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ID Date Author Type Categoryup Subject
  8720   Wed Jun 19 01:12:42 2013 JenneUpdateASCmodel name ASS -> ASC ???

I am proposing a model name change.  Currently, we have an "ASS" model, but we do not have an "ASC" model. 

The ASS is currently using ~17 of 60 available microseconds per cycle.  So, we have some cpu overhead available to put more stuff on that cpu. Like, say, ASC stuff.

So, my proposal is that we change the ASS model name to "ASC", and put all of the ASS-y things in a top_names block, so we retain the current channel names.  The IOO top_names block that is in the current ASS model (which is there to send signals to the LSC DAC for the input tip tilts, even though the names need to be IOO) should obviously stay on the top level, so that things in there retain their names.

Then, I can make a new top_names sub-block for ASC-like things, such as the new POP QPD. 

Inside the ASC block (in the ASC model), I'm currently thinking something simple will do..... QPD inputs, going to a matrix, which outputs to the filter banks in the "length" degree of freedom basis (PRCL, SRCL, etc), then another matrix, going to the ASC suspension paths. 

So, for example, the POP QPD pitch would go to the PRCL_PIT filter bank, and then on to the PRM_ASCPIT path in the SUS screen.

Or, in another example case, IPPOS yaw would go to an input pointing filter bank, then on to TT1's yaw slider.

EDIT:  After a few minutes of thinking, I think I also want triggering, and perhaps filter bank triggering, in the ASC model.  One of the reasons Koji has been pushing for the new automation system is that when the PRC fell out of lock, the ASC path would kick the PRM until Koji ran a down script.  Triggering will fix this issue, and it's the kind of thing that needs to happen quickly, so may not really be appropriate for the Guardian anyway.

  8723   Wed Jun 19 04:56:07 2013 KojiUpdateASCmodel name ASS -> ASC ???

Sounds good.
Or we just stuff any angle control things in to Angular Stabilization System without changing the model name.
The process name itself is not a big deal.

  8728   Wed Jun 19 22:02:03 2013 JenneUpdateASCNew POP path - ready to try

I put the POPDC cable back to the DC output of the bias tee that is the first thing at the LSC rack that the POP110 PD sees.  So, now we should be back to the old nominal PRCL locking, with the addition of the new QPD.

I'm going to give it a whirl.....

  8805   Mon Jul 8 15:31:48 2013 JenneUpdateASCPOP QPD calibration prep

I am prepping to do the POP QPD calibration, and so have turned off the POP QPD, and put it onto a micrometer stage.  My plan is to (after fixing the ASC servo filters to make the servo AC coupled, rather than DC coupled) lock the PRM-ITMY half cavity, and use that beam to calibrate the QPD.  While this isn't as great as the full PRMI, the PRMI beam moves too much to be useful, unless the ASC servo is engaged.

While on the table, I noticed 2 things:

* In order to place the micrometer, I had to temporarily move the POP55 RFPD (which has not been used in quite a long time).  I think it's just that the panel-mount SMA connector isn't tight to the panel inside, but the RF out SMA cable connector is very loose.  I have moved the POP55 RFPD to the very very south end of the SP table, until someone has time to have a quick look. (I don't want to get too distracted from my current mission, since we haven't put beam onto that PD for at least a year).

* The ITMX oplev beam setup isn't so great.  The last steering mirror before the beam is launched into the vacuum is close to clipping (in yaw... pitch is totally fine), and the steering mirror outside of vacuum to put the beam on the QPD is totally clipping.  The beam is falling off the bottom of this last steering mirror.  Assuming the beam height is okay on all of the input optics and the in-vac table, we need to lower the last steering mirror before the oplev QPD.  My current hypothesis is that by switching which in-vac steering mirror we are using (see Gautam's elog 8758) the new setup has the beam pointing downward a bit.  If the problem is one of the in-vac mirrors, we can't do anything about it until the vent, so for now we can just lower the out of vac mirror.  We should put it back to normal height and fix the oplev setup when we're at atmosphere.

  8808   Tue Jul 9 01:18:48 2013 Nic, KojiUpdateASCPRMI locking / PRM ASC adjustment

[Koji, Nic]

- Locked PRMI with REFL165 I/Q

- Aligned the POP beam on the QPD. We found that the vertical motion of the beam appeared in the yaw signal, and horizontal motion in the pitch signal.
  This was fixed by swapping the cables to the ADC. Later it turned out that this was caused by the calibration setup for the QPD.
  We requested Jenne to fix the QPD on the table with the current orientation.

- Re-implemented the AC-coupled ASC servo. The filters were just copied from the previous PRM ASC servo (in the SUS ASC filter).
  The same filter was installed to the pitch and yaw filter modules for now. The gains were adjusted to have some stable lock stretches.
  C1:ASC-PRCL_YAW_GAIN: -0.01
  C1:ASC-PRCL_PIT_GAIN: -0.01

  The power spectra of C1:ASC-PRCL_YAW_IN1 and C1:ASC-PRCL_PIT_IN1 were attached.
  The reference curves are the ones with the servo on. The other two are the free-running stability of the QPD output.

- Modified the up and down scripts for the PRM ASC for the new setup.
  It first turns on the inputs of the filters and then turn on FM2/3.
  It assumes that the outputs are engaged all time.

 

  8810   Tue Jul 9 11:41:22 2013 JenneUpdateASCPOP QPD calibration attempt

I was bad, and forgot to elog the most important part of my work yesterday - that I had rotated the POP QPD by 90 degrees, so that I could fit the micrometer onto the table.  There is a sticker on the front of the QPD to indicate which direction is "X" and "Y" for the output of the readout box.  Right now (and the way that I will mount the QPD to the table, after I redo the calibration today), X is PITCH, and Y is YAW.  Koji and Nic swapped the cables to the ADC to make this all consistent.

Yesterday, I locked the PRM-ITMY half cavity, and tried to take calibration data.  However, with no ASC servo engaged, the beam was still moving.  Also, with only the half-cavity, I had very little light on the QPD, and since it has internal normalization, the outputs can get a little funny if there isn't enough light.  I had checked, and even with the gain cranked up to maximum, the "light level too low" LED was illuminated.  So, my calibration data from yesterday isn't really useful.

Today, hopefully after lunch, I will lock the PRMI with the new AC-coupled ASC servo, so that I can have the servo on, and the PRMI locked on the sideband, so that I have more light on the QPD. 

After that, it seems that the final thing we need to do before we vent is hold an arm near, but off resonance, lock the PRMI, and then swing the arm in and out of resonance a bit.

  8812   Tue Jul 9 16:08:32 2013 JenneUpdateASCPOP QPD calibration attempt

[Jenne, Alex] 

Calibration data for the POP QPD has been taken, with the PRMI locked on sideband (with AS55Q and REFL33I, since it stayed locked longer with those 2).  ASC was on, AC coupled. 

We didn't get too far on either side of center of the QPD, since the ASC servo would go unstable, so we only explored the roughly linear region.  Data / plots / analysis to follow.

  8840   Fri Jul 12 21:23:42 2013 JenneUpdateASCPOP QPD calibration attempt

These are the data, one plot for when the vertical QPD position was changed, and one for when the horizontal (yaw) QPD position was changed. 

The micrometer is in inches, so 1 unit is 0.1 inches, I believe.

Clearly, I need to redo the measurement and take more data in the linear region.

  8851   Mon Jul 15 17:16:59 2013 JenneUpdateASCPOP QPD calibration attempt

I tried to retake POP QPD calibration data again today.  The MC was mostly fine, but whenever the PRMI unlocked, both ITM watchdogs would trip.  I'm not sure what was causing this, but the ITM alignment wasn't perfect after this kind of event, so I felt like I was continuously locking and realigning the arms to get the alignment back.   Then, after turning on the ASC and tweaking up the PRM alignment for maximum POP110I signal, I had to recenter the QPD, so none of my previously taken data was useful.  Frustrating.  Also, I had recentered the PRMI-relevant oplevs, but I had these weird locklosses even with nicely centered oplevs.

I have given up for the daytime, and will come back to it if there's a spot in the evening when arm measurements aren't going on.

Here is the data from last week, and the data from today.  The micrometer readings have been calibrated into mm, and I have fit a line to the linear-looking region.  Obviously, for the Pitch calibration, I definitely need to take more data.

ChangeSideMicrometer_July2013_calib2.png

ChangeSideMicrometer_July2013_calib1.png

ChangeVertMicrometer_July2013_calib1.png

  8854   Tue Jul 16 01:17:21 2013 JenneUpdateASCPOP QPD calibration attempt

[Rana, Jenne]

I took POP QPD calibration data with a new method, on Rana's suggestion.  I locked the PRMI, and engaged the ASC servo, and then used awggui (x8) to put dither lines on all of the PRMI-relevant optic's ASCPIT and ASCYAW excitation points.  I then took the transfer function of the suspensions' oplev signals (which are already calibrated into microradians) to the POP_QPD signals (which are in counts).  This way, we know what shaking of any optic does to the axis translation as seen by the POP QPD.  We can also infer (from BS or PRM motion for PR3, and ITMX motion for PR2) what the folding mirrors do to the axis translation.  Note that we'll have to do a bit of matrix math to go from, say, PRM tilt effect to PR3 tilt effect on the axis motion.

The data is saved in /users/jenne/PRCL/July152013_POP_TFs.xml .  There is also a .txt file with the same name, in the same folder, listing the frequencies used by the awg.

I'll analyze and meditate tomorrow, when my brain is not so sleepy.

  8897   Tue Jul 23 01:30:27 2013 JenneUpdateASCPOP QPD analysis

I have some data for how much motion of any PRMI-relevant optic affects the beam seen by the POP QPD. 

For this, I am using the QPD calibration from the micrometer (elog 8851) to get me from counts to mm of motion.  Note that the pitch calibration hasn't been redone (I tried locking the PRMI this afternoon, but ITMX kept drifting away from me**, so I didn't get any more data.) The pitch calibration is obviously very rough, since I only have 2 points defining my fit line. 

Anyhow, if we assume that's close enough to get us started, I now have a calibrated QPD spectrum:

QPD_spectra_only.png

As detailed in elog 8854, I took single frequency transfer functions, to determine the effect at the QPD from shaking any single PRMI optic.  These transfer functions gave me a conversion factor between the optics' oplev readings (in microradians) to the counts seen at the QPD.  I used this number, as well as the QPD calibration from the micrometer data, to convert each optics' oplev spectra to motion that one would expect to see at the QPD. 

I have not yet completely figured out how to make an estimate of the PR folding optics' affect on the POP QPD spot position, if I know their motion.  The current plan is to do as Den did in elog 8451, and infer the PR2/3 motion from the ITMX/BS motion measured by the oplevs.  My plan was to take the spectra of the oplev signals while the BS/ITMX are undamped, divide by the SOS pendulum transfer functions, then multiply by the TT transfer functions (which I finally wrote down in elog 8564).  I'm planning on using the undamped data, since the oplev signals are still within the linear range of the oplev QPDs, and I won't have to take the SUS damping into account.  Anyhow, after I do that, I'll have an idea of how much the tip tilts are moving, but not what that does to the cavity axis.

However, after looking at the plots below, it seems like the PRM is the main culprit causing the PRC axis motion, although the BS (and to a smaller extent the ITMs) are not innocent.  Since the plots get very busy very quickly, I have many plots, each plot comparing one of the above QPD spectra (either pitch or yaw) with a single optics' oplev inferred motion.

EDIT:  After talking with Koji, I realize that, since the ASC was engaged during the PRM oplev spectrum measurement, I cannot yet say whether the motion is due to PRM, or if it is from PR2 or PR3, and imprinted on the PRM via the ASC servo.  The lump where the PRM-caused motion is greater than the QPD spectra is entirely in the region where the ASC is active.  So, the QPD motion I expect without the ASC would be something like the green trace in the PRM comparison plots.  The blue trace is then the closed loop measurement.  Since the ITMs and BS are below the closed loop values, they aren't the ones causing the big lump.  I should retake all of these spectra at a time when the PRMI is locked, but the ASC is not engaged.  I'm not sure if I'll have a chance to do that tonight or not.  If I can find some GPS times when the PRMI was locked, before we had ASC, I can get the oplev data.

PRM:

QPD_yaw_motion_from_PRM.pngQPD_pit_motion_from_PRM.png

BS:

QPD_yaw_motion_from_BS.pngQPD_pit_motion_from_BS.png

ITMX:

QPD_yaw_motion_from_ITMX.pngQPD_pit_motion_from_ITMX.png

ITMY:

QPD_yaw_motion_from_ITMY.pngQPD_pit_motion_from_ITMY.png

 I think part of the reason PRM is dominating is that it's damped motion is ~10x greater than any other optics', most noticeably the BS'.  I'll write a quick separate elog about this.  Also, note that the ~3Hz resonant gain had been turned off in the PRM oplev loop, but not in any other loops.  This is why there isn't the sharp dip in the PRM's oplev motion.  Also, since the PRM ASC was engaged for this measurement, and the ASC pushes on the PRM to minimize the QPD motion, it isn't totally crazy that the PRM's motion is greater than what we actually see at the QPD, if it is compensating for the motion of other optics.

 

** Re: PRMI locking this afternoon, it was almost as if ITMX were bi-stable.  I aligned both arms, to set the ITM positions.  Then, I would lock and tweak up the michelson to get the AS port nice and dark (usually touching ITMX today, since it seemed like the drifter....ITMX at this point was usually between -7 and -15 microradians in pitch from the center of the oplev QPD).  When I then brought the PRM back into alignment, ITMX was starting to drift away.  As soon as I hit the LSC Enable switch, and looked back over to the OpLev screen, ITMX was misaligned, usually around -65 urad in pitch.  I did this circus probably 3 or so times before giving up.  Koji said that he had seen this bi-stability before, but he didn't remember what fixed it.  The drifting that Koji mentioned in elog 8801 seems to have been fixed by centering all the PRMI oplevs every day, but I had already done that, and was still seeing ITMX drift.

  8926   Fri Jul 26 13:39:30 2013 KojiUpdateASCPOP QPD analysis

It was not actually easy to see from the entry what signal was taken in what condition but from the shape of the spectra
I had the impression that the ASC & OPLEV signals were measured under the presence of the ASC control.
That is (moderately to say) tricky as the ASC control imprints the angular noise
from unkown mirror on the PRM, and then the oplev observes it. The original stability of the oplev is
obscured by the injection from the servo and the fair comparison of the stability is almost impossible.

So the true comparison between the ASC and oplev signals should be done without the control loop.
http://nodus.ligo.caltech.edu:8080/40m/8532

http://nodus.ligo.caltech.edu:8080/40m/8535

We can recover the free running spectrum of the ASC signals by compensating the loop transfer functions
because the ASC signals are the in-loop error signals. The oplev signals should be measured without
the ASC loop engaged.

  8977   Wed Aug 7 15:32:37 2013 KojiUpdateASCASS setting up accelerated (slightly)

I moved bunch of ezcawrite from the ASS Dither On script to a snapshot file.

This accelerated a half of the "up" time but still switching part is not in the snapshot.

If you find anything wrong with ASS, please notify me.

  8980   Wed Aug 7 19:16:20 2013 JenneUpdateASCASS setting up accelerated more

I have furthered Koji's work, and moved the filter on/off state for all the filter banks also to the burt snapshot.  

Turning on the ASS is now much faster than it was originally, with the ezcawrites in series.

  8982   Wed Aug 7 22:18:43 2013 KojiUpdateASCASS update

While Gautam is working on the Xarm green ASS...

The EPICS monitor points for the ASS actuators were added to the ASS model.

This will be used for the offloading the ASS actuations to the alignment biases.
As this modification allowed us to monitor the actuation apart from the dithering,
now we can migrate the ASS actuation to the fast alignment offset on the suspension.
This modification to the offset moving scripts were also done.

Screenshot-Untitled_Window.png

  8997   Mon Aug 12 14:05:34 2013 JenneUpdateASCPRCL ASS software in place

Quote:

- We are ready to implement ASS for PRM

 I have added an IPC sender from the LSC model, to send POPDC to ASS.  I have copied over the structure of the arms' ASS, to do the same for PRCL.  I have set it up to dither the PRM, and feed back to the PRM.  I did not include an LSC set, since I'm assuming that we'll set the input pointing with the arms, and just want to move the PRM to maximize POPDC.

Models have been compiled, installed, and restarted, and the daqd was restarted.

  8998   Mon Aug 12 15:39:40 2013 JenneUpdateASCPRCL ASS screens in place

I have added the PRCL ASS to the main ASS screen, and created the servo and lockin screens.  The filters loaded are the same as those used for the arms (bandpasses and lowpasses for the lockins, and an integrator for the servo).

I'm going to try to lock, and get the ASS to work.

  8999   Mon Aug 12 17:30:03 2013 KojiUpdateASCPRCL ASS software in place

Why POPDC???

  9001   Mon Aug 12 23:13:14 2013 JenneUpdateASCPRCL ASS software in place

Quote:

Why POPDC???

 I guess I was thinking that POPDC was a proxy for any type of PRCL lock.  Even if we're sideband locked, there is still some signal in POPDC (although it is very small relative to a carrier lock - ~40cts vs. 1,000cts).  However, as soon as this question was asked of me, I realized that one of the 2f demodulated signals made more sense. 

Since I want the ability to choose between POP110 and POP22, I have put a little 1x3 input matrix before the PRCL lockins in the ASS model.  Since POPDC was already there, I included it as an option in the matrix (in case we ever want to do some PRCL ASS after we have some carrier resonating as well). 

  9126   Thu Sep 12 01:06:09 2013 JenneUpdateASCSRCL ASS implemented

I have modified the ASS model to also have an ASS for SRCL.  The input options are POPDC, POP110, AS110.  I suppose I could/should have included ASDC.

Screens are modified / made.  I haven't finished setting the servo gains and oscillator amplitudes, and all that jazz yet. 

Using the parameters that Koji had in elog 9116, I was able to get nice long DRMI locks (several on a ~10 minute time scale). 

I tried some pseudo-ANDing for the triggers, to no avail.  I was trying to have the trigger matrix row for the SRCL loop have 1*POP22 and 0.02*AS110, where the 0.02 is to scale AS110 so that it has a similar amplitude to POP22.  I then set threshold levels to ~250 for up, and 100 for down (I tried several different values for the up threshold).  I was watching the TRIG_MON_FAST channels for both PRCL and SRCL, and I wasn't able to get SRCL to be triggered only at the same times as PRCL using this technique.  Since we can get the DRMI to lock, perhaps my AND logic for the triggers is a low priority, but I think we'll need something like that if we want real logic.

 

  9207   Sun Oct 6 20:55:08 2013 ranaSummaryASCMC WFS Limits set based on 40 days of trends

MC3 watchdog gets tripped sometimes when lock is lost. I noticed that there were no limits set in the MC WFS drive. The attached plot shows that over 40 days, the OUT16 channels from the WFS don't exceed 1000 counts. So I've set the limit to be 2000 in all 6 of the MC ASCPIT/YAW filter banks. Please don't turn them off.

OUT16 is really not the right way to measure this, but for some reason, we don't have any DQ channels from the MC WFS screen ??? So we're not able to measure the trend of the high frequency drive signal.

So I added the WFS(1,2)_I_(PIT,YAW)_OUT_DQ and WFS(1,2)_(PIT,YAW)_OUT_DQ channels to the c1ioo.mdl at 2048 Hz. I used Jamie's excellent 'rtcds' utility to build and install:

1) after making the edits to c1ioo.mdl I saved the file/

2) sshing to c1ioo

3) rtcds stop c1ioo

4) rtcds make c1ioo

5) rtcds install c1ioo

6) rtcds start c1ioo

7) telnet fb 8087

8) daqd> shutdown

That seemed to do it OK.

Unfortunately, all of the instructions that we have in the Wiki for adding channels and model building are misleading and don't mention any of this. There are a few different methods listed which all instruct us to do the whole make and make install business in a bunch of non existent directories.

  9249   Thu Oct 17 13:26:13 2013 JenneUpdateASCPOP QPD realigned

I locked the PRMI, and tried to turn on the ASS, but this caused PRMI to lose lock. 

Since this is similar to what happened the other night (see elog 9243, 2nd big paragraph), I looked into it a little further.  I noticed that the POP QPD pitch was very close to the edge of the QPD, so I went out and (while PRMI was locked) recentered the POP QPD.  After doing so, I was able to run the PRM ASS, and it worked very nicely, just as it has before.  So, it looks like something drifted, such that the optimal PRM alignment caused the POP beam to not be fully on the QPD.  Since the ASC loop is triggered by PRMI lock, and is constantly on, falling off the QPD causes lockloss.

While I was out there, I tweaked up the PMC pitch alignment yet again.  The FSS numbers all looked reasonable, however PMC transmission was ~0.75 .  I did a tiny bit of work in pitch, and now we're back to 0.83 transmission. 

  9460   Thu Dec 12 21:30:52 2013 JenneUpdateASCPRMI-relevant oplevs centered

The ITM oplevs were pretty close to the edge of their ranges, and none of the oplevs have been centered in a while, so I centered ITMX, ITMY, BS, PRM after having done alignment (arms, then PRMI).

  9469   Fri Dec 13 19:33:56 2013 DenUpdateASCETM X,Y QPDs

I have modified/compiled/installed/restarted c1scx and c1scy models to include arm transmission QPDs in angular controls.

For initial test I have wired normalized QPD pitch and yaw outputs to ASC input of ETMs. This was done to keep the signals inside the model.

QPD signals are summed with ASS dither lines and control. So do not forget to turn off QPD output before turning on dither alignment.

Medm screens were made and put to medm/c1sc{x,y}/master directory. Access from sitemap is QPDs -> ETM{ X,Y} QPD

  9558   Wed Jan 15 18:42:57 2014 JenneUpdateASCPOP ASC QPD offline for a few hours this afternoon

I was in the lab, near the south end of the ITMX oplev table, looking for something, and I bumped the POP ASC QPD's power supply.  I thought that it was fine, but did not adequately check it.  When EricQ asked me just now about why the PRC is so wobbly today, I checked, and the power for the QPD wasn't properly connected (it's kind of a crappy connector, that if you nudge, contacts or loses contact).  Anyhow, I restored power to the QPD, and the PRC looks a little more stable now.  My fault for not checking more carefully, and my apologies to Q and Gabriele for their frustrations this afternoon.

  9619   Mon Feb 10 18:59:25 2014 JenneUpdateASCPRM ASC better, but not great yet

I have turned off the 3.2Hz res gains in the PRC ASC loops, since those seem to make the loops unstable. 

Right now the pitch gain is -0.001, with FM1,3,9 on.  Yaw gain is -0.004, with FM1,3,9 on. 

Pitch gain can't increase by factor of 2 without oscillating. 

I tried to take transfer functions, but I think the ASC situation is really confusing, since I have OSEM damping, oplev damping, and this POP QPD damping on the PRM.  It's hard to get coherence without knocking the PRC out of lock, and it keeps looking like my gain is 0dB, with a phase of 0 degrees, from ~1 Hz to ~10 Hz.  Outside that range I haven't gotten any coherence.  Moral of the story is, I'm kind of puzzled. 

Anyhow, as it is right now, the ASC helps a bit, but not a whole lot.  I increased the trigger ON value, so that it shouldn't kick the PRM so much.  I wish that I had implemented a delay in the trigger, but I'm not in the mood to mess with the simulink diagrams right now.

  9620   Mon Feb 10 19:56:10 2014 ranaUpdateASCPRM ASC better, but not great yet

Ignoring the OSEM damping loops, the oplev servo loops make it so that the POP ASC loops do not see a simple pendulum plant, but instead see the closed loop response. Since the filter in the OL bank is proportional to f, this means that the open loop gain (OLG):

 

Which means that the CLG that the ASC sees is going to dip below unity in the band where the OL is on. For example, if the OL loop has a UGF of 5 Hz, it also has a lower UGF of ~0.15 Hz, which means that the ASC needs to know about this modified plant in this band.

For i/eLIGO, we dealt with this in this way: anti-OL in iLIGO

  9769   Mon Mar 31 23:57:22 2014 KojiSummaryASCPRM ASC characterization / design

A series of measurements / calculations for the PRM ASC characterization and servo design

1) Actuator characterization

The actuator responses of the PRM in pitch and yaw were measured (attachment figure 1). I believed the calibration of the oplev QPD to be
1 count/urad. The oplev servo loops were turned off at the FM inputs, and the filter banks were turned off so that the response has the open
loop transfer function except for the servo filter.

The measured transfer functions were fitted with LISO. The LISO results (c.f. the source codes) were shown in the figure. The responses also
include the 60Hz comb filter present in the input filters. The responses are well approximated by the single pendulum with f0 of 0.6-0.8 and q of 3.5 and 6.3.

From this measurement, the actuator responses of the PRM at DC are estimated to be 2.2 urad/cnt and 1.8 urad/cnt in pitch and yaw, respectively.

2) Sensor response of the POP QPD

As we already know how the actuators respond, the QPD optical gain can be characterized by measuring the actuator response of the QPD
(attachment figure 2). The QPD signals are such noisy that the response above 1Hz can't be measured with sufficient coherence. Below 1Hz,
the response is well represented by the actuator response measured with the oplev. From this measurement, the optical gains of the QPD
with respect to the PRM motion are 650 cnt/urad and 350 cnt/urad.

3) Open loop transfer function of the current ASC servo

By combining the above information with the servo setting of the servo filters, the open loop transfer functions of the PRM QPD ASC loops
were estimated (attachment figure 3). Actually the expected suppression of the fluctuation is poor. The yaw loop seems to have
too low gain, but in fact increasing gain is not so beneficial as there is no reasonable phase margin at higher frequency.

With the estimated openloop transfer functions and the measured free-running angular fluctuation, the suppressed angular spectra can be
estimated (attachment figure 4). This tells us that the suppression of the angular noise at around 3Hz is not sufficient in both pitch and yaw.
As there is no mechanical resonance in the actuator response at the frequency, intentional placement of poles and zeros in the servo filter is necessary.

4) Newly designed ASC filter

Here is the new design of the QPD ASC servo (attachment figure 5). The target upper UGF is 10Hz with the phase margin of 50 to 60deg.
The servo is AC coupled so that we still can tweak the alignment of the mirror.

As this servo is conditionally stable, at first we should close the loops with stable filter and then some boosts should be turned on.
Estimated suppressed fluctuation is shown in the attachment figure 6. We can see that the fluctuation was made well white between 0.5Hz to 10Hz.

The filter design is shown as follows:


Pitch
FM1: zero at 0Hz, pole at 2000Hz, gain at 2000Hz = 2000

FM3: (boost)
zero: f: 0.5Hz q: 1  /  4.5Hz, q: 1 / f: 1Hz, q: 3
pole: f: 2Hz q: 3  / f: 2.7Hz, q: 2  / f: 1Hz, q: 15

FM9: (HF Roll-off)
pole: f: 40Hz q: 1.7
 
Servo gain: -0.028

Yaw
FM1: zero at 0Hz, pole at 2000Hz, gain at 2000Hz = 2000

FM3: (boost)
zero: f: 0.7Hz q: 2  /  3Hz, q: 7 / f: 2Hz, q: 6
pole: f: 1.02Hz q: 10  / f: 4.5Hz, q: 0.8  / f: 1.5Hz, q: 10

FM9: (HF Roll-off)
pole: f: 40Hz q: 1.7
 
Servo gain: -0.0132


 

  9773   Tue Apr 1 22:03:44 2014 KojiSummaryASCNew PRM ASC is running

[Koji Jenne]

New PRM ASC was implemented. [to be cnt'd]

  9777   Wed Apr 2 19:50:12 2014 KojiSummaryASCNew PRM ASC is running

As the designed ASC filters in this entry had too little phase margins (~10deg), I had to compromise the servo design.

The design was modified and tested again. This will be reported by a following entry.

Incidentally, I have adjusted the demodulation phases of REFL33/55/165 for PRMIsb so that the PRCL is eliminated from the Q signals.

REFL33    125.5 deg -> +136.5 deg
REFL55      45.0 deg -> +  25.0 deg
REFL165   -79.5 deg -> +  44.5 deg

This change of the demod phase for REFL165 was a bit surprising.
I did not check the sign, so it could be -135.5 deg. But still this is a bit change.

  9779   Wed Apr 2 23:08:51 2014 KojiSummaryASCNew PRM ASC is running

The new PRM ASC design


Pitch
FM1: zero at 0Hz, pole at 2000Hz, gain at 2000Hz = 2000

FM5: (boost)
zero: f: 0.5Hz q: 1  /  4Hz, q: 2 / f: 1Hz, q: 3
pole: f: 2Hz q: 3  / f: 2.7Hz, q: 2  / f: 1Hz, q: 15

FM9: (HF Roll-off)
pole: f: 40Hz q: 1/Sqrt(2) (2nd order butterworth)

Servo gain: -0.023

Yaw
FM1: zero at 0Hz, pole at 2000Hz, gain at 2000Hz = 2000

FM5: (boost)
zero: f: 0.5Hz q: 1  /  4Hz, q: 2 / f: 1.5Hz, q: 10
pole: f: 1.02Hz q: 10  / f: 3Hz, q: 5  / f: 2Hz, q: 6

FM9: (HF Roll-off)
pole: f: 40Hz q: 1/sqrt(2)
 
Servo gain: -0.027


The loop gains were adjusted to have the UGFs of 10Hz. The measured openloop transfer functions were compared with the model.
The transfer functions for yaw are well matched. However, the pitch ones don't. It seems that the pitch loop has extra low pass
which I can't locate. The possibility is the analog electronics of the pitch loop.


The effect of the control between 0.3Hz to 3Hz are well represented by the model. The attachment 2 shows the free running
angle fluctuation, the ones with the control engaged, and the estimated spectra. Indeed, the estimated spectra well represent
the measured angular spectra.

  9930   Thu May 8 14:37:02 2014 JenneUpdateASCPOP ASC QPD power

I was thinking about POP today, and wanted to know if there was something to be done to allow us to use the PRCL ASC for at least a little bit farther into arm power buildup.

Anyhow, I checked, and while PRMI is locked on sidebands (ETMs misaligned), POP DC is about 80 counts, and the power measured by the Ophir power meter is 24 microWatts. 

We were on the 3rd gain setting for the QPD's power amplifier.  I turned it down to the "2" option.  (When at 4, the front panel light indicates saturation).

It's not clear to me what the gain settings mean exactly.  I think that "1" means 4*10^3 V/A, and "6" means 4*10^6 V/A (On-Trak OT301 info site), but I don't know for sure how the gain changes for the settings 2-5.  Anyhow, I have changed the digital gain for the ASC to be -0.063 from -0.023 for both pitch and yaw.

  10114   Mon Jun 30 22:06:55 2014 JenneUpdateASCIFO (mostly) aligned - ASS working

[Koji, Jenne]

The Yarm ASS is now working (as is the Xarm ASS).  Both of the TT's pitch servos had a sign flip.  We don't know why.

To start, we lowered the matrix elements that push on the TTs by a factor of 3, to compensate for the new factor of 3 in the slider gains:  ezcastep C1:ASS-YARM_OUT_MTRX_5_5 /3 C1:ASS-YARM_OUT_MTRX_5_7 /3 C1:ASS-YARM_OUT_MTRX_6_6 /3 C1:ASS-YARM_OUT_MTRX_6_8 /3 C1:ASS-YARM_OUT_MTRX_7_5 /3 C1:ASS-YARM_OUT_MTRX_7_7 /3 C1:ASS-YARM_OUT_MTRX_8_6 /3 C1:ASS-YARM_OUT_MTRX_8_8 /3

We turned off all 4 tip tilt ASS servos (in the Yarm ASS servo screen), and turned them on one at a time.  By doing this, we discovered that the pitch servos for both TT1 and TT2 needed to have the opposite sign from what they used to have.  However, the yaw servos kept the original signs.  It really doesn't make sense to me why this should be, but this is the way the ASS servo works.  We left both Xarm and Yarm ASSs on for several minutes, and saw that they didn't push any mirrors out of alignment.

The ASS_DOTHER_ON burt snapshot has been resaved with the new values.

 

Also, earlier this evening, I aligned the Yarm green beam to the cavity, although the cavity was not optimally aligned, so this needs to be re-done.

 

On our to-do list should be to add the tip tilt slider values to the DAQ channels list.

  10124   Wed Jul 2 16:18:32 2014 JenneUpdateASCIFO aligned, PRMI + 2 arms achieved

After the meeting, I aligned the IFO to the IR, and then I aligned the Ygreen to the Yarm.  I then found the beatnotes and used ALS to hold the arms with CARM/DARM, locked the PRMI, and reduced the CARM offset until I had arm powers of about 3.  Given that this was at 3pm, and people were tromping all over inside the IFO room, I feel positive about tonight.  

So, IFO seems ready, carm_cm_up script was successful, and got me to arm powers of 1, and then I further reduced the offset by a bit to go a little higher. 

  10278   Sat Jul 26 14:45:33 2014 GabrieleMetaphysicsASCResponse of POP QPD

 Koji asked me to perform a simulation of the response of POP QPD DC signal to mirror motions, as a function of the CARM offset. Later than promised, here are the first round of results.

I simulated a double cavity, and the PRC is folded with parameters close to the 40m configuration. POP is extracted in transmission of PR2 (1ppm, forward beam). For the moment I just placed the QPD one meter from PR2, if needed we can adjust the Gouy phase. There are two QPDs in the simulation: one senses all the field coming out in POP, the other one is filtered to sense only the contribution from the carrier field. The difference can be used to compute what a POP_2F_QPD would sense. All mirrors are moved at 1 Hz and the QPD signals are simulated:

pop_qpd_all.png

This shows the signal on the POP QPD when all fields (carrier and 55 MHz sidebands) are sensed. This is what a real DC QPD will see. As expected at low offset ETM is dominant, while at large offset the PRC mirrors are dominant. It's interesting to note that for any mirror, there is one offset where the signal disappears.

pop_qpd_carrier.png

This is the contribution coming only from the carrier. This is what an ideal QPD with an optical low pass will sense. The contribution from the carrier increases with decreasing offset, as expected since there is more power.

pop_qpd_sb.png

Finally, this is what a 2F QPD will sense. The contribution is always dominated by the PRC mirrors, and the ETM is negligible.

The zeros in the real QPD signal is clearly coming from a  cancellation of the contributions from carrier and sidebands.

The code is attached.

  10337   Wed Aug 6 10:45:56 2014 GabrieleUpdateASCPOP QPD signals

 In addition to the simulation described in my previous elog, I simulated the signal on a quadrant photodetector demodulated at 2F. The input laser beam is modulated at 11MHz up to the fifth order. There is no additional 55 MHz modulation.

The QPD demodulated at 2F shows good signals for PRC control for all CARM offsets, as expected from the previous simulation.

pop_qpd_2f.png

 

  10338   Wed Aug 6 12:44:52 2014 KojiUpdateASCPOP QPD signals

This is nice. Can we test this idea with POP22 + a razor blade?

Just to take transfer functions in PRMIsb between the PRM angle to POP QPD/POP22+razor blade
as well as the noise spectrum measurement are already useful.

We want to figure out the requirement for the 2f QPD.
(Transimpedance / Noise level / Beam size / etc)

Depending on the requirement we'll see if we need demodulation or just a power detector.

  10398   Fri Aug 15 01:31:44 2014 JenneUpdateASCPOP QPD to ETMs model wiring complete

I have added a few things to the ASS model, and the ASC sub-block, so that we can send POP QPD information down to the ETMs for CARM angular control after we've reduced the CARM offset and gotten some carrier buildup.  I did not remove our ability to actuate on PRM, so that we can still play with it in PRMIsb cases.

The input matrix has been expanded so that it can send signals to new CARM_YAW and CARM_PIT filter banks.  The corresponding filter banks have been created.  The output matrix was also expanded to take in the 2 new servo outputs, and so it can send signals to both ETMs, pitch and yaw.  I did not include any triggering logic for this new CARM situation, since I assume we'll just turn it on and off with our scripts.  (We haven't really been using the triggering capability of the PRM ASC either lately, although it's all still there).  I added the inputs and outputs of the CARM servos to the list of acquired channels.

The ASC sub-block:

ASC_newCARM.png

I also modified the top level of the ASS model.  This was just a simple addition of summing nodes for the ETMs, similar to what was already in place for the PRM, so that we can send both the ASS dither alignment signals and the ASC servo control signals to the optics.

The ASS top level:

ASSoverview_newCARM.png

I also quickly modified the ASC screen to expose all of the new options:

ASC_screen.png

The ASS model was compiled, and restarted.  As usual, this temporarily removes the biases on the input pointing tip tilts, but the pointing seems to have come back without any trouble.

  10454   Thu Sep 4 18:30:13 2014 GabrieleSummaryASCOptimal Gouy phase for POP QPD

 Jenne asked me to simulate the signals on POP QPD when moving different mirrors, as a function of the Gouy phase where the QPD is placed.

I used the opportunity to create a MIST simulation file of the entire 40m interferometer, essentially based on my aLIGO configuration file. I used the recycling cavity lengths obtained from our survey, and other parameters from the wiki page. The configuration file is attached (fortymeters.mist).

Coming back to the main simulation, here is the result, both for the "regular" POP QPD and for a 22MHz demodulated one. The Gouy phase is measured starting from PR2. Cavity mirrors are easily decoupled from PRM in the "regular" QPD. As already demonstrated in a previous simulation, ETMs signals are very small in the 22 MHz QPD. Moreover, it is possible to zero the contribution from ITMs by choosing the right Gouy phase, at the price of a reduction of the PRM signal by a factor of 3-4. Simulation files are attached.

pop_qpd_dc.png

 

  10503   Fri Sep 12 15:10:09 2014 JenneUpdateASCMICH ASS

During the Sim meeting today, I added parts to the ASS model so that we can also dither the BS and minimize the power at AS. 

ASS screen has been updated. 

Model changes required a new sender from LSC for ASDC, so both LSC and ASS were compiled, installed and restarted.  Also on LSC, I added AS110 I&Q to DQ channels, since we haven't been recording them in the past.

I have done a quick trial in MICH-only lock, and it seems to work.  Gain of 10 for both Pit and Yaw servos. 

  10662   Mon Nov 3 17:14:00 2014 ericqUpdateASCIMC to IFO angular motion

Something to note, as we have the IMC angular controls under consideration:

Jenne has the DRMI locked right now. I took a look at the coherence between the POP QPD and MC2 transmission QPDs. (Since she's using ASC, I also included those control signals. The coherences are about the same, unsurprisingly)

Based on the observed coherences, from about 1 to 6Hz, IMC motion is responsible for a fair amount of the DRMI angular motion. Also, PIT and YAW couple differently. 

2014-10-03-MC2T_to_POPQPD.pdf

  10663   Mon Nov 3 17:43:14 2014 KojiUpdateASCIMC to IFO angular motion

I wonder if this is the coherence caused by the beam itself, or caused by the same ground motion.
Jenne should be able to tell us...

  10680   Thu Nov 6 12:53:09 2014 diegoUpdateASCX arm restored

[Diego, Koji]

X arm has been restored, after modifying the two parameters mentioned in http://nodus.ligo.caltech.edu:8080/40m/10676 (C1SUS_ITMX:  LSC/DAMP and LSC/BIAS); after that, a manual re-alignment of ETMX was necessary due to heavy PIT misalignment. I will check the ALS lock once work on the Y arm is done.

  10745   Tue Dec 2 01:27:22 2014 diegoUpdateASCASS Scripts for arms

I updated the medm C1ASS page for the Arm scripts:

ON : same as before

FREEZE OUTPUTS: calls new FREEZE_DITHER.py script, which sets Common Gain and LO Amplitudes to 0, therefore freezing the current output values

START FROM FROZEN  OUTPUTS: calls new UNFREEZE_DITHER.py script, which sets Commong Gain and LO Amplitudes as in the DITHER_ASS_ON.py script, but no burt restore is performed

OFFLOAD OFFSETS: it's the old "SAVE OFFSETS", calls the WRITE_ASS_OFFSET.py script

OFF: same as before

StripTool: same as before

 

 

  10752   Thu Dec 4 00:26:07 2014 JenneUpdateASCPOP yaw razor blade installed

We would like the option of feeding back the POP beam position fluctuations to the PRM to help stabilize the PRC since we don't have oplevs for PR2 and PR3.  However, we cannot just use the DC QPD because that beam spot will be dominated by carrier light as we start to get power recycling. 

The solution that we are trying as of today is to look at yaw information of just the RF sidebands.  (Yaw is worse than pitch, although it would be nice to also control pitch).  I have placed a razor blade occluding about half of the POP beam in front of the POP PD (which serves POPDC, POP22 and POP110).  I also changed the ASS model so that I could use this signal to feed back to the PRM.  Loop has been measured, and in-loop spectra shows some improvement versus uncontrolled.


Optical table work:

The POP beam comes out of the vacuum system and is steered around a little bit, then about 50% goes to the DC QPD.  Of the remaining, some goes to the Thorlabs PD (10CF I think) and the rest goes to the POP camera.  For the bit that goes to the Thorlabs PD, there is a lens to get the beam to fit on the tiny diode.

There was very little space between the steering mirror that picks off the light for this PD, and the lens - not enough to put the razor blade in.  The beam after the lens is so small that it's much easier to occlude only half of the beam in the area before the lens.  (Since we don't know what gouy phase we're at, so we don't know where the ideal spot for the razor is, I claim that this is a reasonable place to start.)

I swapped out the old 50mm lens and put in a 35mm lens a little closer to the PD, which gave me just enough room to squeeze in the razor blade.  This change meant that I had to realign the beam onto the PD, and also that the demod phase angles for POP22 and POP110 needed to be checked.  To align the beam, before placing the razor blade, I got the beam close enough that I was seeing flashes in POPDC large enough to use for a PRMI carrier trigger.  The PRMI carrier was a little annoying to lock.  After some effort, I could only get it to hold for several seconds at a time.  Rather than going down a deep hole, I just used that to roughly set the POP22 demod phase (I -phase maximally negative when locked on carrier, Q-phase close to zero).  Then I was able to lock the PRMI sideband by drastically reducing the trigger threshold levels.  With the nice stable sideband-locked PRMI I was able to center the beam on the PD. 

After that, I introduced the razor blade until both POPDC and POP22 power levels decreased by about half. 

Now, the POP22 threshold levels are set to up=10, down=1 for both MICH and PRCL, DoF triggers and FM triggers.


ASS model work:

POP22 I and POP110 I were already going to the ASS model (where ASC lives) for the PRCL ASS dither readbacks.  So, I just had to include them in the ASC block, and increased the size of the ASC input matrix.  Now you can select either POP QPD pit, POP QPD yaw, POP221 or POP110I to go to either PRCL yaw, PRCL pit, CARM yaw or CARM pit. 

Compiled, installed and restarted the ASS model.


Engaging the servo:

I took reference spectra of POP QPD yaw and POP 22, before any control was applied.  The shapes looked quite similar, but the overall level of POP22 was smaller by a factor of ~200.  I also took a reference spectra of the POP QPD in-loop signal using the old ASC loop situation.

Q looked at Foton for me, and said that with the boost on, the UGF needed to be around 9 or 10 Hz, which ended up meaning a servo gain of +2.5 (the old POP QPD yaw gain was -0.063).  We determined that we didn't know why there was a high-Q 50Hz notch in the servo, and why there is not a high frequency rolloff, so right now the servo only uses FM1 (0:2000), FM6 (boost at 1Hz and 3Hz) and FM7 (BLP40). 

The in-loop residual isn't quite as good with POP22 as for the QPD, but it's not bad. 

Here's the loop:

ASC_PRCLloop_POP22err.pdf

And here's the error spectra.  Pink solid and light blue solid are the reference traces without control.  Pink dashed is the QPD in-loop.  Red and blue solid are the QPD and POP22 when POP22 is used as the error signal.  You can definitely see that the boosts in FM6 have a region of low gain around 1.5Hz.  I'm not so sure why that wasn't a problem with the QPD, but we should consider making it a total 1-3Hz bandpass rather than a series of low-Q bumps.  Also, even though the POP22 UGF was set to 9 Hz, we're not seeing any suppression above about 4Hz, and in fact we're injecting a bit of noise between 4-20Hz, which needs to be fixed still. 

PRC_YAW_QPDvs22_3Dec2014.pdf

  10768   Tue Dec 9 03:34:52 2014 JenneUpdateASCPOP yaw razor tuning

With the re-do of the IFO alignment last week, I think that the beam was no longer about halfway on the POP22 razor blade.  To fix this, I locked the PRMI on sideband, removed the razor blade, and then put it back in such that it occluded about half of the light.  

I'm not entirely sure why, but when I put the razor in, POP22 went from 104(ish) to 45(ish) but POPDC  went from 5200(ish) to 1600(ish).  [The 'ish'es are because the PRC wasn't angularly stabilized, so there was some motion changing the power levels that leaked out to the POP port].  The ETMs were misaligned, so this should not be a carrier vs. sideband effect, since they'll both share the cavity axis defined by the ITMs and the PRM.  It is possible, although I didn't check, that there is some oplev light scattered into the POP photodiode that is now blocked by the razor blade.  This light would only be at DC and not the 2f frequencies.  Since the signal levels for POP22 vs. POPDC didn't change with and without the table top on (and with and without room lights on), I don't think that it is an effect of ambient light getting into the diode.  To check if it is oplev light I should (a) just look, and (b) try to lock the PRMI without the ITMX oplev laser being on to see if there is a difference in the POPDC signal.

Anyhow, under the assumption that the POP22 signal level is correct, I tuned up the PRCL ASC a little bit.  These changes are now in the carm_cm_up script, and the carm_cm_down script resets things.  Before the PRC is locked, I have FM1 and FM7 (the basic servo shape and a 40Hz lowpass) on, the gain set to zero, and the input off.  After lock is acquired, the input is turned on, and the gain ramps from 0 -> 10 in 3 seconds.  Then FM2 and FM6 (boosts at 1 and 3Hz) are engaged.

In the plot below, the dark blue and red curves were taken when there was no angular control on the PRC.  Pink was taken last week with the old QPD yaw ASC on.  Light blue is today's version of the in-loop performance of the POP22 yaw ASC loop.  I didn't save the trace unfortunately, but the DC QPD saw out-of-loop improvement between about 0.8Hz - 4 Hz. 

Also, has anything happened with the LSC rack in the last few weeks that might be causing lots of 60Hz noise? I saw these large lines last week, but I don't think I remember them from the past.

PRC_YAW_QPDvs22_8Dec2014.pdf

After I got the PRCL ASC working, I tried several iterations of locking.  ETMX is still being annoying, although the last hour or so have been okay.  CARM keeps getting rung up right around the transition to the sqrtInv error signal.  Since CARM and DARM are kind of entangled, it took me a few iterations to figure out that it was CARM that is ringing up, and not DARM.  I'm a little worried about the phase loss from the 1kHz lowpass that we turn on just before the transition to sqrtInv.  I want to keep the lowpass off until after we have transitioned DARM also over to DC transmission.  I tried once, but I lost lock before starting the CARM transition.  Anyhow, the ETM alignment issue is annoying.

Also, Jamie, Q, Diego and I were discussing last Friday, but none of us elogged, that we think there might be something wrong with one of the Martian network switches.  I'll start a separate thread about that right now, but it slows things down when you can't trust EPICS channels to be current, and I (without evidence) am a little worried that this might also affect the fast signals.

  10789   Fri Dec 12 04:33:49 2014 JenneUpdateASCASS retuned

[Rana, Jenne]

We decided that tonight was the night for ASS tuning. 

We started from choosing new frequencies, by looking at the transmission and the servo control signals spectra to find areas that weren't too full of peaks.  We chose to be above the OpLev UGF by at least a factor of ~2, so our lowest frequency is about 18Hz.  This way, even if the oplevs are retuned, or the gains are increased, the ASS should still function. 

We set the peak heights for the lowest frequency of each arm to have good SNR, and then calculated what the amplitude of the higher frequencies ought to be, such that the mirrors are moving about the same amount in all directions. 

We re-did the low pass filters, and eliminated the band pass filters in the demodulation part of the servo.  The band passes aren't strictly necessary, as long as you have adequate lowpassing, so we have turned them off, which gives us the freedom to change excitation frequencies at will.  We modified the lowpass filter so that we had more attenuation at 2Hz, since we spaced our excitation frequencies at least ~2.5 Hz apart.

The same lowpass filter is in every single demodulator filter bank (I's and Q's, for both length and transmission demodulation).  We are getting the gain hierarchy just by setting the servo gains appropriately. 

We ran ezcaservos to set the demodulation phase of each lockin, to minimize the Q-phase signal. 

We then tuned up the gains of the servos.  Rana did the Y arm, but for the X arm I tried to find the gains where the servos went unstable, and then reduced the gain by a factor of 2.  The Xarm is having trouble getting good alignment if you start with something less than about 0.7, so there is room for improvement.

Rana wrote a little shell script that will save the burt snapshot, if the gains need adjusting and they should be re-saved. 

The scripts have been modified (just with the new oscillator amplitudes - everything else is in the burt snapshots), so you should be able to run the start from nothing and the start from frozen scripts for both arms.  However, please watch them just in case, to make sure they don't run away.

  10807   Wed Dec 17 01:51:44 2014 rana, jenneUpdateASCASS retuned

Did a big reconfig to make the Y-arm work again since it was bad again.

  1. Undid Koji's topology change. The A2L loops now feedback to the arm mirrors to adjust the cavity axis. The cavity transmission signals now feedback to the input beam.
  2. The UGF of the Trans->Input beam servos is ~5-10x higher than the A2L servos.
  3. The Trans loops have a ~10-15 s settling time.
  4. The Input Matrix has been adjusted to fit with our intuition:The ETM tilt moves the beam equally on the ITM and ETM faces.
  5. The Output Matrix has also been adjusted to do like this: we're using an intuitive matrix inverse rather than one based on measurement. It turns out to be a reasonable guess and we can tune this later.
  6. Seems stable with many kinds of steps and misalignments. Seems not reliable if the arm power is less than ~0.5.
  7. Reducing the dither amplitudes to make the power fluctuation less than 5% made it much more stable.

With the arm aligned and the A2L signals all zeroed, we centered the beam on QPDY (after freezing the ASS outputs). I saw the beam going to the QPD on an IR card, along with a host of green spots. Seems bad to have green beams hitting the QPD alogn with the IR, so we are asking Steve to buy a bunch of the broad, dielectric, bandpass filters from Thorlabs (FL1064-10), so that we can also be immune to the EXIT sign. I wonder if its legal to make a baffle to block it on the bottom side?

P.S. Why is the Transmon QPD software different from the OL stuff? We should take the Kissel OL package and put it in place of our old OL junk as well as the Transmons.

  10811   Wed Dec 17 18:14:36 2014 ericqUpdateASCTransmon QPD -> ASC servos ready for comissioning

 I have completed all of the model modifications and medm screen updates to allow for feedback from the transmon QPD pitch and yaw signals to the ITMs. Now, we can design and test actual loops...

newASCscreen.png

The signals come from c1sc[x/y] to c1rfm via RFM, and then go to c1ass via dolphin. 


Out of curiosity about the RFM+dolphin delay, I took a TF of an excitation at the end SUS model (C1:SUS-ETM[X/Y]_QPD_[PIT/YAW]_EXC) to the input FM in the ASC model (C1:ASC-ETM[X/Y]_QPD_[PIT/YAW]_IN1). All four signals exhibit the same delay of 122usec. I saved the dtt file in Templates/ASC/transmonQPDdelay.xml

This is less than a degree under 20Hz, so we don't have to worry about it. 

  10812   Wed Dec 17 19:04:12 2014 jenneUpdateASCASS retuned

I made the Xarm follow the new (old) topology of Length -> test masses, and Trans -> input pointing.

It takes a really long time to converge (2+ min), since the input pointing loops actuate on the BS, which has an optical lever, which is slow.  So, everything has to be super duper slow for the input pointing to be fast relative to the test mass motion.

Also, between last night and this afternoon, I moved the green ASX stuff from a long list of ezca commands to a burt file, so turning it on is much faster now.  Also, I chose new frequencies to avoid intermodulation issues, set the lockin demodulation phases, and tuned all 4 loops.  So, now the green ASX should work for all 4 mirrors, no hand tuning required.  While I was working on it, I also removed the band pass filters, and made the low pass filters the same as we are using for the IR ASS.  The servos converge in about 30 seconds.

ELOG V3.1.3-