Layout that will be improved upon over the next few days.

Things that need to be updated:
1. Waist size at all optics
2. Beam size at detectors and choice of lenses
3. IPANG & green PD proposed positions

 Here our device under test is the photodiode. So for the reference I wanted to retain the response of the laser diode controller. Otherwise I have to consider the transfer function of that LDC too. I may check both the options at the time of experiment.

Thanks

Den made a nice elog about the PRMI RIN that we see a few weeks ago:  8464.  The RIN that we're seeing is typically about ~30%.  The question at hand is: what is causing this power fluctuation, and more specifically, is it the angular motion of the mirrors?

I find that no, the angular motion that we see does not explain the RIN that we see.

In the attached Mathematica notebook, I calculate the power lost due to angular misalignments of one or more mirrors.  (Math comes from Appendix A of Keita's thesis.)

From calibrated oplev spectra, our mirrors are moving about 1 microradian (RMS, which is dominated by low frequencies).  From a super sophisticated "draw on the TV, then measure" method (details below), I have estimated that the maximum static misalignment that we're seeing is about 2 microradians.

With all of this, I find that for a g-parameter of 0.94, the power lost due to misalignments should, at maximum, be 0.6%.  I need a g-parameter of 0.995 to get a power loss of 23%.  Alternatively, if I take the derivative of the power coupling function, to find the static misalignment at the steepest slope of the curve (and thus, the place where any AC misalignment would have the most effect), for 1urad of AC misalignment, I get 40% power loss. 

So, in order for the AC angular motion that we see to explain the RIN that we see, either our mirrors are very, very misaligned (so much so that we couldn't really be locking), or our cavity is much closer to unstable than expected from Jamie's calculations.  Since both of these cases (static misalignment or incorrect g-parameter calculation) have to be taken to extremes before they approximate the RIN that we see, I do not think that this power loss is due to angular fluctuations.

This means that we have to think of another potential cause for this RIN that we're seeing.

Details on the "draw on TV and measure" technique for determining static cavity misalignments:  Looking at the POP camera view, with the PRM significantly misaligned, I traced the straight-through beam spot.  I then restored the PRM, and during several momentary locks, I traced the beam spot, which I took to be the saturated area of the camera.  The idea here is that the straight-through beam represents the incident beam axis, while the locked beam represents the cavity axis.  I'm assuming that the camera image plane is at the face of PR2. I approximately found the center of each of my tracings, and found them to be ~1/4 inch apart.  I also measured the "spot size" of the sideband-locked PRMI, and found it to be ~3.5 inches.  So, very roughly, the ratio of (distance between spots)/(size of beam) is ~0.07. This corresponds to a static misalignment of either the ITM or the PRM of ~2urad, rounding up. (I use the Jamie's calculated g-parameters from elog 8316, the case of flipped PR2, tangential = 0.94 to calculate the effective RoC of the PRM). 

Koji is elogging separately of his exploration of different configurations.  The lock stretch that I'm looking at here uses the same parameters as Koji had for PRMI sb lock, using AS55Q for MICH and REFL33I for PRCL, with MICH gain of -0.8 and PRCL gain of 0.05 .

All of these plots are the same few second lock stretch, with different zooming.  Jamie's super-sweet getdata python script only accepts integers for the start time and duration parameters, so lots of this zooming happened by hand, but I tried to always keep the time axis aligned within each screenshot.  Sometimes the plot axis labels say differently, but they're lying to you.

Plot 1:  gps start time is 1050915916, duration = 6 seconds.  Overall view of the lock stretch.

Plot 2:  gps start time is 1050915921, duration = 1 second.  We're looking at the lockloss that happens at the left side of the plots.

Plot 3:  zoomed in (along the time-axis) version of plot 2, so much shorter time duration.  Some zooming on y-axes.

Plot 4:  zoomed in (along y-axes) version of plot 2.

It seems to me from these plots that maybe MICH CTRL is drifting away?  It seems like we lose the MICH lock, and that destroys the whole thing. 

Koji made some comments to me earlier, regarding his work this evening, that the MICH signal quality is poor in general, and that we should calculate/think about changing our schnupp asymmetry. 

I contacted Den about malfunctioning of the Yarm ASS.

He found the scripts were modified during the attempt to make it available for Xarm (cf. a related elog entry)
So far, he could manage to make the current scripts being modified to run.
A striptool file is still missing but this is what we can handle locally.

I thank Den for the remote caring of the issue despite the limited network bandwidth.

The ATF NPRO auxiliary laser has been moved on the PSL table. All the optics for beat note measurement are in place and alignment has been done.

The setup for this measurement is the same as described in elog 8333.

I am following the instructions here:

https://www.lsc-group.phys.uwm.edu/daswg/docs/howto/lal-install.html#test

But there as an error when I run the ./00boot command near the beginning.  I have asked Duncan Macleod about this and am waiting to hear back.

For now, I am putting things into /home/controls on allegra.  My understanding is that this is not shared, so I don't have a chance of messing up anyone else's work.  I have been moving slow and being extra cautious about what I do because I don't want to accidentally nuke anything.

[Jenne, Annalisa, with guidance from Koji]

We took data to remeasure the Schnupp asymmetry, using the Valera method that Jamie described in elog 4821. 

1  First, we locked the arms each with their PO(X,Y) signals, to get the alignment of each arm. 

2.  Then, we locked the Xarm with AS55I (Yarm optics, and PRM very misaligned, more than the misalign script).  Since AS55 was saturating, I changed the analog gain from 24dB to 21dB. (After work was completed, the analog gain was put back to the nominal 24dB for both I&Q.)

3.  We set up the Lockin similar to Jamie's description, with a few differences.  We used the same f = 103.1313, but used ampl=10cts.  Sin and cos gain were each 100.  We changed the lowpass filter from 0.1Hz to 0.05Hz (so each measurement had a settling time of at least 20sec).  We were using LSC-Lockin4, so the Lockin matrix was set so Lockin4 was reading from AS55Q, and the LSC output matrix was such that we were actuating on the ETM (X, then Y when we switched arms later).

4.  By hand, we roughly found the zero crossing of the lockin-q output (which corresponded also to zero of the lockin-I, since this is the place where all of the PDH signal was in AS55I, and the lockin was reading AS55Q). 

5.  We took points separated by 0.2 degrees, plus and minus 1 degree from the zero-crossing phase we had found (i.e., for the Xarm, we roughly found the zero crossing at -14.39 deg, so took data from -15.39 to -13.39degrees).  For each phase, we took 5 measurements (using ezcaread), at least 20 seconds apart.  After moving the phase, we waited at least ~40 seconds (watching the lockin outputs on striptool, they had completely settled after 30 or 40 seconds).

6.  We then repeated steps 2, 4 and 5 for the Y arm.  The lockin setup didn't change, except that now we actuate on ETMY.

We did a quick estimate calculation, from our rough zero-crossings to get a rough measurement of the Schnupp asymmetry.  DeltaPhi = (-14.39 -   -19.79) = 5.40 . This gives us (using F_sideband = 5*11066134, the current 11MHz marconi freq) a rough Schnupp asymmetry of 4 cm. 

Analysis to follow.

EDIT, JCD:  The Xarm gain at this time was -0.160, and the Yarm gain was -0.170

When I talked with Den via phone, he recommended to use the trigger and normalization with POP110I.
So I decided to try this approach. Also I investigated how the REFL33 signals are useful.

I could find the state where the PRMI(sb) locks regularly, although the lock is ~1min at most.

PRCL: REFL33I
whitening gain 30dB, -14.0deg (finely tuned in lock)
-> x1.0 -> Triggered by POP110I (20up, 1down)
-> Normalized by POP110I x0.04
-> Gain 0.2~0.12 FM3, 4, 5, 6 always on, no triggered FMs
-> PRM

MICH: REFL33Q
whitening gain 30dB, -14.0deg (finely tuned in lock)
-> x1.0 -> Triggered by POP110I (20up, 1down)
-> Normalized by POP110I x0.04
-> Gain -20 FM4, 5 always on, no triggered FM
-> ITMX (-1.0) and ITMY (+1.0)

I needed to tune the phase very precisely to reach this state. Also the alignment of the michelson and PRM
was very crtiical to acquire the lock.

Later in the same night I was plagued by PRM alignment drift. It seems that the PRM alignment is bistable or
slightly drifting in pitch. I had to align PRM continuously. When the PRMI is locked, the alignment fluctuation
was mainly in yaw. This was as people commented before.

Prior to the locking trials...

scripts/LSC/LSCoffset script had behaved peculiarly:

This script spawns LSC/offset3 in order to remove the dark offset from the channels.
How ever the offsets had been nulled every other PDs
(i.e. The offsets REFL11 I&Q were nulled.
The offsets REFL33 I&Q had been left untouched
The offset REFL55 I&Q had been nulled
and so on.)

I found that the script run many instances of "offset3" scripts in background.
It seemed that tdsavg did not like too many averaging channels at once.

So the "&"s in the LSCoffsets were removed and now the script runs much more slowly,
but works for all of the PDs listed.

I think I have never seen the offsets in REFL33 and REFL165 nulled down to this level before.

 Albert, our new undergrad work force received 40m specific- basic safety training last week. Please read and sign 40m procedures booklet.

 I installed the new version of LAL on allegra.  I don't think it has interfered with the existing version, but if anyone has problems, let me know.  The old version on allegra was 6.9.1, but the new code uses 6.10.0.1.  To use it, add . /opt/lscsoft/lal/etc/lal-user-ench.sh to the end of the .bashrc file (this is the simplest way, since it will automatically pull the new version).

I am having a little trouble getting some other unmet dependencies for the summary pages such as the new lalframe, etc.  But I am working on it.

Once I get it working on allegra and know that I can get it without messing up current versions of lal, I will do this again on megatron so I can test and edit the new version of the summary pages.

 These are the tentative box placements. Roughly. I don't actually have the box finalized yet, but the box should be around that size.

 AS1

BSPRM

ETMX

ETMY

MC2

POX

POY

How do I perspective ._.

While helping Riju out this afternoon, I noticed that the timing fiber that goes to the OMC rack (near the AP table) was bent, and is now possibly kinked, after the installation of the fiber splitter box. 

The fiber was hanging from the back of the rack, and had been strain relieved.  However, the path that the fiber was taking is now occupied by the fiber splitter for the RF PD diagnostic stuff.  So, the installation of the fiber splitter box put the old timing fiber under tension, causing the fiber to be bent at a little over 90 degrees, since it was pulled tightly against the corner of the splitter's front panel. 

I adjusted the strain relief so that the fiber is loose again, although there is still a bit of a kink that you can feel.  Things (for now) seem to be working, since the 1pps light on the front of the box at the top of the OMC rack is still blinking happily, indicating that the 1pps is still getting there. 

We are not using most of the stuff in that rack right now, but if we have problems in the future, we should check out the fiber to make sure it is still good.

Today the locking was not as easy as that was last Friday.
So I tried something new. Today Rana talked about the ASDC locking with POPDC normalization.
This technique was tried. (This is somewhat similar to DC readout.)

PRCL
Signal source: REFL33I / Normalization POP110I x 0.04 / Trigger POP110I 20up 3down, otherwise  untouched from Friday locking
Servo: input matrix 1.00 -> PRCL Servo FM3/4/5/6 Always ON G=+0.06
Actuator: output matrix 1.00 -> PRM

MICH
Signal source: ASDC Offset -109.5 (nominal of the day -49.5) / Normalization POPDC x 1.00 / Trigger POP110I 20up 3down
Servo: input matrix 1.00 -> MICH Servo FM5 Always On G=+10000
ActuaroL output matrix -1.00 -> ITMX / +1.00 -> ITMY

Observation

- POP110I was ~120 during the lock (cf 170 on Friday). So there is some small leakage from the dark port.

- Lock was easier when FM4 of the MICH loop was turned off.

- During the lock horizontal motion of the intracavity mode was visible as usual.

I'm not sure why or when it was tripped, but I have restored the ETMX watchdog.

Annalisa and I met yesterday and fixed the voltage regulator on the breadboard so the QPD circuit is working. We will meet with Eric on Thursday to determine the course of action with measurements.

Back when Gabriele was here, he and I implemented online calibration of the oplevs, into microradians.  A consequence of this is that all of the XY-plots on the medm screens were too small. 

I have gone through all the screens that I could think of (SUS_SINGLE, SUS_SINGLE_OPTLEV_SERVO, OPLEV_MASTER, OPLEV_SUMMARY, OPLEV_SUMMARY_SMALL_SCALE, IFO_OVERVIEW) and made the range of the XY-plots +/- 100, rather than the old scale of +/-1. 

I have also added red boxes behind the numbers on many (but not yet all) of these screens, so that you can see when (a) the oplev sum is too low, or (b) either the pit or yaw value is over 50 microradians. 

While I was putzing around on the IFO overview screen, I also made the oplev sum numbers clickable, with the related display being that optic's oplev servo screen.

Koji is working on PRMI locking with different photodiodes, and rather than typing different numbers into the input matrix, it is more convenient to just be able to click on/off buttons for different filter banks.  So, the CARM filter bank in the LSC model is currently being borrowed as a secondary PRCL filter bank.  I have copied all of the current PRCL filters over to the CARM filter bank. 

Just for reference, although we have not yet used CARM for CARM, the previous filters were the "default" set, +6dB, 0:1, 1:5, 1:50, 1000:10, RG3.2, RG16.5, RG24, empty, empty.  These are currently the same in the DARM and MC filter banks, so we can copy them back over in the future.

[Jenne Koji]

- Today the spots were moving more than the usual. The OPLEV screens showed that the spots are too much off from the center.

- Each vertex OPLEVs were checked and OPLEV wonderland was discovered: Other than the usual misalignment of the spots,
it was found that PRM/ITMX/ITMY beams were clipped somewhere in the paths, BS/PRM oplevs had many loose components
including the input lenses (they are still clamped by a single dog clamp THIS SHOULD BE FIXED ASAP).

- On the ITMY table there were so many stray optics. They were removed and put on the wagon next to the ITMY table.
THIS SHOULD BE CLEARED ON THE WEDNESDAY CLEANING SESSION.

- During this OPLEV session, LSCoffset nulling was run.

- After the OPLEV session, the locking became really instantaneous. We wonder which of the OPLEV cleaning, LSC offset nulling,
and the usual seismic activity decay in the evening was effective to make it better.

- Initially the lock was attempted with REFL33I/Q and some ~10sec lock streches were obtained. During this lock,
  the optical gain of AS55Q was measured in relative to REFL33Q. In deed they were calibrated to be the same
  gain at the input matrix.

- After the MICH signal source was switched to AS55Q, the lock streches became more regular and the minutes long.
We precisely tuned the phase of AS55 and REFL55 in terms of the differential excitation of ITMX/Y using lockin (FREQ 250, AMP 1000).

- We noticed that the AS port spot with AS55Q MICH was darker than the REFL33Q MICH. This suggests the existence of residual offset
in REFL33Q. In deed we observed +30cnt offset in REFL33Q when the PRMI is locked with AS55Q MICH.

- Phases and relative gains of the signals were as follows:

PRCL: REFL33I 1.00 =REFL55I +0.4
MICH: AS55Q 29deg x1.00 = REFL33Q -14deg x1.00 = REFL55Q 118deg 0.03?

- We tried to lock PRMI with AS55Q. The acquisition was not as easy as that with REFL33I. This might be from the saturation of the
REFL55I signal. This configuration should tested with different whitening gain. Handing off using the input matrix went well once the
lock was obtained by REFL33I.

- Handing off from AS55Q to REFL55Q was not successful.

- At the end of the session, Jenne told me that the POP PD still has a large diameter beam. (and a steering mirror with a peculiar reflection angle.)
==> THIS SHOULD BE FIXED ASAP because the normalization factor can be too much susceptible to the misalignment of the spot.

- The configuration of the filters:

PRCL FM3/4/5/6 G=+0.05 / NORM 0.04 POP110I
MICH FM4/5 G=-5.00 / NORM 0.01 POP110I (or none)

 Optics from the car were placed into glass door cabinet E0

 Koji set the IFO in a PRM-ITMY configuration for me, while I went to put a lens on the POP path.  Before putting the lens, the maximum average output that I saw from the diode (on a 'scope) was 4.40mV.  After putting in the lens and realigning the beam onto the diode, the new max DCvalue that I saw was 21.6mV.  This is a factor of 4.9. 

EDIT:  The dark value was -3.20mV, so actually the ratio is ~3.25 .

I have not yet done anything to fix the situation of the large angle of incidence on the first out-of-vac steering mirror.

- Routine alignment

Locked the arm cavties. Ran ASS. As this was not enough precise alignment for PRMI locking, Yarm alignment was re-adjusted by sliders.
Xarm was also aligned in the same way.

- OPLEV alignment

Once the arms were aligned, OPLEV spots were adjusted. For this adjustment, PRM had to be aligned and OPLEV servos needed to be turned off.

- LSC offset nulling

While Jenne was measuring the dark output of the POP PD, LSC offset nulling script was executed.

- Compensation of the POP spot size fix

As Jenne reported the POP path now has a lens and the denominator for the normalization got bigger.
To compensate this change, PRMI(sb) was locked by the same configuration as yesterday (i.e. AS55Q for MICH, REFL33I for PRCL). 
After some try and error, configuration for stable locking was found. 

PRCL
Signal source: REFL33I / Normalization POP110I x 1.00 / Trigger POP110I 80up 10down
Servo: input matrix 1.00 -> PRCL Servo FM3/4/5/6 Always ON G=+8.00
Actuator: output matrix 1.00 -> PRM

MICH
Signal source: AS55Q / Normalization POP110I x 0.01 / Trigger POP110I 80up 10down
Servo: input matrix 1.00 -> MICH Servo FM4/5 Always On G=-30
Actuator output matrix -1.00 -> ITMX / +1.00 -> ITMY

This suggests that POP110I signal is 5~6 times more than before the lens was installed. 

- SQRTing option for POP110I was implemented

The PRMI optical gain is derived from (Carrier)x(1st order Sideband) or (2nd order SB)x(1st order SB).
Here the carrier and the 2nd order sidebands are nonresonant.
Therefore the optical gain is proportional to the amplitude power recycling gain of the 1st order sidebands.
On the other hand, POP 2f signals are derived from the product of the 1st and -1st order sidebands.
This means that we should take a sqrt of the POP signals to compensate the recycling gain fluctuation.

- Locking with SQRT(POP110I)

PRCL
Signal source: REFL33I / Normalization SQRT(POP110I) x 10 / Trigger POP110I 10up 3down
Servo: input matrix 1.00 -> PRCL Servo FM3/4/5/6 Always ON G=+8.00
Actuator: output matrix 1.00 -> PRM

MICH
Signal source: AS55Q / Normalization SQRT(POP110I) x 0.1 / Trigger POP110I 10up 3down
Servo: input matrix 1.00 -> MICH Servo FM4/5 Always On G=-30
Actuator output matrix -1.00 -> ITMX / +1.00 -> ITMY

The lock seems not so different from the ones without SQRTing.

The spot was still moving in yaw direction. If I chose a correct alignment, I could minimize the modulation of the internal power
by misalignment. As you can see in the following plot.

When the alignment was deviated from the optimum, the misalignment induced RIN was much worse although this was the longest lock I ever had with the PRMIsb. (more than 8 min)

- Locking with other signal sources

REF55I/Q trial:

Demodulation phase was adjusted to make the difference of the peak heights for MICH maximized.
After the lock is acquired, I tried to swap the signal source at the input matrix. PRCL swapping was successful but
MICH swapping was not successfull.

It is much more hard to lock the interferometer with REFL55I compared with REFL33I.

REFL165I/Q trial:

As REFL165 PD never produced any useful signal, I tried to swap it with the BBPD used in the green setup.

- Borrowed the PD, power supply from the green setup.

- Put REFL165PD aside. Placed the BBPD in the path. The DC output was 0.8V. This corresponds to the input power of ~5mW.

- Checked the signal but it was very litte (several counts even at the maximum whitening gain).

- Decided to use the power reduction pick off to introduce much more light on the PD.
  This PO mirror is 90% reflector. Therefore I had to be careful no to fry the diode.
  Currently there are OD1.3 (x1/20) power attenuator to reduce the input power down to 6.5V (40mW).

- The resulting signal is very wiered suggesting the saturation of the PD at the RF stages.

- Probably I need to make a new PD circuit which has the high pass filter to reject other low frequency components.

I started to put together optics at the endtable. I am attaching the layout with the green blocks showing the optics that are assembled and will not be moved henceforth unless somebody contradicts.

1. Power after HWP = 314mW
    Power before faraday = 310mW
    Power after faraday = 300mW (the power loss while aligning the faraday earlier was due to the AR coating on the focusing lens before the faraday - it was AR coated for visible and that accounted to the power lost)

2. Since we do not know the length of TGG inside faraday, I measured the beam profile after the faraday so that I can trace the beam without any errors to calculate exact mode matching solutions.

3. The NPRO beam seems to be obviously elliptical as seen on the IR card and also from beam profile measurement. So we cannot skip including cylindrical lenses in the layout.

 LALFrame was successfully installed.  Allegra had unmet dependencies with some of the library tools.  I tried to install LALMetaIO, but there were unmet dependencies with other LSC software.  After updating the LSC software, the problem has persisted.  I will try some more, and ask Duncan if I'm not successful.

Installing these packages is rather time consuming, it would be nice if there was a way to do it all at once.

To aid in lock-loss studies, I made a new program called 'lookback', similar to 'getdata', to look at past data.

When called with channel name arguments, it runs continuously, storing all channel data in a ring buffer.  When the user hits Ctrl-C, all the data in the ring buffer is displayed.  There is an option to store the data in the ring buffer to disk as well.

controls@rosalba:/opt/rtcds/caltech/c1/scripts/general 0$ ./lookback -h
usage: lookback [-h] [-l LENGTH] [-o OUTDIR] channel [channel ...]

Lookback on testpoint data. The specified amount of data is stored in a ring
buffer. When Ctrl-C is hit, all data in the ring buffer is plotted. Both 'DQ'
and 'online' test point data is available. Use NDSSERVER environment variable
to specify host:port.

positional arguments:
  channel               Acquisition channel. Multiple channels may be
                        specified and acquired at once.

optional arguments:
  -h, --help            show this help message and exit
  -l LENGTH, --lookback LENGTH
                        Lookback time in seconds. This amount of data will be
                        stored in a ring buffer, and plotted on Ctrl-C.
                        Default is 10 seconds
  -o OUTDIR, --outdir OUTDIR
                        Output directory to write data (will be created if it
                        doesn't exist). Data from each channel stored as
                        '<channel>.txt'. Any existing data files will be
                        overwritten.
controls@rosalba:/opt/rtcds/caltech/c1/scripts/general 0$ 

Output matrices are added to ASS. Currently ASS is based on the mirror bases.
I prefer to have the actuator bases as the coils are more stable than the sensors.

At this point, the output matrices are identity. So Den's scripts are still working.

Striptool settings were also fixed.

I have looked at / analyzed the Schnupp data that Annalisa and I took last week, as well as some more Yarm data that I took this week.

I only have one set of Xarm data, but 3 sets of Yarm data.  I had intended to do careful error analysis of the data, but from the 3 sets of Yarm data, the variance in the answer I get using any one of the Yarm sets is much larger than the error in a single measurement.

Using the central Yarm zero crossing, I get a Schnupp asymmetry of 3.9cm.  The other 2 Yarm data points give Schnupp asymmetries of 3.7cm and 4.1cm, so I'm claiming a value of 3.9 +\- 0.2cm . This is within error of Jamie's measurement of 3.64 ± 0.32 cm (elog 4821).

About 30 minutes ago the mode cleaner fell out of lock and has since not been able to hold lock for more than a couple seconds.

I'm not sure what happened.  I was in the middle of taking measurements of the MC error point spectrum, which included adjusting the FAST gain.  I've put all the gains back to their nominal levels but no luck.  I'm not sure what else could have gone wrong.  Seismic noise looks relatively quiet. 

As it turned out, the setting of +26dB for the FSS Fast gain was making the NPRO PZT / Pockels cell crossover too unstable. This was the cause of the large ~30 kHz peak that Jamie was seeing in his spectra (more to follow in the morning).

After recovering the locking, etc. by fiddling with the gains, we went about systematically setting all of the gains/offsets. Jamie's elog will show all of the various spectra with different FSS gains.

For offset setting, this was the procedure:

1. We want the MC servo board to have zero voltage on its MCL and MCF outputs (aka MC_SLOW_MON and MC_FAST_MON) with the Boosts ON, so we switched ON the 40:4000 and the 2 Super Boosts and put the VCO gain into its nominal +25 dB setting. This saturates the outputs and makes them impossible to use as readbacks so you have to be careful. Get the outputs close to zero as you turn on each boost. Finally, you will see that +/- 1mV of input offset (aka MC_REFL_OFFSET) will flip the FAST output between +/- 10V. This is the right setting.
2. With the MC board adjusted to send 0 V into the FSS error point, adjust the FSS input offset (with the Common and Fast gains at the nominal values) so that the FAST output voltage goes to +5.5 V. This is the middle of the range for the high voltage driver which drives the NPRO.

3. Let the MC lock and go through the UP script. When the MCL comes on with the integrator, the FAST voltage will shift from +5.5 V to something else. Use the following line: ezcaservo -r C1:PSL-FSS_FAST -g -1 -s 5.5 C1:SUS-MC2_MCL_OFFSET, to automatically tune the MCL offset.

    

   That's all. I have left the FSS common gain at +10.5 and the Fast gain at +23.5. These seem to be close to the optimum. Jamie will have more tuning tomorrow.
    
   I have also changed the 'mcup' script to set the MCL offset and set the FSS Slow setpoint to shoot for +5.5 V of FSS_FAST.
    
   MC_REFL_OFFSET = +1.176 V
   MC2_MCL_OFFSET = +47.8 counts
   FSS_INOFFSET   = -0.85 V

Koji spent some time earlier this evening exploring where the excess RIN that we see in the PRC is coming from. 

He did this by locking the PRMI (MICH on AS55Q, PRCL on REFL33I, Pnorm for MICH = sqrt(POP110) with 0.1, Pnorm for PRCL = sqrt(POP110) with 10, MICH gain = -30, PRCL gain = 8), and then exciting each relevant optic, one at a time, in yaw.  The excitation was always using the ASCYAW excitation point on each of the optics (BS, PRM, ITMX, ITMY), with a frequency of 4.56 Hz, and an amplitude of 30 counts.

He also took reference traces with no optics excited.

Here, I plot (for each excited optic separately) the reference traces and traces during excitation for POP110_I_ERR, POPDC, and the OPLEV_YERROR for the optic that is being excited.

What we are looking for (only in yaw, since we see on the cameras that the dominant motion is in yaw) is an increase in POPDC and POP110 at the same frequency as an optic's excitation. 

We see that neither ITM is contributing a noticeable amount to either POPDC or POP110.  BS is contributing a little bit, but PRM is clearly contributing.  No this entry should be read. (KA)

A week or two ago, I calculated in elog 8489 that the angular motion that we see does not explain the RIN that we're seeing, unless our cavity is much more unstable than Jamie calculated in elog 8316. 

I think that I need to install one of the T240's on the new granite slab, and see what kind of coherence we have between seismic and PRM yaw motion, and if FF can get rid of it.

While looking over Koji's shoulder earlier, I noticed the big peak in the PRM yaw spectrum (and I was starting to get annoyed by the hum....the fibox is so useful in motivating tasks that otherwise get looked over!) 

I used DTT's peak find feature (cursor tab, enable both cursors, select Peak X/Y as your 'statistic', set the 2 cursors to be on either side of the desired peak) to find the frequency of the PRM's violin mode.  It is 627.75 Hz. I adjusted FM5 of the C1:SUS-PRM_LSC filter bank (the "violin" filter) to be centered around this frequency, with the start and stop freqs +\- 4Hz.  I plotted the filter linearly in frequency to ensure that my target freq was not too close to either side of the bandstop.  After loading and engaging the new filter, the hum slowly started to go away. 

Note, for posterity:  The bandstop used to be centered around ~645 Hz or so.  I assume this is a copy-and-paste situation, where we hadn't gone through to check the exact frequency for each optic.

I'm not sure why, but starting ~3.5 hours ago, the WFS seem to not be holding the MC in optimal alignment. 

The WFS are definitely engaged and the loops are closed, but every time the MC locks, the WFS pitch and yaw values start drifting off.  In particular, the WFS loop actuation pushing on MC2 is in the many hundreds of counts after ~90 minutes of drift time.  I tried offloading those values by moving the MC2 slider, but then I unlocked the MC to check what that did to the alignment, and it was decidedly bad.  So, I'm not sure what's up with the WFS, but I need to look at it tomorrow.

No.

While the peak in the PRM OPLEV was more than 10 times higher than the spectrum level without the excitation,
we only saw small peaks in the RIN spectra. This suggests that the PRM angular motion did not contribute to the RIN spectra.

You should divide the POP110I and POPDC spectra by 400 and 450, which was the DC values of these channels, in order to convert them into RIN (1/rtHz)
The OPLEV spectra is calibrated to be urad/rtHz (is this true?) so you can obtain the conversion factor from OPLEV to RIN (1/urad)
by matching the peaks. This way you make a angular noise projection.

Yes we should do that. BTW what should be pushed?

 I am now working on megatron, installing in /home/controls/lal.  I am having some unmet dependency issues that I have asked Duncan about.

Koji asked me to look at what the ideal RF modulation frequency is, for just the PRMI case (no arms).  If we had a perfect interferometer, with the sidebands exactly antiresonant in the arms when the arms resonate with the carrier, this wouldn't be an issue.  However, due to vacuum envelope constraints, we do not have perfect antiresonance of the sidebands in the arm cavities.  Rather, the sideband frequencies (and arm lengths) were chosen such that they pick up a minimum amount of extra phase on reflection from the arms.  But, when the arms are off resonance (ex, the ETMs are misaligned), the sideband frequencies see a different amount of phase.   

We want to know what a rough guess (since we don't have a precise number for the length of the PRC since our last vent) is for the ideal RF modulation frequency in just the PRMI. 

If I take (from Manasa's kind measurements from the CAD drawing yesterday) the relevant distances to be:

L_P[meters] = 1.9045 + 2.1155 + 0.4067

L_X[meters] = 2.3070 + 0.0254*n

L_Y[meters] = 2.2372 + 0.0359*n + 0.0254*n

L_PRCL = L_P + (L_X + L_Y)/2 = 6.7616 meters.

The *n factors (n=1.44963) are due to travel through glass of the BS, and the substrate of the ITMs. 

I find the FSR of the PRC to be 22.1686 MHz. For the sidebands to be antiresonant, we want them to be 11.0843 MHz. This would correspond to a mode cleaner length of 27.0466 meters.  Our current modulation frequency of 11.066134 MHz corresponds to a MC length of 27.091 meters.  So, if we want to use this 'ideal' modulation frequency for the PRC, we need to shorten the mode cleaner by 4.4cm!  That's kind of a lot.

To change the MC length is not the point.

If we can improve the length sensing by the intentional shift of the modulation frequency from the MC FSR, that's worth to try, I thought.

But that is tough as the freq difference is 18kHz that is ~x4 of the line width of the MC.
Not only the 55MHz sidebands, but also the 11MHz sidebands will just be rejected.

Nevertheless: Is there any possibility that we can improve anything by shifting the modulation frequency by ~1kHz?

I'm not sure what's going on today but we're seeing ~80% packet loss on the 40MARS wireless network.  This is obviously causing big problems for all of our wirelessly connected machines.  The wired network seems to be fine.

I've tried power cycling the wireless router but it didn't seem to help.  Not sure what's going on, or how it got this way.  Investigating...

Here's an example of the total horribleness of what's happening right now:

controls@rossa:~ 0$ ping 192.168.113.222
PING 192.168.113.222 (192.168.113.222) 56(84) bytes of data.
From 192.168.113.215 icmp_seq=2 Destination Host Unreachable
From 192.168.113.215 icmp_seq=3 Destination Host Unreachable
From 192.168.113.215 icmp_seq=4 Destination Host Unreachable
From 192.168.113.215 icmp_seq=5 Destination Host Unreachable
From 192.168.113.215 icmp_seq=6 Destination Host Unreachable
From 192.168.113.215 icmp_seq=7 Destination Host Unreachable
From 192.168.113.215 icmp_seq=9 Destination Host Unreachable
From 192.168.113.215 icmp_seq=10 Destination Host Unreachable
From 192.168.113.215 icmp_seq=11 Destination Host Unreachable
64 bytes from 192.168.113.222: icmp_seq=12 ttl=64 time=10341 ms
64 bytes from 192.168.113.222: icmp_seq=13 ttl=64 time=10335 ms
^C
--- 192.168.113.222 ping statistics ---
35 packets transmitted, 2 received, +9 errors, 94% packet loss, time 34021ms
rtt min/avg/max/mdev = 10335.309/10338.322/10341.336/4.406 ms, pipe 11
controls@rossa:~ 0$ 

Note that 10 SECOND round trip time and 94% packet loss.  That's just beyond stupid.  I have no idea what's going on.

I'm just now realizing that the PMC has also not been locked since noon today, and doesn't seem to be responding to anything right now.

wtf is going on here?

I have updated the waists (W)  and beam diameters (D) at 1064nm optics on the endtable.

I am not able to locate the characteristics of QPD-Y and oplev PD and hence took the beam diameter to be half of the detector surface area to determine their positions.

Beam diameter on PDA520 used for TRY was calculated using the transimpedance and responsivity of the PD from an old elog in 2004.

Rana showed up and diagnosed the problem as a railed FSS SLOW output.  The SLOW Monitor about was showing ~6V, which is apparently a bad mode-hoppy place for the NPRO.  Reducing the SLOW output brought things back into a good range which allowed the PMC to lock again.

In attempting to diagnose the problem I noticed that there is -100 mV DC coming out of the PMC RFPD RF output.  This is not good, probably indicating a problem, and was what I thought was the PMC lock issue for a while.    Need to look at the PMC RFPD RF output.

1. Fixed LOCKMC screen to display the SLOWM voltage instead of the ref cav transmission.
2. PSL Status .db file updated to trigger on correct limits for FSS FAST and the FSS and PMC local oscillator levels.
3. SETTINGS_SET screen can now take and display screen snapshots.

All of these changes were committed to the SVN.

Someone for some reason added full-rate DAQ specification to some ADC3 channels in the c1sus IOP model (c1x02):

#DAQ Channels

TP_CH15 65536
TP_CH16 65536
TP_CH17 65536
TP_CH18 65536
TP_CH19 65536
TP_CH20 65536
TP_CH21 65536

These appear to be associated with c1pem, so I'm guessing it was Den (particularly since he's the worst about making modifications to models and not telling anyone or logging or svn committing).

I'm removing them.

Precise arm alignment is more demanded. as the PRMI locking requires good and reliable alignment of the ITMs.

I previously added the output matrix to ASS.

Now the input and output matrix as well as the gains and filters have been updated.

The current concept is

Fast loop: align the arms by the arm mirrors with regard to the given beam.

Slow loop: move the incident beam position and angle to make the spot at the center of the mirrors

This is actually opposite to Den's implementation.

In order to realize the faster alignment of the arm, I increased the corner frequency of the lockins for the arm signals from 0.5Hz to 1Hz.

With the new configuration the arm alignment converges in 10sec and the input pointing does in ~15sec.

The actuation to the input pointing TTs are done together with the feedforward actuation to the arms.
This way we can avoid too much coupling from the input pointing servos to the arm alignment servos.

The corresponding script /opt/rtcds/caltech/c1/scripts/ASS/YARM/DITHER_Arm_ON.py was also modified.

Same ASS setup for the X arm has been done.

Now Arm ASS can run simultaneously.

I reverted the number of the lockin banks from 6 to 8 for future implementation of A2L for the ITMX by coil balancing.
Since A2L for the ITMX is just barely visible for now, I am going to leave the coil balance untouched.

Progress with end table:

Parts in green show assembled optics that will not require any changes. Parts in yellow are in place but will need either change of lenses in their optical path or change in position.