Sheila, Matt, Kiwamu, Carl, Stefan
Earlier today we tried heating TCS CO2 X-arm with 2Watt (0 Watt into Y), and all we saw was a futher drop in recycling gain.
Tonight (07:29 UTC) we tried the opposite TCS: TCS CO2 Y-arm with 1Watt (0 Watt into X). (Half of what we put into x, because we broke lock on the first try.)
Result: Absolutely nothing - all recycling gains remained the same or further dropped.
Conclusion: TCS CO2 cannot get any recycling gain back.
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Log:
UTC 20160713 23:08:09 all TCS CO2 completely off
no effect on any sidebands
UTC 20160713 23:16:22 TCS CO2 X to 1 W
UTC 20160713 23:21:21 TCS CO2 X to 2 W
recycling gains drop, lock loss
UTC 20160714 07:29:00 TCS CO2 X to 2 W, TCS CO2 Y to 0 W
recycling gains drop, lock loss
This lock was brocken by ITMY bounce mode. It looks like we may need to double check all the bounce mode phases to see that they are unchanged at 40 Watts.
There were several problems with PI damping this evening, the recovery of the safe.snap after ETMY's failures today resulted in H1:SUS-ETMY_BIO_L3_PI_ULLL_SW selecting the UL quadrant rather than the LL quadrant resulting in no ETMY damping for the entire evening.
In the 50W lock an ITMY mode (purple trace -80min) reached saturation level, the resulting unstable bounce mode at lock loss may have been associated. The mode was still at elevated amplitudes at the beginning of the next lock but was damped. The damping phase needs careful monitorring a changing sign regularly. I suggest moving to QPD error signals. Finally at -15min I set H1:SUS-ETMY_BIO_L3_PI_ULLL_SW to LL and was able to damp ETMY modes again.
For the bounce mode phasing: is the DARM gain now high enough that the cloop is close to +1 at the bounce mode frequencies?
I've put together some plots of the common and differential lenses as measured by the Hartmann Sensors.
The only change I made to the Hartmann sensor data is to scale the ITMY spherical power (H1:TCS-ITMY_HWS_PROBE_SPHERICAL_POWER) by (17.5/7.5)^2. This is because the magnification has defaulted to 17.5x on HWSY instead of 7.5x which is the actual level. Additionally, I reset both HWS measurements to zero at t=0.
The first plot (LHO_diff_CO2.pdf) shows the HWSY and HWSX measurements as well as common ([X+Y]/2) and differential (Y-X) lenses along with corresponding CO2 laser powers.
The second plot (gain_vs_time.pdf) shows an approximation of the gain: the TR-X_SUM / IMC_OUTPUT. Perhaps someone can point me to a better approximation. You can see the reduction in gain powering up. The very sharp initial spikes can be ignored.
The third and fourth plots show the gain vs common and differential lenses, respectively. Remember, there is an offset in lensing in both of these plots due to resetting the HWS values to zero.
It's certainly not conclusive, but: