Initial alignment was redone following today's PSL work.
Attached is the whiteboard list of tomorrow's scheduled tuesday maintenance activites.
We'll start with some hardware related work, and follow up with an ASC model restart. As usual, please let us know when you are coming and going to VEAs, whether for listed work or not, so we can ensure efficiency of everyone's work.
1st wave tasks:
Fix 1st loop ISS servo card
Install PI AA chassis (Ex, EY)
Install TCSx viewport temp sensor
Finish SEI "safe" .snaps
Stagger start in 1st wave task:
Pcal work at Ey
Sweep VEAs for test equipment that needs to come home
PEM injection setup
2nd wave tasks:
ASC model restart
REVERT EX FE computer to original machine
DAQ Restart
Kiwamu recently found, while trying to to use suspension model to calibrate Pcal, that the use of IIR filter in the front-end results in distortion of the filter response from its actual intended response. (G1501013).
We decided to check all the whitening filters that are use in CAL-CS model to confirm (check) if we see similar effect. The following filters were analyzed:
CAL-DARM_CTRL_WHITEN
CAL-DARM_ERR_WHITEN
CAL-CS_DARM_DEALTAL_CTRL_SUM(L1/L2/L3/M0)
CAL-CS_DARM_RESIDUAL_WHITEN
CAL-CS_DARM_DELTAL_EXTERNAL_WHITEN
The frequency response of these filters deviate from the model by about 2.5% at its max in amplitude and about 8 degrees in phase (at around 5 KHz). Some filters are severe than the other but they produce this effect nonetheless.
I varied a pair of pole frequencies, keeping two zeros at 1 Hz, to see what the effect looks like. From the last plot, we can see that the distortion is more severe if the pole frequencies are higher.
(Evan, Kiwamu. Daniel)
We installed the 45.5MHz EOM driver in the PSL room. It is located below the PSL table and replaces the RF amplifier at the same location. The drive power has been adjusted to be the same as before at 23.2dBm. This is now controlled remotly through medm.
Calibration:
The RF phase shift was compensated by cable length to within 1°.
The RF phase has a slightl dependence on the RF level. At 45.5MHz with 23dBm output level the phase advance of the entire chassis is 121°. The relative phase shift at 17dBm is +4.8° (advance), +8° at 13dBm, and 12.8° at 5dBm—or –0.8°/dBm.
The attached plot shows the RF AM RIN in dBc/Hz for both the in-loop and out-of-loop sensor (double-sided). At 100Hz with 23dBm output we are achieving-170dBc/Hz.
We kept track of the RF phase shift by keeping the interferometer in a freeswinging Michelson configuration while watching the time series of AS45I and AS45Q. Before the swap, we had arctan[Q/I] = arctan[42.0(3)/10.3(3)] = 76.2(4)°. After the swap, we found that the signals had shifted by +144°. [Note that just watching the freeswinging I and Q time series only determines the phase shift modulo 180°. We locked the Michelson and found that instead of the expected dark fringe lock, we got a bright fringe lock—indicating that the phase shift must lie somewhere between +90° and +270°.]
Then we experimented with adding extra cable length between the 45 MHz distribution spigot and the EOM driver. In the end Kiwamu and Daniel made a 150 cm LMR 195 cable, which brought the phase of AS45 back to arctan[41.8(6)/10.1(4)] = 76.4(6)°.
I assume the following SDF setting changes are related to this work, so I have accepted them into the LSC safe.snap for future restores.
[Sheila, Jenne, Kiwamu, Daniel]
It's not totally clear how or when this happened, but at some point today the input pointing PZT driver's power cable came loose. This box is on the PSL table, in the PSL enclosure. The failure seems to have happened before anyone went into the enclosure today, but after the fans were turned on (in preparation for going in).
The big symptom was that we had no light at all on the IMC Refl camera, even though the PMC was locked. There was no light reaching IOT2L, even at the top of the down-periscope. We also found that we were unable to move the input beam with the PZT (moving very large steps had no effect on the spot position), and the beam was very low.
Kiwamu and I confirmed that we were getting signals out of the DAC, so the problem was clearly downstream.
Sheila and Daniel went into the PSL and discovered that the power cable for the PZT driver was loose. The AC adapter for the cable was hanging, with its weight pulling on the power connection on the box. Jiggling the cable caused the LED on the box to illuminate, and we immediately saw beam on the IMC Refl camera. Sheila and Daniel moved the power cable, so hopefully this won't happen again.
A bit of alignment later, and the IMC is locked once again.
Reed E., Erik K., Matt E.
In order to explore the possibility that the big glitches in DARM come from ambient dust events in the arms, we took a look at the transmitted power signals. In a perfect world, these should dip if something falls trough the beam.
We found that that dust glitches also appear in the X and Y TR signals (e.g., ASC-{X,Y}_TR_{A,B}_NSUM_OUT_DQ) with large amplitude (see first 2 plots). Interestingly, both arms are affected, though the arm where the dust is not falling appears to see a low-passed version of the disturbance (e.g., via the DARM cavity pole).
Some of the glitches looked at by Gabriele also seem to appear weakly in the TR signals, though a more sophisticated analysis will be needed to draw conclusions about the efficiency of these signals as a veto.
Sudarshan, Gabriele
Today when the IFO was locked in low noise, we could see the 300-400 Hz peaks in the sensitivity again. Those are know to be due beam jitter caused by the PSL periscope.
We looked into the performance of the ISS second loop, which was closed at the time. The first strange thing that we can't understand is that both the in-loop and out-of-loop signals are dominated by a flat noise background at a level of 1e-8 /rHz. We would expect the out-of-loop to be at this level, but the in-loop should be squeezed down by the larg loop gain.
We changed the ISS gain, anmd discovered that if we turned down the gain at the minimun (-26-20 dB with respect to nominal), and disengage both boost and integrator, the in and out of loop ISS signals got worse, but the sensitivity got better at the 300-400 Hz peaks. So out guess is that beam jitter on the ISS array is actually causing an excess sensing noise on the ISS diodes, which is then re-injected into the laser beam as real intensity noise when the ISS second loop is closed with high gain.
We tried briefly to optimize the centering of the beam on the ISS array. We couldn't find any spot better than the initial one in terms of power on the diodes. One possible strategy would be to move the beam into the ISS array with the IFO in full lock, and use the coupling of a PZT jitter line to the sensitivity as a figure of merit.
I saw the same strange noise floor that were at a level of 1x10-8 RIN/sqrtHz a week ago. See the spectra from this alog:
https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=20148
In light of this strange noise floor, I looked at some of the RIN spectrum I had taken peridocally. This change in In-loop PD noise seem to have happened after we started using the actual DC signal from the PD to obtain RIN ( we were using a hardcoded offset that was an estimate of DC signal). So we implemented a low pass filter with two poles at 10 mHz in the DC signal this morning and the problem is gone. Attached is a spectrum before and after the low pass filter was implemented. SDF table is appropriately updated.
Dan has identified all 8 frequencies that belong to ETMX here. So I added them to the monitor.
The conlog process on h1conlog1-master failed at 12:25PDT Saturday 8th August. The error is shown in the FRS report linked below. I restarted the process this afternoon. Conlog is reporting 412 disconnected channels which relate to the guardian and h1calcs work which was done last week, we will need to regenerate the conlog channel list tomorrow.
After pulling the latest ASC_MASTER.mdl and talking to Adam at LLO, I added the following channels in ASC_MASTER to the science frame in addition to what Adam did:
ASC-DC1_P_OUT_DQ , (also Y, also DC2, DC3, DC4 and DC5): 512Hz
ASC-OMC_A_PIT_OUT_DQ (also YAW and SUM, also B): 2kHz
I then changed H1ASC.mdl to use the new ASC_MASTER. Dave compiled the model without an error. We'll install it tomorrow.
Some details:
0: Pzt outputs for new POPX thing is terminated at LHO.
At LLO this is connected to DAC, but here I simply terminated the output.
1: Initial Alignment system (obsolete, not used these days) are purged from h1 model.
This was purged from the latest ASC_MASTER. To accomodate this, access to ALS_X_REFL_B_LF_RFM, and ALS_X_REFL_B_LF_RFM_IPC_ERR, and their Y-arm counterparts, were all deleted from the top level.
2: DARM_CTRL and IM4_TRANS_PIT and YAW input for the common block are terminated in h1 model
This is a part of LLO dither scheme, but I just terminated these input in h1 model.
3: Unused PZT[12][XY]_[PY] and QPD[12][XY]_[PY] are gone from ASC_MASTER.
These were already obsoleted by green WFS at LHO and were terminated at the top level at LHO. Now these signals are gone.
4: New dither outputs are connected to some masses in h1 model.
New ASC_MASTER has dither outputs to BS, ITMs and ETMs in addition to PRM, PR2 and PR3.
In the old h1 model, RFM sender to corresponding optics already existed but was sending 1 or 2 (constant). In the new h1 model these things are connected to the dither output even though we do not use dither these days.
There are unused RFM sender to SRM, SR2 and SR3, these are kept there.
5: Deleted some obolete text labels and an unused orphaned RFM receiver in h1 model.
JeffreyK, Darkhan
Overview
We found that some of the calculations in the recently implemented CAL_CS front-end model (see LHO alog #20360) do not produce expected results. We found this problem in the division block that takes input of significantly smaller number for denominator vs. number in the nominator.
Since this calculation is done on quantities that should change only as a result of manual input we've decided to calculate these quantities in Matlab and then export final results to EPICS. Tomorrow we will add these EPICS inputs into CAL_CS front-end model.
Details
In this section we show how this bug was identified.
Following EPICS input channels exist in the CAL_CS front-end model: REF_A_TST_REAL and REF_A_TST_IMAG. They form a complex quantity Atst = Re{ Atst } + i * Im{ Atst } = REF_A_TST_REAL + i * REF_A_TST_IMAG.
We wanted to calculate Re{ -1/Atst } and Im{ -1/Atst } as
| Atst |2 = Re{ Atst }2 + Im{ Atst }2
Re{ -1/Atst } = - Re{ Atst } / | Atst |2
Im{ -1/Atst } = Im{ Atst } / | Atst |2
When we provided both inputs (real and imaginary) with quantities their values, the quantity | Atst |2 came out to be about right, but the final values Re{ -1/Atst } and Im{ -1/Atst } were off by several orders of magnitude.
The finals values should have been
Re{ -1/Atst } = 1.39199e+16
Re{ -1/Atst } = -1.14388e+16
We don't know for sure, but it might be possible to avoid this bug by trying rearrange signals in simulink design (e.g. replace division by multiplication by inverse of the quantity or maybe some other way).
For this case we decided to calculate these final quantities in Matlab and into EPICS only final results.
Looks to me that the FE prevents divide-by-zero errors by limiting the denominator to 1E-20.
Leonid.Prokhorov, Jeffrey.Kissel Charge measurements was done on both ETMs. Results are in attachments. For most quadrants we have follow trend: From June, 24 to July, 21 (from discharging to changing the bias sign) data are consistent with positive charging for ETMY and negative charging for ETMX. ETMX Bias: +9.5V, Mean charging rate: -10 V/month (st. dev. +/- 3 V/mon) ETMY Bias: -9.5V, Mean charging rate: +7 V/month (st. dev. +/- 3 V/mon) From July, 22 to Aug, 10 (from changing the bias sign to today's measurements) data for most of quadrants are consistent with the changed sign of charging - negative for ETMY and positive for ETMX. ETMX Bias: -9.5V, Mean charging rate: +17 V/month (st. dev. +/- 9 V/mon) ETMY Bias: +9.5V, Mean charging rate: -20 V/month (st. dev. +/- 14 V/mon) Note, because the standard deviation is less that the mean, it shows that the rate is roughly the same for each quadrant. However, there are outliers (see, e.g. Right quadrants of ETMY). Now the effective bias voltage is about few volts for ETMX, and about 10 volts for most quadrants of ETMY, but ETMY UR shows as much as 15-20 Volts. Probably, it's a good time to reverse the bias sign at ETMY. There are two sets of plots, each which show the same data in a different way: (1) ETMX_Mean.png & ETMY_Mean.png shows both the mean and standard deviation, and weighted mean and sqrt(weighted variance) of the charge measurements for a given day (which can be from ~4 to ~15 of these 12 minute measurements per mean point). We believe this better shows the long-term trend of the charge. (2) ETMX.png & ETMY.png show the "raw" data, where the result of each estimate of the effective bias voltage shown *since* the discharging. Each single data point is an estimate of the effective bias voltage, i.e. the charge, as determined by driving the test mass while varying the requested bias voltage and measuring the response with the optic's optical lever. Related alogs: 19848, 19821
High created an alarm for the PSL north & south A/C temperatures. These will alarm if the PSL temperature goes above 74F.
The anti-aliasing filters deploy AD8622 OpAmp buffers at the input of each signal line. This is before any filtering. So, these OpAmps need to be able to handle the full signal bandwidth. Unfortunately, the slew rate limit of the AD8622 is only 0.28V/µs. This is an order of magnitude lower than the ubiquitous OP27. In other words, the largest signal amplitudes at 1MHz, 100kHz and 10kHz are 45mV, 450mV and 4.5V, respectively. The readbacks of the EOM driver have a signal BW of about 300kHz and a signal amplitude of ~0.5V. This was too much and produced excess in-band noise—more than a magnitude above the digitization noise. We swapped the OpAmps in this path with AD8672 which have a slew rate of 4V/µs.
Plot 1. Green trace is readback with AD8672, amber curve is AD8622, and red trace as inication of digitization noise level.
Scott L. Ed P. Rodney H. The crew hung lights and cleaned 74.3 meters of tube and bellows ending 13.7 meters east of HSW-2-015. Test results for previous tube sections cleaned are posted here.
This morning, with an hour long 60mpc lock behind us, Evan and I cleared SDF from the weekend commissioning efforts. We:
- accepted most of the re-phasing of the ASC/LSC PDs that was done (we reverted a few of his changes which he did not like).
- set the SDF to ignore the LOCKIN channels that had been used over the weekend.
- zeroed out a few ASC loop offsets (MICH, DHARD, etc.) that were put in over the weekend during testing, but were then turned off.
- accepted Dan's change of the 4 OMC dither path gains from 0.1 to 1.0 on Wed Aug 6th (H1:OMC-ASC_P1_CLOCK_GAIN, ...)
Also, I:
- reverted some unused ITM L3 ESD settings from last week that seemed odd (Kissel confirmed).
- accepted the GAIN change of 1 from 25,000 in the LSC-CARM bank which is unused.
This corrected the ASC SDF 44 red errors today - all green!