Sheila, Jenne, Terra, Patrick It appears that we have the same situation as described in alog 27435.
Following the suggestion of alog 29522 we switched the ASC input matrix for MICH_P and MICH_Y (the BS).
The final matrix was
MICH_P = 1.5*AS_A_36_Q_PIT + 0*AS_B_36_Q_PIT
MICH_Y = 1.5*AS_A_36_Q_YAW + 0*AS_B_36_Q_YAW
the old matrix was
MICH_P = 0.666*AS_A_36_Q_PIT + 1*AS_B_36_Q_PIT
MICH_Y = 0.666*AS_A_36_Q_YAW + 1*AS_B_36_Q_YAW
We did the ransition slowly over about 30min. Interestingly the SRM dither loop did a nice job, and the different offset in the error signal was not an issue.
We stayed at 50W a total of 40min.
While working on this input matrix switching, we saw at least locklosses that are a result of LSC_POP_A_RF45 having RF saturations. The 3rd attachment below was from a lock when Stefan was changing the input matrix a little more quickly, and we lost it during this process. The first two attachments are from our 40min lock, with different time scales.
We see that several of the RFMONs get a little high as we get close to breaking the lock, but the POP_A_RF45 is much higher than the steady-state value should be, and goes high almost a second before we lose the lock.
I didn't save any screenshots, but other locks from earlier today did not lose it due to these RF saturations, so this is definitely something that's coming up with the BS input matrix changing.
This is yet another reason that we need to revisit lowering the 45MHz modulation depth, as soon as we have a semi-stable interferometer.
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.
We had an interferometer that was nicely thermalized at 20W today, including a 900Hz frequency line to monitor the REFL9I and REFL45I gain. So we decided to investigate the influence of common TCS on both AS_90 and REFL45 gain.
We thus increased the TCS CO2 central heating by 1W on each optic (to 1.2W on X, 1W on Y). This resulted in a DECREASE (at least initially) of the REFL45 gain (the opposite of what we see going to high power), and at the same time a recovery of the AS_90 buildup.
After letting it settle for about 50min in this configuration, we went to 50W. To our surprise the sign of REFL45I changed. We can only explain that by the 45 sideband going through critical coupling. This would mean a number of our loops in REFL changes sign, so it is not surprising that we lost lock soon afterwards.
The attached plot illustrates that story. Blue: REFL45I gain, Green: REFL9 gain, Orange: AS_90
At the same time, we monitored the intensity coupling as another figure of merit. See the attached. The time t in the legend box is initialized at the start of the test so that it starts with t = 0.
The coupling above 100 Hz initially improved by a factor of few, but then later it came back up and eventually became higher than the initial coupling.
If we compare today's data against what Evan measured back in this February (25476), the latest coupling is higher in most of the frequency band. The current coupling is higher by a factor of 10 at 100 Hz and too high by a few factor at 1 kHz. The second loop was open during the test.
PSL/IOO jitter coupling is high, so, as a first step, we adjusted offsets on IMC_DOF_1(2)_P(Y). We adjusted offsets to minimize peaks in DARM from a 290Hz pitch (1500 counts), and a 310 Hz yaw (390 counts) injection, made using the piezo mirror on the PSL table. The second loop of the ISS was off, and we were at 20 W. This was a first rough alignment (the offsets were at 0). Only DOF_2_P and DOF_1_Y seemed to have much effect. The figure shows that we improved jitter coupling by a factor of 3 or 4 in both pitch and yaw, with the best improvement in pitch. Next we will adjust the ISS array picomotors.
The proposed settings change follows:
IMC_DOF_1_P, was: 0, proposed: 0
IMC_DOF_2_P, was: 0, proposed: -100
IMC_DOF_1_Y, was: 0, proposed: 50
IMC_DOF_2_Y, was: 0, proposed: 0
Robert, Kiwamu
This is a follow-up on the issues seen by h1fw0 as detailed in https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=29452 Yesterday we installed a new build of daqd on h1fw0 and h1fw1. This daqd wrote writes more debug information to logs, to help us see diagnostics of the input stream. Looking at a frame that showed inconsistencies we saw what appears to be a series of 1/16s time slices that were flipped. After reviewing some code with Jim Warner I noticed a bug in the newer code that could allow a time slice to be reordered when there was a stall in one of the producer threads (the producer threads injest the data). This was fixed, and h1fw0 & h1fw1 were restarted. This fix will clear up at least some of the issues we have seen.
Things seem relatively normal compare to the measurement from August 17.
State of H1: locking DRMI1F but not able to get through Engage_DRMI_ASC - Sheila working on alignment by hand to get through this stage
Locking Struggles:
Site Activities:
Changes made to the Ops overview medm screen include:
Please refer any other suggestions for changes to me regarding this screen.
RobertS suggested a look at the BS OpLevs for position drifting. I would say there isn't a lot of drifting looking at three days--First Attachment.
The first attachment is a 3 days showing the BS HEPI work done yesterday 29495 based on the HEPI Catesian location monitors. You can see that the HEPI Cartesian positionas are exactly the same as before the work but the YAW and moreso the Pitch are shifted immediately following the work on HEPI. The second attachment zooms into 9 hours and OpLev change is pretty much immediate with the reisolation of the SEI. I did a quick scan of a few months of this and see most of the time, the OpLev Pitch and Yaw don't change drastically after a de/re-isolation of HEPI. So I think the amount of change seen here yesterday is not the norm.
On the third attachment we see the actual change with the local Sesnors. For the four Horizontal sensors you can see that all shift about positive 4 - 500 counts. These actuators face opposite directions so these shifts essentially cancel and no YAW or Translation should occur. For the verticals, with different Actuator positions, it is hard to imagine not actually shifting the tilt of the table even with the same resolved cartesian position. Certainly the platform strain (in the actuator psoitions) as quantified by the Pringles is different. This is what we have though with AC couple pringle loops. I recommend we study the isolation sequence and maybe we can achieve better repeatability.
It is hard to imagine how this can affect the Optic Pitch but...
In general; Varying levels of higher-than-normal humidity levels in the LASER room and the Osc box and the corresponding temp fluctuations in the xtals are all related to the ongoing chiller issues. The resulting tripping/shutdowns are also evident in these trends as well. The ongoing DB3 issue is addressed here.
| Work Permit | Date | Description | alog |
| 6139.html | 2016-09-06 12:10 | Activity: Vent locally mounted RGA turbo pump while isolated from RGA+Vertex volume via (1) closed 1 1/2" metal valve * Repair turbo vent valve O-ring and confirm with leak detector * Remove turbo from RGA hardware and install with (1) 1 1/2" O-ring valve * Pump to rough vacuum the volume between the newly installed O-ring valve and the adjacent 1 1/2" metal valve | 29507 |
| 6138.html | 2016-09-06 11:20 | Activity: Load new debugging builds of daqd on the frame writers. Load h1fw0 & h1fw2 with a new build of daqd to help diagnose issues seen with h1fw0. Two frame writers are needed in order to do a comparison of additional output to be produced by daqd. | |
| 6137.html | 2016-09-06 10:31 | Activity: swap fw0 and fw1 10GigE fibers to see if retransmission error follows the hardware. | |
| 6136.html | 2016-09-06 09:46 | Activity: Replace the camera that allows views of the VEA with a functioning camer | |
| 6135.html | 2016-09-06 09:33 | Activity: Restore IM1-4 alignment to O1 values and use IM4 Trans and ISS2 QPD to evaluate the IMC and IM alignment. This work is best done before ISS2 array is recentered. This investigation is part of an evaluation of changes in H1 alignment since O1, including input pointing already alogged, and continuing on to changes in IMC/IM alignment. | 29500 |
| 6134.html | 2016-09-06 08:15 | Activity: Removal, repair and reinstall of demod board. | 29502 |
| 6133.html | 2016-09-02 09:39 |
Activity: Remove DC Bias on BS HEPI Servo Position: DeIsolate HEPI Loops, adjust length of Payload Springs to bring position closer to servo'd position. Reisolate. Duration 2 hours. Area of Activity: H1 SEI HEPI BS |
29495 |
| 6132.html | 2016-09-01 09:25 | Activity: Update h0vaclx and h0vacly to add input and output beam tube annulus ion pumps. Restart DAQ to add channels. | |
| 6131.html | 2016-08-31 10:21 | Activity: add all epics diagnostics channels for the frame writers to the DAQ for trending purposes. |
System Updates:
- SEI
- SUS, working, no update
- CDS/Electronics
Jenne, Stefan
- lowered CFSOF gain from 0.5 to 0.2. This avoids an instability due to gain peaking and possible radiation pressure feed-back at 2.15Hz.
- With that the coil driver switching was no longer an issue. In fact we reduced the ramp times all to 1 sec - it worked fine.
- We still keep dropping the sideband recycling gain and lost lock after ~36min. THus we decided to do some loop gain tracking.
- We added a laser frequency modulation line at 900Hz, and demodulated it in REFL_9_I (blue - LSC-LOCKINM_1_DEMOD_4_I) and REFL_45_I (brown - LSC-LOCKINM_1_DEMOD_3_I in the attached plot).
- Additionally we suspected that the BS ASC controls are going wacko. So we but pitch and yaw dither lines on the BS, and demodulated everything.
- Attached are two plots (with different time axis) of the result during a 50W lock.
Remarks:
- The REFL45 gain INCREASED by more than a factor of 2! This is consistent with less 45 sideband going into the cavity, and thus more being available as reference in REFL.
- The AS36_A gains seem to reflect that - i.e. a slight gain drop due to less 45MHz being available.
- The AS36_B gains initally agree, but then go completely nuts: AS36_B_Q_P (orange) keeps dropping, while AS36_B_Q_Y (red) turns around.
- Additionally, the AS36_B_Q_Y- Q dither demoduilation is growing significantly (not plotted). Not sure what to make of that. (the Q dither demodulation of all other signals remaind reasonable.)
Conclusion:
- We suspect that our lock losses might be due to the BS ASC signal becoming unsable. In addition, we have to carefully look at loop gains of all WFS that use 45MHz in REFL - their gain is expected to shoot way up.
- At lest for REFL ASC, it might be time to use the dynamic power normalization.
LEGEND for plot:
H1:LSC-LOCKIN_1_DEMOD_4_I_OUTPUT LSC: laser frequency to REFL_9_I (blue)
H1:LSC-POPAIR_B_RF18_I_NORM_MON 9MHz 2-f in PRC (green)
H1:LSC-LOCKIN_1_DEMOD_3_I_OUTPUT LSC: laser frequency to REFL_45_I (brown)
H1:ASC-ADS_PIT4_DEMOD_I_OUTPUT ASC: BS pit to AS36_A_Q_P (cyan)
H1:ASC-ADS_PIT5_DEMOD_I_OUTPUT ASC: BS pit to AS36_B_Q_P (orange)
H1:ASC-ADS_YAW4_DEMOD_I_OUTPUT ASC: BS yaw to AS36_A_Q_Y (purple)
H1:ASC-ADS_YAW5_DEMOD_I_OUTPUT ASC: BS yaw to AS36_B_Q_Y (red)
Beamsplitter motion as seen by its Optical Lever:
Over the course of the 40 minutes shown in Stefan's plots, the BS optical lever shows that it is moving:
I spent sume time lookin g at the signals form the AS36 diodes during this lock.
The 1st quation was whether all the RF from the length signals ios indeed in the I phase.
- Plot 1 shows the I sum and Q sum of AS_A_36. Most of the signal is in the I phase, but a phase change of -12deg (from -140 to -152 deg) would further improve the situation.
- Plot 2 shows the same thing for AS_B_36. It's overall phasing is as good as we can expect.
- Plot 3 shows the signal of all individual quadrants, I and Q (including the extra -12 deg in AS_A_36). Note that most signal is in quadrant 3. This might be an indication that we also have a centering issue, or it might be the result of an unhealthy about of higher order modes at the AS port.
- Plot 4 shows the Q signals that go into the BS error signals - they are a weighted sum of A and B - currently 0.666*A+1.0*B. For A the trace is plotted with (blue) and without (green) the extra -12deg of phase.
Note that the PIT signals (and to a lesser extend also the YAW signals) show a divergence to opposite direction, because their weighed sum is servod to zero. This is expected if one channel starts seeing more garbage than signal.
- Plot 5: This plot shows the BS dither line strength for PIT and YAW, for both A and B diode. Note that A is well behaved until the end, while B's gain increases significantly for yaw, and drops to almost zero for pit.
Based on plot 4 and 5 I suspect we would be better off using only AS_36_A at 50Watt. THe challenge will be it's offset - we will try this later tonight.
Friday I had improved by a factor of 2x or so the persistent air leak in the Vertex RGA by torquing the suspect "factory" flange between the analyzer and it's protective nipple. This leak turned out to be only a small fraction of the total leak rate observed, i.e. there was more than one leak. Today I again removed all of the heat tapes and aluminum foil to gain access to the CF joints for additional helium leak testing. Note that all joints had been tested individually at various times prior to this most recent bake exercise as well as collectively via bagging the complete RGA assembly. Again, the joints tested good today so I decided to do a "fire hose" test and upped the flow of helium to "audible" values. John W. was physically present this time and his well documented aura was in full effect so we immediately found that the turbo vent valve was the culprit. This is consistent with all of the previous observations as the Turbo vent valve had not been sprayed in earlier hunts, the reasoning being that it is an O-ring seal with a very small cross section and permeates to the point of being a nuisance when leak hunting (normally!). Also, the rate at which is was leaking was just smaller than that which would show up on the foreline pressure gauge but just big enough for the portion that reverse flowed through the turbo stages could account for the value of observed leaking at the turbo inlet - Arrgghh!!!!! I took scans and decoupled the turbo and pump carts and shut all noise sources off. I'll make an entry tomorrow with the scan data.
Attached are the scans taken on 09-06-2016
No overfill required today as we had an LN2 delivery and I had to reduce the LLCV %open from 21% to 18%. ~1635 - 1700 hrs. local -> I visually confirmed that CP3's exhaust line was frosted - dewar vapor pressure at 20 psi. Next overfill to be Friday, Sept. 9th.
So I screwed up (I used to keep a tally of these occurrences but it has become too impractical)! It wasn't until after the LN2 delivery was underway (done?) that I realized that I hadn't proactively reduced CP3's LLCV %open value so as to avoid over pressuring CP3's LN2 reservoir. As I have now demonstrated, we are vulnerable to this on delivery days. Recall that while CP3 is in "Manual" fill mode, we have defeated any ability for CDS to close the Fill Valve (aka LLCV) as a response to overpressure. As such, we are completely reliant on Vacuum Personnel awareness. Gerardo suggested that I notify he and Chandra when LN2 deliveries get placed to lessen the likelihood of this happening again. John suggested that we leave open the exhaust check-valve bypass-valve and not rely on "Vacuum Personnel awareness" - that is why he gets paid the big bucks! I will open the bypass valve the next time I am at the Y-mid - Brilliant!
The OAFIOP Dac has gone bad again. We're just going to leave it at this point. The TCS lasers will need to be turned on in the morning, after this has been addressed.