Posting here to inform everyone of one or more possible failed disks in the LLO aLOG disk array. I am headed to the site now to investigate.
Today at 10:40 am the turbo was spun down and the scroll pump turned off, turbo pump cable still connected, will remove it on Tuesday.
The ion pump for HAM6 was able to mantain the pressure on its own, the pressure keeps going down, see attachment.
Data for the past 3 days.
Arnaud posted about CPS glitches in the CPS HAM5. Though it prudent to scan LHO for similar.
I looked over the past three weeks and found none that were shaped like LLO (very narrow spikes to near 40k counts.) WHAM6 had some associated with the fast shutter although I did not establish cause/effect there.
WHAMs 2 3 4 & 5 all had one exceeding 20k counts at the same time 0030 utc 30 March but was not a single spike, looks more like an Earthquake. Bottom line, we should be ever vigilent but for now, LHOs HAM CPSs are not glitching.
LVEA: Laser Hazard Observation Bit: Commissioning 07:00 Karen & Cris – Cleaning in the LVEA 10:05 John & 3IFO Group – in LVEA taking measurements at beam tube building exits 10:18 Gerardo – At HAM6 to turn off scroll pump 10:30 ISS FSS have been saturation and the IMC is dropping out of lock. Per Peter K. turned off the ISS Autolock to see if that stabilizes the FSS and IMC. 10:43 John & Co – Out of LVEA 10:45 Gerardo – Out of LVEA 12:20 FSS is still saturating and the IMC is dropping out of lock. Per Peter K. dropped the FSS Common Gain from 25 dB to 24 dB. 15:08 Gerardo – Going to H2-PSL enclosure
Below are trends from the past 10 days
As reported in last night entry, we tried to improve the SRCL noise coupling non stationarity by increasing the low frequency gain of the DHARD Yaw loop. In my initial elog entry, I pointed out that the SRCL coupling was fluctuating following ASC-AS_A_RF45_I_YAW_OUT. However, it turned out that this signal is basically equal to the DHARD yaw error signal. Most of the SRCL coupling fluctuations and residual motion of DHARD are at frequencies below 200 mHz, so I designed a boost to increase the low frequency gain of the loop. The improvement is visible in the first attachment (green without boost, red with boost). The loop accuracy improved significantly, as shown in the second sttachment, which is a time series of the error signal.
With this new loop, Evan injected some SRCL noise and I could do the same analysis I did yesterday to study the SRCL coupling non stationarity. Here are my main comments:
This morning after some full lock attempts, the IMC was found to be so misaligned that it did not lock any more. It turned out that this was due to the integrators in IMCASC which kept integrating the intentional offsets that Gabriele had implemented (alog 17888). In order to resolve this issue, we edited the IMC_LOCK guardian so that it disables and enables the offsets when state is DOWN and LOCKED respectively.
Summary: Been going on since late February (~2-24) at ~24 hour period (last week at least.) It is not obvious in the In-Loop or Out-of-Loop HEPI position sensors second trends.
See attached for 70 day trends showing the glitch being revealed after getting the sensor quiet (got lucky) and continuing to today. Second plot zooms into glitch early this week 4-12 ~0400utc. This one is a double glitch; they are not always the same but the first three this week are the sign and about the same magnitude.
Still looking for cause and other potential affects.
It is not incessent but the EndX HEPI Pressure still alarms occasionally at +-3.5 degrees F. So I've opened the no-alarm region to +-4 degrees F. See the attached plot for 1 weeks worth of minute trends. You can see that this change should reduce the number of alarms from several a week to one or less.
Notice how much noisier the EX pressure is than EY or the Corner and the imprinted increase in the controller output. It would be good to quiet down this signal. EE is working on getting another (possibly custom) power supply. Also, what is up with that ~24 hour glitch that hits the EY--warrants investigation.
Nice to see the daily changes on the controller output, presumably based on the temperature. The last column of pressures are out of loop in the mechanical room, I thought those might have shown the cyclic signal too but they don't. Does that mean the temperature isn't that important or is the temp in the MR as well controlled as the VEA...?
Attached is the plot for the front end laser output power for the past year. The change around June 6th 2014 coincides with when the diode box was switched. Not sure what the change around mid-August 2014 was caused by. We should check the power monitoring photodiode alignment and compare its output to a power meter.
Sheila, Evan, Koji
I believe the 1009.62 Hz mode is on ETMY. It can be damped (slowly) using FM6+FM7+FM9 in the MODE1 filter module on L2, with a gain of -200. Some care is needed here because there is another mode on ETMY at 1009.48 Hz. If necessary, this can be damped using FM4+FM6 in the MODE3 filter module, with a gain of +100.
Sheila, Koji, Robert, Evan, Alexa, Dan
We have made several measurements of backscattering from the OMC. It seems like the reflectivity of the OMC is smaller by a factor of about 20 than what was seen at LLO, and it seems that backscatter from the OMC is probably not limiting our DARM spectrum.
Two nights ago, we measured fringe wrapping by exciting the OMC suspension in the longitudnal direction, as well as by exciting OM1. (related alogs 17910 17904 17882) The attached plots show the DCPD RIM, with the DARM loop supression removed, with the excitations on.
Tonight Jeff made a test of turning off the HAM6 sensor correction, as was done at LLO (third attachment) (LLO alogs 16814). The spectrum is attached, but we do not see the dramatic fringe wrapping seen at LLO. We would expect the impact to be smaller here than in LLO because our scattering amplitude is smaller and it is also likely that the microseism could have been smaller here.
Today we Robert Koji and I made injections into all 6 DOFs on the OMC to see fringe wrapping. We saw nothing by exciting roll or vertical, we were able to produce shelves by exciting L, T, P and Y. The last screenshot attached shows the sectra with the various excitations on. For the record, here are times, all excitations were at 0.2 Hz, into the test filter banks. While I've attached spectra of these, several off these shelves were moving around durring the measurement because of some lower frequency motion.
| DOF | ampltide counts | time April 16-17th UTC |
| L | 20000 | 23:47-23:51 |
| T | 20000 | 23:59-0:05 |
| V | 20000 | 0:14-0:18 |
| P | 2000 | 0:24-0:29 |
| Y | 200 | 0:31-0:35 |
| R | 2000 | 0:39-0:42 |
Thanks to Sheila for logging my scattering measurements, apologies for not putting it up myself. A few more relevant comments on it: - The experiment involved turning off both the HAM6 *and* HAM5 sensor correction (independently). - HAM6 shows no affect but HAM5 caused lots of non-stationary noise, from which the captured HAM5 curve is only a representative bump/glitch/effect. - Just after I got that spectra, the IFO broke lock. This is why I didn't get an ASD of the GS13s/CPSs on the ISIs exposing the full region where sensor correction ON/OFF should have an impact (down to ~0.1 [Hz], since we're using the Hua, FIR sensor correction on all DOFs on all the HAMs). My locking skills are still minimal, so I wasn't able to bring the IFO up past 1f DRMI (the ISC_LOCK message complain of to little light on AS90, I tried nudging the BS out of ignorance, and that re-broke the DRMI lock, and the next automation attempt failed during ALS acquisition and I gave up).
There was some question about the shotnoise RIN level in the ISC meeting. We have ~20mA total current on the OMC DCPDs.
This corresponds to the shotnoise of 4e-9/rtHz. It is consistent with these attached plots.
DCPD1 and DCPD2 are perfectly coherent around the shelves.
At Stefan's suggestion, here's the coherence between DCPD1 and DCPD2 around the injection shelves. The coherence is almost 1 for the first shelf. As for the second shelf the coherence is not as perfect but it is almost 1 at the highest peak of the scattering shelf, and the flat part of this shelf is already pretty close to the noise floor.
We're either looking at something that comes through the OMC (as opposed to large angle scattering reflected by some random thing and unfortunately falling on the DCPDs), which is more likely, or something that come from the opposite side of the BS for the DCPDs, which sounds unlikely.
Following up on the TTFSS work in alog 17885, we remeasured the input mode cleaner open loop transfer function.
The ugf is 50 kHz. With 3 dB of additional gain we can push this to 100 kHz and engage the second boost stage. The gain margin will be a little marginal at 1-2 dB, so.
For the measurement the common gain was at 18 dB, the fast gain at –6 dB, the compensation and one boost stage was engaged.
The small feature at 750 kHz is still there but of little relevance. This now closely resembles the iLIGO configuration and behavior.
Again, just because this is how it will be for the forseeable future, I post a more reader-friendly version with notes reflecting the above entry. Hope this helps!
Sheila, Gabriele, Evan, Koji, Dan, Alexa, Elli
Yesterday Koji, Evan and Sheila locked at 15W, and after an hour and a half the lock became unstable and they reduced they power due to suspected PI. A spectrogram ('darmspectrogram3_1.png ') of last night's lock shows a 844Hz line grow in the DARM spectrum (see attached spectrogram from 2015-04-15 09:30:00 UTC). This corresponds to a PI at frequency 15540Hz, which is the first PI LLO saw (LLO alog 15934). The line appears about an hour after the 15W lock began and the power was reduced after 1hr25min. Once the power was reduced to 10W the line got smaller.
This evening we locked at 15W at 2015-04-15 23:40:00 UTC and we saw the same line grow at 843.4Hz, corresponding to a PI at 15540.6Hz (see spectrogram 'spectrogram16April_843HzPI.png '). This line grew untill we lost the lock at 1hr55 mins later ~ 2015-04-14 01:35:00 UTC (not due to the PI). We measured the DARM spectrum around 15.5kHz using the SR785. Attached is a plot '16AprilDARMSpectrum.jpg ' of the growing 15.54kHz line.
Grabriele saw that the 843Hz line was coherent between between the X-arm ASC QPDs and Darm, so we turned on the ETMx ring heater (see alog 17899). The ring heater is requesting 1W total, or 0.5W each on the upper and lower segments. We locked for a second time tonight at 15W at 2015-04-16 05:18:10 UTC. With the ETMX ring heater running, we didn't see any growth in the 15.54kHz line, as measured by the SR785. See 2nd plot '16AprilDARMSpectrum_withETMXRH.jpg '.
Measurement notes:
-Spectrogram generated at LigoDV https://ldvw.ligo.caltech.edu/ldvw using channel H1:CAL-DELTAL_EXTERNAL_DQ.
-Spectrum meaurement taken with SR785 connected to OMC DCPD readout. There is a script in /ligo/home/eleanor.king/netgib/SR785/SPSR785omcdcpds.yml that is used to take the spectrum (use the command < ./SRmeasure SPSR785omcdcpds.yml > to take a measurement).
-Dan points out there are also OMC DCPD 64kHz testpoints which are channels H1:IOP-LSC0_MADC0_TP_CH12 and H1:IOP-LSC0_MADC0_TP_CH13, which correspond to DCPD_A_INMON and DCPD_B_INMON.
How exciting! We have found that 0.4W per segment is best at present. At 0.55W there is another mode that rings up in a very short time, it appears around 1360, or 15004 in the IOP channels. You get a lot earlier warning looking at the IOP channels as mentioned, The IOP ASC_TR_ channel test points at are also nice as they have a lot less mess. Fitting this data as was done by Mathew Evans with in the PI observation paper results in a mechanical Q of 6.9M, the fit is not very good though with essentially 2 data points. Specifically the equation for the fit is τm = 2Qm / (ωm(Rm − 1)) τm - time constant of ring up, Qm - mechanical mode Q, ωm - mechanical mode frequency, Rm mechanical mode parametric gain = const * Power where 'const' is dependent on frequency overlap condition, spatial overlap, Q factors and some other stuff. So it assumes generally the only thing that is varied is the Power.
This seismometer has given us problems for some time: alogs 15510, 14482, 9727. JeffK may point to others too.
On the attached four plots, there are four successive days, Saturday thru Tuesday at 0100pdt. The lower left panels are the Coherences between the HAM2 & HAM5 (STS-A & C) and the ITMY (STS2.) The Upper Left, Upper Right, and Lower Right panels are the ASDs of the X Y & Z DOFs respectively of STS2 A B & C.
The take away is that in general the character of the ITMY (STS2-B) ground seismometer doesn't change like the other two instruments below 100mhz while the HAM2 & HAM5 instruments change more day to day and mostly look like each other.
Details: The Z DOF is most obvious in that below 50 or 80 mhz, ITMY trends up steeply while the A & C seismos do not. For the Y DOF, the HAM2 (STS2-B) signal seems to be the outlier but the day to day doesn't follow a patten between the instruments so I ... The X DOF is pretty good with the A & C instruments tracking each other pretty closely while the B sensor kinda stays at the same power level, mostly. So, like I say, a Case, maybe.
If I remember right, it sits on some kind of thin plastic or rubber mat, while the others sit directly on the concrete. If possible, it might be useful to make it contact the the concrete floor directly by carving out three holes on the mat.
For convenience: Evidence for low-frequency broken-ness LHO aLOG 15510 LHO aLOG 14482 LHO aLOG 9727 Factor-of-2 drop in X channel gain LHO aLOG 16208 LHO aLOG 16305
J. Kissel, R. Schofield Trying to convince Robert to let us borrow the newly-returned PEM vault STS-2 (S/N 88921) (see when it was removed in LHO aLOG 12931), I tried to show him in more detail with a little less curves on a plot what was wrong with the ITMY, B, Beer Garden STS-2 (S/N 88941). In the process, we not only rediscovered the problem Hugh shows above -- that the Z DOF on ITMY, below 50 [mHz] is just junk, but we also discovered that the Y DOF on the HAM2, A, Input Arm STS-2 (S/N 89922) is also junk. The attached PDFs show 5 days worth of corner station STS2 ASDs and COHs. For HAM2, check out the Y COH .pdf first. We see surprisingly low coherence between HAM2's Y and the other two, where the other two are perfectly coherent with each other. Looking at the ASD, it also shows the HAM2 spectra are consistently discrepant between 500 [mHz] and 3 [Hz], as well as below 0.1 [Hz]. For ITMY, again, check out the Z ASD first. From there, it's obvious that every day, the motion below 50 [mHz] is just junk. This is confirmed by the coherence, which shows that HAM2 is coherent with HAM5 every day, and ITMY is coherent with neither every day. The fact that ITMY and the HAM5, C, Output Arm STS-2 (S/N 100145) are always coherent between ... nope I can't make a consistent story. DOFs are inconsistently coherent, where they should all be perfectly coherent from 1 [Hz] down to 10 [mHz]. We really just need to huddle test all four of the STSs we have available in the corner, 89921 "PEM" Back from Quanterra 89922 Currently STS A 89941 Currently STS B 100145 Currently STS C and confirm -- once and for all -- which channel of whose is busted. Unfortunately, this means a whole lot of cable lugging around the LVEA -- a pretty hefty Tuesday task. Further -- LHO really needs more low-frequency seismometers -- because (a) We're already "temporarily" using a T240 at EX (S/N 531, borrowed fron the ETF at Stanford, originally installed at LHO in Feb 2014, see LHO aLOG 9758, and D1400077) because the project couldn't find enough STS-2s for us. (b) Even *if* we use all 5 in our possession (we have one at ETMY, S/N 89938), we still wouldn't be able to have one fail without significant down time. The lab's STS2/T240 Inventory, E1200068 hasn't been updated since the last time we churned up this subject in Oct 2014. I'm working on updating it myself by beating the streets; stay tuned for a -v15. Devil's advocate (inspired by Robert): Looking at the X DOF, there are days where all corner STSs are perfectly coherent between 60 [mHz] and ~2 [Hz]. Looking at the Y DOF, there are days where ITMY and HAM5 are perfectly coherent between 60 [mHz] and ~3 [Hz]. Looking at the Z DOF, there are days where all corner STSs are perfectly coherent between 60 [mHz] and ~1 [Hz]. The above implies that the corner station ground motion is perfectly coherent between 60 [mHz] and ~1 [Hz]. This implies we could try using a single STS-2 to run sensor correction for all chambers in the corner station. In order of risk of common-mode rejection being compromised: - For the BSCs, in X&Y, we only need a good signal around the first SUS resonances at ~500 [mHz] for DeRosa's narrow-band filter (See figure 3.32 P1500005). - For the HAMs in X&Y, we only need good coherence down to the bottom (frequency) edge of Hua's polyphase FIR bump, at 50 [mHz] (See pg 4 of attachment to SEI aLOG 594) - For all chambers, in Z, we need good coherence down to 10 [mHz], the lower end of the Mittleman's tilt free filter (See pg 5 of SEI aLOG 594) So, *if* we find an STS we like in which off of it's DOFs are performing perfectly (hopefully, presumably it's the one that just came back from Quanterra, S/N 89921), then we might be able to get away with running the entire VEA off of one STS2 (or T240). Maybe.
These have thinner wire (43 microns in diameter) to avoid the hysterises seen in the thicker 125 micron wire. Therefore these have to be handled more carefully. The wires are quite unforgiving of any kinks or handling errors.
As agreed, these do not contain BOSEMs. Type-B (one stage before the production line) bosems will eventually be used in these.
The tip-tilts are ready for shipment to 40m. They have been wrapped in Al-foil. For long term storage, these have to be stored in a dry atmosphere to avoid rusting of the "piano wire" fibers. The mirror holders are locked into place for shipment using the eddy current dampers on either side of the mirror mounts.
The Sl nos are 007 and 038 (Bottom Plate). Images of the assembled tip-tilts and their various reference numbers are attached.
Correction: s/n 34 will be sent to CIT (not 38).
