bubba.gateley@LIGO.ORG - posted 11:50, Sunday 26 July 2015 (19941)
Bubba leaving site
Bubba on site to repair frost free wall hydrant on East wall of OSB.
J. Kissel I've come in to find the IFO still cruising along at full power and full sensitivity. With this kind of robustness, I think we might even be ready for and observation run! Nice work all!! Now we just need to refine the calibration... For the record, the observation intent bit was turned ON at Jul 26 2015 10:13:35 UTC Jul 26 2015 03:13:35 PDT 1121940832
I think that evan meant to say he increased the gain for CHARD by 20 dB by engaging FM1
This one is interesting.
Based on step response it has a time constant of something like 15 to 20 s.
J. Kissel I've updated the CAL-CS MEDM screens to go with the front-end model clean up of the time dependence tracking in the DARM calibration installed on Thursday (see LHO aLOG 19875). In addition, I've *created* an MEDM screen for what's currently implemented for PCAL vs. DARM calibration line demodulation, even though at LHO we can't yet ship PCAL information back to the corner station because of RFM IPC errors (see LHO aLOG 18671). See attached screenshots. For Joe: Here's what you need to update on Tuesday: /opt/rtcds/userapps/release/cal/common/models/ Sending models/CAL_CS_MASTER.mdl Sending models/CAL_GAMMA_CALC_MASTER.mdl Sending models/CAL_GAMMA_PCAL_MASTER.mdl /opt/rtcds/userapps/release/cds/common/medm/ Adding DEMOD.adl /opt/rtcds/userapps/release/cal/common/medm/ Deleting medm/CAL_CS_GAMMA_LINE_OVERVIEW.adl Sending medm/CAL_CS_OVERVIEW.adl Adding medm/CAL_CS_TDEP_DARM_DEMOD_OVERVIEW.adl Sending medm/CAL_CS_TDEP_OVERVIEW.adl Adding medm/CAL_CS_TDEP_PCAL_DEMOD_OVERVIEW.adl VERY IMPORTANT: I've rearranged the inputs to the CAL_CS_MASTER model such that there isn't the constantly annoying spaghetti soup of wires going from the IPC parts into the library part. So, you'll need to reconnect all of the IPCs at the top-level model, accounting for the rearrangement. Sadly, looking through this PCAL and DARM demod infrastucture which produces the time-dependence formerly known as gamma(t), documented in T1500206 and T1500121 is now sorely out of date with how we intend to compensate things in O1 with the low-latency pipeline (for which the documentation is not complete, but lives in T1500377). It makes me wish we had kept the idea of performing the time-dependent calculations in a separate front-end model, such that we could play around with it during the science run without it affecting the time-independent calibration. *sigh* hindsight is 50/50, right?
Nice night lock, here is the report from BruCo:
https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_1121900417/
An excerpt. As usual, the selection of channels might not be the most representative of the real noise couplings, but should give some good hints.
Jeff, Evan
Here is a DARM OLTF DTT xml with drive levels that are appropriate for use when the EY ESD LVLN LPF on.
Above 500 Hz, it is hard to get coherence. In this region, we have tuned the drive envelope so that the DAC for each ESD quadrant is putting out somewhere between 10 000 ct pk and 50 000 ct pk.
The current integration time (and number of points) as saved in the file is meant for a long, slow, precise measurement, and it will take about 25 minutes to run. For commissionning purposes, it is prudent to reduce the number of points and the integration time.
Came in to find the interferometer has been locked for 5 hours and the ITMY HWS camera, frame grabber, and SLED beam has been on. Since they don't seem to bother anyone I decided to leave them on and run the ITMY HWS code. The number on ITMY HWS medm screen are constantly changing but in the terminal I kept getting "LHD File Not Written". The .mat files are not being updated constantly so I'm not sure how to tell if the code is actually working. The files are in /home/controls/temp/HWSY_July25
ETM HWS cameras were also on. I just turned them off.
Jeff pointed out that I should leave an instruction on how to kill the code since I left it running on the Ops computer. About 30 minutes after lock loss go to the terminal that has the TCS code running (the only terminal that refreshes itself every second or so), simply kill it by Ctrl+C. Do it repeatedly until the code is killed. I'd wait 30 minutes to allow the spherical power to decrese all the way to the bottom. This way I know the code was actually working and the data make sense.
Attached is the dark noise of REFL9Q, along with an estimate of the shot noise and a conversion of these noises into equivalent frequency noise in CARM.
The dark noise appears to be slightly below the shot noise level.
I took the TNC that goes directly into the common-mode board and put it into an SR785. Also attached is the noise with the input of the SR785 terminated.
I also have tried to estimate how this compares to the shot noise on the diode. In full lock at 24 W, we see 3.6 mW of dc light on the PD (according to the calibrated REFL_A_LF channel). Off resonance and at 2.0 W, we have 13.6 mW of dc light. So the CARM visibility is about 98%.
The shot noise ASD (in W/rtHz) and the CARM optical plant (in W/Hz) are both given in Sigg's frequency response document. With a modulation index of 0.22 rad and an incident power of 24 W, the shot noise is 9.4×10−10 W/rtHz, the CARM optical gain is 11 W/Hz, and the CARM pole is 0.36 Hz. [Edit: I was missing some HAM1 attentuation when first calculating the shot noise level. Out of lock, the amount of power on REFL A should be 24 W × 0.1 × 0.5 × 0.5 × 0.5 = 300 mW. That gives a predicted shot noise level of 7.7×10−11 W/rtHz, assuming a sideband amplitude reflectivity of 0.44. On the other hand, from the measured in-lock power we can calulate 2(hνP)1/2 = 5.2×10−11 W/rtHz for P = 3.6 mW. This includes the factor of sqrt(2) from the frequency folding but does not include the slight cyclostationary enhancement in the noise from the sidebands (although this latter effect is not enough to explain the discrepancy).] Additionally, I use Kiwamu's measurement of overall REFL9 response (4.7×106 ct/W) in order to get the conversion from optical rf beat note power into demodulated voltage (2900 V/W). These numbers are enough to convert the demodulated dark noise of REFL9Q (and the shot noise) into an equivalent frequency noise. At 1 kHz, the shot noise is about 10 nHz/rtHz; as a phase noise this is 10 prad/rtHz (which is smaller than Stefan's estimate of 80 prad/rtHz). The dark noise, meanwhile, is about 5 nHz/rtHz.
Hang, Evan
We measured the input-referred voltage noise of the summing node and common-mode boards.
According to this estimate, the CARM loop is not shot noise limited; rather, at 1 kHz the noise is about a factor of 3 in ASD above shot noise.
I looked back at the CARM sensing noise data I took (on 12 Aug) using the new gain distribution: 0 dB SNB gain, −13 dB CMB common gain, 0 dB CMB fast gain, and 107 ct/ct digital MCL gain.
[For comparison, the old CARM gain distribution was 0 dB SNB gain, −20 dB CMB common gain, 7 dB CMB fast gain, and 240 ct/ct digital MCL gain.]
☞ For those looking for a message in this alog: something about the current frequency noise budgeting doesn't hang together. The projection based on the CARM sensing noise and the measured CARM-to-DARM coupling TF suggests a CARM-induced DCPD sum noise which is higher than what can be supported by coherence measurements.
☞ Second attachment: As expected, the noise (referred to the input of the SNB) is lower; at 40 Hz, it is about 350 nV/Hz1/2. However, we are not really shot-noise (or dark-noise) limited anywhere.
☞ Third attachment: I am also including the CARM-to-DARM coupling TF from a few weeks ago. This TF was taken by injecting into the CARM excitation point and measuring the response in OMC DCPD sum, using the old CARM gain distribution. Then I referred this TF to the SNB input by multiplying by the SNB gain (0 dB), the CMB common gain (−20 dB), and the CMB common boost (40 Hz pole, 4 kHz zero, ac gain of 1).
This gives a coupling which is flat at 1.0×10−2 mA/V, transitioning to 1/f2 around 250 Hz. Or, to say it in some more meaningful units:
☞ Synthesis of the above: based on the measurements described above, at 40 Hz we expect a coupling into the DCPD sum of 350 nV/Hz1/2 × 0.4 mA/V = 1.4×10−7 mA/Hz1/2, which is very close to the overall DCPD sum noise of 3.2×10−7 mA/Hz1/2.
But what is wrong with this picture? If 1.4/3.2 = 44 % of the DCPD sum noise comes from CARM sensing noise, we should expect a coherence of 0.442 = 0.19 between the DCPD sum and the CARM error point.
☞ First attachment: The coherence between the CARM error point and the DCPD sum is <0.01 around 40 Hz. Now, it is almost certainly the case that not all of the CARM error point noise is captured by LSC-REFL_SERVO_ERR, since this channel is picked off in the middle of the CMB rather than the end. Conservatively, if we suppose that LSC-REFL_SERVO_ERR contains only dark noise and shot noise, this amounts to 180 nV/Hz1/2 of noise at 40 Hz referred to the SNB error point, or 0.72×10−7 mA/Hz1/2 referred to the DCPD sum. This would imply a coherence of 0.05 or so.
☞ What is going on here?: Four possibilities I can think of are:
☞ A word about noise budgeting: In my noise budget, there was a bug in my interpolating code for the CARM-to-DARM TF, making the projection too low below 100 Hz. With the corrected TF, the projected CARM noise is much higher and begins to explain the mystery noise from 30 to 150 Hz. However, given that the above measurements don't really hang together, this is highly speculative.
According to the CMB schematic and the vertex cable layout, the CARM error point monitor goes through some unity-gain op-amps and then directly into the ADC. So I don't think we have much chance of seeing the 180 nV/Hz1/2 of shot/dark noise above the 4 µV/Hz1/2 of the ADC.
According to the CMB schematic and the vertex cable layout, the CARM error point monitor goes a gain of 200 V/V and then directly into the ADC. So the 180 nV/Hz1/2 of shot/dark noise appears as 36 µV/Hz1/2 at the ADC. But as Daniel pointed out, this should be heavily suppressed by the loop. For comparison, the ADC's voltage noise is 4 µV/Hz1/2.
For the sake of curiosity, I'm attaching the latest noise budget with the corrected CARM-to-DARM coupling TF. However, I note again that this level of frequency noise coupling is not supported by the required amount of coherence in any of our digitally acquired channels. Additionally, this level of frequency noise coupling is not seen at Livingston, although they've done a better job of TCS tuning than we have. I would not be surprised to find out that this coupling is somehow an overestimate.
J. Kissel, S. Ballmer The ESD / DARM calibration lines have been OFF since the CAL-CS front-end model changes this past Thursday (LHO aLOG 19875), because the channel names that generate them have changed. I've used LHO aLOG 19792 to restart them with the newly high SNR. As Stefan mentions in LHO aLOG 19925, I turned this back on just before the current lock stretch's undisturbed bit was engaged. For the record, the new channels are H1:CAL-CS_TDEP_ESD_LINE1_DEMOD_OSC_FREQ 34.7 [Hz] H1:CAL-CS_TDEP_ESD_LINE1_DEMOD_OSC_CLKGAIN 0.22 [ct] H1:CAL-CS_TDEP_ESD_LINE2_DEMOD_OSC_FREQ 538.1 [Hz] H1:CAL-CS_TDEP_ESD_LINE2_DEMOD_OSC_CLKGAIN 2.4 [ct] I've overwritten the current EPICs database to the SDF safe.snap, and loaded in the new table to initialize all of the newly named channels. A large fraction of them are now not monitored (417 out of 1188), but I've at least gone through the ESD LINE CLKGAIN and FREQs to make sure they're monitored. I would monitor more, but I don't want to sort on substring (see LHO aLOG 19650).
Stefan, Jeff, Starting at 22:24:00 UTC (Jul 25 2015) we left the interferometer undisturbed (H1:ODC-OPERATOR_OBSERVATION_READY was set). For detChar purposes: - All cal lines are on. Our (questionable) calibration reports 60Mpc, but hopefully we ca revise that later. - The winds are hauling with peak gust up to 38mph, but to interferometer seems remarkable indifferent about that.
Adding DetChar, SEI, and SYS Tags and an ASD. For the record, the reference trace is 10 AVGs and the Live trace is 25 AVGs. Not sure why we're using this crazy weird template that doesn't display the number of averages, but I'll pick another battle.
Intent bit was turned off around 2015-07-26 02:24:00 Z in order to save the lock from 1 Hz pitch instability. I turned up the dHard pitch gain by a factor of 2.
1 hour of dHard pitch error signal is attached. The gain was turned up near the end.
Now that h1fw0 is stable, we are testing making h1fw1 stable by having it only write commissioning frames and not science frames. This is a temporary fix to support the current commissioning work where reliability is more important than redundency. The frequent restarts of h1fw1 (whose data is served by h1nds1 which is the default NDS) was causing commissioning issues due to data gaps and unavailability. Also note that we have not had any crashes of the framewriter OS or hardware, and so redundency is less of an issue outside of a science run.
After the 12:02 h1fw1 restart today it is now running the new configuration.
The current DAQ configuration is:
frame-writers
| name | science frames | commissioning frames | trends |
| h1fw0 | YES | NO | YES |
| h1fw1 | NO | YES | YES |
nds-servers
| name | serving | default NDS |
| h1nds0 | h1fw0 Commissioning frames* | NO |
| h1nds1 | h1fw1 Commissioning frames | YES |
* This is a mistake now that h1fw0 is not writing commissioning frames, needs a restart of h1nds0 to fix which could impact on Guardian nodes, so we are delaying this.
at approx 5pm Friday cdsfs1 (the backup server for cdsfs0 and h1boot) froze up. I was able to power cycle it remotely via IPMI. I'll check that it performs its periodic rsyncs of cdsfs0 and h1boot.
I was running an ASC OLTF swept-sine template with a request for a 10 s rampdown time.
From the EXCMON of the drive channel, it seems that this rampdown did not happen. Rather, the excitatation continued at full strength for about 10 s and then cut off abruptly.
Yes, it appears this feature is broken, at least in swept sine mode.
I pushed the abort button around 06:20:00 Z (around the 10 second mark in the attachment). The excitation continues at full strength until the last second. Then, as far as I can tell, there is some slightly different waveform being written to the excitation channel for about a second. Then the excitation stops abruptly, causing a lockloss.
See below for the coherence report.