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ID Date Author Type Categoryup Subject
  10647   Tue Oct 28 15:27:25 2014 ericqUpdateIOOIMC WFS sensing matrix measurement

 I took some spectra of the error signals and MC2 Trans RIN with the loops off (blue) and on (red) during the current conditions of daytime seismic noise.



  10648   Tue Oct 28 20:47:08 2014 diegoUpdateIOOIMC WFS sensing matrix measurement

Today I started looking into the WFS problem and improvement, after being briefed by Koji and Nicholas. I started taking some measurements of open loop transfer functions for both PIT and YAW for WFS1, WFS2 and MC2_TRANS. For both WFS1 and 2 there is a peak in close proximity of the region with gain>1, and the phase margin is not very high. Tomorrow I will make measurements of the local damping open loop transfer functions, then we'll think how to improve the sensors' behaviour.

Attachment 1: 141028_MCWFS_WFS1_PIT_OL.pdf
Attachment 2: 141028_MCWFS_WFS1_YAW_OL.pdf
Attachment 3: 141028_MCWFS_WFS2_PIT_OL.pdf
Attachment 4: 141028_MCWFS_WFS2_YAW_OL.pdf
Attachment 5: 141028_MCWFS_MC2_TRANS_PIT_OL.pdf
Attachment 6: 141028_MCWFS_MC2_TRANS_YAW_OL.pdf
  10653   Thu Oct 30 02:12:59 2014 diegoUpdateIOOIMC WFS sensing matrix measurement


Today we took some measurements of transfer functions and power spectra of suspensions of the MC* mirrors (open loop), for all the DOFs (PIT, POS, SIDE, YAW); the purpose is to evaluate the Q factor of the resonances and then improve the local damping system.

Attachment 1: MC1_OL_PIT.pdf
Attachment 2: MC1_OL_POS.pdf
Attachment 3: MC1_OL_SIDE.pdf
Attachment 4: MC1_OL_YAW.pdf
Attachment 5: MC2_OL_PIT.pdf
Attachment 6: MC2_OL_POS.pdf
Attachment 7: MC2_OL_SIDE.pdf
Attachment 8: MC2_OL_YAW.pdf
Attachment 9: MC3_OL_PIT.pdf
Attachment 10: MC3_OL_POS.pdf
Attachment 11: MC3_OL_SIDE.pdf
Attachment 12: MC3_OL_YAW.pdf
  10681   Thu Nov 6 12:58:28 2014 KojiUpdateIOOWFS offset was reset

IMC WFS operating point seemed to get degraded.

- IMC WFS feedback was relieved.

- WFS servo was turned off.

- IMC alignment was tuned carefully

- /opt/rtcds/caltech/c1/scripts/MC/WFS/WFS_FilterBank_offsets was run

- WFS servo was turned on again 

  10704   Wed Nov 12 20:11:41 2014 KojiUpdateIOOMC WFS gain reduced again

MC WFS was oscillative at 1Hz. I've reduced the servo gain further (x1, x1, x10, x1, x1, and x10).

The MC mirrors were realigned, and the WFS offsets were reset.

  10706   Wed Nov 12 22:22:11 2014 KojiSummaryIOOEstimation of the angular jitter imposed by the TTs

[Koji, Rana, Jenne]

One coil of the TT produce 36nrad/rtHz at DC.

- C1:IOO-TT2_UL_EXC was excited with 5 count_pk at 0.04Hz.

- LSC_TRY exhibited the symmetric reduction of the transmission from 0.95 to 0.90.

1 - (theta/theta0)^2 /2 = 0.90 / 0.95

=> theta / theta0 = 0.32

- 40m beam waist radius is 3.1mm. This means the divergence angle is 1.1e-4 rad.

=> 1.1e-4*0.32 = 3.6e-5 rad

=> 3.6e-5/5 = 7.2 urad/count (per coil)

- DAC noise 1/sqrt(12 fs), where fs is the sampling rate (fs = 16384)

=> 0.002 cnt/rtHz

- One coil causes 7.2u*0.002 = 14 nrad/rtHz (at DC)

- One suspension cause 29 nrad/rtHz (at DC)

Attachment 1: 03.png
  10722   Mon Nov 17 20:28:17 2014 ranaSummaryIOOMC servo summing amp

I modified the /cvs/cds/caltech/target/c1psl/psl.db file to adjust the records for the FSS-FAST signal (to make it go yellow / red at the correct voltages). This was needed to match 5V offset which Koji added to the output of the FSS board back in August.

I also manually adjusted the alarm levels with caput so that we don't have to reboot c1psl. Beware of potential tiimebomb / boot issues if I made a typo! psl.db update in the SVN (also, there were ~12 uncomitted changes in that directory....please be responsible and commit ALL changes you make in the scripts directory, even if its just a little thing and you are too cool for SVN)

  10723   Mon Nov 17 20:40:29 2014 rana, diegoUpdateIOOInvestigating the IMC WFS situation

We've known for years that the IMC WFS sensing chain is pointlessly bad, but until recently, we haven't thought it was worth it to fix.

There are problems in all parts of the chain:

  1. The WFS Photodetectors oscillate ~200 MHz when turned up to full gain. Diego and I confirmed this today by measuring the RF spectrum of the signals going into the WFS demod boards and seeing the oscillation change (not much) with RF gain. I recommend we switch the heads into the full gain mode (turn all of the attenuators OFF). At the moment we are operating with the 2dB and 8dB attenuators ON.
  2. The demod board has some bad gain allocation and noisy opamps.
  3. The whitening board has too much up/down of gain with noise injection along the way. And the range cannot fill up the ADC.
  10728   Thu Nov 20 22:43:15 2014 KojiUpdateIOOIMC WFS damping gain adjustment

From the measured OLTF, the dynamics of the damped suspension was inferred by calculating H_damped = H_pend / (1+OLTF).
Here H_pend is a pendulum transfer function. For simplicity, the DC gain of the unity is used. The resonant frequency of the mode
is estimated from the OLTF measurement. Because of inprecise resonant frequency for each mode, calculated damped pendulum
has glitches at the resonant frequency. In fact measurement of the OLTF at the resonant freq was not precise (of course). We can
just ignore this glitchiness (numerically I don't know how to do it particularly when the residual Q is high).

Here is my recommended values to have the residual Q of 3~5 for each mode.

MC1 SUS POS current  75   -> x3   = 225
MC1 SUS PIT current   7.5 -> x2   =  22.5
MC1 SUS YAW current  11   -> x2   =  22
MC1 SUS SD  current 300   -> x2   = 600

MC2 SUS POS current  75   -> x3   = 225
MC2 SUS PIT current  20   -> x0.5 =  10
MC2 SUS YAW current   8   -> x1.5 =  12
MC2 SUS SD  current 300   -> x2   = 600

MC3 SUS POS current  95   -> x3   = 300
MC3 SUS PIT current   9   -> x1.5 =  13.5
MC3 SUS YAW current   6   -> x1.5 =   9
MC3 SUS SD  current 250   -> x3   = 750

This is the current setting in the end.

MC1 SUS SD  450

MC2 SUS SD  450

MC3 SUS SD  500

Attachment 1: MC_OLTF_CLTF.pdf
  10826   Sun Dec 21 18:46:06 2014 diegoUpdateIOOMC Error Spectra

The error spectra I took so far are not that informative, I'm afraid. The first three posted here refer to Wed 17 in the afternoon, where things were quiet, the LSC control was off and the MC was reliably locked. The last two plots refer to Wed night, while Q and I were doing some locking work; in particular, these were taken just after one of the locklosses described in elog 10814. Sadly, they aren't much different from the "quiet" ones.

I can add some considerations though: Q and I saw some weird effects during that night, using a live reading of such spectra, which couldn't be saved though; such effects were quite fast both in appearance and disapperance, therefore difficult to save using the snapshot measurement, which is the only one that can save the data as of now; moreover, these effects were certainly seen during the locklosses, but sometimes also in normal circumstances. What we saw was a broad peak in the range 5e4-1e5 Hz with peak value ~1e-5 V/rtHz, just after the main peak shown in the attached spectra.

Attachment 1: SPAG4395_17-12-2014_170951.pdf
Attachment 2: SPAG4395_17-12-2014_172846.pdf
Attachment 3: SPAG4395_17-12-2014_175147.pdf
Attachment 4: SPAG4395_18-12-2014_003414.pdf
Attachment 5: SPAG4395_18-12-2014_003506.pdf
  10828   Mon Dec 22 15:11:08 2014 ranaUpdateIOOMC Error Spectra

che tristezza  

What we want is to have the high and low noise spectra on the same plot. The high noise one should be triggered by a high PC DRIVE signal.

  10829   Mon Dec 22 15:46:58 2014 KurosawaSummaryIOOSeven transfer functions

IMC OL TF has been measured from 10K to 10M

Attachment 1: MC_OLTF.pdf
  10832   Mon Dec 22 21:53:08 2014 rana, kojiUpdateIOOSeven transfer functions

Today we were looking at the MC TFs and pulled out the FSS box to measure it. We took photos and removed a capacitor with only one leg.

Still, we were unable to see the weird, flat TF from 0.1-1 MHz and the bump around 1 MHz. Its not in the FSS box or the IMC servo card. So we looked around for a rogue Pomona box and found one sneakily located between the IMC and FSS box, underneath some cables next to the Thorlabs HV driver for the NPRO.

It was meant to be a 14k:140k lead filter (with a high frequency gain of unity) to give us more phase margin (see elog 4366; its been there for 3.5 years).

From the comparison below, you can see what the effect of the filter was. Neither the red nor purple TFs are what we want, but at least we've tracked down where the bump comes from. Now we have to figure out why and what to do about it.

* all of the stuff above ~1-2 MHz seems to be some kind of pickup stuff.

** notice how the elog is able to make thumbnails of PDFs now that its not Solaris!

Attachment 1: MC_OLG.pdf
  10833   Tue Dec 23 01:55:35 2014 rana, kojiUpdateIOOSeven transfer functions

Some TFs of the TTFSS box

Attachment 1: MC_FSS_TF.pdf
  10841   Tue Dec 23 20:50:39 2014 rana, kojiUpdateIOOSeven transfer functions

Today we decided to continue to modify the TTFSS board.

The modified schematic can be found here: https://dcc.ligo.org/D1400426-v1 as part of the 40m electronics DCC Tree.

What we did

1) Modify input elliptic filter (L1, C3, C4, C5) to give zero and pole at 30 kHz and 300 kHz, respectively. L1 was replaced with a 1 kOhm resistor.  C3 was replaced with 5600 pF. C4 and C5 were removed. So the expected locations of the zero and pole were at 28.4 kHz and 256 kHz, respectively. This lead filter replaces the Pomona box, and does so without causing the terrible resonance around 1 MHz.

2) Removed the notch filters for the PC and fast path. This was done by removing L2, L3, and C52.

At this point we tested the MC locking and measured the transfer function. We successfully turned up the UGF to 170kHz and two super-boosts on.

3) Now a peak at 1.7MHz was visible and probably causing noise. We decided to revert L2 and adjusted C50 to tune the notch filter in the PC path to suppress this possible PC resonance. Again the TF was measured. We confirmed that the peak at 1.7MHz is at -7dB and not causing an oscillation. The suppression of the peak is limited by the Q of the notch. Since its in a weird feedback loop, we're not sure how to make it deeper at the moment.

4) The connection from the MC board output now goes in through the switchable Test1 input, rather than the fixed 'IN1'. The high frequency gain of this input is now ~4x higher than it was. I'm not sure that the AD829 in the MC board can drive such a small load (125 Ohms + the ~20 Ohms ON resistance of the MAX333A) very well, so perhaps we ought to up the output resistor to ~100-200 Ohms?

Also, we modified the MC Servo board: mainly changed the corner frequencies of the Super Boost stages and some random cleanup and photo taking. I lost the connecting cable from the CM to the AO input (unlabeled).

  1.  The first two Super Boost stages were changed from 20k:1k to 10k:500 to give us back some phase margin and keep the same low freq gain. I don't really know what the gain requirement is for this servo here at the 40m. The poles and zeros were chosen for iLIGO so as to have the frequency noise be 10x less than the SRD at 7 kHz.
  2. The third Super Boost (which we never used) was changed from 10k:500 to ~3k:150 (?) just in case we want a little more low freq gain.
  3. There was some purple vestigial wiring on the back side of the board with a flying resistor; I think this was a way to put a DC offset in to the output of the board, but its not needed anymore so I removed it.


Attachment 1: MC_OLTF.pdf
Attachment 2: MC_OLTF2.pdf
Attachment 3: matlab.zip
  10842   Wed Dec 24 08:25:05 2014 ranaConfigurationIOOnotes on MC locking

 I've updated the scripts for the MC auto locking. Due to some permissions issues or general SVN messiness, most of the scripts in there were not saved anywhere and so I've overwritten what we had before. 

After all of the electronics changes from Monday/Tuesday, the lock acquisition had to be changed a lot. The MC seems to catch on the HOM more often. So I lowered a bunch of the gains so that its less likely to hold the HOM locks.

A very nice feature of the Autolocker running on megatron is that the whole 'mcup' sequence now runs very fast and as soon as it catches the TEM00, it gets to the final state in less than 2 seconds.

I've also increased the amplitude of the MC2 tickle from 100 to 300 counts to move it through more fringes and to break the HOM locks more often. Using the 2009 MC2 Calibration of 6 nm/count, this is 1.8 microns-peak @ 0.03 Hz, which seems like a reasonable excitation.

Using this the MC has relocked several times, so its a good start. We'll have to work on tuning the settings to make things a little spicier as we move ahead.


That directory is still in a conflicted state and I leave it to Eric/Diego to figure out what's going on in there. Seems like more fallout from the nodus upgrade:

controls@chiara|MC > svn up

svn: REPORT of '/svn/!svn/vcc/default': Could not read chunk size: Secure connection truncated (https://nodus.ligo.caltech.edu:30889)

  10847   Tue Dec 30 00:46:05 2014 ranaUpdateIOOInvestigations into the mad PCDRIVE

Koji and I noticed that there was a comb* of peaks in the MC and FSS at harmonics of ~37 kHz. Today I saw that this shows up (at a much reduced level) even when the input to the MC board is disconnected.

It also shows up in the PMC. At nominal gains, there is just the 37 kHz peak. After tweaking up the phase shifter settings, I was able to get PMC servo to oscillate; it then makes a comb, but the actual oscillation fundamental is 1/3 of 37 kHz (some info on Jenne from elog 978 back in 2008).

Not sure what, if anything, we do about this. It is curious that the peak shows up in the MC with a different harmonic ratio than in the PMC. Any theories?


Anyway, after some screwing around with phase and amplitude of the RF modulation for the PMC from the phase shifter screen**, I think the gain is higher in the loop and it looks like the comb is gone from the MC spectrum.

Another clue I notice is that the PCDRIVE mad times often are coincident with DC shifts in the SLOWDC. Does this mean that its a flakiness with the laser? While watching the PCDRIVE output from the TTFSS interface board on a scope, I also looked at MIXER mon. It looks like many of the high noise events are associated with a broadband noise increase from ~50-140 kHz, rather than some specific lines. Don't know if this is characteristic of all of the noisy times though.


* this 'comb' had several peaks, but seem not be precise harmonics of each other: (f3 - 3*f1)/f3 ~ 0.1%

** I think we never optimized this after changing the ERA-5 this summer, so we'd better do it next.

 *** UPDATE: the second plot show the comparison between the new quiet and noisy states. Its just a broad bump.


Attachment 1: MC_ERR.pdf
Attachment 2: plotFSSerr.ipynb.xz
Attachment 3: MC_ERRcomp.pdf
  10851   Sun Jan 4 22:08:46 2015 ranaUpdateIOOMC loop characterizations: PZT/EOM crossover

 * PMC + MC were unlocked when I came in.

* I fiddled around some more with the mcup/down scripts to make locking snappier. The locking was breaking the PMC lock often, so I re-enabled the MC servo board output limiter during acquisition. It is disabled in the MC UP script.

* Re-measured the MC OLG. Still OK.

* Measured the PZT / EOM crossover (aka the FAST / PC crossover) using the connectors on Koji's summing box. With the FAST gain at 18 dB, the crossover is ~10 kHz. Looks way to shallow. Plots to follow.

* I finally discovered today that the PMC PZT stroke is what's causing the main mis-alignment of the beam going to the IMC. By relocking at a few positions, I could see that the IOO QPDs have steps when the PMC relocks. So the IO beam wander is NOT due to temperature effects on the optics mounts of the PSL table. I wonder if we have a large amount of length to angle coupling or if this is the same as the OMC PZTs ?

P.S. I found that someone is using a temporary bench power supply to power the summing box between the TTFSS and the Thorlabs HV driver...whoever did this has ~48 hours to hook up the power in the right way or else Koji is going to find out and lose it and then you have to wear the Mickey Mouse hat.


The first attachment shows the OLG measurements with 2 different values of the fast gain (our nominal FG is 18 dB). You can see that the higher gains produce some crossover instability; when tuning the gain we notice this as an increase in the PCDRIVE rms channel.

The second attachment shows the measurement of the 'crossover'. Its really just the direct measurement of the IN1 / IN2 from the FAST summing box, so its the crossover measurement where the OLG is high.

Attachment 1: MC_OLGs.pdf
Attachment 2: MC_xover.pdf
  10855   Mon Jan 5 23:36:47 2015 ericqUpdateIOOAO cable reconnected


 I lost the connecting cable from the CM to the AO input (unlabeled). 

 This afternoon, I labelled both ends of this cable, and reconnected it to the MC servo board. 

  10858   Tue Jan 6 10:04:39 2015 SteveUpdateIOOhappy IOO
Attachment 1: IOO.png
  10928   Thu Jan 22 02:56:07 2015 ericqUpdateIOOFSS input offset adjusted

Since Rana's overhaul of the IMC, the FSS input offset had been sitting at zero. 

Over the last day or so, I had noticed the MC refl wall striptool trace looking noisier, and earlier this evening, we were suffering from a fair amount of downtime due to IMC unlocks, and failure to autolock for times on the order of ten minutes. 

While we had used ezcaservo for this in the past, I set the FSS offset manually tonight. Namely, I popped open a dataviewer trace of MC_F, and scanned the FSS offset to make MC_F go to zero. It required a good amount of offset, 4.66 V according to the FSS screen. I did this while the FSS slow servo was on, which held the FSS Fast output at zero. 

That was four hours ago; MC_F is still centered on zero, and we have not had a single IMC unlock since then. The MC refl trace is thinner too, though this may be from nighttime seismic. 

  10931   Thu Jan 22 18:36:11 2015 diegoUpdateIOOMC Flashes

I've been looking into the data of Jan 06 and Jan 15 taken during daytime, as the night before we left the PRC aligned in order to allow the IFO to flash; the purpose is to find out if some flashes from the IFO could propagate back to the IMC and cause it to lose lock; I will show here a sample plot, all of the others are in the archive attached.

My impression is that these locklosses of the IMC are not caused by these flashes: the signals MC_[F/L] seem quite stable until the lock loss, and I don't see any correlation with what happens to REFLDC that could cause the lockloss (apart from its drop as a consequence of the lockloss itself); in addition, in most occasions I noticed that the FSS started to go crazy just before the lock loss, and that suggests me that the lockloss source is internal to the IMC.

I can't see anything strange happen to MC_TRANS either as long as the IMC is locked, no fluctuations or weird behaviour. I also plotted the MC_REFL_SUM channel. but it is too slow to be useful for this kind of "hunt".

Attachment 1: 1104612646_zoom_1.png
Attachment 2: elog.tar.bz2
  10940   Mon Jan 26 17:43:52 2015 ericqConfigurationIOOMC Autolocker update

The MC autolocker hasn't been so snappy recently, and has been especially fussy today. Previously, the mcup script was triggered immediately once the transmission was above a certain threshold. However, this could waste time if it was just an errant flash. Hence, I've added a 0.5 second delay and a second threshold check before mcup is triggered. 

After breaking the lock 5ish times, it does seem to come back quicker.

  10951   Wed Jan 28 17:39:17 2015 KojiConfigurationIOOX Trans Table less crazy but not enough yet

The X-end IR Trans path was cleaned up.

I have been investigating the Xarm ASS issue. The Xarm ASS sensors behaved not so straight forward.
I went to the X-end table and found some suspect of clipping and large misalignmnet in the IR trans path.
Facing with the usual chaos of the end table, I decided to clean-up the IR trans path.

The optical layout is now slightly better. But the table is, in general, still dirty with bunch of stray optics,
loose cables and fibers. We need more effort to make the table maintained in a professional manner.

- Removed unnecessary snaking optical path. Now the beam from the 1064/532 separator is divided by a 50-50 BS before the QPD without
any other steering mirrors. This means the spot size on the QPD was changed as well as the alignment. The spot on the QPD was aligned
with the arm aligned with the current (=not modified) ASS. This should be the right procedure as the spot must be centered on the end mirror
with the current ASS.

- After the 50-50 BS there is an HR steering mirror for the Thorlab PD.

- A VIS rejection filter was placed before the 50-50 BS. The reflection from the filter is blocked with a razor blade dump.

Important note to everyone including Steve:
The transmission of the VIS rejection filter at 1064nm is SUPER angular sensitive.
A slight tilt causes significant reduction of 1064nm light. Be careful.

- As we don't need double VIS filter, I removed the filter on the QPD.

- X-End QPD was inspected. There seemed large (+/-10%) gain difference between the segments.
They were corrected so that the values are matched when the beam is only on one segment.
The corrections were applied at C1:SUS-ETMX_QPDx_GAIN (x=1, 2, 3, or 4).

I decided to put "-20dB" filters on C1:SUS-ETMi_QPD_SUM and C1:SUS-ETMi_TRY (i = X or Y)
in order to make their gain to be reasonable (like 0.123 instead 0.000123 which is unreadable).
Jenne's normalization script reads relative values and the current gains instead of the absolute values.
Therefore the script is not affected.

Attachment 1: IMG_1808.JPG
  10958   Thu Jan 29 17:20:58 2015 manasaConfigurationIOOX Trans Table less crazy but not enough yet

[Koji, Manasa]

We cleared up some optics and optomechanics at the X end table that are not being used and moved them to the SP table. [Ed by KA: They seemed to be leftover of the other projects. I blame them]

  11018   Thu Feb 12 23:40:12 2015 ranaUpdateIOOBounce / Roll stopband filters added to MC ASC filter banks

The filters were already in the damping loops but missing the MC WFS path. I checked that these accurately cover the peaks at 16.5 Hz and 23.90 and 24.06 Hz.

Attachment 1: 59.png
  11094   Tue Mar 3 19:19:15 2015 ericqUpdateIOOPC Drive / FSS Slow correlation

Jenne and I were musing the other night that the PC drive RMS may have a "favorite" laser temperature, as controlled by the FSS Slow servo; maybe around 0.2.

I downloaded the past 30 days of mean minute trend data for MC Trans, FSS Slow and PC Drive, and took the subset of data points where transmission was more than 15k, and the FSS slow output was within 1 count of zero. (This was to exclude some outliers when it ran away to 3 for some days). This was about 76% of the data. I then made some 2D histograms, to try and suss out any correlations. 

Indeed, the FSS slow servo does like to hang out around 0.2, but this does not seem to correlate with better MC transmission nor lower PC drive.

In the following grid of plots, the diagonal plots are the 1D histograms of each variable in the selected time period. The off diagnoal elements are the 2D histograms. They're all pretty blob-y, with no clear correlation. 

Attachment 1: jointplot.png
  11106   Fri Mar 6 00:59:13 2015 ranaSummaryIOOMC alignment not drifting; PSL beam is drifting

In the attached plot you can see that the MC REFL fluctuations started getting larger on Feb 24 just after midnight. Its been bad ever since. What happened that night or the afternoon of Feb 23?
The WFS DC spot positions were far off (~0.9), so I unlocked the IMC and aligned the spots on there using the nearby steering mirrors - lets see if this helps.

Also, these mounts should be improved. Steve, can you please prepare 5 mounts with the Thorlabs BA2 or BA3 base, the 3/4" diameter steel posts, and the Polanski steel mirror mounts? We should replace the mirror mounts for the 1" diameter mirrors during the daytime next week to reduce drift.

Attachment 1: MCdrfit.png
  11109   Fri Mar 6 13:48:17 2015 dark kiwamuSummaryIOOtriple resonance circuit

I was asked by Koji to point out where a schematic of the triple resonant circuit is.
It seems that I had posted a schematic of what currently is installed (see elog 4562 from almost 4 yrs ago!).

(Some transfomer story)
Then I immediately noticed that it did not show two components which were wideband RF transformers. In order to get an effective turns ratio of 1:9.8 (as indicated in the schematic) from a CoilCrfat's transformer kit in the electronics table, I had put two more transformers in series to a PWB1040L which is shown in the schematic. If I am not mistaken, this PWB1040L must be followed by a PWB1015L and PWB-16-AL in the order from the input side to the EOM side. This gives an impedance ratio of 96 or an effective turns ratio of sqrt(96) = 9.8.

(An upgrade plan document)

Also, if one wants to review and/or upgrade the circuit, this document may be helpful:
This is a document that I wrote some time ago describing how I wanted to make the circuit better. Apparently I did not get a chance to do it.

  11112   Fri Mar 6 19:54:15 2015 ranaSummaryIOOMC alignment not drifting; PSL beam is drifting

MC Refl alignment follow up: the alignment from last night seems still good today. We should keep an cool on the MC WFS DC spots and not let them get beyond 0.5.

Attachment 1: Untitled.png
  11145   Thu Mar 19 14:37:17 2015 manasaConfigurationIOOIMC relocked

The autolocker was struggling to lock the IMC. I disabled the autolocker and locked the IMC manually. It seems happy right now. 

With PMC trans at 0.717 counts, the IMC trans sum is ~15230.


The MC autolocker hasn't been so snappy recently, and has been especially fussy today. Previously, the mcup script was triggered immediately once the transmission was above a certain threshold. However, this could waste time if it was just an errant flash. Hence, I've added a 0.5 second delay and a second threshold check before mcup is triggered. 

After breaking the lock 5ish times, it does seem to come back quicker.


  11147   Thu Mar 19 16:58:19 2015 SteveSummaryIOOMC alignment not drifting; PSL beam is drifting

Polaris mounts ordered.


In the attached plot you can see that the MC REFL fluctuations started getting larger on Feb 24 just after midnight. Its been bad ever since. What happened that night or the afternoon of Feb 23?
The WFS DC spot positions were far off (~0.9), so I unlocked the IMC and aligned the spots on there using the nearby steering mirrors - lets see if this helps.

Also, these mounts should be improved. Steve, can you please prepare 5 mounts with the Thorlabs BA2 or BA3 base, the 3/4" diameter steel posts, and the Polanski steel mirror mounts? We should replace the mirror mounts for the 1" diameter mirrors during the daytime next week to reduce drift.


Attachment 1: driftingInputBeam2.jpg
  11149   Fri Mar 20 10:51:09 2015 SteveSummaryIOOMC alignment not drifting; PSL beam is drifting

Are the two  visible small srews holding the adapter plate only?

If yes, it is the weakest point of the IOO path.

Attachment 1: eom4.jpg
Attachment 2: eom3.jpg
  11150   Fri Mar 20 12:42:01 2015 JenneUpdateIOOWaking up the IFO

I've done a few things to start waking up the IFO after it's week of conference-vacation.

PMC trans was at 0.679, aligned the input to the PMC, now it's up at 0.786.

MC transmission was very low, mostly from low PMC transmission.  Anyhow, MC locked, WFS relieved so that it will re-acquire faster.

Many of the optics had drifted away. AS port had no fringing, and almost every optic was far away from it's driftmon set val.  While putting the optics back to their driftmon spots, I noticed that some of the cds.servos had incorrect gain.  Previously, I had just been using the ETMX servo, which had the correct gain, but the ITMs needed smaller gain, and some of the optics needed the gain to be negative rather than positive.  So, now the script ..../scripts/SUS/DRIFT_MON/MoveOpticToMatchDriftMon.py has individually defined gains for the cds.servo. 

Next up (after lunch) will be locking an aligning the arms.  I still don't have MICH fringing at the AS port, so I suspect that the ASS will move some of the optics somewhat significantly (perhaps the input tip tilts, which I don't have DRIFT_MON for?)

  11151   Fri Mar 20 13:29:33 2015 KojiUpdateIOOWaking up the IFO

If the optics moved such amount, could you check the PD alignment once the optics are aligned?

  11152   Fri Mar 20 16:44:49 2015 ericqUpdateIOOWaking up the IFO

X arm ASS is having some issues. ITMX oplev was recentered with ITMX in a good hand-aligned state. 

The martian wifi network wasn't showing up, so I power cycled the wifi router. Seems to be fine now. 

  11158   Mon Mar 23 09:42:29 2015 SteveSummaryIOO4" PSL beam path posts

To achive the same beam height each components needs their specific post height.

 Beam Height Base Plate Mirror Mount Lens Mount  Waveplates-Rotary 0.75" OD. SS Post Height                      
4" Thorlabs BA2   Newport LH-1   2.620"  
4" Thorlabs BA2 Polaris K1     2.620"  
4" Thorlabs BA2 Polaris K2     2.220"  
4" Thorlabs BA2   Thorlabs LMR1   2.750"  
4" Thorlabs BA2     New Focus 9401 2.120"  
4" Thorlabs BA2 Newport U100     2.620"  
4" Thorlabs BA2 Newport U200     2.120"  
4" Newport 9021   LH-1   2.0" PMC-MM lens with xy translation stage: Newport 9022, 9065A    Atm3
4" Newport 9021   LH-1   1.89 MC-MM lens with translation stage: Newport 9022, 9025        Atm2

We have 2.625" tall, 3/4" OD SS posts for Polaris K1 mirror mounts: 20 pieces

Ordered Newport LH-1 lens mounts with axis height 1.0 yes


Attachment 1: .75odSSpost.pdf
Attachment 2: MC_mml_trans_clamp.jpg
Attachment 3: PMCmmLn.jpg
  11175   Thu Mar 26 10:41:06 2015 SteveUpdateIOOThe PMC is not clamped

The PMC is seated on 3 SS balls and it is free to move. I'm sure it will move in an earthquake. Not much, because the input and output K1 mirror frame will act as an earthquake stop.Atm2

Are there a touch of super glue on the balls? No, but there are V grooves at the bottom and on the top of each ball.Atm3


Attachment 1: IMG_0001.JPG
Attachment 2: PMCstops.jpg
Attachment 3: PMCballv.jpg
  11216   Mon Apr 13 19:34:02 2015 ericqUpdateIOOModulation Frequency Tuned to IMC Length

I've been fiddling with the mode cleaner and green beat box today, to try and get an absolute frequency calibration for MC2 motion. The AC measurements have all turned out weird, I get fractional power laws instead of the 1/f^2 that we expect from the MC2 pendulum. At DC, I get a rough number of 15 green kHz per MC2 count, but this translates to ~7e-10 m/count which is in contrast to the 6e-9 m/count from 2009. I will meditate on this a bit. 

In any case, while working at the IOO rack, I tuned the 11MHz modulation frequency, as was done in ELOGs 9324 and 10314, by minimizing one of the beats of the 11MHz and 29.5MHz sidebands. 

The new modulation frequency / current IMC FSR is 11.066209 +- 1 Hz, which is a only a few ppm change from the tuning from last July.

This implies a IMC round trip length of 27.090800m +- 2um.

Attached is a plot showing the beat of 55-29.5 going down as I changed the marconi frequency. 


Attachment 1: fMod_tuning.pdf
  11332   Thu May 28 17:00:04 2015 KojiUpdateIOOFSS SLOW not engaged: is this intentional?

I found that FSS SLOW servo is not engaged. Is this intentional test to keep the NPRO temp constant?
This is making the FSS Fast unhappy (~ -7.5V right now).

  11333   Thu May 28 17:12:32 2015 ericqUpdateIOOFSS SLOW not engaged: is this intentional?

Yes, I had turned it off while looking for the PSL/X AUX beat, and forgot to turn it back on.

I will post an elog with more detail this evening, but I found a temperature which restored the X green beatnote at its nominal amplitude (-30dBm) with no mode hops within +-1 IR beat GHz, and offloaded the slow offset slider to the X-end laser crystal dial. I will look for the Y beatnote after dinner. 

Currently the control room analyzer is hooked up to recieve the Y IR and green beats; no X signals. 

  11343   Tue Jun 2 21:22:07 2015 rana, kojiConfigurationIOOAOM inserted in beam and aligned

We spent an hour today to put the AOM back in the beam before the PMC and verified that the diffraction is working.

  1. The fuse holder was missing from the rack. We inserted a 5A fuse. We expect that the quiesscent draw is < 0.5 A. The power is from the +24V Sorensen supply.
  2. The alignment was tricky, but we optimized it as well as we could in translation and the RZ direction. Its a fixed mount still.
  3. We noticed that according to the datasheet, the polarization is wrong! It wants S-Pol light and we're giving it P-Pol. How come no one noticed this? We expect that the efficiency is reduced because of this. We (Steve) need to brainstorm what kind of mount we can use there to mount it at 90 deg to the plane of the table.
  4. The lens after the AOM has f = +400 mm. The distance from the AOM to the lens is ~800-900 mm so its not so terrible. However, if someone were to put the AOM halfway between the turning mirrors there, the beam diffraction would be canceled.
  5. The AOM input impedance seems to be 50 Ohm as advertised. The previous Koji entry claim of 25 Ohm is mysterious. We checked the Ohmage by sending a signal into the AM input of the AOM using the DS345 which as a 50 Ohm output. 1 Vpp from the DS345 made 1 Vpp on the input of the AM input as measured by Oscope connected by T with high impedance setting.
  6. With 0.5 V offset and a 1 Vpp signal, we get ~20-25% modulation of the power.sad
  7. We have left it running with a 4444.4 Hz modulation and a small amplitude. This is to see if we can use this to measure the cavity poles of the MC and the arms.
  8. We noticed some hash on the Teed input monitor. It was backstreaming of the RF drive. Whoever uses this thing in an ISS feedback ought to make sure to put an RF choke between the servo and this AOM driver.

We also removed a 50/50 pickoff mirror which was used to take one of the NPRO -> EOM polarizer reject beams and send it across the table into a floppy dump. Its now hitting a closer floppy dump. Let's stop using these crappy anodized aluminum flappers anywhere, Steve.

We also noticed that the PMC REFL path uses a W1 from CVI to send the PMC reflection to the REFL RFPD. The dim beam from the AR coated surface is being used rather than the bright beam from the uncoated surface. Ooops. Steve, can you please order another W1 for 1064 from CVI, but get it with a 2-3 deg wedge angle? This one has a wedge which is too small.

  11360   Mon Jun 15 20:36:48 2015 ranaUpdateIOOIOO QPDs centred

after re-aligning the beam into the PMC, I touched up the steering mirros into the IOO QPDs so that the beams are now centered again. Please don't adjust these references without prior authorization and training.

This plot shows the 10-minute trends for these QPDs over the last 400 days.

Attachment 1: Untitled.png
  11447   Mon Jul 27 16:47:53 2015 ericqUpdateIOOMC2 -> MCL Actuator TF

Our noise cancellation SURFS will be doing online subtraction on the mode cleaner length, among other things. 

I made a measurement of the MC2 actuator transfer function by injecting noise from 1-100Hz into LSC_MC2_EXC for about 15 minutes, then estimating the TF from MC2_OUT to IOO_MC_L with CSD/PSD. The inverse of this TF will be applied to their Wiener target data to give us the direct subtration filter we want. 

I figured I would post the results here for posterity. The last time this seems to have been done is in ELOG 5900. There are some differences found here, the effective Q of the 1Hz pendulum resonance seems lower, and the behavior above 20Hz has definitely changed. 

IIR fits will be done by one of the SURFs to be used in their Wiener filter calculations. 

Data attached!

Attachment 1: mc2_2_mcl.png
Attachment 2: MC2_2_MCL_TF.txt.zip
  11453   Tue Jul 28 15:06:27 2015 SteveUpdateIOOPSL HEPA turned on


Attachment 1: noHepa.jpg
  11462   Thu Jul 30 02:06:20 2015 IgnacioUpdateIOOMC2 <-> MCL Actuator TF fitted

Eric downloaded MC2 to MCL transfer function data (H) as well as its inverse, MCL to MC2 (Hinv). He also downloaded new MCL and MC2 data.

I used vectfit to fit the MC2 to MCL transfer function, 

The ZPK parameters for this fit were,

Zeros              1278.36719876674 + 0.00000000000000i
                   -100.753249679343 + 0.00000000000000i
                   -18.6014192997845 + 13.0294910760217i
                   -18.6014192997845 - 13.0294910760217i

Poles              -1.11035771175328 + 7.03549674098987i
                   -1.11035771175328 - 7.03549674098987i
                   -18.8655320274072 + 0.00000000000000i
                   -690.294337433234 + 0.00000000000000i

Gain               0.00207206036014220

Using the above vectfit model, I filtered the raw MC2 signal to get 'MCL'. The PSD's of the raw MCL data and the filtered MC2 result is shown below,

The lack of accuracy of the transfer function at replicating MCL at frequencies lower than 0.7Hz is expected, the vectfit model I generated fails to follow accurately the raw transfer function data. My question: Does it matter? My guess: Probably not. In order to mitigate seismic noise from the mode cleaner we are mainly concerened with the 1-3 Hz region.

I also used vectfit to fit the transfer function for MCL to MC2,

This one was harder to fit accurately for some reason, I could do it with four pairs of zeros and poles but it took some preweighting.

The ZPK parameters for the above fit were, 

Zeros              0.173068278283995 + 0.00000000000000i
                   0.995140531040529 + 0.0268079821980457i
                   0.995140531040529 - 0.0268079821980457i
                   0.894476816129099 + 0.00000000000000i

Poles              -19.9566906920707 + 18.0649464375308i
                   -19.9566906920707 - 18.0649464375308i
                   -109.275971483008 + 0.00000000000000i
                   -1791.88947801703 + 0.00000000000000i

Gain               1237.46417532120

Similarly, using this ZPK model, I filtered the MCL signal to get 'MC2'. I plotted the PSD for the MC2 signal and the filtered MCL to get,

Again, the lack of accuracy of the filtered MC2 at replicating MCL below 0.7 Hz and above 12 Hz is due to the inverse transfer function failing to converge in these ranges.

Attachment 1: TF_BODE.png
Attachment 2: MC2_2_MCL.png
Attachment 3: TF_INV_BODE.png
Attachment 4: MCL_2_MC2.png
  11472   Thu Jul 30 19:12:52 2015 IgnacioUpdateIOOYAW and PIT WFS Wiener filtering

Rana pointed out that another way to mitigate seismic motion at in the mode cleaner would be to look at the YAW and PITCH output  channels of the WFS sensors that control the angular alignment of the mode cleaner. 

I downloaded 45 mins of data from the following two channels:



And did some quick offline Wiener filtering with no preweighting, the results are shown in the PSD's below,


I'm quite surprised at the Wiener subtraction obtained for the YAW signal, it required no preweighting and there is about an order of magnitude improvement in our region of interest, 1-3 Hz. The PIT channel didn't do so bad either.


Attachment 1: YAW.png
Attachment 2: PIT.png
  11488   Mon Aug 10 22:18:19 2015 IgnacioUpdateIOOReady to do some online mode cleaner subtraction

I'm attaching a SISO IIR Wiener filter here for reference purposes that will go online either tonight or tomorrow evening. This is a first test to convince myself that I can get this to work, MISO IIR filters are close to being ready and will soon be employed. 

This Wiener filter uses the STS-X channel as a witness and MCL as target. The bode plot for the filter is shown below,

The performance of the FIR and IIR Wiener filters and the ammount of subtraction achive for MCL is shown below,


Output from quack to be loaded with foton: filter.zip

K bye.

Attachment 1: stsx.png
Attachment 2: performance.png
Attachment 3: filter.zip
  11492   Tue Aug 11 11:30:19 2015 IgnacioUpdateIOOSISO (T240-X) FF of MCL

Last night we finally got some online subtraction going. The filter used is described in the post this eLOG is @eLOG 11488

The results were as follow:

The filter worked as expected when subtracting noise out of MCL,

There is about a factor of 6 subtraction at the ~3Hz resonant peak. The static IIR filter predicted a factor of 6-7 subtraction of this peak as well.

The 1.2 Hz resenonant feature improved by a factor of 3. This should improve quite drastically when I implement the y-channel of the T240 seismo.

There is some high frequency noise being injected, not very noticeable, but present. 

We then took a look at the power in the MC when the filter was on,

The power being transmitted in the cavity was not as stable as with the feedforward on. We believe that the filter is not at fault for this as Eric mentioned to me that the MC2 actuator lacked some sort of compensation that I need to understand a bit better.

YARM was then locked when the filter was on and we took a look at how it was doing. There was stationary sound arising from the locking of the YARM, leading us to believe that the filter might have injected some noise in the signal. IT DID.

The filter injected nasty high frequency noise at YARM from 11 Hz and on. This is to be expected since the filter did not roll off to zero at high frequencies. Implementing a 1/f rolloff should mitigate some of the injected noise.

 Also, as one can see above, subtraction by around a factor of 2 or so, was induced by the mode cleaner feedforward subtraction.

Attachment 1: MCL.png
Attachment 2: MCTRANS.png
Attachment 3: YARM.png
  11495   Tue Aug 11 18:43:42 2015 JessicaUpdateIOOMCL Online Subtraction

Today I finished fitting the transfer function to a vectfit model for seismometers T240_X and T240_Y, and then used these to filter noise online from the mode cleaner. 

The Bode plot for T240_X is in figure 1, and T240_Y is in figure 2. I made sure to weight the edges of the fit so that no DC coupling or excessive injection of high frequency noise occurs at the edges of the fit.

I used C1:IOO-MC_L_DQ as the first channel I filtered, with C1:IOO-MC_L_DQ(RMS) for RMS data. I took reference data first, without my filter on. I then turned the filter on and took data from the same channel again. The filtered data, plotted in red, subtracted from the reference and did not inject noise anywhere in the mode cleaner. 

I also looked at C1:LSC-YARM_OUT_DQ and C1:LSC-YARM_OUT_DQ(RMS) for its RMS to see if noise was being injected into the Y-Arm when my filter was implemented. I took reference data here also, shown in blue, and compared it to data taken with the filter on. My filter, in pink, subtracted from the Y-Arm and injected no noise in the region up to 10 Hz, and only minimal noise at frequencies ~80 Hz. Frequencies this high are noisy and difficult to filter anyways, so the noise injection was minimal in the Y-Arm. 

Attachment 1: SeisX_bode.png
Attachment 2: SeisY_bode.png
Attachment 3: MCL_first.png
Attachment 4: Yarm_first.png
ELOG V3.1.3-