Lisa, Stefan
- We looked at the DC stability of the transmon: over ~week time scale the TMS drifts by
~2 urad in P and Y
<10u in T and V
- This means that a TMS QPD combination that is tuned for SOFT (instead of insensitive to P/Y) will drift the beam waist around by 4.3mm, or about 1/3 of the beam waist - too big (compare this to the 10u in T and V). We thus need to use the TMS P/Y insensitive QPD reference for long term reference. We can blend to a soft/hard basis at AC if we need it for controling the soft degree of freedom.
- For now we added an IF-statement to the Guardian that allows us easily to switch the input matrix and related offsets.
- We also hard-coded the QPD offests (both Sheila's from today and the ones from 5 days ago).
- Running at 20W, we switched back to the 5 days input matrix and offsets, resulting in a PRgain increase from 30 to 32.
- After that we fine-tweaked the soft loop yaw offsets. We just used the offsets in the control filter banks. We got the best recycling gain with
H1:ASC-DSOFT_Y_OFFSET = 0.12
H1:ASC-CSOFT_Y_OFFSET = 0.12
neither of which are in Guardian yet.
- Finally, we tried closing the SCR1 P and Y loops with the following matrix:
A36IP -0.5
B36IP 1.0
A36IY -1.5
B36IY 0.26 (changed today - not in guardian yet)
pitch worked, yaw ran away (see plot). Looks like the signal in A36IY triggered the runaway by flipping its sign. (B36IY had the right sign)
- We also reduced the OMC_DCPD power setpoint (i.e. effectively the DARM offset) to 15mA.
- We thus left the SRM open for the night.
June 25, 5:09 UTC Lock #1: lock up to 40W, recycling gain < 27, locked broken by angular instability
June 25, 5:35 UTC Lock #2: lock up to 35W, optimized recycling gain by adjusting soft loops yaw offset
recycling gain increased from 27 to 30; lost lock by doing pitch adjustment
June 25, 7.15 UTC Lock #3: lock directly to 35W (ISS3 loop engagement now in the guardian) with optimized soft offsets (only YAW offsets effective), recycling gain at 30
started powering up in steps of 1W from 35W
More soft loops tuning to keep recycling gain around 29
8:00 UTC stable at 45W
8:10 UTC 50W recycling gain 27, unlocked at 8:15 due to saturations of some sort -- Terra was checking PI, nothing apparent
Couldn't lock DRMI -- initial alignment
June 25, 9:25 Lock #4: test: tried high power offsets during locking sequence -- worked fine
locking sequence all up to 35W, a few steps to 40W, recycling gain 28
9.51 UTC @ 40W
SRC loop closed at 10 UTC
Bad error signal for SRC YAW, a very short long term test ended 9 minutes afterwards...
June 25, 10:15 Lock #5: Directly to 40W, all in the guardian except OMC whitening switch and SOFT offset engagement
Recycling gain recovered to 28.5, leaving SRM alignment loop open
LEAVING THE INTERFEROMETER LOCKED AT 40W UNDISTURBED (in HIGH NOISE) AT JUNE 25, 10:45 UTC