Jenne, Matt, Patrick, Sheila, Stefan, Kiwamu,
We tried two different differential CO2 settings today at 20W to see if we can improve the imbalanced RF sidebands (29535). One of the two tests was already reported by Jenne et al. on 29553.
According to the tests, the addition of a 10 uD single-pass substrate defocus to the X compensation plate seems to balance the amplitude of the upper and lower 45 MHz sidebands.
[Settings]
The interferometer arrived at a 20 W lock at 22:53 local. We then added a 800 mW of laser power on to CO2X, resulting in a 1 W CO2 power at 22:55:40. As opposed to the previous test (29535), we did not change CO2Y this time and therefore it stayed at 0 W.
The measurement finished at 23:15 and we set CO2X to 700 mW. We then increased the PSL power to 50 W while maintaining the same lock.
[Results]
As expected from the previous test, the imbalance of the 45 MHz RF sidebands, as seen by the optical spectrum analyzer, was improved by this action. After roughly 20 min, we reached a point where the upper and lower sidebands almost had the same amplitude. HWSX was functioning at the beginning of the test (for 10 minutes or so), but then unfortunately started showing some meaningless signals. We have no idea why. Nevertheless, we were able to extrapolate where we would be in terms of the substrate defocus based on the initial rise. It looks like that an additional 20 uD double-pass (= 10 uD single pass) is the good defocus value for ITMX in order to get balanced upper and lower 45 MHz sidebands. A 10 uD single-pass defocus corresponds to a 400 mW CO2 laser on the X compensation plate in equilibrium [assuming a 25 uD/W actuation coefficient (single-pass), 28799].
The attached is a screenshot of OSA outputs in which scans from different time are overlaid. It is clear that the imbalance improved as time elapsed.
On the other hand, the frequency noise coupling became worse by a factor of a few comparing to the initial coupling value at 900 Hz. It did not experience a sign change. Not sure what this means.
- The ISI configuration has been changed from 'Earthquake V2' to 'Windy'. - Each time the ISC_LOCK guardian reaches CARM_15PM it stops and reports a connection error to H1:LSC-PD_DOF_MTRX_SETTING_1_23 (see attached screenshot). Manually running ezca on the guardian machine gets the value with no error. This can be gotten around by taking the node to manual and selecting CARM_10PM. - Making it through the DRMI ASC engagement is hit and miss even with careful alignment of the BS and PRM mirrors. - I was not able to make it past ENGAGE_REFL_POP_WFS until Stefan came back. Stefan and Kiwamu found the DHARD ASC loop to be unstable.
[Sheila, Kiwamu, Matt, Jenne, etc]
We changed the TCS CO2 settings after we had thermalized at 20 W for a while, and were watching several metrics. Here I'll talk about the frequency line at 900 Hz, and Sheila will append her OSA plots as a function of time.
I injected a line at 900 Hz into H1:LSC-EXTRA_AO_2_EXC, which goes to H1:LSC-REFL_SERVO_COMEXC. I demodulated Refl 9 and Refl 45 like Stefan did last night (alog 29509), and also added another demodulator of OMC DCPDs. For each of these, I ran a zservo to adjust the demod phase to keep the Q signal at zero.
In the attached plot, bright red is the PSL power, and yellow and taupe are the X and Y TCS CO2 powers. Purple, cyan and brick red are Q-phase signals, so can be ignored. Green is REFL 9, blue is REFL 45. Orange is OMC DCPDs, indicating the coupling of frequency noise to DARM. Note that the range for blue, green and orange are all symmetric about zero, so while it looks like the frequency coupling is decreasing, in fact it is increasing. Sorry for a poor choice of demod phase.
After about 40 min at 20 W, the CO2 powers were stepped differentially. X went from 0.2 W to 0 W, while Y went from 0 W to 0.2 W. When this happens, you can see that the frequency coupling to DARM gets worse even faster than it had been while thermalizing with the usual TCS settings at 20W. The REFL 45 and REFL 9 traces don't change in character when we alter the TCS settings. Clearly this is the wrong direction for freq noise coupling, but it's nice to see that we can definitely affect it. Sheila will post her results when her plots are ready, but it looks like the sideband imbalance gets worse when we made this TCS step, so it's good that everything hangs together.
Next lock, we'll try increasing the ITMX CO2, and leave the ITMY CO2 at 0 W. This is a combination of common and differential, but it's all we can do before stepping the ring heaters later tonight.
Jenne, Chris Whittle
When exciting H1:SUS-ITMX_L3_LOCK_L_EXC using awggui for ongoing ITMX charge investigations, we observed an output voltage with a sinusoid offset from 0 (i.e. varying between 0 and 1k counts instead of +/-1k), despite having explicitly set offset to 0. This also resulted in a pervasive comb in DARM. We saw this at excitation frequencies 16 Hz and 16.55 Hz (no others were tested).
Closing and restarting awggui resolved the issue.
16:15 Chris S. moving rigging racks from highbay back into LVEA.
15:19 Karen to Optics lab
15:32 Fil to PSL rack isntalling ISS out of loop chasis
15:50 Karen out
Gerado to MX
16:01 Richard to LVEA
10:05 Richard out
16:48 Karen to light bulb room and H2
16:45 Fil back
17:05 Fil+Richard pulling ISS chasis back in
17:15 John to LVEA
17:33 John out
17:53 Kyle to MY
18:07 Fil out
18:24 Kyle back
18:25 Keita+KAGRA crew out of LVEA (was there for ~1hr -- tour)
20:01 Fire drill. Fire alarm in the VEAs *might* have caused a lockloss. There were high frequency noise visible in DARM as soon as the alarm started prior to the lockloss. Will look more into this.
20:26 Karen to MY
21:31 Kyle back
21:50 Kyle leaving MY
22:51 KAGRA crew drive down to EX -- sightseeing(?)
Shortly after 1 P.M. local time, LHO held it's annual fire drill. Response was great, THANKS TO EVERYONE.
This was done at John's suggestion so as to reduce the risk of over pressurization of the LN2 inner vessel during dewar deliveries (Due to obstructed sensing line, the LN2 level for CP3 is determined by a manual setting of the fill valve which maintains the level adequately only for static conditions and must be adjusted as a function of dewar liquid height and vapor pressure)
following a lengthy summer break, and with ER10 approaching, the daily restart report is back.
model restarts logged for Wed 07/Sep/2016
Per FAMIS #7070, Reset HAM4's HEPI L4C Accumulated WD Saturation Monitor (it was at 774 counts). While clearing this Hugh was looking over my shoulder and noticed that HAM1 is missing from the medm screen (he put it on his "To Do" list).
Attached is a plot of IM4 Trans qpd and ISS 2nd Loop qpd signals.
First plot - top - shows that IM4 Trans Pitch and ISS 2nd Loop Pitch don't match well
First Plot - bottom - shows that IM4 Trans Pitch is a good match to the ISS 2nd Loop Yaw signal (yaw modified: multiplied by -0.7 and an added offset of 0.005)
Second Plot - top - shows the IM2 Trans Yaw and ISS 2nd Loop Pitch - raw data
Second Loop - bottom - shows the IM2 Trans Yaw and ISS 2nd Loop Pitch (pitch modified: multiplied by -0.3 and an added offset of 0.8)
The DCS Disk2Disk scripts at LHO, which copy data from CDS to the LDAS archive and scratch disks have been restarted to use the CDS h1fw1 framewriter as the primary source of frames. The backup is h1fw0. This will prevent LDAS from picking up "bad" h1fw0 frames, except in the very unlikely event h1fw1 is down and h1fw0 writes a bad frame at the same time. (See: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=29521 for the latest on the h1fw0 issue.)
Began 15:22 UTC, finished 15:24 UTC
As soon as the restart finished IPC was red. I hit diag reset button and it went away. OAF_L0_MADC1_EPICS_CH25 started to overflow pretty much as soon as the model restart was done.
TCS chillers and lasers are recovered.
The laser tripped this morning. From the laser MEDM screen it looked like the NPRO had tripped which would pull the entire system down. However the Beckhoff screen indicates otherwise; that the fault is associated with the crystal chiller. It should be noted that the crystal chiller has 10468 hours on it. Logs indicate that it tripped around 3 am. Unfortunately I did catch the trip. Further inspection shows that the laser tripped not because of the crystal chiller (see AMPFlow.png). Might be due to flushing of the newly deployed (old) manifold.
Looks like the power meter circuit caused the trip this time around. Doesn't appear to be the crystal chiller, however I am uncertain how often the chiller flow is updated via the RS-232 link.
The PSL trips over the last couple weeks have all been due to the Front End flow glitching. Suspecting the FE flow sensor might be faulty we swapped the PSL water manifold for the spare, with new flow sensors installed on the spare. As Peter says above this latest trip was due to the Power Meter water circuit (first time we've had an issue with this water circuit since the end of July). Unclear at this time what the cause was, although it's likely to be junk stirred up by our manifold swap on Tuesday working its way through the system (as Peter mentions above); Peter has some pictures of the output water filter for the PSL cooling system and there are a few new occupants taking up residence.
Filed FRS #6169.
Keita Marc Fil Daniel
We realized that we can implement the required compensation for the second loop by using the whitened monitor signals (TP10) from the transimpedance board as the inputs to the sum of PD1-4 and PD5-8, respectively—instead of the unwhitened outputs from the transimpedance amplifiers.
The required modifications are:
During testing we noticed that the input transimpedance amplifiers (eight AD797s), were all oscillating between 10-15 MHz with an amplitude of about 500 mVpp. Adding capacitance to the feedback network seemed to have little effect, so we swapped all of them with TLE2027. This solved the oscillation. Using 400 Ohms transimpedance, the input referred noise of a channel is about 25 pA/√Hz between 10 Hz and 10 kHz. This is maybe a factor of 2 below shot noise at high laser input power. The electronics noise is dominated by the Johnson noise of the first 4.87K resistor in the whitening stages.
The output SMA connector which was shortening the negative leg to the chassis has been removed. Instead, we drilled a new hole for an isolated TNC connector.
With the upfront whitening gain the fast monitor points now have too much gain and are saturating. We removed the gain of 50 from ERR1 and ERR2 by replacing R60 with a 4.53K (from 220K). This also removed the 2.7 kHz pole in this path. The OUTPUT channel was also modified for a flat transfer function with a fixed gain of 1. It now looks like the other two. In detail, C52 and C53 were shorted out, and R60 and R61 were changed to 4.53K (from 45.3K).
The transfer function of the ISS outer loop AC coupling is attached. As implemented it should be unconditionally stable with a ugf of 10 Hz. With a gain of ~500 at 10 Hz in the overall outer loop servo, the AC coupling point would be around 0.1 Hz.
Here is a spectrum of the outer loop readbacks at 2W and 50W input power, respectively, with the ISS second loop open. The AC coupling is on. At 50W the third loop is also on. The ERR readbacks are very near saturation at the higher power. Since the error signal is followed by a fixed gain of 3, the output was saturating.
I stopped and reran the Hartman code for ITMX at around 21:30 local.
As suggested by Aidan, I restarted the Hartman code with a fresh template. This time, I restarted both the ITMX and ITMY codes at around 9:40 local.
Note that the last restart before yesterday was done on Aug.8 (28947). It was done for both ITMX and ITMY. They have been running without errors until I stopped one of them (namely ITMX) yesterday.
Kiwamu, Nutsinee
A code is scheduled to run at 9 pm tonight. The code will power up CO2 to 1.3W and power it back down to 0W after 6 hours. Please do not touch ITM optics.
I updated the HWSY centroids with low variance versions.
I also reset the HWSY magnification to 7.5x
controls@h1hwsmsr:~/temp/HWSY$ caput H1:TCS-ITMY_HWS_MAGNIFICATION 7.5
Old : H1:TCS-ITMY_HWS_MAGNIFICATION 17.5
New : H1:TCS-ITMY_HWS_MAGNIFICATION 7.5
Here is the time series for the CO2 heating from last night. Analysis to follow but rough numbers are as follows.
There are two measurements per ITM of the lensing: when CO2 is turned on and again when CO2 is turned off. Hence:
CO2 | HWS | Lens per Watt | |
X | 1.25W | 63 +/- 2 uD | 50.4 +/- 2 uD/W |
Y | 1.1W | 55 +/- 7 uD | 50 +/- 6 uD/W |
One thing that I forgot to mention is that I make the power step down half way and stayed there for an hour before going to 0W. As you can see from the timeseries.
Every time when we restart the HWS code for ITMY, the code sets the MAGNIFICATION value back to default of 17.5 and this had been annoying. So instead of manually changing the value for every restart, I made a hack so that when the code is executed for ITMY, it automatically changes MAGNIFICATION to 7.5, 60 seconds after the execution of the command. This was done by editing the alias setting in ~/.bashrc. Now the alias for Run_HWS_H1ITMY is written as follow.
alias Run_HWS_H1ITMY='/opt/HWS/Run_HWS_0/distrib/Run_HWS_0 & sleep 60; caput H1:TCS-ITMY_HWS_MAGNIFICATION 7.5'
This was tested once and was successful.
I reset the ITMY HWS magnification to 7.5x (it's set to 17.5x by default in the code).
aidan.brooks@opsws4:~$ caput H1:TCS-ITMY_HWS_MAGNIFICATION 7.5
Old : H1:TCS-ITMY_HWS_MAGNIFICATION 17.5
New : H1:TCS-ITMY_HWS_MAGNIFICATION 7.5
Alos, I had a quick look at the change in the spherical power measured by the ITMY HWS after the IFO lost lock this morning.
This is a very rough calculation - and assumes that the HWS-Y beam is correctly aligned (we need to combine our evidence to really confirm this).
Nevertheless, I've set the ITMY absorption to 4E-7 in the simulation.
aidan.brooks@opsws4:~$ caput H1:TCS-SIM_ITMY_SURF_ABSORPTION 4E-7
Old : H1:TCS-SIM_ITMY_SURF_ABSORPTION 4e-09
New : H1:TCS-SIM_ITMY_SURF_ABSORPTION 4e-07
For comparison, ITMX absorption estimated to be 5.7E-7.
I've added this number to the TCS actuator calibration page in the DCC: https://dcc.ligo.org/T1400685-x0
MAGNIFICATION for ITMY is now automatically set every time when the code is restarted. See 29549.