40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
 40m Log, Page 167 of 344 Not logged in
ID Date Author Type Category Subject
15895   Wed Mar 10 15:00:16 2021 gautamSummaryIMCIMC free swinging prep

Did you fix this issue? It is helpful to post a screenshot of the offending MEDM screen in addition to witticisms. The elog says "sitemap>Shutter>PSL" but I can't find PSL under the dropdown for shutters from Sitemap.

 # Moving on to IMC suspensions characterization: - Closed the PSL shutter, to our suprise, the MC was still locked. We thought this would take away any light from IMC but it doesn't. Maybe the IFO Overview needs to show the schematic in a way where this doesn't happen: "No light from any laser entering the MC but it still is locked with a resonating field inside."
15896   Wed Mar 10 15:29:58 2021 AnchalSummaryIMCIMC free swinging prep

No we didn't fix the issue. We'll post some screenshots tomorrow. From "sitemap>Shutter>PSL" we meant in Shutter medm window, we clicked on the PSL close button. As pointed later, it switches C1:AUX-PSL_ShutterRqst while the PSL shutter switch on Lock MC medm screen switches C1:PSL-PSL_ShutterRqst. We were not sure if this was intentional, so we didn't change anything.

15897   Wed Mar 10 15:35:25 2021 Paco, AnchalSummaryIMCIMC free swinging experiment set to trigger at 5:00 am

A tmux session named "MCFreeSwingTest" will run on Rossa. This session is running script scripts/SUS/freeSwingMC.py (also attached) which will trigger at 5:00 am to impart 30000 counts kick to MC1, MC2, and MC3 after shutting PSL shutter and disabling the MC autolocker. It will let them freely swing for 1050 sec and will repeat 15 times to allow some averaging. In the end, it will undo all the changes it does and switches on autolocker on IMC. The script is set to restore any changes in case it fails at any point or a Ctrl-C is detected.

Attachment 1: freeSwingMC.py.zip
16125   Thu May 6 16:13:39 2021 AnchalSummaryIMCAngular actuation calibration for IMC mirrors

Here's my first attempt at doing angular actuation calibration for IMC mirrors using the method descibed in /users/OLD/kakeru/oplev_calibration/oplev.pdf by Kakeru Takahashi. The key is to see how much is the cavity mode misaligned from the input mode of beam as the mirrors are moved along PIT or YAW.

There two possible kinds of mismatch:

• Parallel displacement of cavity mode axis:
• In this kind of mismatch, the cavity mode is simply away from input mode by some distance $\dpi{150} \large \beta$.
• This results in transmitted power reduction by the gaussian factor of $\dpi{150} \large e^{-\frac{\beta^2}{w_0^2}}$ where $\dpi{150} \large w_0$ is the beam waist of input mode (or nominal waist of cavity).
• For some mismatch, we can approximate this to
$\dpi{150} \large 1 - \frac{\beta^2}{w_0^2}$
• Angular mismatch of cavity mode axis:
• The cavity mode axis could be tilted with respect to input mode by some angle $\dpi{150} \large \alpha$.
• This results in transmitted power reduction by the gaussian factor of $\dpi{150} \large e^{- \frac{\alpha^2}{\alpha_0^2}}$  where $\dpi{150} \large \alpha_0$ is the beam divergence angle of input mode (or nominal waist of cavity) given by $\dpi{150} \large \frac{\lambda}{\pi w_0}$.
• or some mismatch, we can approximate this to
$\dpi{150} \large 1 - \frac{\alpha^2}{\alpha_0^2}$

Kakeru's document goes through cases for linear cavities. For IMC, the mode mismatches are bit different. Here's my take on them:

### MC2:

• MC2 is the easiest case in IMC as it is similar to the end mirror for linear cavity with plane input mirror (the case of which is already studies in sec 0.3.2 in Kaker's document).
• PIT:
• When MC2 PIT is changed, the cavity mode simple shifts upwards (or downwards) to the point where the normal from MC2 is horizontal.
• Since, MC1 and MC3 are plane mirrors, they support this mode just with a different beam spot position, shifted up by $\dpi{150} \large (R-L)\theta$.
• So the mismatch is simple of the first kind. In my calculations however, I counted the two beams on MC1 and MC3 separately, so the factor is twice as much.
• Calling the coefficient to square of angular change $\dpi{150} \large \eta$, we get:
$\dpi{150} \large \eta_{._{2P}} = \frac{2 (R-L)^2}{w_0^2}$
• Here, R is radius of curvature of MC1/3 taken as 21.21m and L is the cavity half-length of IMC taken as 13.545417m.
• YAW:
• For YAW, the case is bit more complicated. Similar to PIT, there will be a horizontal shift of the cavity mode by $\dpi{150} \large (R-L)\theta$.
• But since the MC1 and MC3 mirrors will be fixed, the angle of the two beams from MC1 and MC3 to MC2 will have to shift by $\dpi{150} \large \theta/2$.
• So the overall coefficient would be:
$\dpi{150} \large \eta_{._{2Y}} = \frac{2 (R-L)^2}{w_0^2} + \frac{2}{4\alpha_0^2}$
• The factor of 4 in denominator of seconf term on RHS above comes because only half og angular actuation is felt per arm. The factor of 2 in numerator for for the 2 arms.

### MC1/3:

• First, let's establish that the case of MC1 and MC3 is same as the cavity mode must change identically when the two mirrors are moved similarly.
• YAW:
• By tilting MC1 by $\dpi{150} \large \theta$, we increase the YAW angle between MC1 and MC3 by $\dpi{150} \large \theta$.
• Beam spot on both MC1 and MC3 moves by $\dpi{150} \large (R-L)\theta$.
• The beam angles on both arms get shifted by $\dpi{150} \large \theta/2$.
• So the overall coefficient would be:
$\dpi{150} \large \eta_{._{13Y}} = \frac{2 (R-L)^2}{w_0^2} + \frac{2}{4\alpha_0^2}$
• Note, this coefficient is same as MC2, so it si equivalent to moving teh MC2 by same angle in YAW.
• PIT:
• I'm not very sure of my caluculation here (hence presented last).
• Changing PIT on MC1, should change the beam spot on MC2 but not on MC3. Only the angle of MC3-MC2 arm should deflect by $\dpi{150} \large \theta/2$.
• While on MC1, the beam spot must change by $\dpi{150} \large (R-L)\theta/2$ and the MC1-MC2 arm should deflect by $\dpi{150} \large \theta/2$.
• So the overall coefficient would be:
$\dpi{150} \large \eta_{._{13P}} = \frac{(R-L)^2}{4 w_0^2} + \frac{2}{4\alpha_0^2}$

### Test procedure:

• We first clicked on MC WFS Relief (on C1:IOO-WFS_MASTER) to reduce the large offsets accumulated on WFS outputs. This script took 10 minutes and reduced the offsets to single digits and IMC remained locked throughout the process.
• Then we switched off the WFS to freeze the outputs.
• We moved the MC#_PIT/YAW_OFFSET up and down and measured the C1:IOO-MC_TRANS_SUMFILT_OUT channel as an indicater of IMC mode matching.
• Attachement 1 are the 6 measurements and there fits to a parabola. Fitting code and plots are thanks to Paco.
• We got the curvature of parabolas $\dpi{150} \large \gamma$from these fits in units of 1/cts^2.
• The $\dpi{150} \large \eta$ coefficients calculated above are in units of 1/rad^2.
• We got the angular actuation calibration from these offsets to physical angular dispalcement in units of rad/cts by $\dpi{150} \large \sqrt{\gamma / \eta}$.
• AC calibration:
• I parked the offset to some value to get to the side of parabola. I was trying to reduce transmission from about 14000 cts to 10000-12000 cts in each case.
• Sent excitation using MC#_ASCPIT/YAW_EXC using awg at 77 Hz and 10000 cts.
• Measured the cts on transmission channel at 77 Hz. Divided it by 2 and by the dc offset provided. And divided by the amplitude of cts set in excitation. This gives $\dpi{150} \large \eta_{ac}$ analogous to above DC case.
• Then angular actuation calibration at 77 Hz from these offsets to physical angular dispalcement in units of rad/cts by $\dpi{150} \large \sqrt{\gamma/\eta_{ac}}$.
• Following are the results:
Optic Act
Calibration factor at DC [µrad/cts]
Calibration factor at 77 Hz [prad/cts]
MC1 PIT 7.931+/-0.029 906.99
MC1 YAW 5.22+/-0.04 382.42
MC2 PIT 13.53+/-0.08 869.01
MC2 YAW 14.41+/-0.21 206.67
MC3 PIT 10.088+/-0.026 331.83
MC3 YAW 9.75+/-0.05 838.44

• Note these values are measured with the new settings in effect from 16120. If these are changed, this measurement will not be valid anymore.
• I believe the small values for MC1 actuation have to do with the fact that coil output gains for MC1 are very weird and small, which limit the actuation strength.
• TAbove the resonance frequencies, they will fall off by 1/f^2 from the DC value. I've confirmed that the above numbers are of correct order of magnitude atleast.
• Please let me know if you can point out any mistakes in the calculations above.
Attachment 1: IMC_Ang_Act_Cal_Kakeru_Tests.pdf
16163   Wed May 26 11:45:57 2021 Anchal, PacoConfigurationIMCMC2 analog camera

[Anchal, Paco]

We went near the MC2 area and opened the lid to inspect the GigE and analog video monitors for MC2. Looked like whatever image is coming through the viewport is split into the GigE (for beam tracking) and the analog monitor. We hooked the monitor found on the floor nearby and tweaked the analog video camera around to get a feel for how the "ghost" image of the transmission moves around. It looks like in order to try and remove this "extra spots" we would need to tweak the beam tracking BS. We will consult the beam tracking authorities and return to this.

16179   Thu Jun 3 17:35:31 2021 AnchalSummaryIMCFixed medm button

I fixed the PSL shutter button on Shutters summary page C1IOO_Mech_Shutter.adl. Now PSL switch changes C1:PSL-PSL_ShutterRqst channel. Earlier it was C1:AUX-PSL_ShutterRqst which doesn't do anything.

Attachment 1: C1IOO_Mech_Shutters.png
16272   Fri Aug 6 17:10:19 2021 PacoUpdateIMCMC rollercoaster

[anchal, yehonatan, paco]

For whatever reason (i.e. we don't really know) the MC unlocked into a weird state at ~ 10:40 AM today. We first tried to find a likely cause as we saw it couldn't recover itself after ~ 40 min... so we decided to try a few things. First we verified that no suspensions were acting weird by looking at the OSEMs on MC1, MC2, and MC3. After validating that the sensors were acting normally, we moved on to the WFS. The WFS loops were disabled the moment the IMC unlocked, as they should. We then proceeded to the last resort of tweaking the MC alignment a bit, first with MC2 and then MC1 and MC3 in that order to see if we could help the MC catch its lock. This didn't help much initially and we paused at about noon.

At about 5 pm, we resumed since the IMC had remained locked to some higher order mode (TEM-01 by the looks of it). While looking at C1:IOO-MC_TRANS_SUMFILT_OUT on ndscope, we kept on shifting the MC2 Yaw alignment slider (steps = +-0.01 counts) slowly to help the right mode "hop". Once the right mode caught on, the WFS loops triggered and the IMC was restored. The transmission during this last stage is shown in Attachment #1.

Attachment 1: MC2_trans_sum_2021-08-06_17-18-54.png
16480   Tue Nov 23 18:02:05 2021 AnchalUpdateIMCMC autolocker shifted to python3 script running in docker

I finished copying over the current autolocker bash script functionality into a python script which runs using a simple configuration yaml file. To run this script, one needs to ssh into optimus and :

controls@optimus|~> cd /opt/rtcds/caltech/c1/Git/40m/scripts/MC
controls@optimus|MC> sudo docker-compose up -d
Creating mc_AL_MC_1 ... done

That's it. To check out running docker processes, one can:

controls@optimus|MC> sudo docker ps

And to shut down this particular script, in the same directory, one can

controls@optimus|MC> sudo docker-compose down
Removing mc_AL_MC_1 ... done

If the docker image requires to be rebuild in future, go to the directory where Dockerfile is present and run:

controls@optimus|MC> sudo docker build -t pyep .

I had to add PyYAML package in the pyepics docker image already present on docker hub, thanks to Andrew.

For now, I have disabled the MCautolocker service on Megatron. To start it back again, one would need to ssh into megatron and do following:

~> sudo systemctl enable MCautolocker
~> sudo systemctl start MCautolocker

Let's see for a day how this new script does. I've left PSL shutter open and autolocker engaged.

To do: Fix the C1:IFO-STATE epics channel definition so that it takes its bits from separate lock status channels instead of scripts writign the whole word arbitrarily.

16894   Mon Jun 6 21:01:22 2022 yutaUpdateIMCMC1 OSEM sensor sign flipped, MC1/2/3 free swinging overnight for inmat diagonalization

[Tomislav Andric, Rana, Yuta]

We put -1 to MC1 OSEM sensor gains and re-tuned MC1 damping.
We also kicked MC1, MC2, MC3 tonight for input matrix diagonalization.

MC1 damping investigations:
We put -1 to MC1 OSEM sensor gains so that UL/UR/LR/LL/SDSEN_OUT will be positive like other optics.
OSEM damping filter gains were adjusted.
We have also checked if having +1 for all UL/UR/LR/LL/SDCOIL_GAIN is correct or not. It has been like this at least for the past year.
It should be -1 for UR and LL to account for magnets, but if we did put -1 or them, kick in C1:SUS-MC1_PIT_OFFSET mostly gave yaw kick and kick in C1:SUS-MC1_YAW_OFFSET mostly give pitch kick.
So, we reverted them to be +1.

Input matrix diagonalization:
We also kicked MC1, MC2, MC3 tonight input matrix diagonalization.
Kick was done manually at the following times local.
- MC1 20:08 June 6th, 2022
- MC2 20:24 June 6th, 2022
- MC3 20:21 June 6th, 2022
We will leave watchdogs shutdown to free swing overnight (damping loops are "on").
This will help get better angular sensor from OSEMs to calibrate WFS signals.

Next:
- Investigate why MC1 coils gains have +1 for all
- Calculate input matrix. Make sure SUSPOS/PIT/YAW/SIDE_IN will be in the units of um or urad.

Suggestions:
- Add filter ramp time of 1sec for all by default
- Make null stream channel from input matrix for diagnostics

Attachment 1: Screenshot_2022-06-06_21-05-28.png
16895   Mon Jun 6 22:08:55 2022 KojiUpdateIMCMC1 OSEM sensor sign flipped, MC1/2/3 free swinging overnight for inmat diagonalization

Note that MC1 has a new style sat amp because the old one collapsed. The sign flip might have been the result of the replacement

17168   Sat Oct 1 13:09:49 2022 AnchalUpdateIMCWFS turned on

I turned on WFS on IMC at:

PDT: 2022-10-01 13:09:18.378404 PDT
UTC: 2022-10-01 20:09:18.378404 UTC
GPS: 1348690176.378404

The following channels are being saved in frames at 1024 Hz rate:

• C1:IOO-MC_TRANS_PIT_ERR (Same as C1:IOO-MC_TRANS_PIT_OUT)
• C1:IOO-MC_TRANS_YAW_ERR (Same as C1:IOO-MC_TRANS_YAW_OUT)
• C1:IOO-MC_TRANS_SUM_ERR (Same as C1:IOO-MC_TRANS_SUMFILT_OUT)

We can keep it running over the weekend as we will not use the interferometer. I'll keep an eye on it with occasional log in. We'll post the time when we switch it off again.

The IMC lost lock at:

UTC    Oct 03, 2022    01:04:16    UTC
Central    Oct 02, 2022    20:04:16    CDT
Pacific    Oct 02, 2022    18:04:16    PDT

GPS Time = 1348794274

The WFS loops kept running and thus took IMC to a misaligned state. Between the above two times, IMC was locked continuously with very brief lock loss events, and had all WFS loops running.

17169   Mon Oct 3 08:35:59 2022 TegaUpdateIMCAdding IMC channels to frames for NN test

[Rana]

For the upcoming NN test on the IMC, we need to add some more channels to the frames. Can someone please add the MC2 TRANS SUM, PIT, YAW at 256 Hz? and then make sure they're in frames.

and even though its not working correctly, it would be good if someone can turn the MC WFS on for a little while. I'd just like to get some data to test some code. If its easy to roughly close the loops, that would be helpful too.

[Anchal]

Currently, none of these channels are being written on frames. From simulink model, it seems the channels:

• C1:IOO-MC_TRANS_SUMFILT_OUT_DQ

• C1:IOO-MC_TRANS_PIT_OUT_DQ

• C1:IOO-MC_TRANS_YAW_OUT_DQ

are supposed to be DQed but are not present in the /opt/rtcds/caltech/c1/chans/daq/C1MCS.ini file. I tried simply adding these channels to the file and rerunning the daqd_ services but that caused 0x2000 error on c1mcs model. In my attempt, I did not know what chnnum to give for these channels so I omitted that and maybe that is the issue.

The only way I know to fix this is to make and install c1mcs model again which would bring these channels into C1MCS.ini file. But We'll have to run activateDQ.py if we do that which I am not totally sure if it is in running condition right now. @Christopher Wipf do you have any suggestions?

[Rana]

aren't they all filtered? If so, perhaps we can choose whatever is the equivalent naming at the LIGO sites rather than roll our own again.

@Tega Edo can we run activateDQ.py or will that break everything now?

[Tega]

@Rana Adhikari Looking into this now.

@Anchal Gupta The only problem I see with activateDQ.py is the use of the deprecated print function, i.e. print var instead of print(var). After fixing that, it runs OK and does not change the input INI files as they already have the required channel names. I have created a temporary folder, /opt/rtcds/caltech/c1/chans/daq/activateDQtests/, which is populated with copies of the original INI files, a modified version of activateDQ.py that does not overwrite the original input files, and a script file difftest.sh that compares the input and output files so we can test the functionality of activateDQ.py in isolation. Furthermore, looking through the code suggests that all is well. Can you look at what I have done to check that this is indeed the case? If so, your suggestion of rebuilding and installing the updated c1mcs model and running activateDQ.py afterward should do the trick.

I tested the code with:

cd /opt/rtcds/caltech/c1/chans/daq/activateDQtests/

./activateDQ.py

which creates output files with an _ prefix, for example _C1MCS.ini is the output file for C1MCS.ini, then I ran

./difftest

to compare all the input and corresponding output files.

Note that the channel names you are proposing would change after running activateDQ.py, i.e.

C1:IOO-MC_TRANS_SUMFILT_OUT_DQ -> C1:IOO-MC_TRANS_SUM_ERR

C1:IOO-MC_TRANS_PIT_OUT_DQ -> C1:IOO-MC_TRANS_PIT_ERR

C1:IOO-MC_TRANS_YAW_OUT_DQ -> C1:IOO-MC_TRANS_YAW_ERR

My question is this: why aren't we using the correct channel names in the first place so that we have less work to do later on when we finally decide to stop using this postbuild script?

[Anchal]

Yeah I found that these ERR channels are acquired and stored. I don't think we should do this either. Not sure what was the original motivation for this change. I tried commenting out this part of activateDQ.py and remaking and reinstalled c1mcs but it seems that activateDQ.py is called as postbuild script automatically on install and it uses some other copy of this file as my changes did not take affect and the DQ name change still happened.

[Tega]

Ah, we encountered the same puzzle as well. Chris found out that our models have SCRIPT=activateDQ.py embedded in the cds parameter block description, see attached image. We believe this is what triggers the postbuild script call to activateDQ.py. As for the file location, modern rtcds would have it in /opt/rtcds/caltech/c1/post_build, but I am not sure where ours is located. I did a quick search for this but could not find it in the usual place so I looked around for a bit and found this:

controls@rossa> find /opt/rtcds/userapps/ -name "activateDQ.py"

/opt/rtcds/userapps/trunk.bak/cds/c1/scripts/activateDQ.py

/opt/rtcds/userapps/tags/H2OAT_RCG2.5.1/cds/c1/scripts/activateDQ.py

/opt/rtcds/userapps/branches/StanfordGuardianDev/cds/c1/scripts/activateDQ.py

/opt/rtcds/userapps/branches/branch-2.3/cds/c1/scripts/activateDQ.py

/opt/rtcds/userapps/branches/branch-2.4/cds/c1/scripts/activateDQ.py

/opt/rtcds/userapps/trunk/cds/c1/scripts/activateDQ.py

My guess is the last one /opt/rtcds/userapps/trunk/cds/c1/scripts/activateDQ.py.

Maybe we can ask @Yuta Michimura since he wrote this script?

Anyway, we could also try removing SCRIPT=activateDQ.py from the cds parameter block description to see if that stops the postbuild script call, but keep in mind that doing so would also stop the update of the OSEM and oplev channel names. This way we know what script is being used since we will have to run it after every install (this is a bad idea).

controls@c1sus:~ 0\$ env | grep script

CDS_SCRIPTS_PATH=:/opt/rtcds/userapps/release/cds/c1/scripts:/opt/rtcds/userapps/release/cds/common/scripts:/opt/rtcds/userapps/release/isc/c1/scripts:/opt/rtcds/userapps/release/isc/common/scripts:/opt/rtcds/userapps/release/sus/c1/scripts:/opt/rtcds/userapps/release/sus/common/scripts

It looks like the guess was correct. Note that in the newer version of rtcds, we can use rtcds env instead of env to see what is going on.

Attachment 1: Screen_Shot_2022-09-30_at_9.52.39_AM.png
17189   Thu Oct 13 23:25:22 2022 ranaUpdateIMCIMC ASC: summary pages and notes

Tega has kindly made a summary page for the IMC WFS. Its in a tab on the usual summary pages.

One thing I notice is that the feedback to MC2 YAW seems to have very little noise. What's up with that?

The output matrix (attached) shows that the WFS have very little feedback to MC2 in YAW, but normal feedback in PIT. Has anyone recalculated this output matrix in the past ~1-2 years?

I'm going to read Prof. Izumi's paper (https://arxiv.org/abs/2002.02703) to get some insight.

The output matrix doesn't seem to have any special thing to make this happen. Any ideas on what this could be?

Attachment 1: Screen_Shot_2022-10-14_at_3.19.43_PM.png
17190   Thu Oct 13 23:52:45 2022 KojiUpdateIMCIMC ASC: summary pages and notes

The output matrices have been calculated on Aug 4, 2022 by me. [40m ELOG 17060]

Regarding the noise see [40m ELOG 17061]

With regard to the current IMC WFS design, a SURF student in 2014 (Andres Medina) and Nick Smith made the revision.
The telescope design was described in the elogs [40m ELOG 10410] [40m ELOG 10427] and also T1400670.

18   Fri Oct 26 16:19:29 2007 Tobin FrickeRoutineIOOMC resonances
We would like to measure the absorption of the mode cleaner optics. The plan is to repeat <a href="http://ilog.ligo-wa.caltech.edu:7285/mLIGO/Cleaning_the_Mode_Cleaner">Valera's experiment</a> in which we track the MC's thermal resonances to infer their power absorption. Last night Rana and I hooked up a lock-in amplifier to heterodyne the MC servo signal by 28 kHz and piped the output into an ADC using the MC_AO channel. We did not find any resonances.

Valera recommends we drive the POS of the three MC optics with bandlimited noise to excite the resonances.
22   Sun Oct 28 03:03:42 2007 ranaConfigurationIOOThree Way Excitement
We've been trying to measure the MC mirror internal mode frequencies so that we can measure
their absorption before and after drag wiping.

It looked nearly impossible to see these modes as driven by their thermal excitation level;
we're looking at the "MC_F" or 'servo' output directly on the MC servo board.

Today, I set up a band limited noise drive into the 'Fast POS' inputs of the 3 MC coil
driver boards (turns out you can do this with either the old HP or the SR785).

Frequencies:
MC1     28.21625 kHz
MC2     28.036   kHz
MC3     28.21637 kHz


I don't really have this kind of absolute accuracy. These are just numbers read off of the SR785.

The other side of the setup is that the same "MC_F" signal is going into the SR830 Lock-In which
is set to 'lock-in' at 27.8 kHz. The resulting demodulated 'R" signal (magnitude) is going into

As you can see from the above table, MC1 and MC3 are astonishingly and annoyingly very close in
frequency. I identified mirrors with peaks by driving one at a time and measuring on the spectrum
analyzer. I repeated it several times to make sure I wasn't fooling myself; it seems like they
are really very close
but distinct peaks. I really wish we had chipped one of these mirrors
before installing them.

Because of the closeness of these drumhead modes, we will have to measure the absorption by making long
measurements of this channel.
29   Tue Oct 30 00:47:29 2007 ranaOtherIOOMC Ringdowns
I did a bunch of MC ringdown measurements using the PD that Rob set up. The idea is to put a fast PD (PDA255)
looking at the transmission through MC2 after focusing by a fast lens. The input to the MC is turned off fast
by flipping the sign of the FSS (Andri Gretarsson's technique).

With the laptop sitting on the MC can, its easy to repeat many ringdowns fast:
- Turn off the MC autolocker. Relock the MC with only the acquisition settings; no boosts
and no RGs. This makes it re-acquire fast. Turn the MC-WFS gain down to 0.001 so that
it keeps it slowly aligned but does not drift off when you lose lock.

- Use low-ish gain on the FSS. 10 dB lower than nominal is fine.

- Setup the o'scope (100 MHz BW or greater) to do single shot trigger on the MC2 trans.

- Flip FSS sign.

- Quickly flip sign back and waggle common gain to get FSS to stop oscillating. MC
should relock in seconds.

Clearly one can scriptify this all just by hooking up the scope to the ethernet port.

Attached are a bunch of PNG of the ringdowns as well as a tarball with the actual data. A sugar
napoleon to whomever can explain the 7 us period of the wiggle before the vent!
Attachment 1: tek00000.png
Attachment 2: tek00001.png
Attachment 3: tek00004.png
Attachment 4: MC2ringdown.tar.gz
30   Tue Oct 30 13:58:07 2007 ajwConfigurationIOOMC Ringdowns
Here's a quick fit-by-eye to the latter part of the data from tek00000.xls.

The prediction (blue) is eqn 41 of
http://www.ligo.caltech.edu/docs/P/P000017-A.pdf

T1 = T2 = 0.002. Loss1 = Loss2 = 150 ppm.
MC3 assumed perfectly reflecting.
Velocity = 320 um/s (assumed constant), 2 usec into the ringdown.

OK, there's one little fudge factor in the prediction:
I multiplied D by 2.
Attachment 1: CavityRingdown.png
Attachment 2: CavityRingdown.m
% CavityRingdown.m
% Eqn 41 of
% "Doppler-induced dynamics of fields in Fabry–Perot
% cavities with suspended mirrors", Malik Rakhmanov (2000).
% http://www.ligo.caltech.edu/docs/P/P000017-A.pdf

clear all

at = importdata('tek00000.csv');

... 121 more lines ...
35   Wed Oct 31 08:34:35 2007 ranaOtherIOOloss measurements
In the end, we were unable to get a good scatter measurement just because we ran out of steam. The idea was to get a frame
grab image of MC2 but that involves getting an unsaturated image.

In the end we settle for the ringdowns, Rob's (so far unlogged) cavity pole measurement, and the MC transmission numbers. They
all point to ~100-150 ppm scatter loss per mirror. We'll see what happens after wiping.
36   Wed Oct 31 08:38:35 2007 ranaProblem FixedIOOMC autolocker
The MC was having some trouble staying locked yesterday. I tracked this down to some steps in the last
half of the mcup script; not sure exactly which ones.

It was doing something that made the FAST of the PSL go to a rail too fast for the SLOW to fix.
So, I broke the script in half so that the autolocker only runs the first part. We'll need to
fix this before any CM locking can occur.

We also need someone to take a look at the FSS Autolocker; its ill.
39   Wed Oct 31 15:02:59 2007 tobinRoutineIOOMode Cleaner Mode Tracking
I processed the heterodyned mode cleaner data yesterday, tracking the three 28 kHz modes corresponding to MC1, MC2, and MC3. Unfortuntately the effect of our MC power chopping is totally swamped by ambient temperature changes. Attached are two plots, one with the tracked mode frequencies, and the other containing dataviewer trends with the MC transmitted power and the room temperature. Additionally, the matlab scripts are attached in a zip file.
Attachment 1: mode-track.pdf
Attachment 2: trends.pdf
Attachment 3: mcmodetrack.zip
40   Wed Oct 31 15:22:59 2007 robConfigurationIOOMode Cleaner transfer function
I measured the transfer function of the input mode cleaner using a PDA255 and the ISS. First I put the PD in front of the ISS out-of-loop monitor diode and used an SR785 to measure the swept sine transfer function from the Analog IN port of the ISS to the intensity at the PD. Then I moved the PD to detect the light leaking out from behind MC2, using ND filters to get the same DC voltage, and measured the same transfer function. Dividing these two transfer functions should take out the response of the ISS and the PD, and leave just the transfer function of the MC. A plot of the data, along with a single-pole fit, are attached.

The fit is pretty good for a single pole at 3.79 kHz. There's a little wiggle around 9kHz due to ISS weirdness (as Tobin has not been giving it the attention it requires), but this shouldn't affect this result too much. Using the known MC length of 27.0955m, and assuming that MC1 and MC3 have a power transmissivity of 2000ppm and MC2 is perfectly reflecting, the total round trip loss should be about 300ppm. The fitted finesse is 1460.
Attachment 1: MCtf.pdf
45   Thu Nov 1 11:45:30 2007 tobinConfigurationIOOMode cleaner drag-wiping
Andrey, Bob, David, John Miller, Rana, Rob, Steve, Tobin

Yesterday we vented the vacuum enclosure and opened up the chamber containing MC1 & MC3 by removing the access connector between that chamber and the OMC chamber. Rana marked MC1's location with dogs and then slid the suspension horizontally to the table edge for easy drag-wiping access. The optic was thoroughly hosed-down with the dionizer, in part in an effort to remove dust from the cage and the top of the optic. Drag-wiping commenced with Rob squirting (using the 50 microliter syringe) and Tobin dragging (using half-sheets of Kodak lens tissue). We drag-wiped the optic many (~10) times, concentrating on the center but also chasing around various particles and a smudge on the periphery. There remains one tiny speck at about the 7:30 position, outside of the resonant spot area, that we could not dislodge with three wipes.

Today we drag-wiped MC3. First we slid MC1 back and then slid MC3 out to the edge of the table. We disconnected the OSEM cables in the process for accessibility, and MC1 is perched at an angle, resting on a dog. We did not blow MC3 with the deonizer, not wanting to blow particles from MC3 to the already-cleaned MC1. We drag-wiped MC3 only three times, all downward drags through the optic center, with Steve squirting and Tobin dragging. Some particles are still visible around the periphery, and there appears to be a small fiber lodged near the optic center on the reverse face.

Andrey and Steve have opened up MC2 in preparation for drag-wiping that optic after lunch.
61   Sun Nov 4 23:55:24 2007 ranaUpdateIOOFriday's In-Vac work
On Friday morning when closing up we noticed that we could not get the MC to flash any modes.
We tracked this down to a misalignment of MC3. Rob went in and noticed that the stops were
still touching. Even after backing those off the beam from MC3 was hitting the east edge of
the MC tube within 12" of MC3.

This implied a misalignment of MC of ~5 mrad which is quite
large. At the end our best guess is that either I didn't put the indicator blocks in the
right place or that the MC3 tower was not slid all the way back into place. Since there
is such a strong stickiness between the table and the base of the tower its easy to
imagine the tower was misplaced.

So we looked at the beam on MC2 and twisted the MC3 tower. This got the beam back onto the
MC2 cage and required ~1/3 if the MC3 bias range to get the beam onto the center. We used
a good technique of finding that accurately: put an IR card in front of MC2 and then look
in from the south viewport of the MC2 chamber to eyeball the spot relative to the OSEMs.

Hitting MC2 in the middle instantly got us multiple round trips of the beam so we decided
to close up. First thing Monday we will put on the MC1/MC3 access connector and then
pump down.

Its possible that the MC length has changed by ~1-2 mm. So we should remeasure the length
and see if we need to reset frequencies and rephase stuff.
62   Mon Nov 5 07:29:35 2007 ranaUpdateIOOFriday's In-Vac work
Liyuan recently did some of his pencil beam scatterometer measurements measuring not the
BRDF but instead the total integrated power radiated from each surface point
of some of the spare small optics (e.g. MMT, MC1, etc.).

The results are here on the iLIGO Wiki.

So some of our loss might just be part of the coating.
67   Tue Nov 6 10:42:01 2007 robConfigurationIOOmode cleaner locked
Increased the power exiting the PSL by turning the half-wave plate after the MOPA, opened the PSL shutter, and aligned the mode cleaner to the input beam. It wasn't that hard to find the beam with the aperture open all the way on the MC2 camera. The transmitted power is now 2.9 arbitrary units, while the input power is 1.2 arbitrary units. Not sure yet if that's an increase or decrease in efficiency, since no one posted numbers before the vent. Also turned on the input-steering PZTs and saw a REFL beam on the camera.
68   Tue Nov 6 14:51:03 2007 tobin, robUpdateIOOMode cleaner length
Using the Ward-Fricke variant* of the Sigg-Frolov method, we found the length of the mode cleaner to be 27.0934020183 meters, a difference of -2.7mm from Andrey, Keita, and Rana's measurement on August 30th.

The updated RF frequencies are:
3  fsr =  33 195 439 Hz
12 fsr = 132 781 756 Hz
15 fsr = 165 977 195 Hz
18 fsr = 199 172 634 Hz
* We did the usual scheme of connecting a 20mVpp, 2 kHz sinusoid into MC AO. Instead of scanning the RF frequency by turning the dial on the 166 MHz signal generator ("marconi"), we connected a DAC channel into its external modulation port (set to 5000 Hz/volt FM deviation). We then scanned the RF frequency from the control room, minimizing the height of the 2 kHz line in LSC-PD11. In principle one could write a little dither servo to lock onto the 15fsr, but in practice simply cursoring the slider bar around while watching a dtt display worked just fine.
74   Wed Nov 7 00:51:33 2007 andrey, rob, tobinConfigurationIOOMC ringdowns
We completed several ringdown measurements this afternoon; Andrey is currently processing the data.
As Tobin wrote two hours ago, we (Andrey, Tobin, Robert) made a series of ringdown measurements for MC2
in the spirit of the measurement described by Rana -> see
entry from Mon Oct 29 23:47:29 2007, rana, Other, IOO, MC Ringdowns.

I attach here some pictures that we saw on the screen of the scope, but I need to admit that I am not experienced enough to present a nice fit to these data, although I attach fits that I am able to do today.

I definitely learned a lot of new Matlab functions from Tobin - thanks to him!, but I need to learn two more things:

Firstly, I do not know how to delete "flat" region (regions before the ringdown starts) in Matlab ->
I needed to delete the entries for times before the ringdown ("negative times") by hand in the text-file, which is extremely non-elegant method;

Secondly, I tried to approximate the ringdown curve by a function ydata=a*exp(b*xdata) but I am not exactly sure if this equation of the fitting curve is a good fit or if a better equation can be used.

It seems, in this situation it is better for me to ask more experienced "comrades" on November 7th.

P.S. It seems I really like the type of message "Bureaucracy" - I put it for every message. As Alain noted, maybe that is because some things are very bureacratized in the former USSR / Russia. By the way, when I was young, November 7th was one of two most important holidays in the USSR - I liked that holiday because I really liked military parades on the red square. I attach a couple of pictures. November 7 is the anniversary of the Revolution of 1917.
Attachment 1: image-attempt_1.png
Attachment 2: image-attempt_2.png
Attachment 3: image-attempt_3.png
Attachment 4: image-attempt_4.png
Attachment 5: image-attempt_5.png
Attachment 6: Fit-1st_attempt.jpg
Attachment 7: Fit-5th_attempt.jpg
78   Wed Nov 7 13:54:44 2007 robConfigurationIOOMode Cleaner transfer function
I performed the same procedure described here, and re-measured the transfer function of the mode cleaner to see the effect of the drag-wiping. The results are attached in a pdf. We don't seem to have done any damage, but the improvements are barely measurable.

 What Then Now pole frequency 3.789kHz 3.765kHz loss per optic 99ppm 91ppm finesse 1460 1470 trans 86.7% 87.7%
Attachment 1: mctf.pdf
80   Wed Nov 7 14:05:59 2007 tobinConfigurationIOOMC ringdown
Modeling the mode cleaner as a simple cavity with all losses lumped together, we expect the cavity power to be
attenuated by a factor (1-L) after each interval (2l/c)=1/fsr. Therefore we can get the cavity loss L
(including power lost through transmission) from the ringdown time constant tau as:

L = 1 - exp[ - 1/(tau * fsr) ]

From this we have to subtract the 2000 ppm transmission for each of MC1 and MC3, and divide by three to spread
the losses across the three optics.

I get 168 ± 39 ppm loss per optic based on a very simple exponential fit to the tails (t>0) of four of Andrey's data files.

By comparison, I get 154 ± 37 ppm from Rana's data files from before the vent.
125   Tue Nov 27 15:47:17 2007 robConfigurationIOOMC loop
After the FSS running pretty quick, I checked the MC loop. I used TPA 1&2.

MC loop
UGF: 70kHz
Input Gain: 29dB
Boost Level: 2
phase: 40 deg
Attachment 1: MCsmall.jpg
126   Tue Nov 27 16:18:58 2007 robConfigurationIOOMC loop
Reduced the common gain to 22dB in the mcup script, so that the WFS would not blow the lock. The above measure of the OLG was done without the mcWFS running, so may be a low estimate as compared to when the alignment is perfect.
154   Sun Dec 2 21:02:12 2007 ranaConfigurationIOOMC SUS re-alignment
The spot on MC2 was not centered, so I put it back in the center:

• Made sure MC trans was high with the WFS off.
• Moved the Sliders on the MC Align screen until spot was centered (by eye)
• Moved some more until power was maximized.
• Unlock MC
• Center spots on McWFS
• Re-enable autolocker and McWFS loops.
155   Sun Dec 2 21:07:39 2007 ranaConfigurationIOOMC SUS re-alignment
you asked for:   diff 2007/12/01,4:58:48 2007/12/03,4:58:48 utc 'MC.*COMM'
LIGO controls: differences, 2007 12/01 04:58:48 utc vs. 2007 12/03 04:58:48 utc
__Epics_Channel_Name______   __Description__________   __value1____     __value2____
C1:SUS-MC1_YAW_COMM                                    -0.273460        -0.503460
C1:SUS-MC2_PIT_COMM                                     3.624020         3.632020
C1:SUS-MC2_YAW_COMM                                    -0.936800        -1.038800
C1:SUS-MC3_YAW_COMM                                    -3.129000        -3.369000
156   Sun Dec 2 21:13:16 2007 ranaConfigurationIOOMC SUS re-alignment
Attachment 1: e.png
178   Fri Dec 7 00:02:26 2007 ranaSummaryIOOMC/FSS Frequency Noise
The FSS frequency noise is not very bad.

I compared the MC_F spectra between Hanford and the 40m using DTT and its 'User NDS' option.
After Sam, Jenne, and DavidM installed the new MC Servo some time ago, the MC_F spectrum here
has had some whitening before it goes into the DAQ (on board; same as LLO & LHO). The tuning
coefficient of the VCO is also basically the same between all PSLs since everyone has the same
chip in the VCO driver.

Therefore, at the frequencies where the MC gain is more than ~4, the MC_F signal calibration is
the same here as anywhere. Since its the servo control signal, its basically a measure of the
frequency noise incident on the MC -- its just what comes out of the FSS with the table noise on
top. At low frequencies (< 100 Hz) its a measure of the motion of the MC mirrors.

Above 200 Hz ours is the same as theirs; except for the enormous power line spikes. I think that's
either all on the light. But our acoustics are better and the noise above 1 kHz levels off at the
same flat floor (the phase noise of the VCO) as H1. The huge lump around 100 Hz is the MC2 DAC noise and
it goes down to the H1 levels when we flip on the dewhites. The giant excess from 5-50 Hz is just the fact
that our stacks don't do much until 20-30 Hz.

So we can stop blaming the FSS and move on with life as soon as Tobin gets the ISS back in shape.
Attachment 1: fly.pdf
304   Sat Feb 9 13:05:48 2008 JohnSummaryIOOPMC camera/ HEPA
I replaced the Gig-E camera on the PMC trans beam. The PZT was close to railing and I wanted to adjust it. I just did a quick job, there is a little scattered light on the image. If Joe is finished with the Gig-E I'll take another look at it.

The HEPA in the PSL table was turned off for some reason. I turned it back on.
307   Sun Feb 10 21:43:16 2008 robConfigurationIOOMC alignment tweaked

I adjusted the alignment of the free hanging mode cleaner to best transmit the PSL beam.
357   Tue Mar 4 20:14:02 2008 ranaConfigurationIOOMC Alignment
The MC alignment was pretty far off. We were getting TEM01 mode locks only.
Rather than inspect what happened I just aligned the MC suspensions to get
the transmission higher. Now Matt should be able to lock the X arm and collect
361   Wed Mar 5 17:35:24 2008 ranaUpdateIOORFAM during MC lock
I used an ezcaservo command to adjust the offsets for Alberto's StochMon channels. They are all
at +2 V with no light
on the RFAM PD (MC unlocked).

Then I looked at 5 minutes of second trend around when the MC locks. Since Alberto has chosen
to use +2V to indicate zero RF and a negative gain, there is a large RF signal when the StochMon
channels approach zero
.

From the plot one can see that the RFAM for the 133 & 199 MHz channels is much worse than for the 33 and 166.
Its also clear that the turn on of the WFS (when the RFAMPD's DC light level goes up) makes the single demod
signals get better but the double demod get worse.
Attachment 1: rfam.pdf
372   Wed Mar 12 23:05:44 2008 ranaUpdateIOOMC WFS

437   Tue Apr 22 17:08:04 2008 CarynUpdateIOOno signal for C1:IOO-MC_L
C1:IOO-MC_L signal was at zero for the past few days
439   Tue Apr 22 22:51:30 2008 ranaConfigurationIOOMcWFS Status
I've been working a little on the MC WFS in the last few days. I have made many
changes to the sensing matrix script and also to the MCWFSanalyze.m script.

The output matrix, as it was, was not bad at low frequencies but was making noise in
the ~1 Hz band. Turning the gain way down made it do good things at DC and not make
things work higher.

The output matrix generating script now works after Rob fixed the XYCOM issue. Not sure
what was up there. As Caryn mentioned the SUS2.ini channels were all zero after Andrey's
PEM power cycle a few days ago. Rob booted c1susvme to get the SUS1 channels back and
today we did c1susvme2 to get the IOO-MC_L et. al. back.

Even after doing the matrix inversion there is some bad stuff in the output matrix. I
checked that the sensing matrix measurement has good coherence and I measured and set the
MC WFS RF phases (they were off by ~20-30 deg.). Still no luck.

My best guess now is that the RG filters I've used for POS damping and the movement of the
beam on the MC mirror faces has made a POS<->YAW instability at low frequencies. My next
move is to revert to velocity damping and see if things get better. Should also try redoing
the A2L on the MC1-3.
451   Fri Apr 25 20:53:02 2008 ranaConfigurationIOOMC WFS with more gain
Quick update: we found that the reason for the MC WFS instability was that the digital anti-whitening was one but not the analog whitening.

We turned off the digital filters and were able to increase the gain by a factor of ~30. It is left like this, but if it hampers IFO locking then best to just turn it back down to an overall gain of 0.1 or 0.05.
454   Sun Apr 27 02:11:11 2008 ranaConfigurationIOOMC WFS Notes
As noted in the elog from Friday, the WFS has been bad ever since someone switched on the digital whitening filters (FM1 & FM2)
in the MC WFS I&Q filter banks.

On Friday evening, John, Alan, and I went to the rack and verified that although the drawing shows a hookup for the whitening
filters, there is actually no such thing and so we can't have the whitening. So the anti-whitening turns on two lag filters
(2 poles at 4 Hz) and without the hardware this makes the servos unstable by adding 90 deg of phase lag at 4 Hz.

There are still several problems in this system:
- AD797 is used after the mixer. This is an unreliable, noisy part. We need to change this out
with some OP27s so that this becomes reliable and has a more reasonable noise figure.

- Hard wire the whitening filters ON. We never want these to be off. Then we can turn on the
anti-whitening. This will give us a factor of 100 better noise without filtering.

- The AD602 on the front of the whitening board has a 100 Ohm internal impedance and the
resistor between the demod board and the AD602 is 909 Ohms. This results in dividing the
signal by 10.

- The signal at the ADC is ~100 cts peak-peak. The full ADC range is, of course, 65000 cts. So
we could use a lot more gain. The mean quadrant signals are also ~100 cts so we could easily
up the analog DC gain by a factor of 30 on top of the whitening filter increase.

- The AD602 at the input and the AD620 on the output are both variable gain stages but because
of our lack of control are set to ambiguous gain levels. We should set the AD602 on the input
to its max gain of 30 dB. With the -20 dB from the x10 voltage division, this will give us
an overall gain of 3 for the puny demod signals.


455   Sun Apr 27 05:09:30 2008 ranaConfigurationIOOMC WFS Whitening turned on
I hardwired on the MC WFS whitening filters.

The MAX333A switches which choose between whitening and bypass on that board were in the bypass position
because the Xycom220 connections are not there. So the control switch gets +15V but there is no pull
down to set it to the whitened mode.

The least invasive (easiest) change I could do was to tie all of those inputs to ground. This pulls a few mA
through the pull-down resistors but is otherwise innocuous. All of these control lines come in on the A-row
of the P1 connector, so I was able to solder a single wire across all of them to ground them all.

The WFS2 board had a blown electrolytic capacitor on the -15 V line and so there was probably some extra noise
getting in that way. I couldn't find any extra SMD to replace it so I cut the legs off of a 22 uF polarized
tantalum and stuck it in there. Its even close to being the same color. I checked out the other caps, and they were all
close to 68 uF as spec'd. This one had luckily blown open and so didn't suck down the Sorensen and destroy everything.

Plugged everything back in switched the WFS servos back on. Looks good. Took before and after spectra.

In the plot:

GREEN: Open loop dark noise before changes
RED: Open loop bright (MC locked but MCWFS off)
BLUE: Closed loop, MC locked

BLACK: Dark noise after whitening
ORANGE:Closed loop after whitening

The cursor is at 16.25 Hz, the SOS bounce mode.

The I ran the new setMCWFSgains script which uses pzgain to set the UGFs of the 4 loops to 4.01 Hz.
We have in the past had problems with high WFS gains causing instabilities with the CM servo around 10-30 Hz. If this happens we should
just lower the gain by a factor of ~5.
Attachment 1: mcnoise.png
489   Tue May 20 18:33:01 2008 Andrey, JohnConfigurationIOOMode Cleaner is locked again

It was noticed by Mr.Adhikari earlier today that the MC became unlocked at about 11AM.

There is no clear understanding what caused the problem.

Trying to restore the modecleaner locking, we noticed with John that the beam was not centered on the wavesensors (WFS1. WFS2 on the screen "C1IOO_LockMC.adl"). We decided to adjust the beam position moving slightly the bias sliders for pitch and yaw degrees of freedom for MC1.
This allowed to make the MC locked.

Old positions for the MC1 sliders: Pitch = 2.9934, Yaw = -0.6168;
New positions --------//---------: Pitch = 3.0604, Yaw = -0.7258.

At the same time, FSS for PSL is still showing the values in the range 0.720 - 0.750 which is lower than the usual values. The indicator for FSS value is yellow when it is below 0.750.
496   Sun May 25 19:33:16 2008 ranaUpdateIOOMC Bad after Re-alignment
The MC pointing was off and the transmitted power was down after John and Andrey brought it back after the bootfest.

I tried getting it back on Friday but was unsuccessful. Today, after the Phoenix Landing, I got it back to someplace
reasonable, but it still seems to be far off. I will check with Rob before we recenter and of the QPDs.

I had to move all of the MC SUS and also align the beam using the IOO periscope. The attached PDF shows some trends
over the last 80 days. You can see that the drop in MC TRANS is about the same as the drop in PMC TRANS.
Attachment 1: e.pdf
Attachment 2: pmc.png
503   Thu May 29 15:58:44 2008 JohnSummaryIOOMC realignment
I repeatedly adjusted the yaw of the upper mirror on the input periscope and re aligned the MC. With the PRM aligned I tried to optimise MC transmission and DC refl simultaneously. I subsequently centred the beams on WFS1/2. Attached is a 30 day trend of MC alignment and transmission.
ELOG V3.1.3-