Jim and I pulled/pushed all of the blade springs and installed flexures on unit 2 yesterday. Parts needed for unit 3 were discovered to be short of needed quantities have been ordered.

Alexa, Sheila, Stefan

Our goal today was to get a good diff readout going. For this we
- Commissioned the IMTY and ETMY optical levers, See snapshot.
- Recommissioned the x-arm dither - turns out the phases were tuned up for a different suspension setting - we need configuration control on all the suspension settings. Also see the snaphot.
- With that we got fairly stable arm locking - at least for a while - see below.

- Next we tweaked up the DIFF beat note on ISCT1. We got -20dB signal out of the PD.
- Th PLL locked for short stretches, but essentially always runs out of range after a few seconds.

- Thus we decided to work on top-mass slow feed-back: There was a lot of confusion, but once everything was done right, it sort of worked.
- One thing we noticed along the way, is that our 1-3Hz BLRM traces pick up increases in noise with an roughly hourly periodicity. This noise somehow translates into extra length motion at 0.05Hz. 
- We also fine-tuned the ETMY top mass L2P filter - see Arnaud's log
- The slow feed-back gain was however limited by our main suspension resonance, which meant that we couldn't suppress the DIFF motion enough.
- We thus decided to work on the L2L filters, which should give us the ability to increase the UGF of that loop and get more suppression.
- We got a simple L2L measurement going, but more work is needed.

Something is wrong with ETMY stage 2 RX Tbetter....  we clearly have less opLev peak to peak when we turn this to Tcrappy. 

So the configuration we are using now is Tbetter everywhere except Tcrappy on RZ on stage 1 +stage2, and Tcrappy on stage 2 RX, sesnsor correction from the ground to stage 1 in X Y and Z. 

We also briefly tried T750 on stage 1 Z motivated by llo alog 12164, this wasn't good so we will have to do a more thoughfull job of importing those improvements.

Yesterday, the modified UIM coil drivers for ETMY and ETMX were tested in-situ. The transfer functions are showing an average drive increase of ~3.8 for ETMY and ~3.9 for ETMX comparing them before and after, which corresponds to the modification as described in T1400223.
A second test was carried out, using the monitor boards current channels. The test consisted in sending the equivalent of 1V to the coil drivers, to each of the UIM osem channels, and recording the current increase with channel ${QUAD}_L1_FASTIMON_${OSEM}. Jeff K helped me for the calibration of those channels.

The output voltage of the "fast current channel" of the monitor board as described in T1100378 is measured across the resistor Zout. The relation between the current and the ouput voltage is described in the last equation of Jeff's notes attached, with R1/R2 = 1/3 and Zout = 2010 ohms. In other words Current_readback_calibrated (A) = FASTIMON_Readback (cts)* 1/1638.4 (V/cts) * 3/2 * 1/2010 (ohms-1)

For ETMX I measured a transconductance of ~0.6 mA/V for each channel which matches pretty well with the design, but for ETMY it didn't quite match. First, only two channels (even though the mass was moving) were seeing a response, and secondly, the working channels were showing ~3mA increase for 1V drive. Since the transfer function shows that the driver is working as expected we certainly have something going on with the monitor board.

The non functioning channels are LL and UR osems. For UL and LR, when no voltage is sent to the coil driver, the readback sees ~4000 cts (as shown on the screenshot).
 

Days Activities

• Several ISIs were tripped this morning...perhaps due to EQ last night?
• HAM5 cleaning in morning
• Transition LVEA to Laser Safe?
• MY baking of RGA equip late morning
• EX ESD high voltage work this morning (maybe EY later)
• Praxair fill for CP6 at MX (9am?)---Sending CP6 to MAJOR alarm level
• Transition EX to Laser SAFE--probably HAZARD later
• LVEA transitioning to SAFE in the morning
• Septum removal, sealing septum gap, tapping hole in septum, & laying septum down
• Checking clean status at HAM5 (Jeff & Margot)
• Pressure Sensor at MY still is reading HIGH (MAJOR Alarm), but this is because Kyle is doing work on it (it'll be like this on the order of a month)
• LVEA transitioning to laser HAZARD at 3:45-ish
• Matt H, Aiden, and David H. heading out to work on TCS

Went through the Operator check of saturations with HEPI this afternoon.  The HEPI Saturation Counters which I had to reset were: 

HAM2, HAM4, ITMx(BSC3), ITMy(BSC1), ETMx(BSC9), ETMy(BSC10)

A pressure sensor at MY had been MAJOR Alarming the last few days, but this is due to it being worked on.  It will be displaying values of a higher pressure for a month or so while it is valved out and being worked on.  To prevent getting alarms from this, we've bumped up the MAJOR alarm setting to 1x10^-6 (originally it would alarm at 5.11x10-8).

Since the Vacuum computer was really slow, Dave ssh-ed into the computer (still was slow) & did the following:

vacuum@control0:~$ caget HVE-MY:Y5_246BTORR.HIHI
HVE-MY:Y5_246BTORR.HIHI        5.11e-08
vacuum@control0:~$ caput HVE-MY:Y5_246BTORR.HIHI 1.00e-06
Old : HVE-MY:Y5_246BTORR.HIHI        5.11e-08
New : HVE-MY:Y5_246BTORR.HIHI        1e-06

We must revert the alarm setting when the VAC work is complete.

Baking will continue for as long as a few weeks

HEPI safe.snap files had the wrong ..._L4C_THRESH_MAX values recorded, as pointed out by Dave yesterday. Those safe.snap files are now fixed. The new versions are committed under the SVN -r7796.

Details are attached.

The Apollo crew was unable to get wrenches to the large clamp bolts which retract the bellows of the chamber's west side 60" flange.  We needed to remove the Feedtrhu protection shroud and the cabling attached to the feedthru.  So the WHAM6 isi interface electronics were powered down.

model restarts logged for Wed 23/Apr/2014
2014_04_23 08:46 h1nds1
2014_04_23 08:53 h1fw1
2014_04_23 09:03 h1broadcast0
2014_04_23 10:02 h1asc
2014_04_23 11:06 h1susmc2
2014_04_23 11:29 h1susprm
2014_04_23 11:38 h1sussrm
2014_04_23 11:52 h1susmc1
2014_04_23 12:01 h1susmc3
2014_04_23 12:11 h1suspr2
2014_04_23 12:18 h1sussr2
2014_04_23 12:58 h1suspr3
2014_04_23 13:08 h1sussr3
2014_04_23 13:16 h1broadcast0
2014_04_23 13:16 h1dc0
2014_04_23 13:16 h1fw0
2014_04_23 13:16 h1fw1
2014_04_23 13:16 h1nds0
2014_04_23 13:16 h1nds1

no unexpected restarts.

815-828

mike, daniel, stefan, aiden, terry, bubba, margot, ski, matt h, jason, patrick, hugh, jeff, jodi, andres, corey, richard, pablo, david H, jimW, thomas, filiberto

• LVEA Laser HAZARD, but will be made SAFE until afternoon, and then back to HAZARD
• HAM5--cleaning being done, cleanroom modified yesterday (JeffB will inspect)
• Septum:  bolts being pulled, plan to remove today & cover septum hole
  • Will be reinstalled later, and then have windows installed (may require holes being tapped in septum?)
• TCS:  yesterday both TCS tables pushed up against BSC & alignment work
• HAM5 ISI:  SEI crew will need to strip ISI of stuff with forklift when OK to work in-chamber
• bscs press sensor work at end stations--EX first (richard & crew)
• commissioning work:  alignment work in morning & then beatnote work & electronics troubleshooting if necessary
• staging:  3ifo BSC ISI work continues

While the Gate Valves were closed and we were Laser Safe, I installed a pair of aLIGO Camera Housings on the Spool where the ITMx cameras will be. 

Re-did measurements from yesterday.  Daniel brought up point about green light leaking into IR measurements and vice versa.  So addressed this.

IR Laser Light:  Look At filters to attenuate IR

Here we wanted to see which filter was best for viewing the GREEN light, so we wanted the filter which passed green & cut out IR.  With the Prometheus laser we used its IR light.  To make sure there was no Green light, we dropped in a Hoya R72 filter (to remove any Green light from laser).  Then we looked at the filters I bought .  So this is what we had:

• IR light from laser ONLY = 420mW
• Hoya R72 in path = 414mW
• BP550 (+ Hoya) = 3.11mW---best filter for viewing GREEN light
• lp550 (+ Hoya) = 423mW
• lp920 (+ Hoya) = 431mW
• bn532 (+ Hoya) = 167mW

The BP550 is OK, but Daniel says the OD of this filter may be low and we should look for a Schott glass filter (order of 4mm thick, similar to our old iLIGO glasses).  Either that or we can see what a couple of the BP 550s filters look like in series.

GREEN Laser Light:  Look At filters to attenuate Green

Here we want to see which filter is best for viewing IR light, so we want a filter which passes IR & attenuates Green.  With the Prometheus laser we had green light.  To make sure there is no IR light leaking in, we dropped an iLIGO goggle in the beam path as a filter.

• Only Green light = 20.2 mW
• iLIGO Glasses in path = 13.18 mW
• iLIGO + Hoya R72 = less than 5nW
• LP550 (+iLIGO glass) = 39.3 uW
• LP920 (+iLIGO glass) = less than 5nW
• BN532 (+iLIGO glass) = 7.45 mW
• BP550(+iLIGO glass) =8.03 mW

LP 920 may be good...maybe have two in series?

Alexa, Stefan

- With the y-arm o.k. (the remaining glitches were actually bleeding in from x-arm locking), we realigned the x-arm.
- Note: we need to switch back to a better camera view for the x-arm transmitted light. The current one does not provide a lot of information because a) it is completely saturated and b) it is in a guoy phase that is not very sensitive to TMS alignment.
- Once we had both arms aligned and locking fairly reliable, we looked at the DIFF electronics:
- First we found 3 switches on the VCO and FDD that were left off.
- Next we noticed that the DIFF beat note was only -32dBm - we verified the EPICS read-back with the scope.
- So we hooked up the scope on ISCT1, but right then an earthquake struck and knocked out every ISI on site. Thus we went home.

Today we were able to lock the y arm for a significant period of time. Here are some settings:

PDH REFL Servo Board:

• Input 1 gain: -7dB
• Input 1 pol: pos
• Common comp: ON
• Boost 1: ON
• Boost 2: ON
• Fast gain: 0dB
• Fast pol: pos
• Slow option: EN
• rest: zero/off

I took a few measurements:

1. Power at REFL A PD: 6.5mW
2. PDH error signal peak to peak: 780mV
3. PDH loop suppressed error signal (EY_PDH_NoiseSpecV.txt)
4. OLTF: again the UGF was around 3kHz with a phase margin of 68deg (mag --> 125.txt, phase --> 126.txt)
5. With ITMX misaligned, I measured the shot noise of REFL A (EY_PDH_ShotNoiseSpecV.txt) -- this noise is partially limited by the SR785 noise; this is not "pure shot noise"
6. While blocking the PD, I measured the dark noise of REFL A (EY_PDH_DarkNoiseSpecV.txt) -- this noise is limited by the SR785 noise