Jim requested that I unlock the ETMy SUS during a break in his measurements of the ISI it is on. So, I used the last hour to do so, removing 15 brackets and unlocking the 78 associated screws to free all of the masses/blade springs. After confirming the top stage BOSEMs were still pointing the correct direction, Jim was able to enable the damping. Carry on, Jim.
Kiwamu and Dave
WP4449:
modified h1boot to include first install of the h1oaf model.
13:11 started the first instance of the h1oaf model running on the front end h1oaf0.
changed the DAQ configuration to include the new model
13:26 DAQ restart
now changing the overview MEDM screens to include the h1oaf
MEDM updates completed.
BTW: the new model added one Shared Memory IPC channel on the h1oaf0 frontend:
In the latest oaf model, I intentionally deleted the IPC blocks for now which were supposed to receive signals from HEPIs and ISIs. In any case, the original motivation of starting the OAF model was to get the IMC signal received and saved as science frames, and this was achieved by this installation. At some point in the future, we should revisit the model and implement the IPC blocks back, which requires changes in some other models (see the detail in alog 9963).
Reference: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=10152
We removed the HWP that should not be there.
13.5mW total coming to 80:20 splitter for PDH and WFS.
HWP in question is just upstream of this 80:20.
There is a 50:50 splitter for splitting 20% into 10% each for WFSA and WFSB.
(total 13.5mW) | Before removing HWP | After removing HWP |
80:20 PDH path | 11.9mW | 12.2 |
80:20 WFS path | 1.83 | 1.57 |
50:50 WFSA path | 0.85 | 0.84 |
50:50 WFSB path | 0.92 | 0.71 |
Laser Status:
PMC:
FSS:
ISS:
So I took spectra of this, saved some references, controlled down Stage2, brought it back up to the same state and the peak was gone. However, after a short time the peak started growing. Starting out at the Isolation boosts, I found that by disabling the boosts on the X & RY dofs, the peak reversed and started shrinking. It went down but there may be more dofs where this is coming in or the disturbance may come & go or grow and shrink because now I see the peak going up and then dropping down. The first plot shows the full peak (refs) and the currents are with the boosts disabled. The PEM MAG channel is also shown.
Fabrice suggests we likely have a broad area of marginal stability and this feature which doesn't look like the Main 60Hz harmonic according too Robert (looking at Mag channels) is just a symptom. It could be a DC motor that has locked here and maybe restarting a few things and it may go away but we need to fix the marginal stability if we can confirm it. We will run a TF when able to look at the MIMO loop and go from there.
I have added three stages of 1:0 antiwhitening filters for LSC_POP_A_RF9 I and Q and LSC_REFL_A_RF45 I and Q.
The following now all have three such 1:0 filters:
Not that this can't be operator error but see attached. Jim noticed a large output from the ITMX Stage2. 1000s of counts is of concern; 100s is normal. Anyway, looking at dataviewer of the fast channels, I thought this was ~8Hz; but the spectum and the DTT time series says this is 120Hz. Still looking for this peak source.
OK Robert solved my problem--The Dataviewer by default comes up at 128 hz resolution and this 120Hz peak is very large. When I go to a higher 'resolution' in dataviewer it looks correct. User beware.
I am done with the morning red locking.
Status of the interferometer:
PRMI doesn't lock
I have no luck for locking the PRMI this morning -- I was never able to catch a fringe even for a short period of time for some reason. The alignment seemed OK because I could see a build up of about 10000 counts at maximum in POPAIR_B_RF18_I_ERR. I only tried the demod phase of 133 deg in REFLAIR_45. I didn't try to change the LSC gains at all because I ran out the time. Also, all the settings were once set by Stefan's old script, setPRMI, instead of guardian's up-script and then I changed the MICH and PRCL gains to be 40 and -0.4 respectively.
HAM3 ISI was found to be down. So I brought it up with the level 3 isolation as noted by Hugo (alog 10114). According to its watchdog medm screen, it tripped because the payload had tripped at 1076806396 (which corresponds to Feb 19 2014 00:53:00 UTC).
Until the blue team starts working on the WFS.
Also, I disabled the oplev damping loop to avoid unnecessary kick because the oplev beam is almost off from its QPD. I did the following commands:
ezcaswitch H1:SUS-ETMX_L2_OLDAMP_Y OUTPUT OFF
ezcaswitch H1:SUS-ETMX_L2_OLDAMP_P OUTPUT OFF
ETMX is back aligned for Keita and Jax who will do some EX WFS business. The oplev loops are also activated again.
I found that the LSC feedback was left on for the PRLC servo. This kept kicking PRM and PR2 without locking anything. Bad. I disabled it for now.
for some reason the ITMX ISI was using 750 blends, although Hugho left it on Tcrappy friday night (10114) and Hugh checked that things were OK this morning (10122.)
I moved it to Tcrappy on both stages
I was in a hurry; Jim was at the end station and sorely needed my assistance. Anyway, despite several attempts, I was unable to transition either ITM to lower blends with the trilliums. Oddly, the BS went fairly easily...
We used AM laser to check up the ALSX WFS.
AM laser output: 1.8mW (measured with old ophir power meter, 978nm, filterr out)
Modulation source was set to 0.1vpp 24.389310MHz (this frequency was set before fixing the 1.002MHz that was mentioned in another alog).
WFS DC interface was set to low DC gain mode and the DC offset zero-ed.
Demod whitening gain was 21dB, first and the second whitening filter were on and the third off, a-whites were turned on though I don't know if they're put in yet (turns out that the awhites were not yet there when we did this measurement, so the "demod" numbers in the table below are 33dB higher than they should be.).
WFSA DC | WFSA demod (both I and Q) | WFSB DC | WFSB demod (both I and Q) | |
SEG1 | 3000 cts | +-20k cts | 2600 | +-19k |
SEG2 | 3070 | +-20k | 2900 | +-9k |
SEG3 | 2395 | +-12k | 2740 | +-20k |
SEG4 | 2930 | +-18k | 2960 | +-20k |
Seems like the demod signal out of WFSA SEG3 and WFSB SEG2 are both about a factor of 2 smaller than the others. On the scope it seemed that the RF signal coming from the WFS head was already small for these segments.
We confirmed that the whitening gain and filters are working.
Jax found that depending on how the cables were strained on the AM laser the amplitude of AM varies greatly (from nothingness to full). Crappy RF connection?
I didn't see such an effect when I used it at ISCT1 a month ago and the AM power was reproducable. This could be a new issue.
There may have been a miscommunication between me and Keita. When the cables were strained, they applied a torque to the laser, twisting it out of alignment with the WFS aperture (maybe 45 degrees rather than head-on? didn't exactly measure it, just corrected it.) So the power level issues were caused by cable strain, but on a purely mechanical level.
[Yuta, Rana, Evan]
When Stefan left Friday evening, PRMI wouldn't lock. We poked around at MEDM screens for a while before deciding that a more systematic diagnosis was in order. We decided to attack just the Michelson first.
We parked PRM and misaligned ETMX. We then adjusted the LSC MICH filter bank to duplicate was was done for Kiwamu's and Yuta's previous Michelson lock characterization (elog 9698, 31 Jan 2014). Even with a 1:0 integrator engaged, we found that the Michelson would not lock for more than 30 s, and the error signal drifted by about a third of its peak-to-peak.
We were able to measure the OLTF, and found that it had a UGF of 3 Hz with no phase margin. Rana suggested we notch out the bounce mode of the BS suspension with filters from LLO. We got the filter, adjusted the frequency to the LHO BS (17.8 Hz, as measured from the REFLAIR_A_RF45_Q_ERR spectrum), and then added it to FM6 on LSC_MICH. After doing this, we found that the Michelson lock is much more stable --- it appears to lock indefinitely.
In order to calibrate REFLAIR_A_RF45_Q_ERR in terms of mirror motion, we let the Michelson swing freely and recorded the fringing. We know that the fringing amplitude (in counts) as a function of asymmetry l is A sin(4 pi l / lambda), so the linear portion has a slope of A * 4 pi / lambda, in counts per m. I took the swinging data, trended the minimum, median, and maximum, and then took the median of the trended minimum and maximum values. A histogram of these values is attached. From this I find A = 643 counts; this gives the conversion factor as 7.6 counts per nanometer.
We used this value to get a calibrated spectrum of the dark noise of REFLAIR_A_RF45_Q_ERR, which we measured with the modecleaner unlocked. A trended 10-minute time series is attached; we see that the drift is on the order of a few nanometers over this time period. Also attached is a spectrum of the dark noise, along with Yuta's estimate of the control signal (LSC_MICH_OUT) the Michelson, given in terms of length. The estimated length noise was 1.1 um RMS.
An OLTF of the improved Michelson loop is attached. The UGF is now 7.5 Hz, with a phase margin of 20 degrees. Also attached is Yuta's model of the expected OLTF; the agreeement is excellent around the UGF, except for the flat gain. This model uses already existing an already of the triple suspension of the BS (/ligo/svncommon/SusSVN/sus/trunk/Common/MatlabTools/TripleModel_Production).
We assumed that the suspension model gives BS actuation efficiency from H1:SUS-BS_M2_LOCK_L_OUTPUT to the actual M3 motion in m/counts. However, there is a missing factor of 1.7e-3 in this actuation efficiency to fit to the measured OLTF.
Written by Yuta
I found that I forgot to put 0.05 in my OLTF model (I forgot that the output matrix H1:LSC-OUTPUT_MTRX for MICH to BS was set to 0.05). I also forgot to put sqrt(2) to convert BS motion to MICH length change. I updated the OLTF figure, and now, the missing factor is 0.024.
Written by Yuta
The missing factor 0.024 was from the conversion factor in uN/counts.
I assumed that the suspension model I use gives me the transfer function in m/counts, but it was actually in m/uN.
The conversion factor can be calculated using the parameters in G1100968 (for BS specific, see T1100479);
0.963 N/A * 0.32 mA/V * 20.0/2**18 V/counts = 2.35e-8 N/counts = 0.024 uN/counts
The OLTF now agrees well with the expected. Thanks to Jeff K. and Arnaud!
(But still, there is a missing factor in the PD signal chain. The measured value 7.6 counts/nm is used in this expected curve. See alog #9630 and #9857)
Note that this factor(uN/counts) is also missing in the current noise budget model which lives in /ligo/svncommon/NbSVN/aligonoisebudget/trunk/PRMI.
Note, while I was there, I spotted a pile of particulate on a 1" horizontal surface of the ETMy lower structure just below the test mass HR surface. It looks mostly to be glass with some metal - I think broken fiber glass is still raining out of the structure from the fiber break in Dec.