The PRM sensors are no longer effected by IR. What changed? The MC still does.

ETMY damping restored.

 [ericq]

Steve fixed the PRM oplev pointing. I turned on the loops and measured the OLG, then set the pitch and yaw gains such that the upper UGF was ~8Hz (motivated by Jenne's loop design in ELOG 9401)

• Pitch gain: +7
• Yaw Gain: -5

I then measured the oplev spectra of the optics as they were aligned for PRMI. (OSEMs on, oplevs on, LSC off, and ASC off)

Next, Jenne and I need to fix the ASC loop such that it properly accounts for the oplev loop. 

 The input pointing of PRM oplev beam was streered just a touch to remove clipping from it's return. 

The spots  did not move visibly on these two lenses.  The spot diameter on the qpd is  ~1.5 mm,  65 micro W and 3440 counts.  

I'm not happy with the beam position on that first lens, but since it's so crazy in the BS chamber, and the PRM oplev has something like 5 in-vac steering mirrors, I'm hesitant to suggest that we do anything about it until our next vent.  But we should definitely fix it.

[Jenne, Vivien]

We had an oplev tuning party this afternoon.  What we have learned is that we don't have a lot of intuition yet on tuning loops.  But, that was part of the point - to build some intuition. 

I took responsibility for the PRM, and Vivien took ITMX.  I think, in the end, all changes were reverted on ITMX, however Vivien took some data to try and make a computer-generated controller.  Before we got started, I locked and aligned the PRMI, and we centered the PRMI-relevant oplevs.

I moved my "boost bump" around a bit, to do more at higher frequencies, but had to sacrifice some of the "oomph", since it was starting to eat up too much phase at my UGF of ~8Hz.  I also made the stack resonant gain higher Q and lower height so that it didn't eat so much phase.  In the end, I have 25 degrees of phase margin, which isn't really great, but I do win a factor of 2 around 2 and 3 Hz.  Also, now I'm able to engage the 3.2 resgain at all, whereas with the previous filter shape I was not able to turn it on.

Maybe it's because I really want it to have helped, but I feel like the POP spot isn't moving as much when I'm locked on PRMI sidebands as it was earlier (we were seeing a lot of low frequency (few Hz) motion).  So, I think I did something good.

  in order to Win in Loop Tuning, you must draw a cartoon of the cost function on the whiteboard before starting. Some qualitative considerations from our Workshop:

1. We want to use the oplev servo to reduce the motion of the mirror in the frequency band where the Oplev is quieter than the mirror, w.r.t. inertial space.
2. We can estimate the true mirror motion by some simple stack / pendulum model and compare it to the Oplev noise (not the dark noise). There are several contributions to the mirror angular motion due to the cross-coupling in the stacks and pendula.
3. Below ~0.2 Hz, we think that the oplev is not the right reference, but this is not quantitative yet.
4. The high frequency noise in the OPLEV ERROR is definitely electronics + shot noise.
5. We cannot increase the gain of the loop without posting some loop measurements (Bode + steps). Also have to post estimates of how much PRCL noise is being introduced by the Oplev feedback. Oplev feedback should make less length noise than what we have from seismic.

Give us a cost function in the elog and then keep tuning.

Not a whiteboard, but here's a cartoon of my oplev cost function cartoon.  For the "maximize this area" and "minimize this area", I plan to use ratios between the curves, and then give those ratios to a sigmoid function.

 In addition, we have to make sure to not let the suspension DACs saturate and make sure that the impulse response time of the OL servo is short; otherwise the lock acquisition kicks or bumps can make it wiggle for too long.

 It looks like that ETMX have  2 sticky magnets.

It was little bit surprising to me but Rana's professorial rock'n roll excitation released its sticking on the unconfirmed thing by unconfirmed reason.

I aligned the Xarm manually and via ASS.

Now we are back in the normal state.

 I am really, really happy to hear that it was just a sticking situation.  Really happy. 

 This recovery proceeder deserves a pattern

Note: IR shield glass position variations,  Atm4

  UR osem IR shield glass is pushed back. It came out of its clip holder. The magnet is free.

  Atm2,  UL & LL magnets  centered poorly. Almost hinging on opposite sides.

              UR & LR centered well.  There have plenty of room to move in an earth quake.

* EQ Southeast of LA around 45 minutes ago. Callum and I felt it.

* Koji and I came in to recover. MC suspensions had been mis-aligned. ETMs both tripped their watchdogs.

* As before, the ETMX was stuck in its cage and the UR & LR OSEMs were reading zero V.

* We moved the MC sus back to their OSEM values from 2 hours ago. Koji aligned everything else by just using his chee.

* To shake the ETMX loose, I tried a different tactic than the "Great Balls of Fire". I started giving it 20k steps through the ASCYAW filterbank (with ramping OFF). I used the green light in the X arm video to look at the swinging. Using this as a readback I pumped the OFFSET button on ASCYAW to resonantly swing up the yaw motion. I had to turn the watchdog thresh up to 2000 temporarily. After a couple minutes the ETMX was free.

* We then used the bias sliders to steer it back onto the OL center (which Q nicely lined up for us recently) and then X arm locked in green right away.

Fri Mar 28 22:38:04 2014:  We've just ridden through the 5th aftershock. None of the aftershocks have tripped the watchdogs  but they break the IMC lock.

Local earthquake activity is up. Our suspensions are holding well.    ETMX and ETMY sus damping restored.

 We want there to be ~16000 cts of signal per quadrant on the optical levers. I think that most of the QPDs have been modified to have 100k transimpedance resistors.

From the attached 90 day trend, you can see that the ETMX, BS, PRM, and SRM are really low. We should figure out if we need to change the lasers or if the coating reflectivities are just low.

Steve, can you please measure the laser powers with a power meter and then reply to this entry?

Another possibility is that we are just picking a dim beam and a brighter one is available.

I ran the ASS/ADS for the arms because the X-arm was way out. There was also some problem with its locking due to bad ramps in FM2. I copied over the filters from YARM and then adjusted some of the ramps and thresh trigs in the filter file until the transients in POX got smaller. Basically, you should not really be ramping on Integrators. Secondly, we should do some testing when adjusting the filter parameters.

I hooked up the 4395 to the MC servo board OUT2 so that we can monitor the error point when the PCDRIVE goes nuts.

For some reason or another, I decided that we should see if the optical lever servos were injecting too much noise into the test masses. The ITMs are much worse than the ETMs and I am afeared that they might be making the main noise for our arms in the 20-40 Hz region. Jenne is checking up on these feedback loops to see what's up.

To estimate the actuator gains of the mirrors, I turned on 1 count drives from LSC/CAL oscillators into the LSC drives of each test mass at the frequencies shown in the plot with the resulting peaks showing up in in POX/Y with the single arm locks in red. I will leave these going permanently, but with 0.1 count ampltiudes; we need to make it so in the scripts.

We need to go back and have a look at all of our optical lever control filters, and make sure they make sense. 

In particular, we should have a look at the ITMs, since they have a huge amount of motion around 10Hz. 

Notes:  ETMX shouldn't have that lower notch.  The bounce mode Qs should be lowered.

 I'm in the process of filling this table

 I should replace ETMX He/Ne laser

I took loop measurements of ETMX pit and yaw, and set the upper UGF to be ~6Hz for both.  This required a pitch gain of 25, and a yaw gain of 16.

The spectra look similar to what they were before Steve did the swap.

I believe that the Xend aux laser was turned off earlier today, for Steve's work swapping out the oplev.  When I went down there, the red "off" LED was illuminated, and the LCD screen was showing something.  I pushed the green "on" button, and I immediately got green.

Also, I saw that the 24Hz roll mode was very rung up on ETMX.  I looked at the FM5 "bounce roll" filter, and it had some old values, 12Hz and 18Hz for the resonant gains.  All other optics have the proper 16Hz and 24Hz frequencies.  I copied the BS oplev bounce roll filter over to ETMX pit and yaw (both were wrong), and loaded them in.  The mode is starting to ring down.

 ETMX oplev qpd gain has to be increased.

It's starting to get a little crowded, but I modified the IFO_ALIGN screen to have new buttons to show the aligned / misaligned state of each optic.  Koji made a good point, and I left the old restore script functional so that if the slider is moved significantly, we can always go back gently to the burt restored value.  I have removed the old misalign function though, since we shouldn't ever be using that again.

 Atm3, Oplev sum read 12,000 counts when the qpd was disconnected ?

           Dark qpd was zero and normal He/Ne incident on qpd was 1,730 counts.

Anodized aluminum dumps replaced by 6 razor beam dumps.

Two more razor beam dumps added this afternoon.   The picture will updated tomorrow.

 This QPD circuit (D980325-C1 ) uses the nice OP497 Quad FET opamp as the transimpedance amplifier. It has a low enough current noise, such that we can increase the resistors (R1-4) up to 100k and still be Johnson noise limited. We should also make sure that the compensation caps (C3-6) are ~2.2 nF so as to not destabilize the opamp. f_low = 1/2/pi/R/C = 730 Hz.

I will do the swap later today unless someone else gets to it first. (note: check for oscillations w/ fast scope probe after installing)

I did these modification tonight. The slideshow of some images is attached. Instead of 100k, I used 97.6k thin film, since this seemed like an oddball size that doesn't get used otherwise. I forgot to measure the dark noise of the quadrants before doing the swap, but comparing the pit/yaw/sum before/after the swap shows that the signal is basically unchanged (since pit/yaw is normalized by SUM), but that the noise is lower by a factor of a few above 100 Hz due to being above ADC noise now. Previously, it was bottoming out at ~10 prad/rHz. Since the signal is unchanged, I guess that the calibration and therefore the loop gain should not have changed either...

And the sum went up by almost 10x as expected from the resistor change.

 There are 9 razor beam dumps at ETMY-ISCT

 I added two green glass absorbers. The oplev centering may need a touch up when it is well aligned.

ETMX had default 1's for gains, 0's for matrix elements, etc., so I did a burt restore to May 25th, 2pm, which was a few days before the Crash.  It looks fine now.

ETMX medm screen values are blank.

All suspension damping restored. There had to be an earth quake.

[Jenne, Rana]

A few times this evening, I had been having trouble locking CARM and DARM with ALS, and holding it for very long.  When it started happening again, I switched over to locking the individual arms with ALS.  Yarm seems to be totally fine, but Xarm has something funny going on. 

Rana and I have narrowed it down to being a problem with ETMX.  We were watching ETMX's oplev and local damping error signals, and would see occasional glitch events.  This happened when oplev + local damping were both on, both off, and when only local damping was on.  We believe that this points to something weird with the coil driver and actuator chain.

We tried to watch for a while to see if it was a step event (something switching on and off periodically), or an impulse event (some transient oscillation in an opamp perhaps), but the problem went away again.  We have come to no conclusions other than we have a problem that needs watching.

During our investigations, to more softly turn off the damping, Rana set the local damping gains, as well as the oplev gains to zero using a ramp time.  We don't recall the precise numbers, and conlog doesn't have the gains recorded, so we made an educated guess.  The local damping seems fine, but the oplev damping should be re-confirmed.  Steve, can you please show Harry how, and have him help you measure the ETMX pitch and yaw oplev loops, and set the gains so that they match up to the references, and then post the measured bode plots when you're done? 

Flow bench effect on oplev error signal     is here.

I turned off the south X-end flow bench.

I'm starting to lock for the night, and I noticed that PRM is very, very pitched.  Why?  The PRM pitch slider is 5 full integer units higher than the backup (and the backup value is about where I like it, around -0.2).

I am not aware of any scripts that touch the PRM slider values.  The PRM ASS (which I haven't used in ages) offloads the biases to the SUS screen fast channels, so even if someone turned that on and then saved the values, it wouldn't leave the PRM so very, very misaligned.

I have restored it, and relocked the PRMI, so all is well, but it's very weird to have found it so misaligned.

 ITMY oplev was nearly clipping in yaw, causing wonky behavior (POY lock popping in and out frequently). I recentered it and the arm is locking fine now. 

 Here's a fun fact: since the great computer failure of June2014, the PRM Oplev gains have been ZERO.

arrrrggggh

I've restored the gains to their old values, and measured the loop TFs.

 The PRM sus gains checked OK

All other suspension oplev gains setting were checked out OK

ETMX sus damping restored

From old 40m elog 5-29-2007

 ITMX is kicked up periodically.  ITMX_PD_MAX_VAR is lowered to 500 from 1350

It started at Friday morning 8-1

 I noticed some weird behavior on the ETMY oplev that led me to check them all out. 

The short of it is that the ETMY oplev has a pretty small angular range, compared to the displays and other oplevs. I measured how much angular motion each oplev can sense before the beam no longer hits all four quadrants (thus losing the ability to sense).  This could account for some of the additional angular motion of the mirrors... maybe. 

Also, some of the QPD quadrants had offsets as big as 400 counts, thus distorting the zero point. Anyways, here are the angular ranges of each QPD, assuming the current urad/cnt calibrations are valid. 

EMTY

• P: +- 25urad
• Y +- 30urad

ITMY

• P:+-160urad
• Y:+-172urad

BS

• P:+-43urad
• Y:+-40urad

ITMX

(Note: ITMX's oplev pitch and yaw is almost 30 degrees off of the alignment sliders' pitch/yaw coordinates. Steve tells me this is due to the tight nature of getting the oplev beam to the mirror without clipping.)

• P:+-110urad
• Y:+-80urad

ETMX

• P:+-45urad
• Y:+-85urad

PRM

• P:+-50urad
• Y:+-45urad

SRM

• P:+-80urad
• Y:+-80urad

I wrote a script to zero all of the QPD quadrants' offsets (it lives in /scripts/OL) and have used it successfully. The oplev laser must  be off before using it. 

                  2005              ALL oplev servos use Coherent DIODE LASERS # 31-0425-000, 670 nm, 1 mW

    Sep. 28, 2006              optical lever noise budget with DC readout in 40m,  LIGO- T060234-00-R, Reinecke & Rana

    May  22, 2007              BS, SRM & PRM  He Ne 1103P takes over from diode

    May  29, 2007              low RIN He Ne JDSU 1103P selected, 5 purchased sn: T8078254, T8078256, T8078257, T8078258 & T8077178 in Sep. 2007

    Nov  30, 2007               Uniphase 1103P divergence measured

    Nov. 30, 2007               ETMX old Uniphase 1103P  from 2002 dies: .............., running time not known......~3-5 years?

    May 19, 2008               ETMY old Uniphase 1103P from 1999 dies;.....................running time not known.....~    ?

    Oct.  2, 2008                ITMX & ITMY are still diodes, meaning others are converted to 1103P earlier

                     JDSU 1103P were replaced as follows:

   May 11, 2011                ETMX replaced, life time 1,258 days  or 3.4 years

   May 13, 2014               ETMX , LT 1,098 days or 3 y

   May 22, 2012               ETMY,  LT 1,464 days or  4 y

   Oct.  5, 2011                BS & PRM, LT 4 years,  laser in place at 1,037 days or 2.8 y

   Sep. 13, 2011               ITMY  old 1103P &    SRM    diode laser replaced by 1125P  ..........old He life time is not known, 1125P in place 1,059 days or 2.9 y

   June 26, 2013              ITMX 622 days or 1.7 y    note: we changed because of beam quality.........................laser in place 420 days or 1.2 y

  Sep. 27, 2013               purchased 3 JDSU 1103P lasers, sn: P893516, P893518, P893519 ......2 spares ( also 2 spares of 1125P of 5 mW & larger body )

      May  13, 2014             ETMX,  .............laser in place 90 d

      May  22, 2012             ETMY, 

     Oct.  7,  2013             ETMY,  LT  503 d  or  1.4 y............bad beam quality ?

     Aug. 8,  2014              ETMY,  .............laser in place   425 days  or  1.2 y

The instigator of this was that we were seeing ring-ups of ETMs during our ALS locks this evening.  We measured the ETMY violin resonance to be 624.10 Hz, and Rana found an elog saying that the ETMX was around 631 Hz, so we made a 2 notch filter and added it to FM4 of the LSC-SUS filter banks for both ETMs. 

For the ETMY resonance, we measured the frequency in the DARM spectrum, and when we looked at the FINE_PHASE_OUT channels, the resonance was only in the Yarm sensor.  So, we conclude that it is coming from ETMY.

Also in the realm of filter modules, the FM3 boost for CARM, DARM, XARM and YARM was changed from zero crossing to ramp with a 1sec ramp time.