model restarts logged for Fri 16/May/2014
2014_05_16 23:12 h1fw1
No restarts reported for Saturday.
One unexpected restart of h1fw1 over the two days.
Kiwamu, Jamie, Lisa
We figured out why we couldn't reduce the CARM offset below 1kHz while keeping the PRMI locked on REFL 45 I&Q.
The REFL 45 demod phase was tuned without the arms present; it turns out that with the arms, even with a large CARM offset (1 kHz), the demod phase changes enough to make MICH very close to instability.
So, we just tuned the REFL 45 phase by monitored the MICH OL TF and the REFL 45 I/Q decoupling by looking at a PRCL line around 50 Hz.
Not a very advanced technique, but we could recover pretty easily a reasonable shape for the MICH loop and we could reduce the CARM offset.
Kiwamu will post some plots with the MICH OL TF; here are some numbers for the REFL 45 phase:
Without the arms: 144 dg
1 kHz --- 900 Hz CARM offset: 172 dg
800 Hz --- 700 Hz CARM offset: 180 dg
We were happy and ready to do the transition to 3f, but another seismic event like the previous one made the lock of the Y arm more difficult.
We are still debating if we should go home or not...
[Jamie, Kiwamu, Lisa]
The ETM SUS are getting kicked to the point of watchdog trips when the we lose the ALS DARM lock. The DOWN state of the ALS_DIFF guardian was shutting off the INPUT to the LSC-DARM filter bank, but not the OUTPUT, so we were suspecting that leftover filter stuff was being driven out to the suspensions. There are also no LSC triggers associated with the ALS error signals that could shut off the DARM output after lock loss.
I modified the ALS_DIFF DOWN state to turn off the DARM output as well, in the hopes that that would reduce the problem. We thought that that did help, but then we just got another lock loss that did trip the ETMY SUS and ISI ST2 watchdogs, so it didn't elliminate the problem entirely.
I wonder if we'll need to add some LSC triggering based on the ALS inputs, for when we're using ALS signals to feed back to the SUS.
While I was at it, I did a bunch of code cleanup in the ALS_DIFF module. Mostly just to keep things consistent with the guardian style guide (unpublished). I also committed the ALS_DIFF.py module to the USERAPPS svn, and added it to the GUARD_OVERVIEW medm screen.
Kiwamu, Jamie, Lisa
Today we had the illusion that we could start locking before dinner time, but that didn't happen.
While both the X and Y arms were locked on green, something happened in the corner station (visible in the PEM CS SEIS 30-100 mHz channels, especially Z) which affected only the Y arm, while the X arm remained happily locked.
I added a very-low-frequency-boost in the BS oplev damping loop which reduces the motion between 10 mHz to 100 mHz.
When seismic was high as Lisa reported, BS also moved a lot in yaw by 1.5 urad in pk-pk. This was causing a power modulation in the ALS diff beatnote. So I added this filter to reduce the motion at very low frequencies. Also, I increased the gain for this loop from -0.03 to -0.05 as there was a servo instability at 1-ish Hz with the VLF boost engaged. When seismic is at the normal level, do not forget to disengage this VLF boost.
Lisa, ChrisW, Jamie, Arnaud, Kiwamu
We locked the PRMI with the 1f signals at a CARM offset of 1-2 kHz. The goal is to hand it over to the 3f after the CARM offset passes approximately 1 kHz at which the arm cavities resonate with the 2f sidebands. However, we didn't get a real progress tonight. We will continue studying this configuration.
What we did:
"At some point, we noticed that the cavity stay locked without the slow feedback. So we stopped using the slow feedback."
There was high wind last night until around 2 am. Kiwamu's locking successes started when the wind stopped blowing. According to Robert's FOM, the wind was indeed pretty high, around 90% percentile..but still, I claim that we should be able to lock a cavity anyway.
We will try to produce meaningful plots, in the meantime here is the plot which has the times with high wind, as looking at the PEM EX SEIS BLRMS 1-3Hz.
The coupling from the BSC-ISI Stage 1 Z drive to the T240 RZ signal reported a few weeks ago has been lately our first guess as for what's limiting the RZ (Yaw) isolation performance.
This week we modified our real time model to do subtraction tests. The modification has been installed on ITMY.
The first plot attached shows:
- the coupling measurement in green
- a simple fit to be used in the subtraction block, in black
- the expected residual coupling in red
The second plot shows the residual coupling measured after installing the correction. The subtraction results look pretty good. Unfortunately, I did not observe substantial improvement in the optical lever Yaw motion. To be further investigated...
G. Grabeel, D. Hosken, T. Vo CO2X: - Running all day today and last night, turned off at 23:25 UTC. - Shipped out flipper mirrors and central heating masks for testing at CIT. HWS: - Visible laser alignment of the Y section of the HWS optics table complete up till the periscope, excluding the HWS. - Position sensors checked and working properly. - X side of the table has all the optics mounted and we'll set them in place and align on Monday. RH: - ITMX RH is hooked up but the drive is about half as much as we request compared to ITMY. We're investigating the possible causes now, the Beckhoff controls seem to be working alright. Updated to latest MEDM SVN revisions to match LLOs recent changes.
Took PET swipe in HAM5 after the installation of H1-SRM and before we started the alignment.
3rd IFO unit#2 is essentially done testing. Collecting info from minor static tests are all that remains. Unit #3 is built up to a test state for MIT--looking at coupling from the EM actuators to the sensors. We have a few CPSs left to connect and cable. We should be ready to do this test by Wednesday. Once this test is done we'll need to back track a little to build it right and float the table. Something like another week after this special test. Meanwhile we'll dance large plates for Unit #4 around with the Container to get unit#2 out of the Staging building early next week.
Yesterday I aligned the IR transmission to the TMSY ISC table QPDs.
It was easy to bring the beam on both of the QPDs using M14 (downstream pico mirror). I made a very small PIT adjustment using M4 (upstream) before the IFO decided to not to cooperate.
Today I was just fishing for a good flash and found one (attached). Seems like both of the QPDs are reasonably centered: [P, Y]=[0.05, 0.18] for QPDA, [-0.1, -0.1] for QPDB.
And apparently we're still receiving IR light on ISCTEY, even though I didn't touch periscope. This is good enough.
08:50 Arnaud shaking ETMY for ~ 15 minutes 08:58 Jodi and Joe checking that the viewports staged in the LVEA are the ones listed for installation 09:12 Hugh retrieving 3rd IFO helicoils from the LVEA test stand area 09:15 Andres to HAM5 to work on SRM alignment 09:17 Jason to HAM5 to work on SRM alignment 09:31 Dale to LVEA to take pictures of HAM4, 5 09:31 Betsy to HAM4 09:36 Hugh out of LVEA 09:52 David H. and Thomas V. to LVEA to work on HWS table 09:55 Jeff B. to HAM5 for SRM work 10:28 Travis to LVEA teststand to work on ACB 12:13 David H. and Thomas V. out of LVEA for lunch 12:25 Andres and Jason out of LVEA for lunch 12:49 Karen to end Y 13:00 Hugh looking for hardware in the LVEA 13:16 Hugh out of LVEA 13:25 Andres back to HAM5 13:37 David H. and Thomas V. back to the HWS table 13:46 Peter K. going back into H2 PSL enclosure 13:56 Karen done at end Y 14:13 Jeff B. back to HAM5 15:30 Andres, Jeff B. back from LVEA Richard and I worked on communications to the dust monitor in the H1 PSL diode room.
As Jason said, we ran out of adjustment range on the Top Mass Pitch Slider and there is no pitch adjustment slider at the Intermediate level. To correct the pitch we (1) put the Top Mass Pitch Slider back into its neutral position, (2) Removed the left, right, and T1 BOSEMs (they can interfere with pitch), and (3) made several rounds of moving addable masses from front to back and back to front to dial in the pitch. Once we were close to the correct pitch alignment by shifting addable mass at the Intermediate Mass level, we made the final fine adjustments using the Top Mass Pitch Slider. We reinstalled and aligned the BOSEMs. Transfer functions are running overnight. If these look good, we will be ready for fine tuning on Monday.
This morning I (and a little we):
- used the proper cookie cutters to set the 4 smallish baffles and 1 scraper baffle into place, dogged all ~35 dogs.
- reset the HWS steering mirror in front of SR2 into position, dogged it down.
- attempted to layout the temperature sensor cable using the notes from LLO - this unfortunately didn't go well as I broke one of the sensors off (even though I was warned that this could happen and I was being very careful). LLO reports a broken one as well. Long story short, I set the cable on the table anyways such that the heavy connector weight is on the table. A separate alog will have more details to the break and a fix or swap sometime in a week or 2 after SEI is done.
- Mounted the 4 HWS lenses onto the mounts - note, the HWS spec calls for 8-32s that are too long, we swapped in appropriate ones.
So, the only things "out of spec" on the table as now, which will be addressed before chamber close up are:
- the obvious HWS alignment work
- swap/fix temperature cable (there is a spare)
- add witness 2 light weight witness plates
- add light weight 1" witness optic
- pull FC sheet from SR2-HR
(Betsy, Travis)
The ACB has been fully payloaded, suspended, and coarsely aligned. I'll consult with the experts on fine tuning next week. Then, we'll take it back apart and wrap and bag it for transport to the ITMy staging area.
Came in this morning to find the BS ISI stage 2 GS13 watchdog tripped. Unclear why.
The strange thing is that the trip appears to have occured at GPS 1084253752, which is 10:30pm last night, whereas commissioning finished up around 4:30am. Did they just run with the BS tripped all night?
The watchdog was reset and guardian recovered everything fine.
The ISI-BS is a little peculiar: we know that the Michelson feedback could send a kick to the ISI and trip ST2 watchdogs. It's very often that the commissioners work with ST2 tripped, and I wouldn't be surprised that's what happened last night.
Given that, you should double check with the crew to see if it was really the case.
This was indeed the case. The michelson lock was kicking the BS and tripping stage 2, so they just ran with it tripped.
This is obviously an untennable solution, so we need to figure out how to prevent the BS ISI from tripping during acquisition.
J. Kissel The Messages: (1) The effective bias voltage charge on the test mass is -28 [V_pk], which quite small compared to the BIAS range of 400 [V_pk] (and in conflict with Keita's assessment from the optical levers [see LHO aLOG 11905]). (3) The force actuation strength is asymmetric with respect to bias voltage, confirming Keita's result (see LHO aLOG 11872) (2) The force coefficient at 11 [Hz], measured as a function of bias voltage, is roughly 0.5e-10 [N/V^2], a factor of 8 below the expected 4.2e-10 [N/V^2] (expected from pg 7 of G0900956) DETAILS ------------- Brett: please proof read: ------------- Note, no linearization algorithm was used during this experiment. (1) Using the time-honored MIT method of measuring test-mass charge (e.g. from Brett, John, and Lisa), I drove a single frequency line into the control voltage H1 SUS ETMX ESD drive, looking at the X arm cavity length (as measured by green), while stepping the bias voltage through its entire range. As one steps down the bias voltage, we expect the linear response to drop to zero. Further, one can take the slope of the response as the bias decreases from both the positive and negative side and predict an effective bias voltage created by residual charge on the test mass. I attach the results. Using a linear regression, weighted by the coherence as follows, unc = sqrt( (1 - coh) / 2*nAvgs*coh ) weight = 1 / unc^2; I calculated the intersection of the two slopes to be -27.99 [V_pk]. I took an excessive amount of data points, because I didn't know what I was doing when I started and wasn't sure how the results would turn out. The template is here for excitation: /ligo/svncommon/SusSVN/sus/trunk/QUAD/H1/ETMX/SAGL3/Data/2014-05-15_H1SUSETMX_L3_ChargeTest.xml For the record, I tried using the script recommended by Brett (LHO aLOG 11914), but after updating all the necessary channel names and input variables. it failed deep with in its subfunctions because of some xmlconv library that's now gone missing since 2009. I didn't have the time nor expertise to debug, so I just changed the bias by hand and measured the ten averages with the GUI DTT session, capturing references as I went, and exported at the end for processing. (2) No further details here, it's obvious that the drive strength is weaker with positive bias voltage than with negative. I have no good explanation for this. (3) From these displacement response results, one can also obtain the force coefficient for each bias step. The calculation is as follows: disp_mpk = 1e-12 * sqrt(2) * sqrt(binWidth) * disp_pmrtHz; force_Npk = disp_mpk * 1./compliance_11Hz.mpN; V_CTRL.Vpk = nActs * sqrt(2) * sqrt(binWidth) * esdGain * excChannel.amplitude.V_DAC.VrtHz; V_BIAS.Vpk = bias.V_ESD; forceCoefficient = abs(force_Npk ./ (2*V_CTRL.Vpk * V_BIAS.Vpk)); where disp_pmrtHz = displacement response of the arm cavity length at 11 [Hz] during each bias voltage setting, in [um] (which I subsequently turned into [pm] for plotting clarity) as measured from the calibrated ALS control signal, H1:ALS-X_REFL_CTRL_OUT_DQ sqrt(2)*sqrt(binWidth) = sqrt(2)*sqrt(0.09375 [Hz]), calculation needed to change from noise units ?_{rms}/rtHz to amplitude units of ?_pk 1e-12 = 1e-12 [m/pm] compliance_11Hz.mpN = 5.3e-06 [m/N], TST to TST, L to L transfer function at 11 [Hz], obtained from the QUAD model. excChannel.amplitude.V_DAC.VrtHz = 12.45 [V/rtHz], measured output request voltage from the DAC (calibrated from counts out of the digital last output to ESD, i.e. H1:SUS-ETMX_L3_MASTER_OUT_LL_DQ using the 180bit DAC gain, 20/2^18 [V/ct]) esdGain = 40 [V/V], gain of the ESD driver sqrt(2)*sqrt(binWidth) = sqrt(2)*sqrt(0.09375 [Hz]), calculation needed to change from noise units ?_{rms}/rtHz to amplitude units of ?_pk nActs = 4, since the calibrated output requested voltage is only from one channel. and I've computed the force coefficient, a, using only the linear term, since I used the amplitude of the linear term alone F = a (V_CTRL sin(wt) - V_BIAS)^2 = a V_CTRL^2 sin^2(wt) - 2 a V_CTRL V_BIAS sin(wt) + a V_BIAS^2 [ sin^2(wt) = 1/2 - 1/2 cos(2wt) + O(4w) ] = a(V_BIAS^2 + 1/2 V_CTRL^2) - 2 a V_CTRL V_BIAS sin(wt) + - 1/2 a V_CTRL^2 cos(2wt) DC Term Linear Term Bi-linear Term =>> Linear Term, a = F (2 V_CTRL V_BIAS) Confusingly, this resulting coefficient, a = 0.5e-10 [N/V^2] is a factor of 8 weaker than expected, which is *different* than the factor of 4 weaker that was needed to explain the linear transfer functions taken last week (see the second attachment of LHO aLOG 11676). The script that processes the measurements is here: /ligo/svncommon/SusSVN/sus/trunk/QUAD/H1/ETMX/SAGL3/Scripts/analyzeesdcharge_20140515.m
Jeff, This is getting pretty mysterious. Suggest that you try to establish whether you actually can see the capacitance change with relative motion of the test mass with respect to the recoil mass in each ESD quadrant. The bridge circuit would be a good way of doing this. I will be at LHO starting Monday and could help out with the measurement. One explanation is that you do not really have a solid connection to either the bias or the control electrodes - an open connection with either only capacitive coupling or a high resistance. RW
Jeff, 1 piece of good news - this amount of voltage implies that the isolation performance is probably not compromised by the charge. Long ago I did a rough estimate for how much charge could be on the optic in a blob near the tip of the earthquake stop. https://dcc.ligo.org/T080214 Although the field gradient is the important thing, and this is a function of both of the amount of charge and the spatial distribution there-of, one can say the if the blob is about the size of the stop, then the voltage of it is about 140 V before it compromises the isolation performance. -Brian
J. Kissel, B. Shapiro, Brett has caught a mistake in my calculations above, in that I *should not* multiply the control voltage, V_CTRL.Vpk, by a factor of four (i.e. nActs). My thoughts on including the factor of four were that I was measuring the requested DAC output of *one* quadrant, and since there're 4 quadrants, I add the force created by each of them. However, given how the force coefficient was defined for all four quadrants, it's better to think of each of the four quadrants creating a ring of control voltage, all held at the same requested value. It's then the potentional difference between this control ring and the bias ring that generates the forces on the test mass. Hence the caluclation for the force coefficient should be disp_mpk = 1e-12 * sqrt(2) * sqrt(binWidth) * disp_pmrtHz; force_Npk = disp_mpk * 1./compliance_11Hz.mpN; V_CTRL.Vpk = sqrt(2) * sqrt(binWidth) * esdGain * excChannel.amplitude.V_DAC.VrtHz; V_BIAS.Vpk = bias.V_ESD; forceCoefficient = abs(force_Npk ./ (2*V_CTRL.Vpk * V_BIAS.Vpk)); (Thanks for the clarification Brett!) In addition, while debugging, I caught another error: The uncertainty from each data point as calculated above computes the *relative* uncertainty. As displayed on the graph, since the plot shows absolute amplitude of the displacement, the uncertainty should be displayed in absolute units, as in unc = disp_pmrtHz.full .* sqrt( (1 - coh) / 2*nAvgs*coh ) weight = 1 / unc^2; Finally, even more dumb of a mistake, a copy and paste error meant I was using the asd vector as my coherence vector. All of the above errors, bugs, and mistakes have been corrected, and I attach a revised plot. The new force coefficient is roughly 2.2e-10 [N/V^2].
Fig.1 MICH open loop transfer functions. The pink curve is the one after we adjusted the demod phase at a CARM offset of 1 kHz. Everything else is the ones before the adjustment. You can see that the funny bump between 20 and 50 Hz dissappered as we adjusted the demod phase.
Fig.2 PRCL open loops. The red curve is the one after the demod phase adjustment. The blue one is before the adjustment. Not a significant difference.
Fig.3 Various error signals for the length control. The references were taken when the CARM offset was at 1 kHz and the live traces are the ones with the offset at 800 Hz. REFL45I sees more noise above 40 Hz which is seemlingly from the common mode. A peak at 50 Hz is our injection in PRCL for calibrating the responses.