I wanted to try turning on HEPI sensor correction at EY this morning, but I've run into an issue. When I turn on just the new Mitt_sc filter no numbers come out of the outputs. However, when I turn on the filters associated with the fir sensor correction, numbers come out. Even when I just turn on the path, with no filters engaged, numbers come out of the output block. Something about engaging the sensor correction filter completely cuts the signal. I will try copying the filter to a different fm when I get a chance.
As the wandering laser intensity continues I intend to learn more about these systems. I can only report the findings and make the adjustments. ISS diffracted power is down to ~5% this morning. REFSIGNAL was at -2.04V as it was set by me yesterday. Today I have adjusted REFSIGNAL to -2.02V to bring the diff power to ~8.6%. Attached is a past 5 day trend. the spikes, i am told, are likely caused by activations on MC2? (for example)
model restarts logged for Tue 04/Nov/2014
2014_11_04 09:13 h1suspr3
2014_11_04 09:18 h1susbs
2014_11_04 09:18 h1sussr3
2014_11_04 09:20 h1susitmx
2014_11_04 09:22 h1susitmy
2014_11_04 09:24 h1susetmx
2014_11_04 09:25 h1susetmy
2014_11_04 09:41 h1lsc
2014_11_04 09:46 h1broadcast0
2014_11_04 09:46 h1dc0
2014_11_04 09:46 h1fw0
2014_11_04 09:46 h1fw1
2014_11_04 09:46 h1nds0
2014_11_04 09:46 h1nds1
2014_11_04 10:34 h1calex
2014_11_04 10:35 h1caley
2014_11_04 11:12 h1iopoaf0
2014_11_04 11:12 h1pemcs
2014_11_04 11:14 h1oaf
2014_11_04 11:14 h1odcmaster
2014_11_04 11:14 h1tcscs
2014_11_04 12:36 h1broadcast0
2014_11_04 12:36 h1dc0
2014_11_04 12:36 h1fw0
2014_11_04 12:36 h1fw1
2014_11_04 12:36 h1nds0
2014_11_04 12:36 h1nds1
no unexpected restarts. Maintenance Day. Jeff SUS and LSC model work (with associated DAQ restart). Dave CAL work (with associated DAQ restart, plus latest Guardian and Beckhoff EDCU channels)
Greg, Sheila and Dave
Peter Fritschel asked us if we could get a sense of which channels were compressing well in the frame, as part of the decision making of which channels should go into the science frame. Greg wrote a script which calculates the compression rate on a channel by channel basis. To keep the numbers manageable we limited the channels to those with acquisition rates of 1024 or higher.
Sheila suggested a time where the H1 IFO was in its best state to give our most realistic compression rates. The time chosen was 1am PDT Friday 31st October, GPS time 1098777600.
The results are appended as a text file showing 2918 channels (name, acquisition rate, compression ratio).
Also attached is a histogram plot showing the distribution of the compression rates.
Evan, Sheila, Nic, Lisa To answer Peter's questions , we have relocked the DRMI (without arms) on 1f and 3f (10W input power, 27 mW on the BBPD photo-detector). The DRMI was very stable in both cases, here are the good times: Nov 5, 6:00 - 6:15 UTC DRMI locked on 1f, WFS on Nov 5, 6:30 - 6:45 UTC DRMI locked on 3f, WFS on Evan is about to post plots with error signal spectra. It is probably a good idea to make some plots with ground motion/ISI/optical lever signals to "capture" these good times.
These are the corresponding RFPD spectra. The analogous LLO measurement is LLO#15430. LLO's measurement of RF135 seems pretty surprising, since the 3f demodulated spectra appear to be almost entirely noise-dominated above 20 Hz.
What's this 2449.25Hz line that grows over time?
In the attached left, the error signal for PRCL and SRCL grew larger and larger toward the end of the lock.
In the attached right, red, blue and green correspond to the end, middle and the beginning of the lock. The difference in noise floor might be that they were switching from 1f and 3f or vice versa.
Regardless, a line at 2449.25Hz grew larger over time and it was dominating the error signal RMS.
Is this something intentional? Oscillation somewhere? Rogue line?
I am not sure what the 2449.25 Hz line is; there is not a line there that I know of...
In terms of the difference in the noise floor, I can confirm that this comes from the 1f to 3f transition. Keita's green trace was taken from 5:50 PM UTC, blue trace from just after 6:20 PM UTC, and red trace was taken at 6:50 PM UTC. I have attached a dataviewer snap shot showing the LSC PD input matrix of the MICH (2_23), PRCL (3_20), SRCL (4_22) 3f signals around that time. The MICH and PRCL signal transistion at around 6:17 PM UTC, which explains why the blue and red traces in those plots go up. Meanwhile, SRCL transitions a bit later at 6:26 PM UTC, which explains why only the red trace goes up in the noise floor.
According to Dennis the lowest elastic mode of the beamsplitter is expected to be at 2458 Hz (right circular cylindrical without wedge angle, bevels, wire standoff-prisms).
Looking at past data in DQ channels on the ETM suspensions, I tried to estimate the bounce and roll mode frequencies.
I used the top stage V and R degrees of freedom, as well as the oplevs. I used 0.001Hz BW.
I could see the modes in ETMY, but ETMX did not have these modes rung up apparently.
ETMY bounce: 9.730 0.001 Hz
ETMY roll: 13.816 0.001 Hz
Comparison of ion yields with purge air and pure nitrogen are given in the attached pdf file.
Summary:
HAM2 moved by about -10 to -8 urad in YAW (in SUS coordinates) and some unknown angle in PIT. This was apparently triggered by the maintenance work for HEPI. Even though Hugh had to back off all the changes due to some other problem they have found, and made sure that SEI sensors are brought back to the original readings, ISI never went back to its original angle.
This is not the first time HEPI or ISI apparently moved though SEI sensors told otherwise.
Details:
In the attached, all plots start before the maintenance and end right when HAM2 was brought back to the old SEI sensor readings. Also, at the end of the plot, MC WFS was engaged.
In CH3 and CH4, you can see that the HAM2 ISI OPLEV saw some big change both in PIT and YAW. The numbers, especially YAW, cannot be trusted too much as the beam is almost all in the right half of the quad diode and nobody took time to confirm the calibration/sign, you can still assert that the ISI angle is totally different from where it used to be.
According to PR3 oplev (CH1 and 2) the HAM2 ISI oplev data in that ISI moved -10 urad in YAW. The optic moved by +4 urad in PIT but this doesn't mean that the ISI moved by this amount.
Other optics on HAM2 are without oplev and therefore don't have an independent measure of the angle external to ISI, but you can see small changes in the OSEMs.
In addition, after the MC locked and the WFS brought the alignment to wherever it thought was good, all MC mirrors settled to different OSEM readings than the original. This means that MC mirrors are sitting at different angles relative to the ISI.
Anyway, the AS beam was at a totally wrong location and we were worried that our alignment was completely wrong, because there's apparently a centering servo for IM4 transmission acting on PZT mirror, but in the end twisting PR3 back by +8 urad in YAW and -2urad in PIT seemed to take care of most of the bad things.
I confirmed that these shifts in optics on HAM2 are NOT due to the bias slider or IFO ASC.
Just like yesterday, I now have new controllers developed with the really correct local <--> cartesian matrices ready to try. It would be nice if I could give some quantifiable change in the controllers to make the arguement that these will actually work but, I can't without lots more time.
See the first attachment to compare the matrices used by the controller development (in the matlab window) with the matrices actually used currently by the platform. I can't fathom how this all actually holds it together but at the worst it only rings rather than blows up (see the second attachment of the ISO outs.)
Finally--the third attachment is the new controllers I tried this moning. The last attachment are the controllers I want to try tomorrow morning developed with the correct matrices. I predict that these will not blow up nor ring...
Please postpone putting this in until next maintenance.
Attached shows the DC sum of AS_C QPD (normalized by the maximum measured) VS the YAW offset of PR2. I haven't touched PIT.
Green vertical line is where we're at now.
After doing the scan represented by red crosses, I took another set of scan (blue circles) to see how the measurement fluctuates, and it seems like it didn't change much (which is good).
No further analysis yet.
What was done:
Feed back the AS_C QPD signal to ITMX using ASC. Input matrix DHARD-AS_C =1. ASC ouput matrix from DHARD to IX PIT=1, YAW=-1.
Scan PR2 in YAW. Measure 10 sec average of AS_C DC SUM using tdsavg.
Alexa, Evan, Sheila, Jeff, Nic, Lisa The plan for tonight was to try again the CARM offset reduction with the DRMI locked on 3f as it was done a few nights ago . However, sadly, we couldn't really stably lock the arms on green by engaging ALS DIFF (feed-back to the ETMs). Nothing was (at least intentionally) changed with respect to the "nominal" configuration which has worked in the past. In the process of collecting and analyzing several lock losses, we identified the following list of problems/action items: * L2P for ETMY is significantly worse than for ETMX, we should fix this: as soon as the differential feed-back to the ETMs is engaged, the ETMY green light fluctuates consistently with PIT fluctuations as seen by the optical lever. This effect was really bad in the afternoon (30% power fluctuations; it got somehow better later in the evening); * ringing up of the 13 Hz ETMY roll mode (again, see Kiwamu's entry): Nic tried to damp this mode by using optical lever PIT as error signal and pushing on L2 PIT, but that didn't work. We will try tomorrow to use the LLO strategy by using ALS DIFF; * at least once we lose lock because of a 3Hz oscillation in the ESD drive (we should remeasure the cross over L1/L3). While trying to debug the ALS, we did some work on the DRMI to investigate the tricky demod phase business (see Evan's entry).
We had tried feeding back only to ETMX ESD, to remove the large 13 Hz peak in the ALS DIFF spectra. We had done this in the past, but we could not get it to work. At one point, I also tried adjusting the L3 LOCK L gain in case the ESD charge had changed the crossover. However, not surprisingly this did not make a difference since the ALS DIFF spectra did not show any gain peaking at the crossover frequency.
These are some plots which show the problem described in this entry (13 Hz roll mode oscillation and 3 Hz loop oscillation in bad alignment state, L2P filters worse for ETMY than ETMY). It might be worth checking if the ground / ISI motion was somehow higher than usual last nigh for the arm cavity optics. P.S.: In the process of doing some lock loss analysis, I realized that our new awesome lock loss tool didn't like empty lines in the channel configuration file. I think this explains while Sheila et al have been observing unexplained script failures when trying to add more channels (by the way, the max number of channel per file is 20). Nic fixed this problem in this way, now it works well. def load_channel_list(path): channels = [] with sys.stdin if path == '-' else open(path, 'r') as f: for line in f: # skip empty lines if line.isspace(): continue channels.append(line.strip()) return channels
Rana, Alexa, Sheila, Peter, Evan
Given last night's strange behavior from REFLAIR_B, we wanted to check the RF powers coming out the BBPD and going into the ISC rack.
With DRMI locked (on 1f, and then on 3f), we used the HP4395A to take an RF spectrum of the "direct" output of the REFLAIR_B diplexer board. This should be the raw RF signal out of REFLAIR_B, with 12 dB of attenuation from a coupler inside the diplexer.
The spectra (adjusted for the 12 dB coupler) are attached.
For 27 MHz, the power into the diplexer is -41 dBm. Using the diplexer schematic (D1300989), this should give -23 dBm at the diplexer's 3x output, which is well below the compression point of the amplifier (ZHL-500HLN+; 1 dB comprsesion occurs at +16 dBm). Similarly, for the 15x output we expect -13 dBm.
The analogous LLO measurement is at LLO#10494.
Power levels were as follows:
Dan remeasured the modulation indices (LHO#14801).
A quick estimate of the amount of distirtion in the BBPD amplifiers (MAR-6SM+ and GALI-6+):
The total amount of RF power in the attached spectrum is about +1 dBm (coming mostly from 4f1). Before the GALI-6+ in the BBPD, that's −11.2 dBm at the output of the MAR-6SM+.
The output-referred IP3 of the MAR-6SM+ is +18.1 dBm. Assuming the third-order distortion of the amplifier grows like the cube of the input power, this means the expected power of the third-order distortion is −11.2 dBm − 2×(18.1 dBm + 11.2 dBm) = −70 dBm out of MAR-6SM+. Then after the GALI-6+, the distorted power is −58 dBm.
[Koji, Rana]
The preamp chain of the BBPD was electrically tested. It turned out that intermodulation can explain the observed RF signals at 27MHz and 135MHz.
Method:
A spare BBPD at the 40m was used for this test.
The photodiode was removed from the BBPD circuitry and an SMA connector was soldered instead. (Attachment 1)
The measurement setup is depicted in Attachment 2.
The RF signals from two signal sources were combined with a power combiner and fed to the modified BBPD.
The output was connected to a network analyzer in order to monitor the output levels at each frequency.
Measurement 1:
Firstly, Intermodulation produced from strong 9MHz and 35MHz components was tested.
WIth these two signals injected, our taget signals appear at 26MHz and 44MHz.
This way we can avoid the interference by the third harmonic distortion of the 9MHz signal.
The result is shown in Attachment 3. The 9MHz and 35MHz input levels were adjusted such that the output levels are -10dBm and 0dBm respectively.
These levels were obtained from the measurement in alog14807 (above).
It is clearly seen that symetric intermodulation appeared at 26MHz and 44MHz. The intermodulation level is linear to the level of the 35MHz signal.
In fact, -10dBm@9MHz and 0dBm@35MHz explain -40dBm@26MHz which Evan observed in the inlock spectra.
Measurement 2:
In the second measurement, it is tested if the intermodulation can produced enough amount of 135MHz signal.
Evan's measurement shows that both 45MHz and 90MHz have -15dBm.
From the lmitation of my setup, I had to use 30MHz and 80MHz to produce 110MHz, instead.
This indeed produced the 60dBm intermodulation, which is consistent with Evan's measurment.
Meaning of this measurement:
What happens if the intermodulation overwhelms the intrinsic signals at 27MHz and 135MHz?
- The intermodulation without fluctuation itself imposes unreasonable offsets in the 3f signals at DC.
- Power fluctuation of the sideband power in the 36MHz (f1-f2) or 91MHz (2xf2) causes unnecessary (=meaningless) signal to the 3f demodulated signals.
- The londitudinal IFO error signals in the 9MHz or 45MHz signals are imprinted to the 3f signals at a certain unknown demod phases,
and thus screw up the demod phase of 3f signals, as well as the immunity of them against the carrier audio sidebands.
Remedy:
- Lower the light power on the PD, if possible to maintain lock.
- Notch out/filter out unncesessary RF components before the BBPD preamps by adding components on the BBPD boards.
- Use resonant type photodetectors in stead of the broadband one to selectively amplify the desired lines.
This is related to Hugh's log 14774. To elaborate a bit on Hugh's log, I made a measurement with Stage 1 Damped only and HPI isolated. The first plot shows the GND_T240_X , ST1_T240_X and HPI L4C (out of loop witness). There was no coherence with ground below 0.1 Hz but there was significant coherence with HPI L4C. This meant that HPI was somehow introducing excess low-frequency motion.
We then did the same measurement on ETMY and saw no such excess motion. The second pdf shows the corresponding measurement. Stage 1_Y was very coherent with ground_Y. Jim mentioned he had modified the HPI controllers on ETMY as described in Hugh's log, so we decided to try the same on ETMX in X and Y.
This has made a significant difference to the low frequency performance of Stage 1 as shown in the third file. Performance below 0.1 Hz is much closer to ground motion now.
Some more plots of the old vs new isolation filters, per Jeff's request. I dug into the foton file to find numbers to back up what I thought the original design was. The gains of the old and new foton filters are shown in the first image, they show that not much was done to the filter design, just that the gain was reduced. Solid lines are the old design(higher gain, UGF), dashed lines are the current design. Second and third images are the currently installed plant design and a reconstruction of the orignal design (no plots were found from the original design from earlier this year). The solid and dashed orange lines tell most of the story, mostly we just cut the UGF to 2hz, and modified the boost to get more phase margin. No idea why this affect the very low frequency noise, Jeff and Krishna suggested maybe we were re-injecting IPS noise with the higher gain.
Here is another look at the controller with the amplitude scale zoomed out to see the lowest frequencies of the open loop.
J. Warner, K. Venkateswara
We repeated this measurement today and did not see the same results. Sensor correction was off. The attached pdf shows the before (old controller) and after (new low gain UGF controller) data. Very strange. We may have been fooled by different ground motion or perhaps by sensor correction. There is good coherence with ground till ~60 mHz in either controllerconfiguration.
Jim has reverted to the new low gain UGF controller as it should help with ringing of HEPI at 9 Hz.
I screwed this up. Dave found that I had installed a filter with a gain of something like 10^-11, then fixed the gain, but never loaded the code into the front end. So foton showed a reasonable filter, but the front end was running a filter with a gain of zero. This is fixed now.