Took over from Nutsinee. Dan, Kiwamu and Darkhan also here. 07:15 UTC Lock loss. SUS OMC SW WD tripped. Possible earthquake. 07:21 UTC Touched up SUS ETMX pitch for locking on green. X arm green power remaining around .8 07:26 UTC Requested INIT, DOWN then NOMINAL_LOW_NOISE. Did not help. 07:39 UTC Dan suggested adjusting TMS alignment. This brought the X arm green power over 1. Guardian moved on. 07:44 UTC Reloaded TJ's script on video5 per his earlier request. DRMI alignment looks bad, misaligned SRM to lock on PRMI, did not help 07:50 UTC Started initial alignment per Dan's suggestion 08:35 UTC Darkhan left. Kiwamu and Dan still here. 08:38 UTC Got to and stopped at DC_READOUT_TRANSITION. Dan modifying guardian to run measurement on OMC. 08:48 UTC Kiwamu left. Just Dan and I here. 08:57 UTC Checked that the PSL cameras are not frozen. Lights are off in the PSL enclosure. Checked mid and end station cameras. All dark, but end X does not move. mid Y still has flickering green lines. Lights are on in the LVEA. 09:03 UTC Dan starting measurement. 09:58 UTC Dan stopping measurement. Investigating possible issues with calibration left over from measurement. 10:52 UTC Observing mode. More ETMY saturations.
23:00 IFO has been locking. The operation mode is OBSERVING. We're hoping for a record breaking today (I was told that the longest lock we had was 20 hours during ER7).
Craig, Kiwamu, Darkhan, Sudarshan doing calibration work, Robert doing PEM injections.
23:59 Robert picking things up in LVEA, then go to EY to do more injections.
Intent bit switched to Commissioning.
01:30 Robert back.
03:00 Robert done for tonight. Dan and Evan working on PZT. Intent bit remains Commissioning.
04:36 Go back to Observing.
05:01 Wind picking up speed. A wind gust just reached 40 mph but seems to be coming down quickly.
05:44 THE INTERFEROMETER HAS STAYED LOCKED FOR 24 HOURS and is continuing to do so!
07:00 Hand over to Patrick.
The ifo dropped lock at 7:13 UTC due to a 5.6M earthquake in Alaska. A new lock stretch record is set at 25 hours 30 minutes =D
As discussed at today's run meeting on Teamspeak on the JRPC channel:
The LDAS (DCS) stream of 4 s hoft generation using gstlal_compute_strain started writing to LDAS disks at 1125451520 == Sep 05 2015 01:25:03 UTC.
There already exist two redundant DMT streams of 4 s hoft writing to LDAS and DMT (GDS) disks. These are now vetted for diffs in the STRAIN and ODC channels.
Aggregation of hoft into 4096 s frame files for offline analysis is now configured (via the diskcache) to use the DMT hoft if the STRAIN and ODC channels agree in the two DMT streams; otherwise it will use the LDAS stream. (This can be easily switched back to using only the two DMT streams as it has been using prior to the time given in this alog, if problems arise).
Injection |
Time of first injection, UTC |
Injection spacing |
Total number of injections |
Good channels for environmental signal |
|
Sept. 5 |
|
|
|
crowd (10 people) walking randomly for 2 or 3s periods in control room |
1:39:00 |
5s |
12 |
HAM2 seismometer, vertex seismometer H1:PEM-CS_ACC_LVEAFLOOR_HAM1_Z
|
crowd (10 people) walking randomly in hall just outside control room |
1:41:00 |
5s |
12 |
same |
External door near control room shutting by itself |
1:44:00 |
5s |
12 |
same |
chair rolling in control room (most common chair) |
1:46:00 |
5s |
12 |
same |
Single large steps in control room |
1:50:00 |
5s |
12 |
same |
Airlock door (door to lab area near control room) shut by hand |
1:52:00 |
5s |
12 |
same |
slamming office door (Sheila, Kiwamu, Me) |
1:54:00 |
5s |
12 |
same |
hammer dropped from waist height in vacuum lab |
1:59:00 |
5s |
12 |
same |
setting car battery down in OSB shipping area |
2:02:00 |
5s |
12 |
same |
continuous bouncing for 5s on exercise/seating ball |
2:07:00 |
10s |
6 |
same |
I've attached the result. Quick observation from the spectrograms tell me that dropping hammer from waist height in vacuum lab (aka Kyle's lab) and setting car battery down in OSB shipping area coupled into DARM.
Instead of plotting the spectogram starting at the time of injection, this time I did +/- 10 seconds instead so it's more clear when the injection started and when it's ended.
Since I have never really explained what I did in finding noises in the sensors and in DARM, I'm taking some time to explain it in this alog. First I looked for injections in appropreiate sensors (accelerometer, microphone, seismometer). I zoomed in the spectrograms until I get the signal to show up >3 pixels or so in both frequency and time domain (as Robert suggested). Once I was certain that the injections were there, I went to look for them in DARM. I started with the same frequency range that the injections showed up in the sensors I used, if I couldn't find anything then I move up/down in frequency domain to look for any possible up/down conversions with increments depending on how wide the injections were in terms of frequency. Until I reached the lowest/highest frequency that the injections could possibly showed up, if I still didn't see anything only then I would conclude that the injections didn't show up in DARM.
More investigations on how some of these injections coupled into DARM will take days, weeks, I don't know. The point of these injections was to determine what activities can and cannot be performed during Observing run. This is why I posted spectrograms first and not wait until I'm done with the analyses. I simply let DARM spectrogram speaks for itself.
I have also attached better spectrograms of the super ball injection, produced using Dan's script.
C. Cahillane I have been busy trying to calculate kappa_tst, kappa_pu, kappa_C,and f_c from ER8 data so I might begin finding the uncertainty associated with these numbers. The uncertainty in all of these calibration coefficients depend heavily on our calibration line measurements (See T1500377 for the calculation of these coefficients from model params and calibration lines). I was curious to see if uncertainty in our calibration line measurements will be a significant source of uncertainty in the total budget, or if I can ignore it for now. I took 100 GPS times starting at 1125316818, each ten seconds apart, and computed the 10 second FFT of DARM_ERR, X_TST, X_CTRL, and X_PCAL. Then, I found their values at the calibration line frequencies at H1: f_tst = 35.9 Hz f_pcal = 36.7 Hz f_ctrl = 37.3 Hz f_pcal2= 331.9 Hz and took the following ratios: X_TST(f_tst) / DARM_ERR(f_tst) X_PCAL(f_pcal) / DARM_ERR(f_pcal) X_CTRL(f_ctrl) / DARM_ERR(f_ctrl) X_PCAL(f_pcal2) / DARM_ERR(f_pcal2) and plotted their amplitudes below. Percent uncertainties: X_TST(f_tst) / DARM_ERR(f_tst) = 0.98% X_PCAL(f_pcal) / DARM_ERR(f_pcal) = 0.95% X_CTRL(f_ctrl) / DARM_ERR(f_ctrl) = 0.84% X_PCAL(f_pcal2) / DARM_ERR(f_pcal2) = 1.05% Since I am just starting to compute the uncertainty expressions for the calibration coefficients in Mathematica, this study informed me that there is ~1% uncertainty in all of our calibration line amplitudes, which is significant enough to be included in all uncertainty calculations. Two notes: (1) I am assuming for now there is no quantization noise in our digital signals DARM_ERR, DARM_CTRL, X_TST, X_CTRL, and X_PCAL. This is almost certainty a secondary consideration in the total budget for now. (2) The method I used for dewhitening X_PCAL is known to be incorrect, so their absolute values should not be taken too seriously. But since all I cared about here is the statistical uncertainty, any systematic errors are a simple gain that is common to all data points, so this result is still valid.
C. Cahillane, E. Hall I have made some updates because of Evan. He suggested that I switch the measurements to be Response / Excitation as is the norm with transfer functions, so now my plots are of DARM_ERR / X_{TST, CTRL, PCAL}. In addition he suggested that I take more data and make histograms of the DARM_ERR / X_{TST, CTRL, PCAL} plots to better see the distribution, to see if it looks like a Gaussian or Rayleigh distribution. (Plot 2 is the Histogram, Plot 1 is the standard scatterplot) Plot 3 is the line amplitude. In the case of PCAL, we can make readouts, leading to the statistical uncertainty we see only in X_PCAL on this plot. The others, X_CTRL and X_TST, we cannot make readouts and must trust that our excitation is constant over all time. Plot 2 looks like a nice Gaussian distribution for all the observed calibration lines. We will still need to consider these statistical uncertainties in the total uncertainty budget.
While Jeff and Darkhan have been trying to get the actuactor coefficients right for calibration, I worked on an orthogonal task which is to check out the latest optical gain of DARM.
Summary points are:
The plots below show the measured optical gain measured by Pcal Y with the loop suppression taken out by measuring the DARM supression within the same lock stretch.
I used the data from Aug 28 and 29th (alog 21190 and alog 21023 respectively). The parameters were estimated by the fitting function of LISO. I have limited the frequency range of the fitting to be avove 30 Hz because the measurement does not seem to obey physics. I will metion this in the next paragraph. The cavity pole was at around 330 Hz which claims a bit lower frequency than what Evan indendently estimated from the nominal Pcal lines (alog 21210). Not sure why at this point.
One thing we have to pay attentin is a peculiar behavior of the magnitude at low frequencies -- they tend to respond lesser by 20-30 % at most while the phase does not show any evidence of extra poles or zeros. I think that this behavior has been consistently seen since ER7. For example, several DARM open loops from ER7 show very similar behavior (see open loop plots from alog 18769). Also, a recent DARM open loop measurement (see the plot from alog 20819). Keita suggested makeing another DARM open loop measurement with a smaller amplitude, for example by a factor of two at a cost of longer integation time in order to detemine whethre if this is associated with some kind of undesired nonlinearity, saturation or some sort.
I did a similar fit that Shivaraj did at LLO (alog # 20146), to determine the time delay between PCAL RX and and the DARM_ERR. Both signal chain have one each of IOP (65 KHz), USER model (16 Khz) and AA filter between them. The expected time delay between the PCAL and DARM_ERR as shown in the diagram below should be about 13.2 us in total. I used the Optical gain as 1.16e+6 from the alog above and fitted for cavity pole and time delay. I got cavity pole estimate of 324 Hz, close to what Kimamu got from his fitting and time delay of 21 us. This is 7.8 us more than what we expected from the model.
9/4 DAY Shift: 15:00-23:00UTC (08:00-16:00PDT), all times posted in UTC
Summary: Able to get a few hours of Observation time during the shift. Also had a few hours of PEM Injections by Robert. Coordinated a bit with LLO with regards to when to drop out of Observation as well. All of this is pointing us toward a goal of having long double-coincidence duty cycles for the next week so we can get an idea of the state of our machines going into O1.
Robert plans to continue with injections into the evening so he can have a lighter day tomorrow.
Handed off a nice H1 (~70Mpc) to Nutsinee with quiet seismic and slight winds.
Poll of Control Room Work: PCal/OMC model work, Calibration Analysis, PEM Injection analysis, Ops Script work.
Support: Had Commissioners around, but not needed since H1 was locked the whole time (since 16UTC / 10pm PST)
Day's Activities
ECR: https://dcc.ligo.org/LIGO-E1500373
userapps/cal/common/models/PCAL_MASTER.mdl
userapps/omc/h1/models/omc.mdl
userapps/omc/common/models/omc.mdl
h1calex, h1caley and h1omc were all successfully built but not installed. These will be installed on next Tuesday.
The seized up compressor on the supplemental chiller unit for the staging building, commonly described as the AAON Unit has been replaced, charged, and is now running at 100%.
Chris S. Joe D. Both 70% This week the guys have cleaned the original caulking and installed metal strips on 200 meters of tube enclosure on the top side. They have also cleaned the caulking on an additional 60 meters of enclosure.
I had stepped out the control room for ~15min, and when I came back the first thing I noticed was a YELLOW "OK" on the GWIstat screen. I asked around the Control Room to see if anyone knew why we were out of Science Mode (granted I should have announced my exit), but no one seemed to notice the drop from OBSERVATION.
I took us back to Observation Mode immediately since there was no reason given for having us out. I looked in the Verbal Alarm terminal, and did not see a note of the Intent Bit being changed. (So, I've talked to TJ about getting this in the Verbal Alarm script. And to also have time stamps attached to the Intention Bit alarms so we'll know when these come up.
Keita admitted he was the culprit; he opened a DTT session [which has an excitation], and then started it. (We tested this, while in Observation mode, and we were able to open this DTT session, which had excitation selected, and this did not drop us out. Robert & I thought that just opening a session would drop us out. He mentioned that maybe this is the case with AWG. We should test whether it can drop us out.). So this is when we were out:
16:19-16:29UTC Out of OBSERVATION
Addendum:
Prior to PEM Injections, Robert and I wanted to check if AWG does in fact have a different effect with regards to staying in Observation Mode with Excitation channels. Robert opened an AWG session (no drop), but once he merely selected an excitation in AWG, we were dropped out of Observation Mode. This is even WITHOUT hitting the "Set/Run" button!
When you do this, the DIAG_EXC guardian Node gets an orange box and has the message: EXC: [system] excitation!
We were dropped out of Observation at: 20:10UTC due to this excitation being selected (and NOT run) (this was different from what DTT did).
The noise below 30 Hz looks a bit non stationary, see the zoom in of the attached spectrogram.
The behavior of the noise reminds me very much of scattered light, but I'm not 100% positive right now.
For some reason Evan is reluctant to make a new post about it: LHO alog 21210, comment 5 (H1NB_2015-08-27_123000.pdf)
Due to a crazy big offset of -0.5 in Y_TR_B_PIT (for SOFT modes sensing), Y IR QPDB is almost always railing a bit in 24W operation, and Y IR QPDA is not too far.
Next time IFO drops out of lock, somebody needs to lower the whitening gain by 3dB and set a new dark offset for each quadrant.
These whitening gains are controlled by the ISC_LOCK guardian. We already lower them by 6 dB in the DRMI_ON_POP state (which produces the momentary fake jump in arm power that everyone asks about), so it sounds like we should be lowering them by 9 dB instead.
[Shamefully, we don't change the dark offsets when we change the whitening in this step.]
Shame.
DRMI_ON_POP now turns down whitening gain from 18 dB to 9 dB.
Dan, Daniel, Evan
The addition of a 9.1 MHz bandpass on the OCXO output has removed the broadband excess noise between DCPD sum and null. The dashed lines in the figure show the sum and the null as they were three days ago (2015-08-31 7:00:00 Z), while the solid lines show the sum and the null after the filter was inserted.
Since at least June (probably longer), we've had a broadband excess noise between the sum and null DCPD streams. Stefan et al. identified this as 45.5 MHz oscillator noise a few weeks ago (20182).
In parallel, we switched the 9 MHz generation from an IFR to the OCXO (19648), and we installed Daniel's RFAM driver / active suppression circuit (20392), but the excess noise remained (20403). For a while we suspected that this was 45.5 MHz phase noise (and hence not supressed by the RFAM stabilization), but the shape and magnitude of the oscillator phase noise coupling (20783) were not enough to explain the observed noise in the DCPDs, under the assumption that the OCXO phase noise is flat at high frequencies (20582). For that matter, the shape and magnitude of the oscillator amplitude noise coupling were also not enough to explain the observed noise in the DCPDs, assuming a linear coupling from the RFAM (as sensed by the EOM driver's OOL detector) (20559).
Daniel et al. looked at the 45.5 MHz spectrum directly out of the harmonic generator in CER, and found that most of the noise is actually offset from the 45.5 MHz carrier by 1 MHz or so (20930), which is above the bandwidth of the RFAM suppression circuit. This suggested that the noise we were seeing in the DCPDs could be downconvered from several megahertz into the audio band.
Yesterday there was a flurry of work by Keita, Fil, Rich, et al. to find the source of this excess noise on the 45.5 MHz (21094 et seq.). Eventually we found circumstantial evidence that this excess noise was caused by baseband noise out of the 9.1 MHz OCXO.
Tonight we installed a 9.1 MHz bandpass filter on the OCXO output. This has removed the huge 1 MHz sidebands on the 45.5 MHz signal, and it also seems to have greatly lowered the coherence between DCPD A and DCPD B above a few hundred hertz.
The chain from OCXO to filter to distribution amplifier currently involves some BNC, since we could not find the right combination of threaded connectors to connect the filter to the amplifier. This should be rectified.
Also, it appears that our sum is lower than our null in a few places (400 Hz in particular), which deserves some investigation.
"NULL>SUM" problem is just DARM loop. You're talking about 10%-ish difference, and DARM OLTF gain is still 0.1-0.2 at 400Hz.
See attached.
I don't know how to obtain official DARM OLTF model, so I just took 2015-08-29_H1_DARM_OLGTF_7to1200Hz_tf.txt in
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/ER8/H1/Measurements/DARMOLGTFs/
The coherence for this OLTF measurement was much larger than 0.95 for the entire frequency range shown on the plot.
On the bottom is |1+OLTF|. I interpolated this to the frequency spacing of SUM and NULL spectra, and plotted SUM*|1+OLTF|, SUM, and NULL at the top.
Note that DARM OLTF template measures -1*OLTF.
Nice work. After O1 we can figure things out now you have narrowed it down.
Nice work!
Great job! Following up on the discussion during the commissioning meeting today, at LLO Evan's equivalent plot of the coherence between the two OMC PDs is already below 10^-3 (below 3 kHz).
Fil and I replaced the BNC cable with an SMA/N cable.
I took a look at the integrated DARM 0-2000 Hz spectrum from 50 hours of 30-minute FScans SFTs taken over the last few days. A couple of sample plots are shown below, and a more extensive set of plots is attached in a zip file. The alphabetic labels on narrow lines conform to those defined in this earlier pre-ER7 report. Highlights and lowlights: * The 0.1698-Hz comb seen before is gone. * The 3.9994-Hz comb seen before is gone. * The 36.9725-Hz comb seen before is gone. * The 16-Hz comb seen in ER7 is still prevalent throughout the spectrum. The 64-Hz harmonics are no longer marked separately, since they don't seem as special as they once did. * There is a new 1-Hz comb with a 0.5-Hz offset, that becomes visible at about 16.5 Hz and peters out around 69.5 Hz (for this integration time). This comb seems likely connected to there being strong digital lines at 0.5 Hz and 1 Hz. There are some new single lines marked here and there (with 'x'), plus some new calibration lines. I have not removed singles marked previously, in case they reappear with deeper integrations to be done after more ER8 data is available. Figure 1 - 0-2000 Hz Figure 2 - 20-100 Hz (note the new 1-Hz comb marked with 'O' for 'One'
We ran the coherence tool on the first week of ER8 data at Hanford, and calculated the coherence between h(t) and numerous auxiliary channel. For the 1 mHz resolution, the results are here: https://ldas-jobs.ligo-wa.caltech.edu/~eric.coughlin/ER7/LineSearch/H1_COH_1123891217_1124582417_SHORT_1_webpage/ We are looking into some of the lines that Keith Riles observed and summarized here https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=20790 Specifically, we concentrated on "There is a new 1-Hz comb with a 0.5-Hz offset, that becomes visible at about 16.5 Hz and peters out around 69.5 Hz (for this integration time). This comb seems likely connected to there being strong digital lines at 0.5 Hz and 1 Hz." Here are the channels where we see this structure in the coherence, and a few observations as well for some of the channels H1:SUS-ITMY_L2_NOISEMON_UR_DQ_data There is a 16.5 Hz line here, and others off by 0.5 Hz at low frequencies. H1:SUS-ITMY_L2_NOISEMON_UL_DQ H1:SUS-ITMY_L2_NOISEMON_LR_DQ H1:SUS-ITMY_L2_MASTER_OUT_UR_DQ H1:SUS-ITMY_L2_MASTER_OUT_UL_DQ H1:SUS-ITMY_L2_MASTER_OUT_LR_DQ H1:SUS-ITMY_L2_MASTER_OUT_LL_DQ H1:SUS-ITMX_L2_NOISEMON_UR_DQ H1:SUS-ITMX_L2_NOISEMON_UL_DQ H1:SUS-ITMX_L2_NOISEMON_LL_DQ Coherence at 10.0, 12.0, 12.5, 14.0, 15.5, 18.0 (big), 21.0, 24.0 30.0 Hz etc H1:SUS-ITMX_L2_MASTER_OUT_UR_DQ H1:SUS-ITMX_L2_MASTER_OUT_UL_DQ H1:SUS-ITMX_L2_MASTER_OUT_LR_DQ H1:SUS-ITMX_L2_MASTER_OUT_LL_DQ H1:SUS-ETMY_L3_MASTER_OUT_UR_DQ H1:SUS-ETMY_L3_MASTER_OUT_UL_DQ H1:SUS-ETMY_L3_MASTER_OUT_LR_DQ H1:SUS-ETMY_L3_MASTER_OUT_LL_DQ H1:SUS-ETMY_L2_NOISEMON_UR_DQ H1:SUS-ETMY_L2_NOISEMON_UL_DQ H1:SUS-ETMY_L2_MASTER_OUT_UR_DQ H1:SUS-ETMY_L2_MASTER_OUT_UL_DQ H1:SUS-ETMY_L2_MASTER_OUT_LR_DQ H1:SUS-ETMY_L2_MASTER_OUT_LL_DQ H1:SUS-ETMX_L3_MASTER_OUT_UR_DQ H1:SUS-ETMX_L3_MASTER_OUT_UL_DQ H1:SUS-ETMX_L3_MASTER_OUT_LR_DQ H1:SUS-ETMX_L3_MASTER_OUT_LL_DQ H1:SUS-ETMX_L2_NOISEMON_UR_DQ H1:SUS-ETMX_L2_NOISEMON_UL_DQ5 H1:SUS-ETMX_L2_NOISEMON_LR_DQ H1:SUS-ETMX_L2_NOISEMON_LL_DQ H1:SUS-ETMX_L2_MASTER_OUT_UR_DQ H1:SUS-ETMX_L2_MASTER_OUT_UL_DQ H1:SUS-ETMX_L2_MASTER_OUT_LR_DQ H1:SUS-ETMX_L2_MASTER_OUT_LL_DQ H1:PEM-EY_MAG_EBAY_SUSRACK_Z_DQ 16.5 Hz is here. And more 0.5 Hz harmonics after. Not super strong, but they are there. H1:PEM-CS_TILT_LVEA_VERTEX_Y_DQ Not clear for this channel. A real mess of lines at low frequencies. 25.5 Hz is distinct. Also 12.5, 26.5, 30.5, 32.5 Hz too. H1:PEM-CS_TILT_LVEA_VERTEX_X_DQ Also a mess at 16.5 Hz, but the line is there. There are lines at 12.5, 14.5, 32.0, 40.0 Hz H1:PEM-CS_MAG_LVEA_OUTPUTOPTICS_X_DQ Starts at 14.5 Hz, and the lines then appear consistently every 0.5Hz. H1:PEM-CS_MAG_LVEA_OUTPUTOPTICS_QUAD_SUM_DQ H1:PEM-CS_MAG_EBAY_SUSRACK_Z_DQ Seems to start at 14.5 Hz, and then this 0.5 Hz harmonic continues to appear noticeably and consistently. H1:PEM-CS_MAG_EBAY_SUSRACK_Y_DQ 6.0, 7.0, 7.5, 8.0, 8.5, 12.0 Hz, then some small but observable coherences continue at 15.0, 15.5, 16.0, 16.5 Hz. 18.0 Hz and 21.0, 21.5, 22.5, 23.5, 24.0, 30.0, 35.0 Hz are big again. H1:PEM-CS_MAG_EBAY_SUSRACK_X_DQ Some example coherence plots are given. Nelson, Michael Coughlin, Eric Coughlin, Pat Meyers
This entry is meant to survey the sensing noises of the OMC DCPDs before the EOM driver swap. However, other than the 45 MHz RFAM coupling, we have no reason to expect the couplings to change dramatically after the swap.
The DCPD sum and null data (and ISS intensity noise data) were collected from an undisturbed lock stretch on 2015-07-31.
Noise terms as follows:
The downward slope in the null at high frequencies is almost certainly some imperfect inversion of the AA filter, the uncompensated premap poles, or the downsampling filter.
* What is the reasoning behind the updated suspension thermal noise plot?
* Its weird that cHard doesn't show up. At LLO, cHard is the dominant noise from 10-15 Hz. Its coupling is 10x less than dHard, but its sensing noise is a lot worse.
I remade this plot for a more recent spectrum. This includes the new EOM driver, a second stage of whitening, and dc-lowpassing on the ISS outer loop PDs.
This time I also included some displacement noises; namely, the couplings from the PRCL, MICH, and SRCL controls. Somewhat surprising is that the PRCL control noise seems to be close to the total DCPD noise from 10 to 20 Hz. [I vaguely recall that the Wipfian noise budget predicted an unexpectedly high PRCL coupling at one point, but I cannot find an alog entry supporting this.]
Here is the above plot referred to test mass displacement, along with some of our usual anticipated displacement noises. Evidently the budgeting doesn't really add up below 100 Hz, but there are still some more displacement noises that need to be added (ASC, gas, BS DAC, etc.).
Since we weren't actually in the lowest-noise quad PUM state for this measurement, the DAC noise from the PUM is higher than what is shown in the plot above.
If the updated buget (attached) is right, this means that actually there are low-frequency gains to be had from 20 to 70 Hz. There is still evidently some excess from 50 to 200 Hz.
Here is a budget for a more recent lock, with the PUM drivers in the low-noise state. The control noise couplings (PRCL, MICH, SRCL, dHard) were all remeasured for this lock configuration.
As for other ASC loops, there is some contribution from the BS loops around 30 Hz (not included in this budget). I have also looked at cHard, but I have to drive more than 100 times above the quiescient control noise in order to even begin to see anything in the DARM spectrum, so these loops do not seem to contribute in a significant way.
Also included is a plot of sensing noises (and some displacement noises from LSC) in the OMC DCPDs, along with the sum/null residual. At high frequencies, the residual seems to approach the projected 45 MHz oscillator noise (except for the high-frequency excess, which we've seen before seems to be coherent with REFL9).
Evidently there is a bit of explaining to do in the bucket...
Some corrections/modifications/additions to the above:
Of course, the budgeted noises don't at all add up from 20 Hz to 200 Hz, so we are missing something big. Next we want to look at upconversion and jitter noises, as well as control noise from other ASC loops.
When we got back to low noise at 0958 UTC, we noticed the DARM gain was too low by about 30%. This was probably because we performed the gaurdian steps out of sequence: we increased power on RF DARM to allow for OMC modescans, with the DARM boost on, and then handed of to DC readout. Performing the RF-->DC handoff with the DARM boost enabled can spoil the coherence of the gain-matching calculation and lead to a value for the OMC-READOUT_ERR_GAIN that is off by tens of percent. Really we should be doing this calculation with a driven excitation, rather than relying on unsuppressed length fluctuations to provide coherence between AS45_Q and DCPD_SUM. But we haven't taken the time to code up a tdssine measurement (or tdsresp? something in cdsutils?) in the OMC guardian.
Anyways after some head-scratching we adjusted OMC-READOUT_ERR_GAIN so the height of the 331.9Hz calibration line was the same as it was twelve hours ago.