps to keep the PSTAB
coupling close to zero
unlocked during the SR TY transient, within a few seconds of sending
one of the commands to adjust MICH SET. My impression is that there is
often a glitch at the beginning and end of a MICH SET ramp.
Relocked in LN2 at the second attempt (one unlock at the CARM NULL
3F/1F transition). And turning on parts of LN3 by hand.
Increased SDB1 drift control gain to LN3 values
Adding BS TY/TX offset to zero frequency noise coupling in LN2. BS TY
positive offset improve Q quadrature but maybe makes I quadrature
slightly worse, BS TX doesn't seem to have a significant effect.
16:33 UTC BS TY SET = 6e-4, BS TX SET = 0.
16:36 UTC turned of PyUGF, PyDiag and reduced LSC lines
16:39 UTC reduced fully LSC lines
16:41 UTC adjust optical spring gains -
16:42 UTC (7min) reference time
16:52 UTC reduced angular dither lines (test masses, DIFFp and SR)
16:53 UTC (6 min) reference time
Turned on 50Hz feed-forward
Changed MICH and SRCL filters
17:14 UTC (4 min) reference time
Reduced SSFS lines to LN3 amplitudes
17:20 UTC (3 min) reference time
Unlock
Changes done from LN2 are listed in LN2asLN3() function of /virgoDev/AEI_SQZ/changeDCP.py
