[Koji, Jenne, Manasa, Annalisa, Rana, Nic]

PRMI locked using 3f signals and Y arm brought to resonance using ALS

<<Procedure>>

Preparation:

- After we checked the functionarity of the Yarm ALS, both arms were locked with the IR, and aligned by ASS.

- Disengaged the LSC feedback. Approximately aligned the PRM.

- Recorded the current alignment biases. Turned off all of the oplevs.

- Went into the lab, aligned all of the oplevs on the QPDs (except for the SRM).

- Check the locking of the PRMI.

- Once it is locked, go into the lab again and align the POP QPD.

- Check everything of the PRMI LSC/ASC works.

- Misalign PRM by 0.2

- Lock the arm again. Run ASS again.

- Miaslign ETMX.

ALS:

- Lock the Xarm with green. Adjust the beat freq between 30-50MHz.

- Reset Phase Tracker history.

- Check if there is any offset for the ALS. If there is, adjust it to zero.

- Stabilize the arm with the ALS. We should check the sign of the servo before it is cranked up to the nominal.

- Confirm if the offset FM has LPF (30mHz LPF).

- Run excastep for the ALS offset until we find the TEM00 resonance of the IR

- Record the offset at the resonance.

- Step back by 5 count (=100kHz)

PRMI+ALS:

- Started from the offset of -5.

- Aligned the PRM and the PRMI was locked by REFL165I(x0.8)nadQ(x0.2).

- PRM ASC engaged

- Moved the offset to -4 by ezcastep C1:ALS-OFFSETTER2_OFFSET +0.01,100 -s 0.1

- Moved to -3, -2, -1.5, -1. During the sweep PRCL/MICH gain was tweaked so that the gain is reduced.
  Nominal locking gain was PRCL x+2.5/MICH -30 . During the sweep they were +2.2 / -12
  PRCL FM2/4/5 ON, Later FM3/6 turned on and no problem.

- Moved to -0.9, .... , and finally to 0.

NEXT STEP

- Automation of the PRMI+one arm

- PRMI locking with BS/PRM

- Better sensing matrix

- PRMI+two arms

- Use of the DC signals form the transmission monitors. (High power /low power transmon).

AWESOME!  You guys rock.

Fantastico! :-)

 [Eric, Alex]

Our RF Switch arrived today, and we mounted it in rack 1Y1 (1st attachment). 

We connect our input fiber and all of our output fibers to our 1x16 optical splitter (2nd attachment). Note that the 75 meter fiber we are using for the splitter's input is in a very temporary position (3rd attachment - it's the spool).

We successfully turned our laser on and tested the optical splitter by measuring output power at each fiber using our Thorlabs PM20 power meter. Data was taken with the laser running at 67.5 mA and 24 degrees Celsius:

Detector name                  Power

Last night, I took sensing matrix data at various different offsets for the Yarm.  The sensing matrices I measured were of the PRMI, while the Yarm was (a) Held off resonance, (b) Held at ~50% peak power, and (c) Held on resonance.

The dither lines were clear in the MICH and PRCL spectrum, so I think I'm driving hard enough, but something else seems funny, since clearly the REFL165 I and Q signals were not completely overlapping last night.  If they were, we wouldn't have been able to lock the PRMI using REFL 165 I&Q.

Anyhow, here's the data that was taken.  Data folder is ...../scipts/LSC/SensingMatrix/SensMatData/

Yarm off resonance, SensMat_PRMI_1000cts_580Hz_2013-07-18_012848.dat

Yarm at ~50% resonance, SensMat_PRMI_1000cts_580Hz_2013-07-18_013937.dat

Yarm on resonance, SensMat_PRMI_1000cts_580Hz_2013-07-18_013619.dat

Hmm. I agree that something was funny.
Let's take the matrix without the arms and confirm the measurement is correct.

 Here I have included the full schematic (so far) of the proposed ISS. There are two sheets: the first schematic details the filter stages and their accompanying circuitry while the second schematic details the RMS threshold detection and subsequent triggering.

The first schematic is fairly self explanatory as to what different portions do, and I have annotated much of the second schematic as there are some non-traditional components etc.

I have not yet included some mechanism to adjust the threshold voltage in real time or any of the power regulation, but these should follow fairly quickly.

 Path to data (retreived using getdata)

/users/manasa/data/130717/YALS_scan

Data retrieved using getdata (30 minutes trend) saved at

/users/manasa/data/130717/PRMI_YALS

I found CDS rt processes in red. I did 'mxstreamrestart' from the medm. It did not help. Also ssh'd into c1iscex and tried 'mxstreamrestart' from the command line. It did not work either.

I thought restarting frame builder would help. I ssh'd to fb. But when I try to restart fb I get the following error:

controls@fb ~ 0$ telnet fb 8088
Trying 192.168.113.202...
telnet: connect to address 192.168.113.202: Connection refused

daqd was restarted.

- tried telnet fb 8088 on rossa => same error as manasa had

- tried telnet fb 8087 on rossa => same result

- sshed into fb ssh fb

- tried to find daqpd by ps -def | grep daqd => not found

- looked at wiki https://wiki-40m.ligo.caltech.edu/New_Computer_Restart_Procedures?highlight=%28daqd%29

- the wiki page suggested the following command to run daqd /opt/rtcds/caltech/c1/target/fb/daqd -c ./daqdrc &

- ran ps -def | grep nds => already exist. Left untouched.

- Left fb.

- tried telnet fb 8087 on rossa => now it works

Yesterday and today I was in the lab doing many cavity scan.

First I did many measurement with the cavity aligned in order to get the position of the 00 modes, then I misaligned the beam in many different ways to enhance the higher order modes.

In particular, I first misaligned the mode cleaner to make the beam clipping into the Faraday. To do this, I set to 0 the WFS gain, but I left the autolocker still enabled. In this way, the autolocker couldn't bring the mirrors back to the aligned position.

Then I misaligned also the TT2 to get even more HOMs.

Eventually, Rana came and we misaligned TT1 to clip the beam, and using TT2 we aligned back the beam to the arm.

To increase the SNR, we changed the gain of the TRY PD, setting it to 20dB (which corresponds to a factor 100 in digital scale)

I attached one scan that I did with Rana on Sunday night. I could not upload a better resolution image because the file size was too big, but here's the path to find all of the scans:

../users/annalisa/sweep/Yarm

There are many folders, one per each day I measured. In each folder there are measurements relative to aligned cavity, Pitch and Yaw misalignment.

 RXA EDIT:

The PDA520 used for TRY was set to 0 dB analog gain. This corresponds to ~500 counts out of 32768. The change to 20 dB actually increases the gain by 100. This makes the single arm lock saturate at ~25000 counts (obviously in analog before the ADC). The right setting for our usual running is probably 10 dB.

For the IMC WFS, we had disabled the turn on in the autolocker to use the IMC to steer the beam in the FI, but that was a flop (not enough range, not enough lever arm). In the end, I think we didn't get any clipping.

[Annalisa, Manasa, Jenne, Koji]

We are working on the vent preparation.

First of all, there was no light in the interferometer.
Obviously there were lots of IFO activity in the weekend. Some were elogged, some were not.
Annalisa took her responsibility to restore the alignment and the arms recovered their flashes.

The odd thing was that the ASS got instable after we turned down the TRY PD gain from +20dB to +10dB (0dB original).
We increased the TRY gain by factor of 10 (that's the "10dB" of this PDA520. See the spec sheet) to compensate this change.
This made the ASS instable. Anyway we reduced the gain of TRY PD to 0dB. This restored the ASS.

Jenne took some more data for the QPD spectrum calibration.

Link to the vent plan

Pre-vent checklist

• Center all oplevs/IPPOS/IPANG
• Align the arm cavities for IR and align Xgreen and Ygreen lasers to the arms.
  (X green+PSL green = TRX ~0.7 pre-swap and ~ 0.6 post-swap, Ygreen +PSL green TRY ~600 counts an hour or so after green was aligned to the arm.)
• Make a record of the MC pointing
• Align the beam at the PSL angle and position QPDs
   
  
• Record good OSEM values.
   
• Reduce input power by placing wave plate+PBS setup on the PSL table either BEFORE or AFTER THE PMC. (We will try attenuating the power using the WP + PBS that already exist after the laser. If this does not help attenuate enough, we will introduce WP+PBS after the PMC). Refer elog 6892 and elog 7299 for after the PMC detailed procedure.
   
• Replace 10% BS before MC REFL PD with Y1 mirror and lock MC at low power.
• Check the MC spot position measurement under the low power mode.
   

• Close shutter of PSL-IR and green shutters at the ends
• Make sure the jam nuts are protecting bellows

The results of today's MC spot position measurements:

spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
[2.3244717046516197, -0.094366247149508087, 1.6060842142158149, -0.74616561350974353, -0.67461746482832874, -1.3301448018100492]

MC1 and MC3 both have spots that are a little high in pitch, but everything else looks okay.

Actual Script:

/opt/rtcds/caltech/c1/scripts/ASS/MC/mcassMCdecenter

Plotting Script:

/opt/rtcds/caltech/c1/scripts/ASS/MC/MC_spotMeasurement_history.py

I have just centered IPPOS, as well as PSL POS and PSL ANG (also called IOO POS and IOO ANG on the screens).  Annalisa is working on placing mirrors to get the IPANG beam to its QPD, so that one will be centered later.

[Gautam, Manasa]

Green steering mirrors have been swapped with PZT mirrors at the X end table. We aligned the green to the X arm.

X arm green transmission +PSL green  ~ 0.95

That's better than before the swap...woohooo

FE Web view was broken for a long time. It was fixed now.

The problem was that path names were not fixed when we moved the models from the old local place to the SVN structure.

The auto updating script (/cvs/cds/rtcds/caltech/c1/scripts/AutoUpdate/update_webview.cron) is running on Mafalda.

Link to the web view: https://nodus.ligo.caltech.edu:30889/FE/

The spot on the IPANG QPD was checked. The spot is higher than the center and South side of the lens.
Some photos are found below.

The spot on the IPANG steering mirrors in the ETMY chamber was also checked.
It is clipped at the top of the steering mirror. (See attachment 4)
So basically the spot is about 1" above the center of the mirror.

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

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

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

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

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

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

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

PRM:

BS:

ITMX:

ITMY:

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

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

Centering of the oplev beams: done

Recording the OSEM values: done

There seems to be an unexplained oscillation in X arm cavity transmission for IR when the cavity is locked using the POX error signal.

Their origin is not related to the oplevs because the oscillation does not exist when LSC is OFF and the arms are controlled only by the oplevs and OSEMs.

 In light of recent events and the decision to test the piezo tip-tilts for green beam steering on the X-end table, I have set up 8 excitation points to channels 8 through 15 of the DAC on c1scx (as was done earlier for the DAC at 1Y4 with Jenne's help) in order to verify that the pin-outs of the DAC interface board. I have not yet compiled the model or restarted the computer, and will do these tomorrow, after which I will do the test. The channels are named YYY_CHAN9 etc. 

[Koji Jenne]

Low power MC locking

- Rotated HWP right after the laser

- Put a knife edge beam dump at the output of the PBS after the HWP.

- Replaced the PO mirror for the MC refl by an HR mirror.

- PMC:
Input offset from 0 to 0.29
Servo Gain from 10 to 30
=> Transmission 0.84 (1.2W at the MC input) to 0.069 (100mW)

- MC:

VCO Gain from 25 to 31
MC REFL: Unlocked 3.6 Locked 0.38-0.40

After Koji and I lowered the power into the PMC and saw that the MC locked nicely, I remeasured the spot positions (no alignment on the PSL table, or of the MC mirrors has been done.  Also, WFS are off, since there isn't any power going to them).

spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
[1.1999406656184595, 0.63492727550953243, 1.0769104750021909, -1.0260011922577466, -1.059439987970527, -1.2717741991488549]

The spot positions seem to have actually gotten a bit better in pitch (although between 2 consecutive measurements there was ~0.5mm discrepancy), and no real change in yaw.  This means that Rana was right all along (surprise!), and that decreasing the power before the PMC reduces alignment pain significantly.

After everyone's work today (good teamwork everybody!!), we are a GO for the vent.

Steve, please check the jam nuts, and begin the vent when you get in.  Thanks.

Thanks for the good preparation.  IFO pressure P1=20 Torr

The MC was manually aligned. The spot positions were measured and it is consistent with the measurements done yesterday.

 The 40m IFO has reached  atmospher in 5 hours. It is ready to open chamber condition. The RGA is pumped with the maglev.

P1 pirani gauge is contact dependent as you see it on the linear plot It will be replaced during this vent.

The venting speed was 2-4 Torr / min

Atm2 shows how the BS is sensing the venting air cylinder changes. 

The 4th cylinder of instrument  grade air  bump is overlapping with our janitor working at the BS chamber.

[Annnalisa Koji]

Full alignment of the IFO was recovered. The arms were locked with the green beams first, and then locked with the IR.

In order to use the ASS with lower power, C1:LSC-OUTPUT_MTRX_9_6 and C1:LSC-OUTPUT_MTRX_10_7 were reduced to 0.05.
This compensates the gain imbalance between TRX/Y siganls and the A2L component in the arm feedback signals.

Despite the IFO was aligned, we don't touch the OPLEVs and green beams to the vented IFO.

 I just compiled and installed the model with the excitation points on c1scx and then restarted framebuilder. The channels I set up are now showing up in the awggui dropdown menu. I will do the tests on the DAC channels shortly.

Just to keep things on record, these are the steps I followed:

• opened the model c1scx (path: /opt/rtcds/userapps/release/sus/c1/models) with MATLAB
• Added 8 excitation points and saved the model. A copy has been saved as c1scx.mdl.r2010b because of the recent upgrade to r2013a. 
• ssh to c1iscex (computer running the model c1scx). 
• Entered the following sequence of commands in terminal: rtcds make c1scx ,  rtcds install c1scx , rtcds start c1scx 
• ssh to framebuilder, and restarted the framebuilder by entering telnet fb 8088   and then   shutdown.

 After the vent, the IPang spot position on the steering mirrors on the Yend table moved approximately by 1 inch down.

Inside the chamber, the spot position is in the center of the steering mirror. (difficult to take a picture because the PSL beam power has been reduced)

 I just finished carrying out the same checks for the DAC at 1X9 (with channels 9 through 16 that are unused as of now) as those I had done for the DAC at 1Y4, as the hardware prep up till now was done with the characterisation of the DAC at 1Y4. Conclusions:

• The accessible range of output voltage are -10 V to +10V w.r.t ground --> No change needs to be made to the gain of the HV amplifier stage on the PZT Driver Board
• The pin-outs of the DAC Adaptor Board at 1X9 is identical to that at 1Y4 --> Custom ribbons do not need to be modified.
• The PSD of the DAC output has a peak at 64 kHz --> Notches on AI Board do not need to be moved again.

I will now proceed to install various pieces of hardware (AI Board, PZT driver board, HV Power Supply and cabling) at 1X9, while not making the connection to the PZTs till I receive the go ahead. 

Thesedays we were continuously annoyed by unELOGGED activities of the interferometer.

MC2 LOCKIN was left on and has continuously injected frequency noise and beam pointing modulation
during all of the comissioning / vent preparation.

C1:SUS-MC2_LOCKIN2_OSC_FREQ was 0.075
C1:SUS-MC2_LOCKIN2_OSC_CLKGAIN was 99

For more than a week ago we noticed that the curve of the MC WFS stripchart suddenly got THICKER.
MC WFS, arm transmission, beam pointing... everything was modulated.
It was not WFS instability, and it was not the cavity mirrors.

Today I made the investigation and finally tracked down the cause of this issue to be on MC2 suspension.
Then it was found that this LOCKIN was ON.
There is no direct record of this lockin in the frame files.
From the recorded channel "C1:IOO-WFS2-YAW_OUT16" (which is the trace on the StripTool chart on the wall)
It was turned on at July 10th, 2:00UTC (July 9th, 7PM PDT)

We will open the BS and ITMY doors first thing tomorrow morning. I plan to try to be in around 9 am. The first order of business will be to flip the folding mirrors that are not currently flipped (SR2, SR3, PR3).

 Jenne, Annalisa & Steve

[Jenne, Annalisa]

SR2 is flipped, and reinstalled.  We did that before lunch, and we're about to go in and work on SR3 and PR3.

EDITS / Notes:

I set dog clamps to have a reference position of where the tip tilt was, then I removed SR3 from the chamber.  Once out, I followed the same procedure I used for PR2 during the last vent - I removed the whole suspension (top mount, wires, optic) from the cage, and laid it down flat.  Then I loosened the set screw which pushes on the teflon nudge, removed the mirror, inspected it, and put it back in, with the HR side facing the back side of the ring.  Then I replaced the suspension system in the cage, and put the mirror back into the chamber. 

When I loosened the teflon nudge at the top of the mirror holder ring, the optic seemed to fall down a tiny bit.  I think this implies that the HR surface of the optic did not used to be parallel to the front face of the mirror holder ring.  When I put the suspension back onto the cage, the pitch balancing was very bad.  We checked the level of the table that I had the cage on, and it was miraculously pretty level, so I did the pitch balancing out of the chamber. 

Also, during my quick inspection of the mirror (not thorough, just using room lights), I noticed a small fleck of lint near the edge of the optic on the HR surface.  The HR surface is now on the outside of the SRC, but we should still blow at the optic with the ionized nitrogen to get it off.

I did not think to check the fine-tuning alignment of SR2....Koji did that after lunch (which I will elog about in a separate elog).

Yes, this was not ELOG'd by me, unfortunately. This was the MC tickler which I described to some people in the control room when I turned it on.

As Koji points out, with the MCL path turned off this injects frequency noise and pointing fluctuations into the MC. With the MCL path back on it would have very small effect. After the pumpdown we can turn it back on and have it disabled after lock is acquired. Unfortunately, our LOCKIN modules don't have a ramp available for the excitation and so this will produce some transients (or perhaps we can ezcastep it for now). Eventually, we will modify this CDS part so that we can ramp the sine wave.

After the first flipping, X/Y arms were aligned and locked. Then the ASS aligned the arms.

 I have made significant changes to the ISS schematic, mostly in the form of adding necessary subsystems.

Some changes I have made:

• Added a front page with sheet symbols that are representations of the other schematic sheets.
• Added an 'Excitation' subsystem for use in determining the closed-loop transfer function
• Added an instrumentation amplifier (with ADA4004s at Rana's recent suggestion) to handle the differential input from the PD
• Included a switchable inverting amplifier (Gain of 1 or -1) to ensure we have the correct polarity
• Made it so the first filtering stage is immediately active when the ISS loop is closed
• Added LP filters with large time constants to buffer/delay trigger signals
• Added test points all over the board
• Refined a few buffer amplifiers

On the front page, all inputs and outputs are currently BNC ports, although this is most likely not the final design that will be used. For instance, the ports ENABLE, INPUT GND and INVERT are supposed to be logic inputs for a MAX333a switch. These will most likely be front panel switches that either connect the switch's logic pin to GND (Logic 0) or something like a +5 V supply (Logic 1).

I also have not included power regulation for my board although I have some of the actual D1000217 Chasis Power Regulator boards and I'll incorporate those in my design soon.

There was no progress tonight after Jenne left.
I could not find any reasonable fringes of the IFO after 3 hours of optics jiggling.

* I jiggled TT1 and TT2. The slider has not been restored.
We should probably look at the value in the day time and revert them.
(Still this does not ensure the recovery of the previous pointing because of the hysteresis)

* The arms are still aligned for the green.
It's not TEM00 any more because of the vent/drift but the fringe is visible (i.e. eigenaxis is on the mirror)

* As we touched PR3, the input pointing is totally misaligned.

To Do / Plan

* We need to find the resonance of the yarm by the input TTs. Once the resonance is found, we will align the PRM.

* Move the BS to find the xarm resonance.

* Finally align SRM

* It was not possible to find the resonance of the yarm without going into the chamber. Definitely we can find the spot on the ITMY by a card, but we are not sure the beam can hit the ETMY. And the baffles makes the work difficult.

* One possibility is to align the input beam so that the ITMY beam is retroreflected to the PRM. I tried it but the beam was not visible form the camera.

 I realized I totally forgot to post this last week, but I prototyped the comparator and boost triggering portion of the ISS, at least in part. Below is a schematic that shows the prototype circuit I made. Note that it includes ports for the oscilloscope channels that appear in the second image included. Essentially, I was able to verify that the output from the LT1016, as it's currently constructed in the ISS schematic, would be sufficient logic to switch the MAX333a.

Below, we can first see that the comparator is switching its output as desired. When the DC level of the input drops below a certain threshold (~1.6 V) the output of the comparator switches on to ~4 V. When the DC level of the input goes back up above the upper threshold (~3.2 V), the comparator switches off to ~0.3 V. The exact values of the threshold voltages can be determined/tuned at a later date, but this is the basic behavior that the comparator circuit will have.

To detect whether or not the MAX333a was switching properly, I connected the common terminal of one of the switches to a +5 V supply, and looked at the voltage coming off both the 'open' and 'closed' terminals of said SPDT switch. We can see that with Logic 0 (comparator output ~0.3 V) Channel 4 exhibits a ~5 V signal, just as we would expect from the above schematic. With Logic 1 (comparator output ~4 V), Channel 3 exhibits the characteristic 5 V signal.

[Jenne, Annalisa, Manasa]

After yesterday's flipping of PR3, we lost our input pointing. Koji spent a few hours last night but couldn't restore the Y arm. I did my set of trials this morning which also didn't help.

So Jenne and I went ahead and requested Steve to get the ETMY door off.

We set the tiptilts TT1 and TT2 to the slider values from yesterday and started aligning the PR3 to hit the center of ITMY.
When we were hitting close to the center of ITMY, we decide to use the tip-tilts because the movement of PR3 was coarse at this point.
We used TT1 to get the beam to the center of ITMY and TT2 to get the beam at the center of ETMY. We did this iteratively until we were at the center of both the ITMY and ETMY.
We then went to fix IPANG.
The IPANG steering mirror on the BS table was steered to hit the center of the steering mirrors at the ETMY table. We aligned the beam to the IPANG QPD on the green endtable. The steering mirror on the BS table was then steered to misalign the beam in pitch by an inch at the last IPANG steering mirror. This should fix the IPANG clipping we have everytime we pump down.
We closed the chambers with light doors and saw IR flashing in the arm cavity. Koji is now trying to lock the cavity with IR.

Yesterday afternoon, I went back into the BS chamber, and flipped both PR3 and SR3. Now all of the recycling cavity folding mirrors have been flipped.

For PR3, I followed the same procedure as SR2, setting a reference position, removing the optic, flipping it, etc.  When I put it back in, I realized that since this has a 41 degree angle of incidence, the beam going to the BS had translated north by ~1cm.  After some fiddling, Koji pointed out that the 2 degree wedge probably had a more significant effect than just the HR surface having moved back a small amount.  Anyhow, we adjusted PR3 such that we were going through the BS aperture, as well as the ITMY aperture. 

During the flip of PR3, Annalisa and I noticed that the arrow on the barrel of the LaserOptik mirrors also indicates the thickest part of the wedge.  This is opposite of our SOS optics, where the arrow's position on the barrel indicates the thinnest part of the wedge.  For both PR3 and SR3, I kept the arrow on the same side of the optic as it was originally.

I then flipped SR3, following again the same procedure.  PR3 I had done a tiny bit of pitch rebalancing, although I think it was unneccessary, since it is within what we can do with the poking/hysterisis method.  SR3 I did not do any pitch rebalancing.  With PR3 aligned at least to the ITM, Koji and I aligned SR3 and SR2 so that the AS beam was hitting the center of all the SRC optics.  We also adjusted the steering mirrors after the SRM to get the beam centered on PZT3, the last optic on the BS table, which launches the beam over to the OMC chamber.  We scanned around a bit by turning the PZT's knobs, but we were unable to see the AS beam on the camera. 

 Once you install a matlab newer than 2012a, you can install ligoDV as a matlab app and get the NDS2 client software for free. So you can easily get the 40m data from the outside world now and do the analysis on your own computer rather than login through nodus.

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

So the true comparison between the ASC and oplev signals should be done without the control loop.
http://nodus.ligo.caltech.edu:8080/40m/8532
http://nodus.ligo.caltech.edu:8080/40m/8535
We can recover the free running spectrum of the ASC signals by compensating the loop transfer functions
because the ASC signals are the in-loop error signals. The oplev signals should be measured without
the ASC loop engaged.

I constructed a regulator board that can take ±24 V and supply a regulated ±15 V or ±5 V. I followed the schematics from LIGO-D1000217-v1.

I was going to make 2 boards, one for ±15 V and one for ±5, but Chub just gave me a second assembled board when I asked him for the parts to construct it 

 More changes that I've made:

• Added daughter boards for power regulation. Currently I have ±24V going into two boards, with ±15V coming out of one and ±5V coming out of the other. Again, these are based off of LIGO-D1000217
• Added an optional Dewhitening filter (with p=1Hz and z=100Hz, although these can easily be changed) to accommodate any PD's that have whitening
• Added a bypass to allow the boosts (stages 2 and 3 of the filtering servo) to be enabled/disabled by a front panel switch
• I also put in jumpers that can be used to provide Logic 1 (boost enabled) to both Boost 1 and Boost 2 without depending on the internal RMS detection/triggering
• Changed the input grounding switch so that it's set up correctly. Before, it was taking the PD signal and sending it to GND, not actually grounding the input to the rest of the ISS 

[Koji, Manasa]