patrick.thomas@LIGO.ORG - posted 14:10, Wednesday 05 March 2014 - last comment - 16:59, Wednesday 05 March 2014(10556)
Hugh to HAM4 to work on HEPI
Jeff and Betsy will swap the glass optic into the SR3 suspension when Jeff gets back from end Y.
Betsy out of LVEA.
Work is done.
Swapping cable on dust monitor.
about 20 min ago
H1 ISI ETMX trips again on actuators. Got up to: Level 2 isolation on both stages, TCrappy blends on both stages, ST1-ST2 sensor correction on Went back to what I was doing, then ~5 minutes later, both ST1 and ST2 actuators trip. What is the difference between when visiting commissioners design all of these improvements vs. when they trip? Day time vs. night time? Weekends vs. During the week? There's something systematically wrong with our commissioning process.
For the records. GPS time 1078083583. Tripped on Actuators. Level 2 isolation on both stages, no ST1-ST2 sensor correction on. Had been running on "Start" blends on both stages for quite some time, T240s were pleasantly green. Tried moving ST1 from "Start" to "TCrappy", tripped halfway through on actuators. First glitch in captured screen show is start of switching third spike killed it. Since glitch appears much larger in horizontal, we'll try switching vertical first (Z, RX, RY), then horizontal (X, Y, RZ).
Blending from "Start" to "TCrappys" on verticals (Z, RX, and RY) then horizontals (X, Y, and RZ) worked much better. I've tried twice (thanks to another trip from unstable ST1 ST2 SC). We should change the SWITCH ALL script to performed the blend switching as such. Note that it also might be the difference between starting the switch process at human-button-click speed vs. computer speed, so we might wanna consider staggering the start of the blend switching.
All is within spec, we are ready to move forward with HEPI actuator attachment; IAS will take another look afterwards to ensure we are still within spec.
Back from end X.
going to end Y.
Done
Done. It was a bad belt.
Has been for about 20 min.
Done
We had a lot of trouble early in the evening isolating ETMX, we kept tripping the watchdog on stage 2. We tried reseting the CPS offsets, and eventually were able to get it to isolate with Tcrappy and level 2 controllers, but the motion was rather large (~ten fringes per second). We left stage 2 with damping only.
Were you sending any particularly large locking transients to the ETM, to the top mass in particular? What did the input motion look like? Did it trip on actuators, or some sensor?
We haven't been using feedback to HEPI, and turned off the feedback to the top mass when we started having trouble. there were acutator trips, GS13 trips, and T240 trips (I frogot to disable the T240 watchdog once).
Also, at one point last night I turned on the sensor correction with the blend filters still on Start, this was obviously bad although nothing tripped. Maybe this is only intended to be used with T240s, or only with Tcrappy blends.
Alexa, Daniel, Sheila
We normalized the refl PDH error signal, and saw that we can stay in the linear range of this signal with only ALS COMM locked.
We first normalized LSC-X_TR_A_LF by adding a gain of 0.000154 so that the tranmission peak is at roughly 1. We set LSC-REFLBIAS to REFL_A_RF9_I over the transmitted power (LSC-X_TR_A_LF). The first screen shot is the PDH, the transmitted power, and the normalized error signal as we move the COMM VCO set frequency. In the red trace we moved the frequency by 2kHz; meanwhile, in the blue trace we moved half as fast over 1kHz. We used Alexa's equation from alog 7054 to roughly calibrate the signal: 80Hz cavity pole/150 counts pp of the PDH signal=0.533Hz/count.
We put this gain into the REFL_BIAS filter, we will do a more carefull calculation in the morning. With this calibrated error signal we were able to measure an out of loop spectrum of the noise between the arm cavity and the PSL. Attached are some of the spectra that we took. In the top panel the green trace is a reference with the cleanroom over HAM1 on, in the red trace we turned the cleanroom off and Alexa tried to tune up the arm cavity alignment by maximizing the green transmitted power. This realingment clearly helped at low frequecies, and reduced the coherence with the ETMX PIT oplev.
The RMS we measured is completely dominated by low frequency noise that changed, probably because the alignment was drifting. The RMS down to 0.1 Hz varied from 30Hz-70Hz, we also measured an RMS of 58Hz down to 0.01 Hz.
We saw coherence with the end station PDH reflected signal above 1kHz, coherence with the PIT oplevs (mostly ETMX, which currently has level 2 controlers on Stage 1 and damping only on stage 2) around the PIT resonances (0.4-0.5 Hz), and coherence with YAW OpLevs from 0.04-0.5 Hz. We also looked for coherence with some of Robert's PEM sensors, we have coherence from the periscope on ISCT1 from about 50-100Hz, as we kind of expected.
Tonight the noise is much worse than it was on saturday, the transmitted power was not stable at all over time. This might be because we don't have as good of an alignment, or be because the arm cavity motion is larger because of the problems with ETMX ISI. We also measured the spectrum with higher and lower gains in the COMM board, higher gain did not seem to help, which is different from the situation on saturday alog 10439 .
Did you have the ALS WFS servos running for these measurements?
Note, this same measurement at LLO looks strikingly similar: see LLO aLOG 11265!
No WFS, dither alignment, or longitudnal feedback to the test mass was on for any of these measurements.
When comparing this spectrum to the LLO one has to undo the red cavity pole in the above spectra. It is a little bit more complicated, since we are dividing by the red transmitted power which itself can carry noise. With this correction both spectra are referenced to the input laser frequency and look more or less identical.
When comparing this spectrum to the HIFO-Y spectrum in T1300688, the story at mid frequencies is more or less the same:
Exited LVEA 1630pst.