[Koji, Osamu and Kiwamu]
We found that the ETMX free swinging spectra showed a strange resonant frequencies.
We are going to inspect the suspension today.
In a ideal case the SOS (Small Optic Suspension) is supposed to have the following resonant frequecies.
(Although we didn't carefully identify which corresponds to which)
f_POS ~ 0.98 Hz
f_PITCH ~ 0.66 Hz
f_YAW ~ 0.8 Hz
f_SIDE ~ 0.99 Hz
However ETMX showed the following resonant frequencies.
f_POS ~ 0.91 Hz
f_PITCH ~ 0.7 Hz
f_YAW ~ 0.93 Hz
f_SIDE ~ 1.0 Hz
Especially f_YAW looks pretty high. Also the others are not at the right frequencies.
So we are suspicious that something wrong is happening on the ETMX suspension.
We checked the ETMX suspension and found the UR OSEM was close to the magnet.
So we rotated the UR OSEM so that it won't touch the magnet any more.
We will check the resonant frequencies again by taking the spectra.
In fact the ETMX stacked when we applied a big angular offset to Yaw direction.
This was because that the magnet was actually touching the UR OSEM.
The earthquake stops were fine, they weren't touching the test mass.
Also we looked at the wire and the standoffs, they seemed fine.
We aligned the beam axis pointing down to both X and Y arm.
Now the beams are hitting the centers of both ETMX and ETMY.
Amazingly Osamu made X arm flashing by aligning the cavity.
(what we did)
- opened almost all the chambers except for the MC2 chamber.
- locked and aligned the MC.
We set Marconi to the right frequency, which had been set to the default values, probably due to the power outage in the last weekend.
Also we found a DAC cable disconnected from the IO chassis of c1sus. So we connected it in order to damp the MC suspensions.
- aligned MMT2 and PZT2 in order to let the beam go through the center of PRM.
- checked the beam centering at the two TTs (PR2, PR3).
- rotated PR3 to make the beam go through the centers of both ITMY and BS at the same time.
- tried finding the beam spot at the ETMY chamber, and successfully found it.
To see such faint beam spot, we used an IR viewer.
In addition to that, we put a large piece of aluminum foil as a screen in the chamber.
- aligned the beam to the center of ETMY by tweaking the PZT mirror (SM2).
- aligned the BS so that the reflected beam at the BS goes through the center of ITMX.
- tried finding the beam spot at the X end, and successfully found it hitting the wall in the chamber.
- aligned the BS in order to let the beam hit the center of ETMX.
- tried aligning ETMX and ITMX to the beam.
Eventually we made the X arm flashing.
However the flash was a bit too weak to completely align the cavity.
(plan for tomorrow)
- reinstall some steering mirrors into the BS chamber
- check and neutralize PZT1
- alignment of IP_ANG
Good news. I feel multi-chromatic-locking success is just around the corner.
By the way, there's a new presentation on the DCC from the ANU group where they've locked a short single cavity with both colors - G1000735:
This plot shows ETM oplev and OSEM trend for 10 hours on day before yesterday as almost the same as plot shown this entry. I reported the 10-30minites fluctuations were seen, but I noticed it comes from not suspension but from oplev power fluctuation.
After Kiwamu fixed the ETM OSEM touch yesterday afternoon, still the same trend was seen, so we had thought what we fixed was not enough. This morning I looked at the yesterday's and day before yesterday's trend and noticed the simila trend both the pit and yaw in ETM oplev but not on the OSEM trend. Kiwamu suggested me to put the oplev sum on the same plot. It was!
So, ETMX is not bad, but in fact, still alignment fluctuation exist on the cavity. ITM?
This graph shows 5 hours data in minute trend for ITMX and ETMX from 5am to 10 am today. ITM pitch drift is 3 times lager than ETM pitch if the OSEM sensitivity is assumed to be the same.
This graph is last 1 hour data of above graph in second trend.
It is clealy seen that ITM yaw is jumping between two stages. I guess ITM is something wrong, touching magnets or earthquake stops?
I wish I could use a bigger font for this, but, the suspension work is totally done for the upgrade!!!
Now, nobody break any suspensions, or we're not going to be friends for a while.
Koji and I put ETMY back in its tower, and made sure that both scribe lines are at the correct height. We also confirmed that the balance is good (as Suresh mentioned in a previous elog, since we balanced using the AR surface, the HR surface is pointing downward a little bit, but it's well within the OSEMs ability to correct.
While we were in there, we also looked at Tip Tilt number 002. As mentioned in elog 3645, the pitch pointing was off by a little bit. Since the TTs don't have actuators, the pointing has to be pretty good. We tweaked the balancing, and now the reflected beam goes completely back into the laser aperture, so it's as balanced as it's going to get. This TT is now ready for installation onto the ITMY table as part of the SRC.
Kiwamu confirmed that he's going to install these optics tomorrow, since he's doing some other alignment work today.
Just for good measure, the Table:
I found that a few connections in the simulink model of c1scx was incorrect, so I fixed them correctly.
It had been a mystery why we had to put a funny matrix on ETMX (see this entry).
But now we don't have to do such a voodoo magic because the problem was solved.
Now the damping of ETMX is happily running with an ordinary output matrix.
I looked at the wiring diagram of the ETMX suspension (it's on Ben's web page) and confirmed that the coils are arranged in order of UL, LL, UR, LR.
But then I realized that in our simulink model they had been arranged in order of UL, UR, LL, LR.
So UR and LL had been swapped incorrectly !
So I just disconnected and plugged them into the right outputs in the simulink model.
I rebooted c1iscex in order to reactivate c1scx front end code.
After rebooting it, I changed the output matrix to the usual one, then everything looked okay.
(actually it's been okay because of the combination of the wrong connections and the funny matrix).
The alignment of the ITMs and the PRM has been done.
As a result their reflections now come out at the REFL port successfully.
The vacuum work is going on well as we scheduled at the last meeting.
(plan for tomorrow)
- installation of ETMY
- installation of OSEMs on ETMY
- alignment of the beam to the center of ETMY
- alignment of the ETMY to the beam
- final alignment of IP_ANG
- setting up the oplev for ETMY
- replace one of the steering mirrors at the RFEL path by a 0 deg mirror (see here).
- setting up POX/POY (if there are time)
- aligned the PRM tower such that the reflected beam goes back to exactly the same path as that of the incoming beam.
- leveled the ITMY table because the OSEMs of ITMY had been completely out of range.
- aligned the ITMY and ITMX in order to let the reflections back to REFL.
- with a help from Osamu, we put a CCD camera, which actually had been used as OMC_T, just after the view port on the AP table.
- looking at the CCD monitor we were able to see the reflected lights from the ITMs. (In fact sensor cards didn't help looking for the lights.)
- playing with the alignment of the ITMs, we easily obtained Michelson fringes, which were also visible on the CCD monitor.
[Zach and Kiwamu]
We installed the new ETMY tower and successfully aligned the beam to the center of ETMY.
Also we finished the final alignment of IP_ANG.
(what we did)
- took the old ETM out from the chamber and put it on the flow bench at the X end.
- with a help from Joe and Osamu, we brought the new ETM and put it roughly on place.
- did a fine positioning of ETMY.
- covered the ETM tower with a large peace of aluminum foil in order to see the spot on a video monitor.
- stoled a compact video monitor that was sitting on the PSL table since we don't have any monitors at the Y end.
- made a ~1cm hole on the foil as a target for the beam.
- steered PZT1 in order to correct the beam position on ETMY. This is done by looking at the spot on the video monitor.
- steered IPANG_SM1 to let the beam hit a steering mirror in the ETMY chamber which Koji installed recently.
Now we have IP_ANG coming out from the viewport of the ETMY chamber.
[Koji, Oasmu and Kiwamu]
We made the following progresses :
(1) installation of the last TT called SR2.
(2) fixing an earthquake stop issue on the BS
(3) fixing a clipping of beams at the dark port
(earthquake stops on the BS)
- When we were aligning the BS, we found that the BS showed funny behaviors.
For example a kick on LR didn't shake LRSEN, and a big DC angular offset (~ 8 in the medm screen ) was needed to keep a horizontal beam axis in the reflection.
We checked all the earthquake stops and found two suspicious earthquake stops at right bottom side.
They looked like slightly touching the BS. So we moved them further away from the BS.
Then the problem had gone. We doublechecked the health by kicking, applying an angular offset and so on.
We found transmitted/reflected beams from the BS to the dark port was clipped at the BS tower.
We moved the BS tower by ~1cm and realigned the rotation of the BS tower.
We also found the beam spots on the two TTs, PR2 and PR3, were offcentered. Especially the beam spot on PR3 was almost on the edge of the mirror.
Probably this was because we touched PZT1 when aligning the beam to the Y end.
So it means, it is not a good idea to align the beam to the end only by steering PZT1. We should use PR2 and PR3 as well when we align the beam to the Y end.
We realigned them such that the beam hits the center of PR2, PR3 and ETMY.
We worked on some more vacuum businesses. Today we finished did the following works:
- alignment of the POX mirrors
- alignment of the POP1 and POP2 mirrors
- installation of OSEMs onto SRM
- alignment of the SRM tower
(alignment of POP mirrors)
Since a beam on the POP path was quite too weak to see even by IR viewers, we used a He-Ne laser to imitate the real beam instead.
We injected the He-Ne beam from an optical bench to the chamber, and made it go through the PRM and PR2 by using some steering mirrors.
The pin assignment was flipped in a way of mirror image due to the extension cables which cause a mirroring.
So we made mirroring connectors to flipp them back to the correct pin assignment, and plugged the mirroring connectors in between the feedthrough of the BS chamber and the SRM satellite box.
This is a picture showing how they are connected now.
The sole thing that has been deviated from the optical layout was that the SRM returning beam had to be reroute
as the SRM has better reflectivity on the AR surface in stead of the HR one.
I suppose that if we were really clever we would intentionally choose either the AR or HR surface so as to minimize the effect of the thermal lensing and/or thermal expansion from the locked interferometer absorption.
[Kiwamu, Jenne, Koji, Osamu]
We have mostly prepared the IFO for pump down.
After lunch [Steve, Bob, Koji, Kiwamu, Jenne, Joe, Joon Ho, Vladimir, Osamu] put the access connector back in place. Hooray! Steve still has to check the Jam Nuts before we pump down. Kiwamu checked the leveling of the IOO table, and fixed all of the weights to the table.
For all 4 test masses, bars (upside-down dog clamps) were placed to mark the alignment of 2 sides of the suspension tower. All test mass tables were re-leveled, and the weights fixed to the tables.
For ETMY, PRM, BS, SRM, we confirmed that the OSEMs were close to their half-range. ETMX was already fine. ITMY (the screens and the optics wiki are still old-convention, so this is listed as ITMX! No good!) OSEMs are pretty much fine, but ITMX desperately needs to be adjusted. Unfortunately, no one can find the standard screwdriver (looks like a minus), to adjust the ITM OSEMs. All the other towers had hex-key set screws, but the ITMs need a screwdriver. We will ask Bob to sonicate a screwdriver in the morning.
Yesterday, a sequence of force and gain measurement was made to determine the imbalance in the
quadrant, magnetic-levitation prototype. This was the reason why it failed to achieve a stable levitation.
The configuration is shown schematically by the figure below:
Specifically, the following measurements have been made:
(1) DC force measurement among four pairs of magnets at fixed distance with current of the coils on and off
From this measurement, the DC force between pair of magnets is determined and is around 1.6 N at with a
separation of 1 cm. This measurement also lets us know the gain from voltage to force near the working point.
The force between pair "2" is about 13% stronger than other pairs which are nearly identical. The force by the
coil is around 0.017 N per Volt (levitation of 5 g per 3 Volt); therefore, we need around 12 volt DC compensation
of pair "2" in order to counterbalance such an imbalance. Given the resistence of the coil equal to 26 Om, this
requires almost 500 mA DC compensation. Koji suggested that we need a high-current buffer, instead of what
has been used now.
(2) DC force measurement among four pairs of magnets (with current of the coils off) as a function of distance
From this measurement, we can determine the stiffness of the system. In this case, the stiffness or the
effective spring constant is negative, and we need to compensate it by using a feedback control. This is
one of the most important parameters for designing the feedback control. The data is still in processing.
(3) Gain measurement of the OSEM from the displacement to voltage.
This measurement is a little bit tricky due to the difficulty to determine the displacement of the flag.
After several measurements, it gave approximately 2 V/cm.
Plan for the next few days:
From the those measurements, all the parameters for the plant and sensor that need to determine the
feedback control are known. They should be plugged into the simulink model and to see whether the
old design is appropriate or not. Concerning the experimental part, we will first try to levitate the configuration
with 2 pairs of magnets, instead of 4 pairs, as the first step, which is easier to control but still interesting.
The crontab for op340m which runs various IFO maintenance activities has been set to the wrong path for the watchdog rampdown script since the CDS changeover.
This is a dangerous situation. With the watchdog thresholds set as high as 1000, the magnets can be broken if the new CDS has some mental problems. This kind of thing happened before at LHO (which is why Stan invented the watchdogs). Please try to make sure that the watchdog thresholds are not set that way - its our only defense against bad CDS.
I've now corrected the crontab. The watchdog thresholds are being stepped down every 30 minutes as before.
However, out test points are gone again, so who knows how things are behaving.
I have put an offset of 1000 counts to C1:SUS-ETMX_ALS_OFFSET. This actually misalign the mirror a lot.
While the offset is applied. I adjusted the balance of the coil matrix.
UL 1.580 UR 0.620
LL 0.420 LR 1.380
> ezcaread C1:SUS-ETMX_TO_COIL_0_0_GAIN
C1:SUS-ETMX_TO_COIL_0_0_GAIN = 1.58
> ezcaread C1:SUS-ETMX_TO_COIL_0_1_GAIN
C1:SUS-ETMX_TO_COIL_0_1_GAIN = 0.62
> ezcaread C1:SUS-ETMX_TO_COIL_0_2_GAIN
C1:SUS-ETMX_TO_COIL_0_2_GAIN = 0.42
> ezcaread C1:SUS-ETMX_TO_COIL_0_3_GAIN
C1:SUS-ETMX_TO_COIL_0_3_GAIN = 1.38
Now, we can keep TEM00 for green with +/-1000counts of push although the fast step of the offset make the lock lost.
It turned out that the step longitudinal input temporary misalign the mirror in pitch because the length and pitch are coupled.
I guess that we don't excite pitch if we push the mirror slowly. Eventually, we need f2p transfer function adjusted in the output matrix.
I sat down in the control room to find that ETMX and PRM's watchdogs had been tripped. I don't know how long they've been crazy, but there was a big something that showed up in the seismometers around 16:30UTC, or ~11:30 this morning. I don't find any significant earthquakes on the USGS site for that time though, so it might be more local, i.e. work next door or trucks or whatever.
I take back the suggestion that it was that seismic event. Clearly the PRM and the ETMX were kicked at different times, neither of which is the same as the seismic action. Mystery. You can see they have been ringing down for a while though, which is neat.
All of the SUS used to have only 1 filter module for SIDE. They now have 3 filter modules for SIDE just like the other DOFs.
Today I moved the filters around so that the sensor filters are in SDSEN, the servo filters are in SUSSIDE, and the dewhitening for the coil is in SDCOIL.
I noticed along the way that the bounce/roll mode notches for all of the suspensions are still set for the frequencies of the previous suspensions. Suresh has 'volunteered' to find the new frequencies and make the new bandstop filters by looking up the seminal work on this by Dan Busby / Sam Waldman.
The f2p measurements are done on ETMX and ITMX with the real time lockin systems.
The f2p measurements are done on ETMX and ITMX with the real time lockin systems.
I don't explain what is the f2p measurement in this entry, but people who are interested in it can find some details on an old elog entry here or somewhere on DCC.
So far the resultant filters looked reasonable compared with the previous SRM f2p filters.
- backgrounds -
Some times ago I found that the coils on ETMX had not been nicely balanced, and it made a POS to angle coupling when I tried green locking (see here).
In addition to that, accuracy of A2L kind of measurement including the dithering techniques depend on how well the coils are balanced. Therefore we need to balance the coils basically at all the suspended optics.
There used to be a script for this particular purpose, called f2praio.sh. This script does measure the imbalances and then balance the coils.
However this time I used the realtime lockin system to measure the imbalances instead of using the old f2p script.
One of the reasons using the real time system is that, some of the ezca and tds commands for the old script don't work for some reasons.
Therefore we decided to move on to the real time system like Yuta did for the A2L measurement a couple of months ago.
The f2p measurement finally gives us parameters to generate a proper set of filters for POS and also the coil gains. We apply those filters and the gains in order to eliminate the POS to angle coupling and to balance the coils.
- results -
The followers are the resultant filters and coil gains.
The plots below show new f2p filters according to the measurement.
ITMX (assuming pendulum POS has f0 = 1 Hz and Q = 1)
ULPOS fz = 1.009612 Qz = 1.009612
URPOS fz = 1.125965 Qz = 1.125965
LLPOS fz = 0.873725 Qz = 0.873725
LRPOS fz = 0.974418 Qz = 0.974418
ETMX (assuming pendulum POS has f0 = 1 Hz and Q = 1)
ULPOS fz = 1.055445 Qz = 1.055445
URPOS fz = 1.052735 Qz = 1.052735
LLPOS fz = 0.944023 Qz = 0.944023
LRPOS fz = 0.941600 Qz = 0.941600
C1:SUS-ETMX_LLCOIL_GAIN = 1.07233
The precision of the coil gains looked something like 1% because every time I ran the measurement script, the measured imbalances fluctuated at this level.
The precision of the filter gain at DC (0.01 Hz) could be worse, because the integration cycles for the measurement are fewer than that of the coil gains done at high frequency (8.5 Hz).
Of course we can make the precisions by increasing the integration cycles and the excitation amplitudes, if we want to.
The plot below shows how the f2p filters work.
At -2 min I turned on the f2p filters.
Cheater cables for SRM sus tied up. They were dangling aimlessly on the floor.
As a part of the DRMI preparation,
I leave all the suspensions free from the watchdogs for 5 hours from now.
Please DO NOT touch them.
I will check the spectra and the mechanical resonant frequencies on Monday.
Also I will renew all the input matrices of the local dampings based on these free swinging spectra.
There is a useful script for this particular job : shutting down all the suspensions and bringing it back to operation after 5 hrs.
It is called opticshudown, which resides in /cvs/cds/rtcds/caltech/c1/scripts/SUS/.
Also I added this script on the list in the wiki where all the scripts will be listed.
If you find any other useful scripts, please add them on the wiki.
I had a quick look at PRM optical lever.
The He-Ne beam is still successfully coming out from the chamber and I could guide it to the QPD by using steering mirrors.
But the beam size looks too big for the QPD. We should slide the lens which is standing before the injection to get a moderately smaller beam size at the QPD.
- activation of PRM oplev
The returning spot diameter on the qpd ~10 mm. In order to reduce the spot size I moved the f 1145 mm lens toward the PRM ~ 25 cm. The spot size was reduced to ~8 mm, 3200 counts.
I'll try to find an other lens tomorrow.
Here are the free-swinging spectra for the BS, ETMX, ETMY, ITMX, ITMY, MC1, MC2, MC3, and PRM chambers. Kiwamu left the suspensions free for 5 hours this weekend, starting at Sat Apr 30 00:15:26 2011.
This is GPS time 988 182 941. Quick tip: you can do local to GPS time conversions using lalapps_tconvert, which is a lot like tconvert but with special powers. It is installed on pianosa.
$ lalapps_tconvert Sat Apr 30 00:15:26 2011
I generated these figures with the attached Python script, measure.py.
Notice that the C1:SUS-ITMX_SENSOR_UL and C1:SUS-MC3_SENSOR_UL spectra fall as 1/f. Jenne suggested that this might indicate that there is a loose electrical connection.
Also, notice that C1:SUS-ETMY_SENSOR_LR, C1:SUS-ITMY_SENSOR_LL, and C1:SUS-PRM_SENSOR_SIDE are a lot noisier above 10 Hz.
Jenne went through all the suspension racks and pushed all the connectors.
After pushing them, we had a quick look at those spectra and found no funny noise spectrum except for C1:PRM-SENSOR_UL.
We then checked connection around the SCSI cables and eventually found the connection between ADC_card_0 and a SCSI was loose.
We put short standoffs on the ADC card so that the screws from the SCSI can nicely reach to the ADC card. Now everything looks fine.
SUS diagnostic is quite useful !
Atm 1, PRM oplev inward path with 2 lens solution: 14 cm gap between F 1145 and F 1545 mm lenses.
Atm 2, The PRM beam size 3 mm and the beam quality is still bad. The BS path only needed alignment.
[Leo w/ a little help from Kiwamu]
Leo summarized the mechanical resonances of all the suspensions, based on the free-swinging spectra taken on Sat Apr 30.
Since Leo doesn't have the wiki account I helped him putting the information on the wiki.
Good work, Leo !
I am tuning the notch filters for the bounce modes in the suspensions, starting with the ITMs and ETMs. I'll do the MCs, the PRMs, and the SRMs next.
I noticed that the filter for ITMX (in the file C1SUS.txt, the module ITMX_SUSPOS, the selection BounceRoll) that the filter was composed of two bandstops (and a constant gain). It looked like this:
Valera said that one of these was for the roll mode and the other for the bounce mode. However, looking at the spectra that Kiwamu and I made this week, I don't perceive a resonance between 11.4 and 12.2 Hz. So, we're taking a guess that this was for a mode that has moved due to new pendulum designs. For many of the suspensions, in the free swinging test we noticed a line around 23 Hz; we thought we might as well re-use one of these elliptical filters to avoid exciting this line. Of course, if this line does *not* result from excitation of an uncontrolled degree of freedom, this will not help and could be detrimental. When we talk to Valera again, we can review this decision and at that point we might decide just to take out that bandstop.
ITMX is done. I'll continue tomorrow. I've attached closed-loop spectra for before the tuning (itmx-before.pdf) and after (itmx-after.pdf).
(Update: the following day, I took closed loop spectra with (itmx-withbounceroll.pdf) and without (itmx-nobounceroll.pdf) the bandstops. It looks like the bandstops made the bounce mode slightly worse, but the roll mode slightly better.)
I tuned the ITMY bandstops -- 'before' and 'after' spectra attached. Note that the after the tuning, the bounce mode at ~16 Hz is about twice as quiet!
However, notice that in the 'before' plot the roll mode at about 23.5 Hz did not show up at all, whereas it is quite prominent in the 'after' plot. I was concerned that this line could have been a result of placing the bandstop there, so I made another plot with the BounceRoll filter turned off. Sure enough, the 23.5 Hz line is still there. So I'm not crazy: the roll mode did start acting up at some time between my 'before' and 'after' plot, but not as a result of the tuning.
The SRM qpd cable was removed from the BS-table. It's path was changed from 1x4 to ITMY-table following the inner cable tray.
New f2p filters were installed on ETMY.
The statistical error of the coil gain settings are now about 0.8% at high frequency (i.e. above the resonant freq of the pendulum mode)
What I did :
- measured and corrected the coil imbalances on ETMY using a script called F2P_LOCKIN.py
- made the new f2p filters based on the measurements and installed them.
Next step :
- do the same adjustment for all the suspensions including PRM, SRM, BS, ITMs and ETMs
(Notes on F2P_LOCKIN.py)
F2P_LOCKIN.py is a script that I've made in python. This is basically the same as the old script, f2pratio, but uses the realtime LOCKINs instead of ezcademods.
The script automatically measures the coil imbalances on an optics of interest by driving the local LOCKIN oscillators.
In the first step the script automatically balances the coil gains at high frequency (8.5Hz).
In the next step it gives some coefficients, which basically represent the coil imbalances at low frequency (0.01Hz)
Then with those coefficients one will be able to design the f2p filters.
It is not well polished yet, so I will spend some more times to make it user-friendly and readable.
Example usage : F2P_LCKIN.py -o ETMX
It currently resides in /cvs/cds/rtcds/caltech/c1/scriptss/SUS/
(new f2p filters)
The plot below shows the new f2p filters. Note that they are already installed.
I found that a He-Ne laser which has been used for ETMX_OPLEV was NOT giving the light.
Since I didn't find the switch key for it I have no idea if the laser is simply off or dead.
The dead laser was replaced by new JDSU 1103P of 2.6mW. The return beam is big ~5 mm diameter of 0.3 mW, 1400 counts
Laser diode oplev SRM is working. Qpd matrix values were reset like others.
In 0.44mW, returning 0.1mW, -500 counts.
New f2p filters were installed on ITMY this morning. The statistical error of the coil gain setttigs are about 0.6 % at high frequency.
NEXT : PRM, SRM, BS, ITMX and ETMX.
Pendulum mode = 0.988 Hz, Q = 1
C1:SUS-ITMY_ULCOIL_GAIN = 1.02482
C1:SUS-ITMY_URCOIL_GAIN = -1.06831
C1:SUS-ITMY_LLCOIL_GAIN = -0.996671
C1:SUS-ITMY_LRCOIL_GAIN = 0.91079
UL: fz = 1.014824 Hz, Q = 1.027150
UR: fz = 0.975038 Hz, Q = 0.98688
LL: fz = 1.000229 Hz, Q = 1.012378
LR: fz = 0.972688 Hz, Q = 0.946116
The coil imbalances are now about 0.8% at high frequency (i.e. above the resonant freq of the pendulum mode)
The dead laser was replaced by new JDSU 1104P of 2.6mW. The return beam is big ~5 mm diameter of 0.3 mW, 1400 counts
Whenever replacing any Oplev laser, please also put into the ELOG when it was installed so that we have an electronic record of the laser lifetime.
I tuned the bounce and roll mode bandstops for ETMY, although it was difficult for me to tell if there was improvement with the bandstops on relative to the bandstops off because it seemed like the bounce and roll modes were being excited intermittently. I'll take spectra with the filters both on and off during an evening next week.
The f2p adjustment for all the suspensions are done (except for MC1,2,3)
Last night I found that the sign of the oplev control of PITCH on ETMY was wrong. I flipped it to the correct sign.
We've been locking the Y arm by feeding a signal back to ITMY because pushing ETMY somehow made the lock unstable in the angular motion.
After the correction of the oplev contol sign, I was able to keep the lock robustly by pushing ETMY.
Today Steve was working around the 1X5 rack to strain relief the cable jungles and the jungle is now getting less jungle.
During the work he disconnected and reconnected some cables.
So for a doublecheck I checked all the suspensions to see if the suspensions are still healthy or not.
Aha, then I found a mistake.
See the pictures below. It's a very subtle difference. This wrong connection prevented MC1 and MC3 from damping.
The UL signal of the shadow sensor on ETMY went to zero this evening.
This was due to a loose connection on the cross connection board on the 1Y4 rack.
In order to make them tighten, a combination of stand-offs and screws were installed on the connectors. They won't be loose any more.
ETMY's watch dogs were found tripped. They were restored.
A new library part was made for the single suspension controller (it was originally made from the c1scx controller), using the following procedure:
Once the new sus_single_control library part was made and the library was committed to the cds_user_apps repo, I replaced all sus controller subsystems with this new part, in:
All models were rebuild, installed, and tested, and everything seems to be working fine.
Some weeks ago, Joe, Jamie, and I reworked the ETMY controls.
Today we found that the model rebuilds and BURT restores have conspired to put the SUS damping into a bad state.
1) The FM1 files in the XXSEN modules should switch the analog shadow sensor whitening. I found today that, at least on ETMY and ETMX, they do nothing. This needs to be fixed before we can use the suspensions.
2) I found all of the 3:30 and cts2um buttons OFF AGAIN. There's something certainly wrong with the way the models are being built or BURTed. All of our suspension tuning work is being lost as a consequence. We (Joe and Jamie) need to learn to use CONLOG and check that the system is not in a nonsense state after rebuilds. Just because the monitors have lights and the MEDM values are fluctuating doesn't mean that "ITS WORKING". As a rule, when someone says "it seems to work", that basically means that they have no idea if anything is working.
3) We need a way to test that the CDS system is working...
We measured the OSEM PD whitening transfer function of the ETMX OSEM UL whitening stage (D000210) by comparing the input signal to the whitening amplifier (single pin LEMO monitor) to the output signal - both were piped into the DAQ. The transfer function was close to constant 0 dB/180 deg independent of the whitening switch selection (FM1 filter engaged/disengaged) up to ~20 Hz where we run out of coherence. All other ETMX and ETMY spectra at the input of the digital whitening compensation don't change when the whitening is switched on/off so by induction we conclude that all the ETMX/ETMY OSEM PD hardware whitening filters are not on.
Joe discovered today that ETMY in fact has no binary output module at all, so there is actually no digital control of the whitening filters at ETMY.
We suspect that the ETMY binary output module was maybe harvested to put in the LSC rack, but we're not sure.
We found a spare binary output adapter pcb, which I will try to assemble into a module to install in ETMY.
This does not explain what's going on with ETMX, though. ETMX has a binary output module, that appears to be properly hooked up. I'll try to debug what's going on there as well.
In the mean time, I've removed the ETMX binary output module to use as a reference for putting together another identical module for ETMY.
I checked the state of the whitening filters for the ETMY shadow sensors.
Result : They've been OFF (i.e. flat response).
(measurement and setup)
I measured the transfer functions of the whitening board (D000210) by looking at the signal before and after the whitening stage.
The whitening board handles five signals; UL, UR, LR, LL and SD, and there are five single-pin lemo outputs for each signal on the front panel.
A good thing on those lemo monitors is that their signals are monitored before the whitening stages.
Rana suggested me to use these signals for the denominator of the transfer functions and consider the sensor signals as excitation signals.
So I plugged those signals into extra ADC channels via an AA-board and measured the transfer functions.
In the measurement the coherence above 4 Hz was quite small while the suspension was freely swinging.
Therefore I had to excite the ETMY suspension by putting random noise in a frequency band from 5 Hz to 35 Hz to obtain better coherence.
The response is flat over frequency range from ~ 0.2 Hz to ~40 Hz, see the plot below.
According to the spectrum of each signal the measurements above 10 Hz are just disturbed by the ADC noise.
If the whitening filters are ON, a pole and zero are expected to appear at 30 Hz and 3 Hz respectively according to the schematic, but no such features.