The power supplies in the I/O chassis are magnetically noisy and can couple to internal boards and the signal and power cables and connectors that are near the I/O chassis (here). CDS set up a test stand with a BNC AA chassis connected to an I/O box for testing a new type of power supply. Figure 1 is a photograph of the setup with the old supply (box in the back corner) and new supply (card with the gloved magnetometer on it). I was able to switch back and forth between the supplies. Two of the channels passing through the I/O box were used, one to carry the magnetometer signal, and a blank channel that was terminated at the AA chassis input. Figure 2 shows the spectra of the magnetometer channel for each power supply (the magnetometer was moved back and forth to sit on the active supply), and the coherence between the magnetometer channel and the blank channel. The magnetic field from the old supply can be orders of magnitude larger than that of the new supply over broad regions. The old supply also displays the drifting features of beating high frequency oscillators. The new supply only showed coherence at harmonics of 60 Hz while the old one impressed several lines and a region of increased coherence onto the blank channel. When the new supply was used, the blank channel level was a little lower, and did not have the drifting features most likely produced by beating high frequency oscillators in the old power supply (Figure 3).
The second problem with the I/O chassis is that the fans at the front produce peaks in the channels that pass through it by power supply ripple (here - the peaks go away when a separate supply is used for the fans). Figure 3 shows that these fan peaks are present with both the old and the new power supply. One possible configuration to test is to power the fans directly off of the power supply card instead of off of the main board.
Robert, Richard, Dave, Jim
One of the accelerometers on the PSL table (PEM-CS_ACC_PSL_TABLE2_Z) is glitching once per second. The other accelerometers don't seem to have this problem. We noticed this because it was messing up our hVeto results. I searched for where these started, and as far as I can tell it's Apr 14 2:30 UTC (that's 7 PM on Monday local, I think). The onset takes a few minutes. The first plot is an Omega scan from a few hours ago, showing the glitching. The second is a spectrogram of the onset. We are seeing something similar in some of the ISI GS13s (maybe only ones in the center building?). They also have a once per second glitch, though it's not clear if it's related. Detchar will track that down more, and I'll alog it separately.
I have seen large 1 Hz combs in many places at the CS that are due to the Hartman Wavefront Sensor running at 1 fps (the capture rate of 57 at end stations makes a comb of huge peaks in DARM). I think that Ellie is going to keep the HWS off most of the time until we figure out why.
Do you mean a 1 Hz comb in the spectrum, or glitches every second? This is the latter. Do you have an example of what this looks like? Also, is there an easy way to tell when the HWS is on?
We're implementing a Guardian script for ETM HWS control which engages the HWS when we lock, takes a measurement during the initial transient, then turns it off after thirty minutes or so. We'll look into implementing this at the corner station too.
Longer term - we need to look into what we might be able to do to eliminate the camera noise.
The camera can be turned on and off from Beckhoff. The channels you're looking for are:
H1:TCS-ITMX_HWS_DALSACAMERASWITCH
H1:TCS-ITMY_HWS_DALSACAMERASWITCH
There are two channels to look at which are:
H1:TCS-ETMX_HWS_RCXCLINKSWITCH
H1:TCS-ETMX_HWS_DALSACAMERASWITCH
We've known for a while now that we can move the ITMs (ITMX pitch goes down by several urad, iTMY up by about 1 urad) to get a recycling gain of 32-33, but we've seen that the IFO isn't stable like this. Elli looked into two sudden lockloss that happened after we tuned up the recycling gain on Thursday, (17921 ) and saw that something is going wrong in the MICH loops (both LSC and ASC) before the lockloss. Yesterday, Gabriele Evan and I noticed that the MICH LSC loop was marginal in the final low noise state, Gabriele designed a filter (called comp, in FM10 of the MICH bank.) to make the loop more stable. (before and after screen shot atached)
Today I tried a few more times to increase the recycling gain, we were locked for about 20 minutes with a recycling gain of 32.5, but most of the day we have had unexplained locklosses and difficulty locking, both with and without improved recycling gain. I've edited the guardian to request 10 Watts instead of 15 and leave things trying to lock.
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.
LLO aLOG is back online. https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=17770
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...?
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.
MICH feedforward seems to be doing its job, although there is room for improvement by implementing a frequency-dependent subtraction.
SRCL coupling into DARM seems to be very nonstationary. Consequently, the feedforward is not working.
We injected band-limited white noise (elliptic bandpass, 10 Hz to 1 kHz, 6 ct amplitude) first into MICH, then into SRCL, to test the feedforward that was implemented a few weeks ago.
For MICH, frequency-independent subtraction is fair to middling (red) compared to no subtraction (blue); at best we get 20 dB of subtraction around 150 Hz. Note that the TFs in this plot use the whitened DARM channel. The whitening is undone for the spectra in the fourth pad.
For SRCL, the 1/f2 feedforward via ITMY L2 gives no subtraction at all. The attachment shows the TF of SRCL control → DARM with the feedforward off and with broadband noise injected into the SRCL error point. Unlike MICH, appearance of this excitation in DARM is highly nonstationary, fluctuating by a factor of 2 or so in a frequency-dependent way. Additionally, the coherence is poor above 20 Hz, despite the excitation elevating the DARM noise by more than an order of magnitude from 20 to 100 Hz.
The shape of the excess noise is more or less the shape of the 100 Hz elliptic cutoff that we put into SRCL a few weeks ago. Is it possible that the SRCL control noise explains the nonstationary, 100 Hz "scattering" shelf that we've seen in the DARM spectrum this past week?
Using the measurements described above, here is a projection of MICH and SRCL control into DARM. It seems that these two noise sources, along with DAC→ESD noise, can explain most of the DARM noise from 10 to 70 Hz. There is still some excess from 80 to 200 Hz, and an overall excess in the high-frequency noise floor.
For MICH, I used the coherent transfer function we measured earlier. For SRCL, I estimated the TF magnitude by dividing the ASDs of DARM and SRCL (after subtracting off their quiescent values). The dtt files are in evan.hall/Public/2015/04/FullIFO/Noise
as MichNoise.xml
and SrclNoise.xml
.
Some times (all UTC):
After these measurements, I also tuned the PRCL→SRCL subtraction in the LSC input matrix from 0.005 to -0.04 (using in-vac POP). This reduced the appearance of a 122 Hz PRCL excitation in the SRCL error signal by 20 dB.
For completeness, here is the same budget as above, with intensity and frequency noises included.
We suspect that the sharp shelf at 100 Hz in the frequency noise projection might be coupling via SRCL, rather than directly to DARM. So between the frequency and SRCL projections, there may be some double-counting of noise in DARM.
Frequency, intensity, and DCPD dark noise are not enough to explain the excess noise between 200 Hz and 4 kHz. It seems they can somewhat explain the uptick in noise above 4 kHz.
Slightly updated/corrected version attached.
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).