Dan, Evan, Sheila
Tonight we started to look at the angle to length couplings of our test masses. We injected lines into pitch and yaw on the PUMs, and adjusted the A2L gains to minimize them. Using the math in the 40 meter alog and Jax's alog, we can estimate the miscentering from these measurements
| Gain P2L | vertical miscentering (mm) | Gain Y2L | horizontal miscentering (mm) | |
| ETMX | 1.6 | 21 | 1.1 | 14.4 |
| ETMY | 0.69 | 9 | -0.3 | -3.9 |
| ITMX | 2.4 | 31.5 | 1.15 | 15 |
| ITMY | 1.5 | 19.7 | N/A (-1.7 to -2) |
After we had adjusted these, we saw an improvement in the spectrum below 20 Hz. The line in the attached screen shot at 16.6 Hz with sidebands at half a hertz are the excitation. Keep in mind that this is on the new ESD driver and we haven't redone the calibration yet, but clearly this improved the noise below 20 Hz.
Earlier in the evening we were having difficuulty powering up because of a pitch instability at the main suspension resonant frequency that showed up in all the test masses. We moved the QPD offsets for pitch back to what they were may 15th, (they had been changed last tuesday). We then remeasured the miscentering for pitch only, things were a little bit better. Once we increased the power to 17 Watts, the IFO was stable and we repeated some of the measurements. We were able to power up to 23 Watts without seeing the instability twice, but lost the lock quickly for other reasons.
| Gain P2L | vertical miscentering (mm) | 17 Watts P2L | ||
| ETMX | 0.7 | 9.18 | 0.8 | |
| ETMY | -0.57 | -7.5 | -0.49 | |
| ITMX | 2.1 | 27.6 | 2.4 | |
| ITMY | 1.2 | 15.7 | NA |
DARM OLTF file attached. This template has reduced drive strength so that the ESD does not saturate in the LVLN state.
At last I was able to switch the DARM actuation over to ETMY at 25 W with the LPF engaged on the LVLN driver. We had discovered that the L1 LOCK filters on the ETMs were charging up because of small amounts of ringing in the lower stage filters. Therefore, the L1 filter for ETMX is zeroed after actuation is moved to ETMY, and the lock filters for ETMY are cleared after lockloss. Also, the INCREASE_POWER state now automatically increases the power to 25 W once again.
I tried the LOWNOISE_ESD_ETMY state at 25 W once, and it seemed to work. I then turned on some pieces of the LSC_FF state (namely the SRCL gain reduction, the SRCL cutoff, and the MICH FF). I am leaving the IFO locked with the intent bit undisturbed.
One last note: the power was 3 Watts in the spectrum attached, and to repeat, the calibration is not updated since the actuator change. They're working on it
The displacements in mm are wrong here, we were measureing from the PUM.
Another DARM OLTF, this time with the ETMY LPF off.
There are two DARM Open Loop Gain TFs attached as comments to this entry that represent the first two DARM OLGTFs taken with the new low noise ESD driver and the new L1L2L3 hierarchical control scheme. I've downloaded them and submitted them to the CalSVN for use later: - From LHO aLOG 18662, DcDarmLVLN.xml, measured starting 2015-05-28 13:17:00 UTC, has been copied to /ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER7/H1/Measurements/DARMOLGTFs/2015-05-28_H1_DARM_OLGTF_LHOaLOG18662_ETMYL3LPON.xml - From LHO aLOG 18709, DcDarmLVLN.xml, measured starting 2015-05-30 03:07:00 UTC, has been copied to /ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER7/H1/Measurements/DARMOLGTFs/2015-05-30_H1_DARM_OLGTF_LHOaLOG18709_ETMYL3LPOFF.xml. I attach conlogs of all relevant DARM filter banks and BIO switches, where the date in the file name corresponds to each measurement.
