cheryl.vorvick@LIGO.ORG - posted 11:00, Sunday 07 June 2015 (18955)
17:53:30UTC - airplane heard in CR
Chatted with Will (LLO Operator) early in the shift. He said he and Carl were working on getting L1 UP (& they did shortly after).
5:08 landscaper truck on site, and they seem to be driving noticeably slow around the site (a good thing!).
For the current lock segment, it's been odd in that the range started out nice at 62Mpc, but over the following hours it trended down and leveled off at 58Mpc. I hand this segment over to Cheryl.
NOTE: Also talked with Sheila again. If the odd 25.4Hz noise comes back she suggested going to lower power (for Operators that would mean going to Manual Mode ith the ISC_Lock Node, selecting "Increase Power" on the Guardian, and then taking the PSL rotation stage to 17W).
BS ISI Watchdog Trip
During this current segment, Ed noticed from home and emailed me about a RED ISI for the BS. Turns out the Stage2 Watchdog for the BS ISI GS13 was tripped (so red blocks for Stage2 FF & ISO....BUT the BS is unique in that we don't use the ISO for Stage2 anyway). So we could do a RESET ALL and this shouldn't affect anything, but we (Cheryl & I) are deciding to do this after the segment ends. [Thanks to HUGH for help over the phone...and Ed for keeping an eye remotely!]
Due to BS's unique configuration for the ISI, we can ride through a WD trip like this. (but it's something which could go unnoticed unless you happen to be watching the OPS overview). For other ISIs, if a WD trip happened on this stage, the ISO filters are in effect and they definitely would raise one's attention because things would definitely (most likely) swing around.
So maybe we should have an audio alarm for this special case? Or maybe we can NOT have the WD affect this path in some way....just a thought.
model restarts logged for Sat 06/Jun/2015
no restarts reported
As soon as L1 locked up, H1 nosedived with a huge noise source at 25.37Hz (big ugly peak with sidebands) & its harmonics (Sheila could not find a SUS resonance at this frequency). This dropped sensitivity from 60Mpc to 30Mpc. After about 15min, I intentionally broke lock to see if a new lock would improve sensitivity. (Note: It wasn't clear to me how to break lock with our new fandangled aLIGO H1 detector. I hit DOWN in the ISC Lock Guardian Node, but this just made the whole node fault RED. Ultimately, I went to the LSC Overview & pushed the OFF button for LSC Mode & that did the trick.
I wanted to quickly go back up, so I saw the Yarm was a bit ugly, so I tweaked on ETMy, but could only get up to 0.86counts (I thought WFS would kick in to get me over 1.0). ISC_LockGuardian spouted off about "waiting for arms to lock" and never progressed with locking. At this point, I went to the phone, and got a hold of Sheila. She mentioned I could tweak TMSy, but I might do better to do a full Initial Alignment. I ended up trying both.
Alignment was fairly straightforward (this was really only my 4-5th time to go through and alignment, AND I've never sat at the chair and had H1 lock by my own powers!).
Then I went for locking. First attempt, I waited about 3-4min for DRMI to lock, but it dropped out during the "Switch to qpds". Second attempt had me wait a whopping 3min for DRMI to lock. And for this, lock I went all the way up to LSC_FF (Bounce modes were nice and well below 10^-12).
Once all the way through, I wasn't completely clear on what I had to do with the ETMx ESD Driver. ESD ACTIVE was RED, but the monitors were all a few hundred counts negative (range was about 55Mpc). So, I clicked on the "HI" button, which made ESD ACTIVE go GREEN briefly and then back to RED, and this sent the monitors close to zero (and range went up to 62Mpc).
SDF looked all GREEN, and Intent Bit set to Undisturbed at 3:58am (10:58utc), and H1 joined L1.
[Time for lunch.]
Not much to report here. I walked in with Cheryl and Stefan locking H1 and then I didn't touch it at all.
John called and said that he saw the EY VEA temp starting to rise so he turned off a heat source and it leveled back out nicely. It went up to a max of about 68.6F
There was one BIG glitch at ~20:30 pst but it held lock.
I have to say how impressed I am with the lock stretches lately, a lot of hard how is really starting to show.
Handing it off to Corey, good luck!
The summary pages report 18h of lock in low noise with an average of 65 Mpc (WOW!). I believe the longest lock of the aLIGO era is the 30h long lock of L1 (no pressure! :-) However, I think this H1 lock now sets the new record of the best time-volume lock ever, equivalent to about ~26 days of eLIGO @ 20 Mpc.
LIKE! I have the remote MEDM screens. I've been stalking. :) The only bummer is, it looks like coincidental locking time isn't quite as good.
The YEND is having trouble keeping cool in the hot part of the day. We can make adjustments on maintenance day or sooner if needed.
TJ and I talked on the phone and decided that I should proceed and turn off the remaining heat in the VEA. We will monitor the response tonight. Tomorrow or Tuesday Bubba and I need to lower the chilled water setpoint at YEND. For some reason it is 10F higher than Xend. I thought we had made the site rounds and set all chillers for the spring heating season.
IFO was locked most of the shift.
Broke lock 30 minutes before shift end. Relocked to Violin and Bounce Mode, then handed off to Stefan and TJ.
Glitches in the IFO look suspiciously like Big, Smaller, Smaller, Smallest, and at the time I left I could see three sets of glitches that look that way.
I monitored the ASC OUTMONs for all the optics, and IM4 glitched at some point and PRM and SRM did as well, but more like a response.
Attached is my striptool of the ASC OUTMONs at Lock Loss, which also shows that IM4 went first and lock loss followed.
We had one lock loss about an hour ago, but Cheryl took us right back up. I did update the ISC_LOCK Guardian with the request for 23W during INCREASE_POWER. The only other thing we had to do manually t the very end is turn off the ESD X driver again. We also did check the the calibration line at 538.1 remained the same within measurement tolerances.
Using two hours of undisturbed data from last night's 66 Mpc lock, I repeated Den's sum/null stream analysis in order to see if we have a similar 1/f1/2 excess in our residual.
I took the OMC sum/null data (calibrated into milliamps), undid the effect of the DARM OLTF in order to get an estimate for the freerunning OMC current, and then scaled by the DARM optical gain (3.5 mA/pm, with a pole at 355 Hz) to get the equivalent freerunning DARM displacement. The residual is then the quadrature difference between the sum and null ASDs.
The attachment shows the sum, null, and residual ASDs, along with the anticipated coating Brownian noise from GWINC. [Just to be clear: the "sum" trace on this plot corresponds to our usual freerunning DARM estimate, although in this case it comes purely from the error signal rather than a combination of the error and control signals.]
If there is some kind of excess 1/f1/2 noise here, it is not yet large enough to dominate the residual. Right now it looks like the residual is at least a factor of 2.2 higher than the expected coating noise at all frequencies. We already know some of this is intensity noise.
The other thing to note here is that we are evidently not completely dominated by shot noise above 1 kHz.
I repeated this on a lock stretch from 2015-06-07 00:00:00Z to 02:00:00Z, but the result is pretty much the same. The best constraint we can put on coating noise right now from the residual is about a factor of 2.2 higher than the GWINC prediction. I also think the residual is not yet clean enough in this frequency band to make an inference about its spectral shape.
I tried increasing the CARM gain by 3 dB to see if the residual would decrease, but it does not (except maybe round 6 kHz; see the attached dtt pdf). So this broadband excess in the sum may not be frequency noise.
There is an error in the above plots.
Only the DCPD sum should be corrected by the DARM OLTF to get the equivalent freerunning noise. The DCPD null should not be corrected. To refer to noise to DARM displacement, however, all these quantities must be corrected by the DARM cavity pole.
This time I've included the DCPD dark noise (sum of A and B), also not corrected by the loop gain.
A few more corrections and additions:
Jess, Andy, TJ, Duncan, Detchar,
In entry 18783 (at 19 UTC on June 2) Jeff et al performed an autocal on the SUS DACs for the Modecleaner, in response to the report in log 18739. He asked Detchar to report if the glitches are gone, if they come back over time, etc.
What we've found so far is that the DAC glitches are still present on MC2 M3 zero crossings. Their amplitude (seen in LSC MCL and IMC alignment channels) has reduced by a factor of 2. And their amplitude does not appear to be increasing over time since the restart, on the timescale of days.
Figure 1 shows normalized spectrograms of the DAC glitches witnessed by LSC MCL before and after the Autocal.
Figure 2 shows a time vs SNR plot of the individual glitches (only during observation intent time) in LSC MCL (at frequency < 200Hz to be dominated by DAC glitches). The many glitches with signal-to-noise ratio of 30 are now many glitches with SNR 15-20. Autocal occurs at hour 19.
Figure 3 shows the same plot for IMC-DOF_1_P_IN1_DQ, another good witness of these glitches.
Figure 4 caption: The Glitchgrams on the bottom show glitchiness of IFO, not related to the MC2 DAC glitches (we think) but just to see when IFO is locked and in good state. The top plots are all normalized spectrograms. The left two plots are before autocal, MCL glitches are really loud. The right five plots are after autocal, most glitches are less loud. Where "loud" is assessed by top of color bar (admittedly poor measure).
Figure 5: Same for two IMC alignement channels DOF 1 P and DOF 2 Y that are both good witnesses of DAC glitches.
Jess wrote nice scripts to make the glitch vs time plots so we will keep an eye on these to see when/if the amplitude increases.
Notes: Sorry Jeff, Peter, et al, I realize now that amplitude rather than SNR, calibrated units, and the SUS VOLTMON channels would be more useful for assessing the size of the DAC glitches. We'll work on that.
We've also made timeseries plots of the glitches in the noisemons before, just after, and several hours after the auocalibration. The glitches seem to come back most strongly in the LL DAC. The first three slides have a 10,100 Hz bandpass so the glitches can be seen clearly. The last two slide have just one second of data, so a single glitch can be seen in the raw data.
Josh, Detchar,
Our algorithms (hveto, upv) found that the end-Y magnetometers witness EM glitches once every 75 minutes VERY strongly and that these couple into DARM. Attached is a PDF that goes through the story somewhat narratively. Robert is aware of these and I hope that from the timing information on the last page of the PDF he may be able to predict a good time to visit EY. A good full omega scan is linked in the document too for folks that might want to look at how this couples into a bzillion channels.
The BruCo report for the improved sensitivity can be found here:
https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_1117636216/
Some highlights:
Gabriele: I was wondering whether you see any significant differences in coherences between the data pre 2015/6/6 7:32 UTC (pick a good time where we saw about 70Mpc range) and the data after 2015/6/6 8:32 UTC. alog 18931 suggest there was an alignment shift of the signal recycling cavity between them. (I attached the summary page range plot.)
Hang, Stefan Our lock is at 14h and counting. Attached are the output control signals for the 10 optics that are controlled by the ASC system. (All of them are relieved to the top mass, so the top mass output is what I am plotting.) There is some funny behaviour in PR2 pitch, and some of it also shows up in the BS pith nd yaw. Also - interestingly, the sharp rise in SR2 PITCH about 10.5h ago (2015/06/06 07:55 UTC) corresponds to a drop in the inspiral range by about 10% (6Mpc), and comes from the 80Hz to 300Hz region. Whatever this noise is, it seems to be related to SRC alignment. The third attached plot shows the difference between before that SR2 move (2015/6/6 7:32 UTC, 67Mpc) and after (2015/6/6 8:32 UTC, 61Mpc). Sounds like SRC ASC work is not done yet.
Here are some plots of the AS_A_RF36 and AS_B_RF36 signals around the time of the SRC cavity shift (2015/06/06 07:55 UTC). PITCH: AS_B_RF36_I and AS_B_RF36_Q are servoed to zero - the don't see any jump. AS_A_RF36_I and AS_A_RF36_Q both show a clear jump at that time, so there is a good chance to find a better PIT error signal. YAW: The jump does show up in the two I sensors in YAW as well. While the current YAW input matri seems to work for stability (18h locks), I am still not sure about its lock-point. More work needed.
Daniel and I looked at three of the locklosses from Travis's shift last night, from 14:40, 14:02 and 11:33 UTC. The earlier two both seem to be related to an alignment drift over 2-3 minutes before the lockloss, which shows up clearly in SR3 PIT. (there is currently not feedback to SR3 PIT) According to the witness sensors, this drift is only seen on M3. No optics saturated until after the lockloss. The DC4 centering loop, as well as both of the SRC alignment loops respond to the drift.
Its unclear what causes the drift to accelerate in the minutes before the lockloss. There is also a drfit of SR3 when we power up, as we noted yesterday, but this happens on a slower timescale than the dirfts that preceed a lockloss (3rd screenshot). Also, there is a longer, slow drift that happens whenever we are locked.
With Patrick and Cheryl I have engaged a DC coupled optical lever for SR3 PIT, we will see if this helps. The last screen shot attached shows the MEDM screen used to turn this on or off.
If the operators need to disable this (due to an earthquake, a trip, or if the optic becomes misalinged for any other reason) you can get to this screen from SR3, M2 OLDAMP.
Turning off:
turn off FM1 (labeled DC), then the input
Turning it back on:
Once the optic has settled and the beam is back on the oplev QPD, turn on the damping loop (with FM1 still off). Average INMON (in a command line tdsavg 10 H1:SUS-SR3_M2_OLDAMP_P_INMON), type -1 times the average into the offset, make sure the offset is engaged, and finally turn on FM1 to make the loop DC coupled.
Since this is just a trial, Jeff is not including these changes in his current SDF cleanup campaign.
Looking at the initial power up, we can see that an increase of a factor of ~10 causes ~0.7 µrad of pitch misalignment. During the accelerated drift in the last 3-5 minutes before the lock loss another 0.4 µrad of pitch misalignment was acquired with only ~10% of power increase. One might wonder, if we see a geometrically induced wire heating run away.
I modeled how much the two front wires have to heat up to casue a bottom mass pitch of 1 microradian. A very small temperature increase is needed to predict this.
* Assuming a constant temperature profile along the wire length (I'm sure this is not the case, but it is easy to calculate), it is
0.003 [C]
* Assuming a linear temperature profile where with the max temperature is in the middle, and the ends of the wire have no temperature increase
0.006 [C]
So we can say an order of magnitude estimate is greater than 1 mC / urad and less than 10 mC / urad.
Calculations:
From gwinc, the thermal coefficient of expansion for C70 steel wire is
alpha = 12e-6 [1/C].
From the HLTS model at ../SusSVN/sus/trunk/Common/MatlabTools/TripleModel_Production/hltsopt_wire.m
wire length L = 0.255 [m]
front-back wire spacing s = 0.01 [m]
The change in wire length for pitch = 1 urad is then
dL = s * pitch = 0.01 * 1e-6 = 1e-8 [m]
* For uniform wire heating of dT, this change comes from
dL = alpha * L * dT
So, solving for dT
dT = dL / (alpha * L) = 1e-8 / ( 12e-6 * 0.255 ) = 0.0033 [C]
* For a linear temperature increase profile (max at middle, 0 at ends), I break the wire into many constant temperature segments of length Lsegment.
The temperature increase profile is a vector defined by
dT = dTmax * TempPrile
where TempProfile is a vector of the normalized shape of the temperature prodile. It is triangular, 0 at the ends and 1 at the peak in the middle. Each element of the vector corresponds to a constant temperature segment of the wire. dTmax is a scalar representing the maximum temeprature increase at the middle of the wire.
The change in wire length is then given by
dL = sum( alpha * Lsegment * TempProfile ) * dTmax
solving for dTmax
dTmax = dL / sum( alpha * Lsegment * TempProfile )
with 101 segments, this gives us
dTmax = 0.0063 [C]
about double the uniform heating case.
* I also considered that since the wire has significant stress due to the test mass weight, the Young's modulus's temperature dependence might cause a different effective thermal expansion coefficient alpha_effective. This appears to be a negligible effect.
From gwinc, the temperate dependence of the young's modulus E is
dE/dT = -2.5e-4 [1/C]
and young's modulus E is
E = 212e9 [Pa]
from https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=12581, we know that the change in spring length due to the modulus of eleasticity dependence is
dL = -dE/dT * dT * Tension / Stiffness
where Tension is the load in the wire and Stiffness is the vertical stiffness of the wire.
The Stiffness is given by
Stiffness = E * A / L = E * pi * r^2 / L
where A is the cross sectional area of the wire, and r is the radius.
So plugging this in above
dL = -dE/dT * dT * Tension * L / ( E * pi * r^2 )
We get the correction on alpha by dividing this by L and dT, which eliminates both from the equation. From the HLTS model, the bottom mass is 12.142 kg and the wire radius is 1.346e-4 m.
Tension = 12.142 * 9.81 / 4 = 29.8 [N]
The correction on alpha is then
-dE/dT * Tension / ( E * pi * r^2 ) = 2.5e-4 * 29.8 / (212e9 * pi * 1.346e-4^2) = 6.2e-7 [1/C]
This changes alpha from
12e-6 to 12.6e-6 [1/C]
Not enough to matter for the estimates above.
Localizing the heat source:
I made a calculation of the heat absorption by wires.
Based on Brett's temperature estimate, assuming the radiation as the only heat dissipation mechanism, the heat the front wires should be absorbing is about 1uW total per two wires when SR3 tilts by 1 urad regardless of the temperature distribution.
If you only look at the power, any ghost beam coming from PRC power (about 800W per 20W input assuming recycling gain of 40) can supply 1uW as each of these beams has O(10mW) or more.
I looked at BS AR reflection of X reflection, CP wedge AR both ways, and ITM AR both ways. I'm not sure about the first one, but the rest are mostly untouched by anything and falls on SR3 off centered.
The attachment depicts SR3 outline together with the position of CP wedge AR (green) and ITM AR (blue) reflections, assuming the perfect centering of the main beam and the SR3 baffle on SR3. Note that ITMX AR reflection of +X propagating beam falls roughly on the same position on SR3 as ITMY AR reflection of +Y propagating beam. Ditto for all ITM and CP AR reflections. The radius of these circles represent the beam radius. The power is simply 20W*G_rec(40)*(AR(X)+AR(Y))/4 (extra factor of 2 due to the fact that the AR beam goes through the BS) for ITM and CP, and 20W*40*AR/2 for BSAR of -X beam.
I haven't done any more calculations and I don't intend to, but just by looking at the numbers (total power in green and blue beams in the figure is about 240mW, 5 orders of magnitude larger than the heat absorbed by wires), and considering that the centering on SR3 cannot be perfect, and that SR3 baffle is somewhat larger than SR3 itself, and that CP alignment is somewhat arbitrary, it could be that these blobs seeps through the space between the baffle and the SR3 and provide 1uW.
The red thing is where BSAR reflection of -X beam would be if it is not clipped by the SR2 scraper baffle. If everything is as designed, SR2 scraper baffle will cut off 90% of the power (SR2 edge is 5mm outside of the center of the beam with 8mm radius), and remaining 10% comes back to the left edge of the red circle.
Any ghost beam originating from SRC power is (almost) exhonerated, because the wire (0.0106"=0.27mm diameter) is much smaller than any of the known beams such that it's difficult for these beams to dump 1uW on wires. For example the SRC power hitting SRM is about 600mW per 20W input, SRM AR reflection is already about 22uW.
Details of heat absorption:
When the temperature on a section of wire rises, the stretching of that section is proportional to the length of that section itself and the rise in temperature. Due to this, the total wire stretch is proportional to the temperature rise integrated over the wire length (which is equial to the mean temperature rise multiplied by the wire length) regardless of the temperature distribution as is shown in effect by Brett's calculation:
stretch prop int^L_0 t dL = mean(t) * L
where L is the length of the wire and t is the difference from the room temperature.
Likewise, the heat dissipation of a short wire section of the length dL at temperature T+t via radiation is
sigma*E*C*dL*[(T+t)^4-T^4] ~ 4*sigma*E*C*dL*T^3*t
where sigma is Stefan-Boltzmann constant, E the emmissivity, C the circumference of the wire, T the room temperature (about 300K). The heat dissipation for the entire length of wire is obtained by integrating this over the length, and the relevant integral is int^L_0 t dL, so again the heat dissipation via radiation is proportional to the temperature rise integrated over the wire length regardless of the temperature distribution:
P(radiation) ~ 4*sigma*E*T^3*(C*L)*mean(t).
I assume the emmissivity E of the steel wire surface to be O(0.1). These wires are drawn, couldn't find the emissivity but it's 0.07 for polished steel surface and 0.24 for rolled steel plate.
I used T=300K, t=3mK (Brett's calculation for both of the temperature distributions), C=pi*0.0106", L=0.255m*2 for two front wires, and obtained:
P(radiation) ~ 0.8uW ~ 1uW.
ITM AR:
ITM has a wedge of 0.08 deg, thick side down.
ITM AR reflection of the beam propagating toward ETM is deflected by 2*wedge in +Z direction. For the beam propagating toward BS, ITM AR reflects the beam, deflecting down, and this beam is reflected by ITM and comes back to BS. Deflection of this beam relative to the main bean is -(1+n)*wedge.
AR beam displacement at BS is +14mm for +Z-deflection and -17mm for -Z-deflection. Since the BS baffle hole "radius" seen from ITMs is 100+ mm, and since the beam radius is about 53mm, AR beams are not blocked much by BS baffle and reaches SR3.
ITM AR reflectivity is about 300ppm.
CP AR:
Similar calculation for CP except that they have horizontal wedge, thick part being -Y for CPX and -X for CPY.
CP wedge is about 0.07 degrees.
I only looked at the surface of CP that is opposite of the ITM, and assumed that the surface facing ITM is more or less parallel to ITM AR, within an accuracy of O(100urad).
I assumed that S1 is the surface close to the ITM, and took S2 AR numbers from galaxy web page (43.7ppm for X, 5ppm for Y).
BS AR propagation:
BS wedge is 0.076 degrees, with a reflectivity of 50ppm.
Deflection of BS AR reflection of -X beam relative to the main beam is NOT -2*wedge as BS is tilted by 45 degrees. With some calculation it turns out that it is about -0.27 degrees, with a displacement of +48mm (positive = +X).
This beam is not obstructed at all by the BS baffle, hits SR3 and makes it to SR2 baffle edge. What made it to the SR2 surface doesn't go to SRM and instead comes back to SR3 as SR2 is convex and the beam is heavily off-centered.
If there's no SR2 baffle and if SR2 is much larger, the center of the reflected beam is going to be 50cm in -X direction from the center of SRM, which happens to be on SR3.
I don't know what happens to the edge scattering and the reflection from SR2, but both of these are highly dependent on SR2 centering.
GerardoM and RickS GUIDANCE FOR A SYSTEM THAT IS ALREADY LOCKED On the PSL_ISS.adl MEDM screen (see attached image), look at the strip chart in the top-right corner. The diffracted power level should be about 7%. A few percent more or less is OK, but I suggest setting to near 7% at least once per week, say Tuesday during the maintenance period. To change the diffracted light power, one adjusts the “REFSIGNAL” field in the lower left corner. A change in this parameter of 0.01 changes the diffracted power by about 1%, so make small changes. A larger negative number (say going from -2.00 to -2.01) will decrease the diffracted light level. This REFSIGNAL field is the DC laser power level (ignoring the minus sign) that the servo compares with the “Output AC” level on the PD that is selected in the middle-left portion of the screen. Note that in the screen snapshot the REFSIGNAL is at -2.03 and the PD A Output AC signal is at 2.03. This indicates that the loop is operating properly; the loop tries to make the PD output be equal to the reference level (without the minute sign, of course). Notice that the diffracted light level is varying a bit but is close to 7% on the strip chart. At the middle-right edge of the screen the Diffracted Power field indicates 7.38%. This is the field that is plotted in the strip chart. GUIDANCE FOR WHEN THE SYSTEM IS NOT LOCKED In the case that the ISS servo is not locked and you are having difficulty locking it, I suggest the following: With the loop unlocked (Autolock OFF), observe the PD A AC output level. This may be a bit hard to do if the value is swinging a lot quickly. Set the REFSIGNAL level to about ten percent below this observed mean value. Close the loop (Autolock ON) and observe the diffracted light time series in the strip chart. If the diffracted light level increases and goes off screen at the top, then your REFSIGNAL setting is too low (absolute value is too small) so you are not requesting enough light and the servo is trying to diffract a lot of light to give you the low level you requested. Increase the (absolute value) of the REFSIGNAL field. If the diffracted light level decreases and goes off screen at the bottom, then your REFSIGNAL setting is too high (absolute value too large) and you are requesting more light than the servo can give you and still maintain some diffracted light headroom. Decrease the (absolute value) of the REFSIGNAL field. Once the system stabilizes, set the diffracted light level to be close to 7% by making small adjustments to the REFSIGNAL value. Be patient, the time constant is pretty long and small changes make a big difference (on order one or two percent per 0.01 increments in the REFSIGNAL value). Once the diffracted light level is near 7%, observe a few minutes of the strip chart data. The variations should be on the order of what is shown in the attached screenshot. If all else fails, feel free to call me (Rick) at any hour, any day, and I will try to help over the phone. My numbers are in the site directory.
The reference to PD A only applies to the image provided. We are currently using PD B as the in loop PD. In either case, the graphic provided on the medm screen will show the path of the loop.
Sheila suggested I take a look at the TMS QPDs to look for the noise source observed earlier. However when I looked at the TMS QPDs, I did not see any of the noise. However I was able to see the 25.4Hz noise on the OMC QPDs.
I am having trouble saving pdfs from DTT so I just took a snapshot of my DTT session (the references are from the noisy period). Also including the Cal Delta L channel (i.e. DARM) which shows the harmonics of this noise source.