We've provided acoustic excitation using speakers on the AS table and saw that PSD of YARM feedback signal increased in the frequency range 50 - 100 Hz. Meanwhile, XARM feedback signal did not change. Moreover, YARM noise is much higher at these frequencies compared to XARM.

The problem was with YARM oplev servos. Both ITMY and ETMY produced noise to YARM length. ITMY oplev signal had a huge resonance at 55 Hz. We measured coherence with accelerometers, it was 0.8. It turned out that one of the mirror mounts was not fixed in the oplev path. When we fixed it, noise has gone.

Note: speakers were on AS table but mirror mounts could steel feel it on ITMY table.

Then we had a look on ETMY table. We saw a mirror on suspiciously long mirror mount that was used in the ETMY oplev path. We slightly kicked long mount with a small screwdriver and YARM control signal went up with resonance at 100 Hz.

I will just leave the picture of spectrum that shows the injected acoustic sound effects due to the oplevs.

red line: POY error without oplev feedback nor acoustic noise
blue line: POY error without oplev feedback but with acoustic noise
brown line: POY error with oplev feedback but without acoustic noise
green line: POY error with oplev and acoustic noise

You can see there is noise only at green line around 70 - 100 Hz. And it does not look like the acoustic signal is injected directly to the arms but the acoustic sound couples to the original noise source.

 Today I wanted to check that AS and REFL beams are real and contain proper information about interferometer. For this I locked YARM using AS55_I and REFL11_I. Then I compared spectrum with POY11_I locking. Everything is the same. I've also adjusted phase rotations of AS55 (0.2 ->24) and REFL11 (-34.150 -> -43).

Then I've locked MICH and aligned EMTs such that ASDC was close to zero. Then I locked PRCL and aligned PRM. Power buildup was 50. 

 I studied more carefully beam path inside DRMI using PRM face camera and found that beam is clipping on PR3 edge.

Step 1: PRCL LOCK, MICH LOCK, power build up 30.

Note: left is right and vice versa on the PRM camera

 Step 2: PRLC - UNLOCK, MICH - LOCK, PRM is still aligned. Right photo is AS port. I've slightly misaligned ITMs such that disturbance of AS beam is clearly seen.

Step 3: PRCL - UNLOCK, MICH - LOCK, PRM misalined in yaw such such that the beam LASER -> PRM -> PR2 -> PR3 -> BS -> ITMX -> BS -> PR3 -> PR2 -> PRM -> PR2 -> PR3 is completely clipped on the TT edge. AS beam is now not clipped.

So the conclusion is that when PRC is not locked and beam is thin, it can avoid clipping. When PRC locked, beam size grows and it starts to clip. I think we need to move the mount next to PR3 because of it we to not have enough space to align the TT.

Step 4: PSL shutter is closed.

 Some explanation of how you define power buildup please. Also some plots showing the evidence.

 I think about power buildup as a ratio of the power in the cavity when it is locked and unlocked = (POYDC_LOCKED - POYDC_OFFSET) / (POYDC_UNLOCKED - POYDC_OFFSET). I do not multiply this number by PRM transmission.

POYDC_OFFSET = -0.006

POYDC_UNLOCK = 0.063

For example, on the plot below power buildup is 15.

That's OK, but its best to use standard notation. The power recycling gain is defined as the power incident on the BS divided by the power incident on the PRM from the laser side. You should also compare it with the PRC gain that you expect from mirror transmissions.

Leo fixed an issue with the new nds2-client packages that was preventing it from retrieving online data.  It's working now from matlab, python, and octave.

Here's an example of a dataviewer-like script in python:

#!/usr/bin/python

import sys
import nds2
from pylab import *

# channels are command line arguments
channels = sys.argv[1:]

conn = nds2.connection('fb', 8088)

fig = figure()
fig.show()
for bufs in conn.iterate(channels):
    fig.clf()
    for buf in bufs:
        plot(buf.data)
    draw()

 I've made snapshots of PR2, PRM, ITMY and ITMX mirrors. Power buildup recycling gain (POWER BS / POWER PRM) was equal to 3-4.

How NOT to:

The janitor can not clean in areas like this. He may only steps on these cables accidentally as he dust wiping our chambers.

 Motivation

We observed that oplev servos affect the arm spectra badly (elog #7798). Some of them are fixed, but still they inject noise into the arms.
So I tried to turn the oplevs off and to see the acoustic noise effect. However, the mirrors moves so much that the signal does not seem to be linear any more, and the noise spectrum of arms changes especially around 60 - 100 Hz as you can see the spectrogram of YARM error signal below. This makes it difficult to find acoustic coupling noise. Therefore, I tried to fix the oplev servos so that the noise spectra do not get worse when the oplev servos are on.

Checking oplev UGFs

I checked the oplev open loop transfer functions. The UGFs of oplevs are all around 1-3Hz and phase margin looks enough except the BS oplev.
The gain of the BS oplev OLTF has so low that the signal is not fed back. Moreover, there is much phase delay in the BS feedback loop than the others'.
The counts of BS oplev sum is not changed so much for this 4 months, so the oplev beam seems to hit the BS correctly.
I am not sure what makes difference.

Clipped oplev beam fixed

Den and I found the output beam of ETMY oplev was clipped the other day. Also I found the scattered beam of ITMY oplev was on the edge of the mirror inside the vacuum and it made more scattered lights.
(before) -> (after)

  I fixed both of the clipped beam. But still the oplev feedback inject the noise into the arm. (red: oplev off, blue: oplev on)
   

 Sorry for the mess. I fixed it.

[Manasa, Ayaka]

I found that MC got unstable this morning. This is caused by the drift of PMC. The transmission of PMC was going down and eventually unlocked PMC.

We adjusted 'Slow Actuator Adjust' in FSS and now the PMC is locked with transmission of ~ 0.735.
Also we aligned the MC to be locked. Now it is locked with transmission of ~ 0.5 with WFS and MCL on.

[Ayaka, Koji]

Ayaka pointed out that the PMC has too low unity gain frequency. We checked the history of "C1:PSL-PMC_GAIN"
and found that the gain was minimum from the Friday night. It was returned to nominal gain of 10.

The PMC screen had the gain status indicator always red. This was because C1:PSL-STAT_PMC_NOM_GAIN was 2 instead of 10.
This was fixed by the following command.

ezcawrite C1:PSL-STAT_PMC_NOM_GAIN 10

This will be recorded by the snapshot in an hour.

Another annoying false alerm on the PMC screen was the PMC transmission monitor.
In order to fix this, the following commands were executed.

ezcawrite C1:PSL-PMC_PMCTRANSPD.LOLO 0.75
ezcawrite C1:PSL-PMC_PMCTRANSPD.LOW 0.8
ezcawrite C1:PSL-PMC_PMCTRANSPD.HIGH 0.9
ezcawrite C1:PSL-PMC_PMCTRANSPD.HIHI 0.95

Also the corresponding EPICS database (/cvs/cds/caltech/target/c1psl/psl.db) has been updated accordingly.

[Rana, Ayaka]

The BS oplev pitch feedback came back.

The problem was that 300^2:0 filter was off. And I turned on all the low pass filters (ELP35), then the oplev servo does not seem to inject big noise into the arms as long as I see the spectra of POY and POX. These low-pass filters will be modified tomorrow so that the acoustic coupling noise is minimized.

I have updated the layout to fix all the issues brought up. The last couple of 2" green steering mirrors will hold the PZTs for input steering. I will update with the list of optical components that we will be ordering for this layout. The ETMY endtable layout will be similar to this one, except that we will have IPANG setup at the empty space in the right top corner.

[Koji, Ayaka]

Last night, I injected acoustic noise at POX table and AS table with oplev controls on (LPF is on).

1. acoustic noise at the POX table

I set the microphones and speakers at the POX table and see the acoustic coupling.

I could see slight change around 40 Hz. This can be caused by the oplev feedback loop because the speaker was on the same table as the ITMX oplev.

2. acoustic noise at the AS table

I controlled XARM with AS error signal and set the microphones and speaker on the AS table.

The resonance a 200 Hz seemed to be enhanced. But still we are not sure that it is caused by acoustic noise. Because this resonance is enhanced when the OL gain is high, and the gain adjustment was so critical that this resonance was easily enhanced even when the acoustic noise is not injected. And sometimes it has gone away.

I have updated the BSC layout to include the new tip-tilts. The bigger footprints of the tiptilts are on in the way of the existing PRM oplev path. So I have recalculated new PRM oplev paths. The proposed layout requires a new oplev mirror to be included.

I have setup cameras looking at the back of PR3 (through the north viewport on the MC chamber) and the face of PR2 (through the north viewport on the ITMX chamber). We would like a view of the face of PR3, but that isn't possible without placing another in-vac mirror.  The best we can do is the current PRM_BS camera setup, which sees a small portion of the PR3 face.  Most of the face is obscured by the PRM itself. 

I have taken images with the PRM misaligned.  The spot near the top of PR2 is the first reflection from the pitch-misaligned PRM, so it should be ignored for the purposes of trying to see the straight-shot, no PRM beam.

Images are taken with my videocapture50 script, in ..../scripts/general/videoscripts.  This takes 10 sets of 50 images and saves them.  Then ImageBkgndSubtractor.m located in the same folder takes the images (you must edit the beginning of the script to tell it where the images are), averages the noBeam images (PSL shutter closed), and averages the withBeam images, and subtracts them.  Results below:

I repeated my experiment to get noise level. To get that I disconnected the bandpass filter SBP-10.7  from channel A of network analyzer AG4395A and terminated both the open ends (open end of filter and open end of channel A) with 50ohm terminator.

Reference level had been corrected, signal and noise data had been collected separately w.r.t that level.

Command for GPIB:   ./netgpibdata.py -i 192.168.113.105 -d AG4395A -a 10 -f filename

The result is as follows

I fixed the illuminator setup.  ETMY was not hooked up, and the screen wasn't configured quite right.  The ITMX illuminator still needs to be hooked up to the vertex switch.

I made an updated illuminator script that works more like the videoswitch scripts, with a saner interface, and is located here:

/opt/rtcds/caltech/c1/scripts/general/illuminator

I also fixed up the illuminator MEDM interface a bit and added it to the VIDEO screen:

While I was at it, I cleaned up the sitemap a bit:

I hope everyone won't be too confused.

 Looking at the PEM BLRMS, I noticed that the GUR1Z channel had a much reduced microseism compared to the GUR1X. Looking at the BLRMS screens everything seems ON, although its a mess (too many filters in the banks, etc. - clean this up, PEM people).

 Looking at the Z channel in DTT, I see that the Z spectra looks double high pass filtered below ~1 Hz.     Needs some attention in the daytime.

From Den and Ayaka's elog entry from Nov 29, its clear that this problem is there at that time. It seems that the seismometer was not even hooked up before then. Perhaps Tara returned the seismometer around Thanksgiving and then someone here hooked it up but neglected to log this work? If so, please make an elog now describing the installation of this sensor at the 40m and log any future work which takes place at the 40m lab even if you think it is inconsequential.

 We've looked at PR2 face camera when PRM, BS and one of the ITMs were aligned. We saw an extra beam at PR2 when ITMX was aligned (right plot). This spot stays on the PR2 when prcl is locked.

Then we looked at PR3 transmission mirror and saw that the main beam is not on the edge of the mirror. Secondary beam is clipping on the mirror mount of PR3 that we see on BS_PRM camera.

Measured beam spot positions:

"+" for pitch means that the beam is too high, "-" too low

"+" for yaw means that the beam is left if you look from the back, "-" is right

Beam spots were measured using x, y arm and prcl locking to the carrier.

I think the angle of incidence on TT inside BSC will be too large because of eddy current damping brackets. I've measured max possible angle of incidence

This means that we do not have too much range and there is a probability that 45 degree incident beam will start clipping. I think we should just cut off the central part of the bracket. We do not need it anyway, our eddy current damping due to corner magnets is good enough.

I've left the brackets near the laptop in the clean room.

Tonight we've noticed that ITMX local damping was kicking the optics. This happened because LR shadow sensor was not working. In ~30 minutes it started to work again. Evan and I were working on installation, moving and focusing cameras and locking prcl and mich. We've installed a camera on BSC and plugged it in to PSL_SPARE input.

I'm not sure that this can be correlated to ITMX LR shadow sensor behaviour.

 I calibrated MC_F signal into Hz/rtHz unit using the transfer function from MC_F to PMC feedback signal.

Here is the diagram:
  

n_mcf is MC_F signal we can get at dtt. I measured n_pmc/n'_mcf using SR.

Other information I used:

G_out = 2.49/123.49 (see the document D980352-E01-C)

Fout has 1 pole at 10 Hz (see the document D980352-E01-C)

A_pzt = 371e+6/63 [Hz/V] (see elog)

F_wt has 1 pole at 100 Hz and 1 zero at 10 Hz.

Then, calibration transfer function of H is fitted as 1e+9/f [Hz/V]:

Then, the calibrated spectrum of MC_F is below:

This calibration have about 20 % error.
Compared to the spectrum in Jenne's paper (elog), above 20 Hz it seems to be laser frequency noise. But now we have extra unknown noise below 10 Hz.

Note: calibration value of laser's PZT is ~ 1MHz/V. This is reasonable compared to the data sheet of the laser. (This is calculated by combining result of H and transfer function of the circuit box1 and FSS.)

 Yesterday, I made new mounts for microphones.

I glued a microphone on a pedestal. The cables are attached loosely so that its tension does not make any noise.
At the bottom of the mount, I attached the surgical tube forming a ring by double-side tape so that it damps the seismic vibration.

I made 6 mounts and these are all on the AS table now.
I took some data of XARM signal controlled by AS.

My plan is to find/set an upper limit on acoustic coupling noise in AS signal.
The acoustic noise can be estimated by the Wiener filter, but it is not accurate because it may see residual correlation between AS and microphone signals that should be 0 when the data is long enough.
I will find/set an upper limit by the analysis based on Neuman-Pearson criterion, that is analog of a stochastic GW background search.
If I can find the acoustic coupling noise should be below the shot noise, I am happy. If not, some improvements may be needed someday.

 Yesterday I wanted to recenter Guralps. I turned them off, understood that would be able to center them because we do not have power cable to Guralp box from Tara yet and turned them back on.

I've switched Guralp cables and spectrums are fine now.

I've estimated max possible angle of incidence on TT if we allow 20mm tolerance for the beam size and 5 mm tolerance for spot location on the mirror. It turns out to be

alpha = 43 degrees

So we need to cut the central part of the bracket. Then the max possible angle of incidence will be

alpha = 63 degrees

We can start the vent on Monday and use TT with an old bracket for yaw damping and later during the week we can install the brackets after they will be baked.

At least, we don't want to use Al-coated mirrors. We should use multilayer dielectric mirrors.

But have you looked yet at what angle we need? The first input string mirror has a quite small incidence angle. The other input steering mirror maybe borderline, based on your estimates. Also, have we considered just having new brackets made and cleaned? Is there a reason we would prefer to modify the ones we have?

I calibrated the AS error signal into the displacement of the YARM cavity in the same way as I did before (elog).

The open loop transfer function is:

The transfer function from ITMX excitation to AS error signal is:

Then I have got the calibration value : 5.08e+11 [counts/m]

The calibrated spectrum in unit of m/rtHz is

REF0: arm displacement
REF1: dark noise + demodulation circuit noise + WT filter noise + ADC noise (PSL shutter on)
REF2: demodulation circuit noise + WT filter noise + ADC noise (PD input of the circuit (at 1Y2) is connected to the 50 Ohm terminator)
(The circuit and WT filter seem to be connected at back side of the rack. Actually there is a connector labelled 'I MON' but it is not related to C1:LSC-ASS55_I_ERR)

Also we changed the AS gain so that ADC noise does not affect:

However, this did not make big change in sensitivity. I guess this means that circuit noise limits the sensitivity at higher frequencies than 400 Hz.
I tried to adjust the AS gain carefully but I could not do that because of the earthquake. Further investigation is needed.

There was an earthquake around 2:30 am. Now all the mirrors except SRM are damped.

 SRM, ITMY and MC3 moved some what, but how are the TT? It may worth looking at them before we vent.

This is NOT calibrated. Its sort of calibrated in the 500-1000 Hz area, but does not correctly use the loop TF or the cavity pole.

As for the noise, remember that the whole point of changing the AS whitening gain was to turn on the whitening filter AFTER locking. With the WF OFF, there's no way that you can surpass the ADC noise limit.

No, I did not apply open loop TF to it (actually I could not measure the open loop TF because of the earthquake last night). So I should not have said it was the displacement.

Also I changed the AS gain with whitening filter on and xarm locked. Still it does not make any change.

Photodiode PDA10CF was under test. The RF out signal of AG4395A had been divided by splitter with one output of the splitter going to R channel of the network analyzer and the other to the laser. The splitted laser beams - splitted with beam splitter - fall on two photodiodes - one reference and the other on PDA10CF. The outputs of these two photodiodes go to channel B and A respectively of the network analyzer. The measured transimpedance data had been collected using the GPIB connection.

The result is as follows:

Since I found that the the AS sensitivity seems to be limited by circuit noise, I inserted a RF amplifier just after the AS RF output.
Now, the sensitivity is improved and limited by the dark noise of the PD.

(Note: I did not apply the open loop TF on this xml file.)
REF3: dark noise + circuit noise + WT filter noise + ADC noise
REF4: circuit noise + WT filter noise + ADC

With this situation, I injected the acoustic noise:

REF5, 6, 7: with acoustic excitation
no reference: without acoustic excitation

We could see the coherence only at the same frequencies, around 200 Hz as we saw before (elog).

Wednesday night, there was ~0.4 V on the PMC transmission PD. I adjusted the steering mirrors into the PMC and got the transmission up to 0.81 V.

I'm not sure when this was done, but there were beam dumps in front of the lasers for BS/PRM oplevs as well as ITMY/SRM oplevs.  MICH wasn't holding lock very nicely, so I poked around, and the Sum values for all of these optics' oplevs seemed too low, so I went to look, and found dumps.  I have removed these, and now BS and ITMY oplevs are back to normal.  (PRM and SRM are still misaligned right now, so I'll check those later, but they should be fine).

BS's oplev has been enabled while non-existant, at least for the whole weekend, since I found it enabled.  ITMY I found misaligned, so it's oplev servos were off.

In other news, we should get back in the habit of restoring all optics before we leave for the night / whenever locking activities are finished. 

 Put them back to normal.

[Jamie, Jenne]

Koji and Jamie locked the PRMI, and then Jamie and I took some videos. 

Video 1:   https://www.youtube.com/watch?v=jszTeyETyxU shows the face of PR2.

Video 2:   https://www.youtube.com/watch?v=Tfi4I4Q3Mqw shows the back of PR3, the face of PR2, as well as REFL and AS.

Video 3:   https://www.youtube.com/watch?v=bLHNWHAWZBA is the camera looking at the face of PRM and (through a viewing mirror) BS.

If you watch video 1, you'll see how large the beam gets on the face of PR2.  The main spot, where the straight-through, no-cavity beam is, is a little high of center.  The rest of the inflated beam swirls around that point.

Video 2 shows the same behavior, but you also see that we're much too high on PR3, and too close to the right (as seen on the video) side.

Video 3 is very disconcerting to me.  The main, stationary beam spot seems nicely centered, but the resonant beam, since it inflates and gets big, is very close to the right side of the PRM (as seen on the video). 

It wouldn't surprise me if, were we able to quantify the beam clipping loss on PR3 and PRM, the clipping were the reason we have a crappy PRC gain.  This doesn't explain why we have such a weird inflated beam though.

I centered IPPOS.  I do not find any IPANG beam on the ETMY table, even waving the IR card in the black beam tube.

I took photos of the PZT2 HV supplies with the new camera, but I can't figure out how to get the pictures off the camera.  I guess the camera is smarter than I am.

I have updated the Seismic Striptool display which is plotted on the wall in the control room. Please take a look and make comments. We should finalize it and not change it anymore.

By having an unchanging display, we can get used to small changes in the seismic environment which disrupt our locking.

1. y-scale is now linear; the log-scale was suppressing the factor of 2-3 variations which are important to us.
2. Just as the rainbow does, the colors now go from red to purple to represent the noise from 0.1 - 30 Hz: the red traces are 0.1-0.3 Hz, the green/yellow traces are 0.3-3 Hz, and the blue/purple traces are 3-30 Hz.
3. This is just showing GUR1. Let's try to keep this seismometer working so that we can have some long term record of the seismicity here. This means don't click off the buttons, disconnect the sensor, reboot the machine, etc. When you do do these things, elog them.

We will vent tomorrow (12/18)

After lengthy discussion, I have determined that we should vent now, with the primary goal of this vent to replace the input steering PZTs with the new active tip-tilts.  Since we still don't understand exactly what's going on with the PRC, it's unclear what we would do to attack the problem.  We need to do more modeling and measurements first.  We should limit the goal of this vent to replacing the PZTs, and then close up and do more measurements with better modeling and improved input point in hand.

There is limited time this week before everyone leaves for two-week holidays on Thursday or Friday.  The reason to not vent would be that we don't want to leave the IFO at air during the two week holiday.  People seem to think that this is not a problem, so we don't gain anything by waiting.  Therefore we vent now and do what we can before people take off.

The goal for this week is to replace PZT1 only:

Now: Jenne and Manasa are doing vent prep.  Manasa is lowering the input power and preparing the mode cleaner.  Jenne centered IPPOS and IPANG.  This will allow us to check how the input alignment changed during the vent.

12/18: Steve is going to start the vent as soon as he gets back from the dentist, at around 10am.  He will regulate the vent such that we are ready to lock the mode cleaner by 4pm.  At that time we will lock the MC and recheck the input alignment with IPPOS/ANG, with the idea being to see if anything moves during the vent.

12/19: First thing in the morning we take off the access connector ONLY.  The access connector is all we'll need to replace PZT1.    Put light door on the OMC chamber side immediately, since we won't need to get in there at all.  We won't need the light access connector.

For the rest of Wednesday we'll remove PZT1 and install the new active TT.  We'll be using the current out-of-vac cable for PZT1 for the new TT.  We should only have to modify the rack end of the cable to accommodate the coil driver.  This should be a small modification.  Given that we have no wiring diagrams we'll have to pin it out in situ.

12/20: Hopefully finish up TT installation.

Jenne leaves 12/20, Manasa and Jamie leave 12/21.  We will either leave light doors on access connector holes, or possibly Rana, Koji, and Steve will replace access connector on Friday so that we can pump down to 1 Torr or something so that we leave it there over the holiday.

After we return from vacation:

PZT2/TT2 installation.  This will be less straight forward since the new TT has a bigger foot print than PZT2 and will block the PRM optical levers.  We'll need one additional steering mirror to redirect the oplev around the TT.  See elog 7815.

Once the new TTs are installed, we'll reevaluate where we're at.  If PRC modeling has progressed and we have an idea of something to work on with the PRC, we can.  Otherwise, we'll just button up, pump down, and get on with some better PRC measurements.

I aligned the PSL angle and position QPDs...then attenuated the input laser power using HWP-PBS-HWP combo from 1.28W to 100mW following instructions from elog 6892 and elog 7299.

To enable MC locking, I replaced the 10% BS before the MC_REFL PD with Y1 mirror. I tweaked the steering mirrors at the PSL table a teeny tiny bit to enable MC locking. MC is now locked at low power with 1.0 transmission.

Just in case we want to retrofit the Tip/Tils with Beryllium Copper wire, here are links to a few sources which have a supply of the right composition and temper:

http://www.lfa-wire.com/Tempered-Alloy-25_C17200.htm

http://www.alloywire.com/beryllium_copper_CB_101.html

http://www.ngk.co.jp/english/products/electronics/berylliumcopper/wire/index.html

http://www.goodfellow.com/E/Copper-Beryllium-Wire.html

I don't think its worth it to do something to modify them unless we get a real reduction in the hysteresis - need a benchtop test setup ASAP.

i just heard a rather large exploding sound in the control room.
I tried to locate the source and found the projector is not illuminating the wall anymore.
There is a slight smell of burning, but nothing is smoking.

Probably the lamp ended its life.

Rana and I just talked about the projector life time an hour ago! It must have been hearing!

 LOL

We should try purchase a projector with LED this time...longer lifetime! I guess the price of replacing the lamp in the one we have will be more or less same as a new one!

...Nah. The projector is pretty new (t<1yr) and this is the first time to have the lamp busted after the installation last year in Jan.

We just should purchase two bulbs.