All suspension damping restored. There had to be an earth quake.
A few times this evening, I had been having trouble locking CARM and DARM with ALS, and holding it for very long. When it started happening again, I switched over to locking the individual arms with ALS. Yarm seems to be totally fine, but Xarm has something funny going on.
Rana and I have narrowed it down to being a problem with ETMX. We were watching ETMX's oplev and local damping error signals, and would see occasional glitch events. This happened when oplev + local damping were both on, both off, and when only local damping was on. We believe that this points to something weird with the coil driver and actuator chain.
We tried to watch for a while to see if it was a step event (something switching on and off periodically), or an impulse event (some transient oscillation in an opamp perhaps), but the problem went away again. We have come to no conclusions other than we have a problem that needs watching.
During our investigations, to more softly turn off the damping, Rana set the local damping gains, as well as the oplev gains to zero using a ramp time. We don't recall the precise numbers, and conlog doesn't have the gains recorded, so we made an educated guess. The local damping seems fine, but the oplev damping should be re-confirmed. Steve, can you please show Harry how, and have him help you measure the ETMX pitch and yaw oplev loops, and set the gains so that they match up to the references, and then post the measured bode plots when you're done?
Flow bench effect on oplev error signal is here.
I turned off the south X-end flow bench.
I'm starting to lock for the night, and I noticed that PRM is very, very pitched. Why? The PRM pitch slider is 5 full integer units higher than the backup (and the backup value is about where I like it, around -0.2).
I am not aware of any scripts that touch the PRM slider values. The PRM ASS (which I haven't used in ages) offloads the biases to the SUS screen fast channels, so even if someone turned that on and then saved the values, it wouldn't leave the PRM so very, very misaligned.
I have restored it, and relocked the PRMI, so all is well, but it's very weird to have found it so misaligned.
ITMY oplev was nearly clipping in yaw, causing wonky behavior (POY lock popping in and out frequently). I recentered it and the arm is locking fine now.
I've restored the gains to their old values, and measured the loop TFs.
The PRM sus gains checked OK
All other suspension oplev gains setting were checked out OK
ETMX sus damping restored
From old 40m elog 5-29-2007
I was investigating several issues on the IFO. As many of you noticed and not elogged, ITMX had frequent kicking without its oplev servo.
Also I had C1:LSC-TRY_OUT flatted out to zero even though I could see some fringes C1:SUS-ETMY_TRY_OUT.
Restarted all of the realtime models (no machine reboot).
Now I don't find any beam on REFL/AS/POP cameras.
If I look at BS-PRM camera, I can see big scattering, the beam is in the BS chamber.
I jiggled TT1 but cannot find neither a Michelson fringe nor POP beam.
So far I can't figure out what has happened but I'm leaving the lab now.
IMC is locked fine.
I can see some higher order mode of the Yarm green, so the Y arm alignment is no so far from the correct one.
ITMX is kicked up periodically. ITMX_PD_MAX_VAR is lowered to 500 from 1350
It started at Friday morning 8-1
I noticed some weird behavior on the ETMY oplev that led me to check them all out.
The short of it is that the ETMY oplev has a pretty small angular range, compared to the displays and other oplevs. I measured how much angular motion each oplev can sense before the beam no longer hits all four quadrants (thus losing the ability to sense). This could account for some of the additional angular motion of the mirrors... maybe.
Also, some of the QPD quadrants had offsets as big as 400 counts, thus distorting the zero point. Anyways, here are the angular ranges of each QPD, assuming the current urad/cnt calibrations are valid.
(Note: ITMX's oplev pitch and yaw is almost 30 degrees off of the alignment sliders' pitch/yaw coordinates. Steve tells me this is due to the tight nature of getting the oplev beam to the mirror without clipping.)
I wrote a script to zero all of the QPD quadrants' offsets (it lives in /scripts/OL) and have used it successfully. The oplev laser must be off before using it.
2005 ALL oplev servos use Coherent DIODE LASERS # 31-0425-000, 670 nm, 1 mW
Sep. 28, 2006 optical lever noise budget with DC readout in 40m, LIGO- T060234-00-R, Reinecke & Rana
May 22, 2007 BS, SRM & PRM He Ne 1103P takes over from diode
May 29, 2007 low RIN He Ne JDSU 1103P selected, 5 purchased sn: T8078254, T8078256, T8078257, T8078258 & T8077178 in Sep. 2007
Nov 30, 2007 Uniphase 1103P divergence measured
Nov. 30, 2007 ETMX old Uniphase 1103P from 2002 dies: .............., running time not known......~3-5 years?
May 19, 2008 ETMY old Uniphase 1103P from 1999 dies;.....................running time not known.....~ ?
Oct. 2, 2008 ITMX & ITMY are still diodes, meaning others are converted to 1103P earlier
JDSU 1103P were replaced as follows:
May 11, 2011 ETMX replaced, life time 1,258 days or 3.4 years
May 13, 2014 ETMX , LT 1,098 days or 3 y
May 22, 2012 ETMY, LT 1,464 days or 4 y
Oct. 5, 2011 BS & PRM, LT 4 years, laser in place at 1,037 days or 2.8 y
Sep. 13, 2011 ITMY old 1103P & SRM diode laser replaced by 1125P ..........old He life time is not known, 1125P in place 1,059 days or 2.9 y
June 26, 2013 ITMX 622 days or 1.7 y note: we changed because of beam quality.........................laser in place 420 days or 1.2 y
Sep. 27, 2013 purchased 3 JDSU 1103P lasers, sn: P893516, P893518, P893519 ......2 spares ( also 2 spares of 1125P of 5 mW & larger body )
May 13, 2014 ETMX, .............laser in place 90 d
May 22, 2012 ETMY,
Oct. 7, 2013 ETMY, LT 503 d or 1.4 y............bad beam quality ?
Aug. 8, 2014 ETMY, .............laser in place 425 days or 1.2 y
The instigator of this was that we were seeing ring-ups of ETMs during our ALS locks this evening. We measured the ETMY violin resonance to be 624.10 Hz, and Rana found an elog saying that the ETMX was around 631 Hz, so we made a 2 notch filter and added it to FM4 of the LSC-SUS filter banks for both ETMs.
For the ETMY resonance, we measured the frequency in the DARM spectrum, and when we looked at the FINE_PHASE_OUT channels, the resonance was only in the Yarm sensor. So, we conclude that it is coming from ETMY.
Also in the realm of filter modules, the FM3 boost for CARM, DARM, XARM and YARM was changed from zero crossing to ramp with a 1sec ramp time.
The SRM qpd was moved to accommodate the HeNe laser qualification test for LIGO Oplev use.
The qpd was saturating at 65,000 counts of 3 mW
ND1 filter lowering the power by 10 got rid of saturation. I epoxied an adapter ring to the qpd.
Atm3 was taken before saturation was realized with Koji's help.
Atm4 ND1 on SRM qpd. Now it is working and everything is moving.
ITMY oplev should be centered. I worked too much around it.
SRM as set up in Atm4 26,000 count compared with ETMY oplev servo in operation 7,500 counts for 3 days
Next steps: measure beam size at qpd,
place qpd on translation stage for calibration,
change 1103P mount to single one
SRM qpd is installed on translation stage and the shims removed from laser V mounts.
The ETMY oplev servo is on.
SRM oplev servo: 100 microrad/count is an estimate, not calibrated one.
Steve and EricG are moving their oplev test for aLIGO over to the SP table, so that we can have the SRM optical lever back.
I have pulled out an Ontrak PSM2-10 position sensor and accompanying driver for the sensor. This, like the POP QPD, has BNC outputs that we can take straight to the ADC.
In the c1pem model I have created 3 new filter modules: C1:PEM-OLTEST_X, C1:PEM-OLTEST_Y, and C1:PEM-OLTEST_SUM. I built, installed and restarted the model, and also restarted the daqd process on the frame builder. On the AA breakout board on the 1X7 rack, these correspond to:
BNC # 29 = OLTEST_X
BNC # 30 = OLTEST_Y
BNC # 31 = OLTEST_SUM
By putting 1Vpp, 0.1Hz into each of these channels one at a time, I see on StripTool that they correspond as I expect.
Everything should be plug-and-play at this point, as soon as Steve is ready with the hardware.
SRM qpd is back to its normal position. The mount base is still on delrin base. SRM and ITMY need centering.
Tomorrow I will set up the HeNe laser test at the SP table with Ontrack qpd
ETMY oplev servo on. SRM qpd with ND1 ------no component------- 1103P
The sum vs. pitch and yaw signals for the SRM QPD weren't making sense to me - centering on the PD lowered the sum, etc. So, I had a look at the SRM oplev setup.
The beam going in to the chamber looked fine, but the beam coming out was weird, like it was being clipped, or diffracted off of a sharp edge. The beam was spread out in yaw over almost 1cm as seen by eye. I looked into the vacuum window, and the beam was sitting on the edge of one of the in-vac steering optics. So, I adjusted the yaw of the beam-launching optic on the out of vac table so that I was roughly centered on both of the in-vac SRM steering mirrors. This required moving the first out of vac mirror for the SRM oplev path on the way to the QPD to move a small amount to one side, since the beam was near-ish the edge of the optic. I then centered the beam on the oplev (I had the SRM roughly aligned already).
Now the SRM oplev makes more sense to me. I have turned on FMs 1, 2, 5, 9 to match ITMY's loop shape. I have set the gains to -10 for pitch and +10 for yaw, to make the upper UGF about 6 Hz.
IP POS cable was swapped with old SP-QPD sn222 at the LSC rack. So there is NO IP POS temporarily.
This QPDsn222 will be used the HeNe oplev test for aLIGO
QPDsn222 is on translation stage with ND2 filter on SP table. The 1103P is mounted with two large V mounts 1 m away.
This qpd will be calibrated Monday. It has only slow outputs.
The PRM side was kicked up
Steve asked about calibrating the QPD, so I set up some new epics records so that we can have calibrated versions of the QPD output.
The new channels are called C1:ASC-TESTQPD_Y_Calc and C1:ASC-TESTQPD_X_Calc for pitch and yaw, respectively.
* I modified /cvs/cds/caltech/target/c1iscaux/QPD.db to add 2 new channels. Since we are currently plugged into the IPPOS channels, I didn't want to modify the units of IPPOS, which is why I created new channels. The new channels are just the IPPOS normalized X and Y channels, multiplied by a calibration factor. Steve has already done a rough calibration for his setup, so I used those numbers (0.15 urad/ct for pitch and 0.25 urad/ct for yaw).
* Rebooted c1iscaux. This required adding it to chiara's /etc/hosts file.
* Added the channels to the /opt/rtcds/caltech/c1/chans/daq/C0EDCU.ini file so that the channels would appear in dataviewer.
* Restarted the framebuilder daqd process.
How to modify the calibration:
1) On a control room workstation, cd /cvs/cds/caltech/target/c1iscaux to get to the right folder. (Note that this is still in the old cvs/cds place, *not* the new opt/rtcds place)
2) open the epics database file by typing sudo emacs QPD.db. Since this is a protected file, you need to use the "sudo" command, and will have to type in the usual controls password.
sudo emacs QPD.db
3) Find the "records" that have the channel names C1:ASC-TESTQPD_Y_Calc and C1:ASC-TESTQPD_X_Calc by scrolling down. (Right now they are on lines #550 and #561 of the text file).
4) For each of these 2 records, modify the calibration in the line that says something like field(CALC,"(A*0.25)"). In this example, the current calibration is 0.25 urad/oldCount. Change the number to the new value.
5) Save the file. If you followed the procedure in step2 and used the emacs program and you can't use the mouse, do the following: Hold down the "ctrl" key. Keeping ctrl pushed down, push the "x" key. Still keeping ctrl pushed down, push the "s" key.
6) Close the file. If you followed the procedure in step2 and used the emacs program and you can't use the mouse, do the following: Hold down the "ctrl" key. Keeping ctrl pushed down, push the "x" key. Still keeping ctrl pushed down, push the "c" key.
7) Reboot the slow computer called c1iscaux. You should be able to do this remotely by typing telnet c1iscaux, and then typing reboot. If that doesn't work, you may have to go into the IFO room and power cycle the crate by turning the key. This computer is in 1Y3, near the bottom.
8) Check that you can see your channels - you should be finished now!
For steps 3 and 4, here is a screenshot of the lines in the text file:
TEST QPD sn 222 was calibrated with 1103P directly looking into it from 1 m. ND2 filter was on the qpd.
Sep. 27, 2013 purchased 3 JDSU 1103P lasers, sn: P893516, P893518, P893519 ......2 spares ( also 2 spares of 1125P of 5 mW & larger body )
Sept. 5, 2014 new 1103P, sn P893516 installed at SP table for aLIGO oplev use qualification
The room temp drops 1 degree C on the 4th day. The weather has changed.
ITMY in vac table needs leveling.
ETMX is misbehaving again. I went to go squish his cable at the rack and at the satellite box, but it still happened at least once.
Anecdotally and without science, it seems to happen when ETMX is being asked to move a "big" amount. If I move the sliders too quickly (steps of 1e-3, but holding down the arrow key for about 1 second) or if I offload the ASS outputs when they're too large (above 10ish?), ETMX jumps so that it's about 50 urad off in yaw according to the oplev (sometimes right, more often left), and either 0 or 50urad off in pitch (up if right in yaw, down if left in yaw).
So far, by-hand slowly offloading the ASS outputs using the sliders seems to keep it happy.
I would ask if this is some DAC bit flipping or something, but it's happening for outputs through both the fast front ends (ASS offloading) and the slow computers (sliders moved too fast). So. I don't know what it could be, except the usual cable jiggling out issue.
Anyhow, annoying, but not a show stopper.
Okay, now ETMX's badness is a show-stopper. I'm not sure why, but after this last lockloss, ETMX won't stay put. Right now (as opposed to earlier tonight) it seems to only be happening when I enable LSC pushing on the SUS. ETMX is happy to sit and stay locked on TEM00 green while I write this entry, but if I go and try to turn on the LSC it'll be wacky again. Daytime work.
Anyhow, this is too bad, since I was feelin' pretty good about transitioning DARM over to AS55.
I had a line on (50 counts at 503.1 Hz pushing differentially on the ETMs), and could clearly see the sign flip happen in normalized AS55Q between arm powers of 4 and 6. The line also told me that I needed a matrix element of negative a few x10^-4 in the AS55Q -> DARM spot. Unfortunately, I was missing a zero (so I was making my matrix element too big by a factor of 10) in my ezcastep line, so both times I tried to transition I lost lock.
So. I think that we should put values of 0.5 into the power normalization for our test case (I was using SRCL_IN1 as my tester) since that's the approximate value that the DCtrans uses, and see what size AS55Q matrix element DARM wants tomorrow (tonight was 1.6-3 x 10^-4, but with 1's in the normalization matrix). I feel positive about us getting over to AS55.
Also, Q is (I assume) going to work some more tomorrow on PRMI->REFL165, and Diego is going to re-test his new IR resonance finding script. Manasa, if you're not swamped with other stuff, can you please see if you can have a look at ETMX? Maybe don't change any settings, but see what things being turned on makes ETMX crazy (if it's still happening in the morning).
I looked at what are the situations that make ETMX lose alignment.
This is not occur all that often this morning; less than 10 times in may be the last 4 hours of poking the X arm. I found that the bad behavior of ETMX also exists in certain other cases apart from the case when we enable LSC.
(I) Even the MISALIGN and RESTORE scripts for the suspensions make the suspension behave bad. The RESTORE script while in the process of bringing back the suspension to the place where it was, kicks it to some place else sometimes (even with LSC disabled)
(II) The suspension also gets kicked while realigning ETMX manually using sliders at 10^-3 (pace of 2-3 steps at a time).
I am suspecting something wrong right at the coil inputs and gains of the suspension.
Also, I recollect that we haven't done a check on the X arm LSC limiters and filters ramping times like it was done for the Y arm ( Elog 9877 ). We should do this check to be sure that we are not seeing a mixed puddle of problems from 2 sources.
PRM sus damping recovered and PMC locked.
We copied the new SRM filters over onto the OL banks for the ITMs and ETMs. We then adjusted the gain to be 3x lower than the gain at which it has a high frequency oscillation. This is the same recipe used for the SRM OL tuning.
Before this tune up, we also set the damping gains of the 4 arm cavity mirrors to give step response Q's of ~5 for all DOF and ~7-10 for SIDE.
PRM, SRM and the ENDs are kicking up. Computers are down. PMC slider is stuck at low voltage.
We noticed last night that the yarm couldn't handle the old nominal gain for the ASS servos. We were able to run the ASS using about 0.3 in the overall gain. So, I have reduced the gain in each of the individual servos by a factor of 3, so that the scripts work, and can set the overall gain to 1.
EDIT: some images look bad on the elog, and the notebook is parsed, which is is bad. Almost everything posted here is in the compressed file attachment.
As we've been discussing, we want to reduce the laser's jitter effect on the QPDs of the OpLevs, without losing sensitivity to angular motion of the mirror; the current setup is roughly described in this picture:
The idea is to place an additional lens (or lenses) between the mirror and the QPD, as shown in the proposed setup in this picture:
I did some ray tracing calculations to find out how the system would change with the addition of the lens. The step-by-step calculations are done at the several points shown in the pictures, but here I will just summarize. I chose to put the telescope at a variable relative distance x from the QPD, such that x=0 at the QPD, and x=1 at the mirror.
Here are the components that I used in the calculations:
I used a 3x3 matrix formalism in order to have easier calculations and reduce everything to matrix multiplications; that because the tilted mirror has an annoying addictive term, which I could get rid of:
Therefore, n the results the third line is a dummy line and has no meaning.
For the first case (first schematic), we have, for the final r and Theta seen at the QPD:
In the second case, we have a quite heavy output, which depend also on x and f:
Now, some plots to help understand the situation.
What we want if to reduce the angular effect on the laser displacement, without sacrificing the sensitivity on the mirror signal. I defined two quantities:
Beta is the laser jitter we want to reduce, while Gamma is the mirror signal we don't want to lose. I plotted both of them as a function of the position x of the new lens, for a range of focal lengths f. I used d1 = d2 = 2m, which should be a realistic value for the 40m's OpLevs.
Plot of Beta
Plot of Gamma
Even if it is a bit cluttered, it is useful to see both of the same plot:
Plot of Beta & Gamma
Apart from any kind of horrific mistakes that I may have done in my calculations, it seems that for converging lenses our signal Gamma is always reduced more than the jitter we want to suppress. For diverging lenses, the opposite happens, but we would have to put the lens very near to the mirror, which is somehow not what I would expect. Negative values of Beta and Gamma should mean that the final values at the QPD level are on the opposite side of the axis/center of symmetry of the QPD with respect to their initial position.
I will stare at the plots and calculations a bit more, and try to figure out if I missed something obvious. The Mathematica notebook is attached.
I stared a bit longer at the plots and thanks to Eric's feedback I noticed I payed too much attention to the comparison between Beta and Gamma and not enough attention to the fact that Beta has some zero-crossings...
I made new plots, focusing on this fact and using some real values for the focal lengths; some of them are still a bit extreme, but I wanted to plot also the zero-crossings for high values of x, to see if they make sense.
If we are not interested in the sign of our signals/noises (apart from knowing what it is), it is maybe more clear to see regions of interest by plotting Beta and Gamma in absolute value:
I don't know if putting the telescope far from the QPD and near the mirror has some disadvantage, but that is the region with the most benefit, according to these plots.
The plots shown so far only consider the coefficients of the various terms; this makes sense if we want to exploit the zero-crossing of Beta's coefficient and see how things work, but the real noise and signal values also depend on the Alpha and Theta themselves. Therefore I made another kind of plot, where I put the ratio r'(Alpha)/r'(Theta) and called it Tau. This may be, in a very rough way, an estimate of our "S/N" ratio, as Alpha is the tilt of the mirror and Theta is the laser jitter; in order to plot this quantity, I had to introduce the laser parameters r and Theta (taken from the Edmund Optics 1103P datasheet), and also estimate a mean value for Alpha; I used Alpha = 200 urad. In these plots, the contribute of r'(r) is not considered because it doesn't change adding the telescope, and it is overall small.
In these plots the dashed line is the No Telescope case (as there is no variable quantity), and after the general plot I made two zoomed subplots for positive and negative focal lengths.
If these plot can be trusted as meaningful, they show that for negative focal lengths our tentative "S/N" ratio is always decreasing which, given the plots shown before, it does little sense: although for these negative f Gamma never crosses zero, Beta surely does, so I would expect one singular value each.
ETMX sus damping restored and PMC locked manually.
Earlier this afternoon, while locking PRMI, I saw a big peak at 1883.48 Hz. This comes closest to the PRM's 627.75 Hz *3, so I infer that it is the 3rd order harmonic of the PRM violin mode.
While putting this in, I noticed that my addition of ETM filters the other day (elog 10746) had gotten deleted. Koji pointed out that Foton can do this - it allows you to create and save filters that are higher than 20th order, but secretly it deletes them. I went into the filter archive and recovered the old ETM filters, and split things up. I have now totally reorganized the filters, and I have made every single optic (ETMs, ITMs, PRM, SRM, BS, MC2) all the same.
FM1 is BS 1st and 2nd harmonics, and FM6 directly below that is a generic 3rd order notch that is wide enough that it encompases 3*BS.
FM2 is the PRM 1st and 2nd order, and FM7 below it is the PRM 3rd order.
FM3 is the SRM 1st order, FM4 is the ETMs' 1st order, and FM5 is the MC2 1st and 2nd order filters.
All of these filters are triggered on if any degree of freedom is triggered. They all have a ramp time of 3 sec. We may want to consider having separate trigger options for each optic, so that we're not including the PRM notch on the ETMs, for example, and vice versa.
When all of these filters are on, according to Foton we lose 5.6 degrees of phase at 100 Hz.
We looked at the spectra of POX and POY during IR lock, and Q saw a peak at 1285 in POX only. We're actuating on the ETMs, so it must be an ETMX violin mode, although it doesn't match the others that are in the table.
Anyhow, I added it to FM9. While I was doing that, I realized that yesterday I had forgotten to put back the 3rd order ETM violin notch, so that is also in FM9.
All suspensions were tripped. Damping were restored. No obvious sign of damage. BS OSEM-UR may be sticking ?
The BS was showing some excess motion. I think I've fixed it. Order of operations:
I'm not sure how this might have gotten switched on...