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Schedule for BSC09 "Abbreviated Vent & Closure": Earth Quake Stop Adjustment of EX Test Mass, January 7-8, 2015

Approved work to be done:

1.  Assessment of earth quake stops gaps for the test mass
2.  Set lower  EQ stops gaps to ~1.5 mm

Wednesday, Jan. 7

• Turnoff EX BRS (Seismic Beam Balance)
• Cleaning of BSC9
• Verify or transition to “Laser Safe”
• Move Clean Room (CR) into position for BSC9, check rooftop of Clean Room and attach sock, verify fans are working
• Turn on purge air for BSC9
• Verify supplies: Green Lantern, Flashlights, ion gun, etc. and make sure CR supplies are in place (gowns, change room, ...)
• Dust Monitors - verify operation and take readings for before and after entry
• Verify safe.snap files to save settings
• Follow M1300464-v4, "Procedure for preparing aLIGO IFO for pumpdown", Turn off high voltage
• Review and follow E1201035, "aLIGO Chamber Entry & Exit Procedures" checklist as annotated by Calum and Dennis for abbreviated entry
• Review and follow M1100068-v1, "Hanford Checklist - BSC Door Removal", Review door removal procedure with crew
• Start vent on BSC9

Thursday, Jan. 8

• Remove door
• Document entrance
• Enter , assess quality of HR surface of ETMX with green flashlight
• Adjust EQ stops gaps.
• Verify optic, its suspension, and the reaction chain are free
• Assuming all goes well, obtain approval and signatures for volume closure, LHO (E1400474-v1).
• Obtain signoff signatures for chamber closure
• Notify door crew to hang door
• Verify readiness to pump down, follow M1300464-v4, "Procedure for preparing aLIGO IFO for pumpdown". Confirm all high voltages are off.
• Notify Vacuum crew of readiness to start pumps

The last step is at the time and discretion of the Vacuum crew.

Alexa, Thomas, Evan

Over the past 24 hours, the alignment slider values of MC1, MC2, and MC3 have been changed. (Perhaps the WFS offloading script was run?) However, these new alignments weren't saved.

This morning, we changed the IMC guardian from LOCKED to DOWN to do a scattering test with the Y arm. When we brought the IMC guardian back to LOCKED, we found that the WFSs would cause MC2 trans to ramp continually in a saw-tooth fashion, from about 100 % nominal transmission to less than 50 % transmission.

Eventually Alexa figured out it was because the guardian had restored the old, previously saved alignments for MC1, MC2, and MC3, and this had caused the beam to fall off WFS A and WFS B. Dialing in the new slider values for MC1, MC2, and MC3 (and then saving them on the IFO ALIGN screen) made the WFS loops work again.

The TFs I took this morning show that the rubbing is back on the ETMx main chain now that we are back down to 7 Torr in pressure.  The rubbing TF looks exactly like the rubbing TF we had before I opened up the gap of the EQ stops around the test mass.  While we knew that the rubbing could have been possibly due to the barrel stops around the test mass OR the PUM mass above the test mass, we assumed it was specifically the stops around the test mass since those were the only ones adjusted during the Dec vent.  I did not check the PUM stops (or any other stops further up the chain) yesterday.  Darn it, I should have!  The temp+buoyancy effect is the same on the PUM as it is on the Test mass, so the gap of the EQ stops should be bigger around the barrel there too.

So, we are re-venting today to now:

- Inspect other EQ stops, look for outliers in gap settings further up the main chain

- Open up the gap around the barrel of the PUM to the 1mm (top stops) and 1.5, (bottom stops)

We'll employ the same stripped down version of the entry/exit checklist as yesterday, namely to inspect and DI Nitrogen blow the HR face of the ETMx on the way out.

The reaction chain TFs continue to look healthy, so no problems there.

Seismic:  
Working on HAM3 sensor correction problem.
3IFO HAM storage retrofit prep work.

Suspensions:	
Check out of ETM-X after vent for EQ stop work.
Brett working ESD charging scripts.

PCal:	
Software upgrade at End-Y.
Calibration work at END-X; End-X will transition back to laser hazard.

Commissioning: 
Will be enforcing stricter limits to LVEA access and work during the afternoon. 
All persons entering LVEA or end stations must check in and out with operator.

3IFO:
Rodica and Jodi working on finding 3IFO parts and sorting optics.
Work continues on removing the H2 test stand electronics from LVEA.      	  	 

[Sudarshan K, Suresh D]

  We looked at the data to see if work associated with engaging the IMC WFS DC centering loops resulted in a shift of the IMC output beam pointing.    There was no evidence to support that conjecture.    The last known instance when ISS outerloop was reliably locked was on Dec 9th.   We could not trace the reason for the shift of the beam to any specific event other than that mentioned below.

  In the attached set of time series plots we see that the IM4_TRANS_QPD segments started saturating several weeks ago and three out of four segements were continuously saturated from Dec 27th onwards.  Therefore this QPD could not be used subsequently to determine if the beam moved during the IMC centering loop work (which commenced on Jan 4th)

 However we can see that there was a change in the DC values of the  ISS QPD pitch and yaw signals around 27th Dec.  We can see an associated change in the signals of the IM4 QPD segments as well.   It is most likely that the IMC output beam shifted around that time and was probably associated with the recovery from the power glitch on 26th.  I could not find any other logged activity around that time.

[suresh]

As early as 10th of Dec we can see from the 40 day trend (attached) that the segs 3 and 4 of IM4 QPD had started to saturate.   We could not therefore use this sensor to monitor the beam position since that time.

I have reduced the Whitening gain on the IM4 TRANS QPD ( from 36dB to 0 dB ) and  recentered the spot on the QPD by using the IM4 TRANS QPD picomotor.   We can monitor the beam motion from now onwards to see if there is any effect from the DC spot centering loops in the IMC ASC.

Keita, Elli

Continuing with Evan's and my attempts to lock the auxiliary laser or IOT2 to the PSL with a frequency offset in order to continue the PRC measurements started by Paul Fulda...

Today Keita and I got the auxiliary laser locked for periods of ~20s.  Then PLL servo control signal would reach its maximum of 5V and the lock would drop.  The beat note between the aux laser and the PSL was continually drifting in one direction- this may have been due to temperature instability on the table (the fan was off to start with and then I turned it on for a while when adjusting the Aux laser temperature.)  I am watching

The PLL is controlled by an SR560 servo controller with 10Hz low-pass filter cutoff and 500 gain. A 7dBPm signal is demodulated with the beat signal between the PSL and the auxiliary laser for the error signal.

09:03 Vern to end X
09:07 Jim W. and Sebastian to LVEA to turn off HAM3 HEPI pier pods
09:14 Hugh craning in LVEA
09:26 Jim W. and I turned off sensor correction at end Y
09:31 Corey and Grant to the squeezer bay
09:37 Jeff B. and Andres to LVEA west bay to move 3IFO parts
09:43 Travis to end X
09:57 Hugh craning in LVEA
10:00 Jodi out of LVEA, reports clean room between HAM2/3 is on
10:03 Doors back on end X
10:39 Mitchel parking crane in LVEA
10:52 Hugh and Mitchel out of LVEA
10:57 Rick to end Y to work on photon calibrator
11:11 Sheila and Evan turned off clean room at HAM1
11:12 Manny done
11:19 Pepsi truck through gate
11:35 Jeff B. and Andres out of LVEA
11:48 Doug measuring distances for optical lever light pipes near HAM3/4
11:55 Kyle and Gerardo back from end X (started pumping)
12:52 Betsy putting parts in the cleaning bay
13:02 Filiberto to end X to look at cabling
13:04 Corey to squeezer bay
13:28 Aaron to end Y, PCAL cabling
13:51 Aaron done
14:40 Elli working on IOT2

Cyrus and I ran fsck on h1conlog3
Dave tested compilation of frontend models against RCG 2.9
In chamber work was completed at end X

Attached is a trend of the average LVEA temperature showing the daily ~0.2 deg C temp swing.  The plot is for the month of August 2014 when we were finishing installation of the vertex.  When we are vented and adjusting the EQ stops of a suspension we may see a ~0.06mm change in the gap of the EQ stops around the barrels of the PUM and Test Masses in the QUAD daily.   (0.2degC change x ~0.3mm/1degC temp change = 0.06mm)

This is pretty negligible.  Phew.  However, this temp change pitches the suspension, so now I'll try to find out by how much.  To be continued...

I performed a "make World" compile of all front end models. The following failed compilation:

• all ISI models (ham and bsc)
• SUS models PRM, PR2, SRM, SR2
• h1lsc

All the failures are due to filtermodule-with-control parts with disconnected inputs (unused inputs must be grounded for RCG2.9). The compiler fails at the first error, more parts may need grounding.

ISI-HAM

part not grounded: HAMn_L4CINF_V1

file: isi/common/models/isihammaster.mdl

ISI-BSC

part not grounded: OPTICNAME_ST1_L4CINF_H1

file: isi/common/models/isi2stagemaster.mdl

LSC

part not grounded: PSL_POWER_SCALE

file: lsc/common/models/lscpsl.mdl

SUS

part not gounded: <RC>_M3_LOCK_L

file: sus/common/models/RC_MASTER.mdl

This file is unique to LHO, L1 still uses the MC_MASTER.mdl

The sensor correction is installed and ON on all the chambers, but with a nominal matching gain of 1.

I made a small script to calculate the correct matching gain for X, Y, Z. The script works only for the HAM-ISIs for now, but it will be pretty easy to adapt. What it does:

- Grab the ground seismometer and GS13 data in X, Y, Z.

- Calculate the ASDs and calibrate them in m/rt(Hz).

- Calculate the GS13 over Ground ratio.

- Take the mean of the ratio for a [0.1Hz 0.4Hz] bandwidth.

Before running this process, the ISI needs to be in High blend mode (750mHz) on all DOFs with sensor correction OFF.

I've done this exercise for HAM4-ISI. The numbers seem a little small (Gain for X: 0.8784, gain for Y: 0.8702, gain for Z: 0.8574) but brings some improvement (see plot attached).

This has been done during the day, we might want to do it overnight for better tuning.

I'll do the other chambers ASAP. The script that I made is for now commited in the HAM4 folder of the svn:

/ligo/svncommon/SeiSVN/seismic/HAM-ISI/H1/HAM4/Misc/gain_matching_calculation.m

Sheila, Jeff, Thomas

We changed the H1:SUS-$(OPTIC)_ODC_CHANNEL_BITMASK from 1 to 0 for all the LOCK States for the following optics:

• - BS
• - ITMs
• - ETMs
• - PRs
• - MCs
• - OMC

J. Kissel, R. McCarthy

At my request, after seeing that the EY BSC 10 vacuum pressure has dropped below 1e-5 [Torr] (see attached trend), Richard has turned on the H1 SUS ETMY ESD at ~2pm PST. I'm continuing to commission the chain, and will post functionality results shortly. 

Also -- 

I've found the ESD linearization force coefficient (H1:SUS-ETMX_L3_ESDOUTF_LIN_FORCE_COEFF) to be -180000 [ct]. I don't understand from where this number came, and I couldn't find any aLOGs explaining it. I've logged into to LLO, their coefficient is -512000 [ct]. There's no aLOG describing their number either, but I know from conversations with Joe Betz in early December 2014 that he installed this number when the LLO linearization was switched from before the EUL2ESD matrix to after. When before the EUL2ESD matrix the coefficient was -128000 = - 512000/4 so we was accounting for the factor of 0.25 in EUL2ESD matrix. I suspect that -128000 [ct] came from the following simple model of longitudinal force, F_{tot} on the optic as a result of the quadrant's signal voltage, V_{S} and the bias voltage V_{B}, (which we know is incomplete now -- see LLO aLOG 14853):
     F_{tot} = a ( V_{s} - V_{B} )^2
     F_{tot} = a ( V_{s}^2 - 2 V_{s} V_{B} + V_{B}^2)
     F_{lin} = 2 a V_{s} V_{B}
where F_{lin} is the linear term in the force model, and a< is the force coefficient that turns whatever units V_{S} and V_{B} are in ([ct^2] or [V_{DAC}^2] or [V_{ESD}^2]) into longitudinal force on the test mass in [N]. I *think* the quantity (2 a V_{B}) was mistakenly treated as simply (V_{B}) which has always been held at 128000 [ct] (or the equivalent of 390 [V] on the ESD bias pattern) and the scale factor (2 a) was ignored. Or something. But I don't know.

So I try to make sense of these numbers below.

Looking at what was intended (see T1400321) and what was eventually analytically shown (see T1400490), we want the quantity 
       F_{ctrl}
       -------
      2 k V_{B}^2
to be dimensionless, where F_{ctrl} is the force on the optic caused by the ESD. Note that comparing John / Matt / Den's notation against Brett / Joe / my notation, k = a. As written in T1400321, F_{ctrl} was assumed to have units of [N], and V_{B} to have units of [V_{esd}], such that k has units of [ N / (V_{esd}^2) ], and it's the number we all know from John's thesis, k = a = 4.2e-10 [N/V^2]. We now know the number is smaller than that because of the effects of (we think) charge (see, e.g. LHO aLOG 12220, and again LLO aLOG 14853).

In the way that the "force coefficient" has been implemented in the front end code -- as an epics variable that comes into the linearization blockas "Gain_Constant_In,"  (see attached) -- I think the number magically works out to be ... close. As implemented, the linearized quadrant's signal voltage is as shown in Eq. 13 of T1400490, except that the EPICs record, we'll call it G, is actually multiplied in
     V_{S} = V_{C} + V_{B}(1 - sqrt{ 2 [ (F_{ctrl} / V_{B}^2) * G  + 1 + (V_{C}/V_{B}) + (V_{C}/V_{B})^{2} * 1/4 ] )}
Note, that we currently have all of the effective charge voltages set to 0 [ct], so the equation just boils down to the expected
     V_{S} = V_{B}(1 - sqrt{ 2 [ (F_{ctrl} / V_{B}^2) * G  + 1] )}
which means that 
     G == 1 / (2 k) or k = 1 / (2 G)
and has fundamental dimensions of [V_{esd}^2 / N]. So let's take this "force coefficient," G = -512000 [ct], and turn into fundamental units:      
     G = 512000 [ct]             {{LLO}}
         * (20 / 2^18)     [V_{dac} / ct] 
         * 40              [V_{esd} / V_{dac}] 
         * 1 / (V_{B} * a) [(1 / V_{esd}) . (V_{esd}^{2} / N)]
     G = 9.5391e9 [V_{ESD}^2 / N]
   ==>
     k = 5.37e-11 [N/V_{ESD}^2]  {{LLO}}
where I've used V_{B} = 400 [V_{esd}] and the canonical a = 4.2e-10 [N/V_{esd}^2] originally from pg 7 of G0900956. That makes LLO's coefficient  assume the actuation strength is a factor of 8 lower from the canonical number. For the LHO number, 
     G = 180000 [ct]             {{LHO}}
         * (20 / 2^18)     [V_{dac} / ct] 
         * 40              [V_{esd} / V_{dac}] 
         * 1 / (V_{B} * a) [(1 / V_{esd}) . (V_{esd}^{2} / N)]
     G = 3.2697e9 [V_{ESD}^2 / N]
   ==>
     k = 1.53e-10 [N/V_{ESD}^2]  {{LHO}}
Which is within a factor of 3 lower, and if the ESD's as weak as we've measured it to be it may be dead on. So maybe whomever stuck in 180000 is much smarter than I.

For now I leave in 180000 [ct], which corresponds to a force coefficient of a = 1.53e-10 [N/V_{ESD}^2].

J. Kissel, K. Venkateswara, K. Izumi, J. Warner

While Kiwamu was trying to lock the Michelson, several things went wrong, but it uncovered a flaw in the new gain switching of the GS13s that has been implemented in the Guardian (see LHO aLOG 15537. Here's what happened.
(1) Kiwamu incorrectly brought up the BSC ISI in "fully isolated," which turns on stage 2 isolation loops, and switches the GS13s to high-gain mode.
(2) As expected, while trying to acquire MICH lock, impulses sent to the SUS BS kick the cage as well, which is attached to the BS ISI ST2, and trips the ST2 on the GS13s watchdog.
(3) We then reset the watchdog, and switched to "isolated damped," and this triggered the new guardian feature to *start* switching the GS13s back to low gain, but with MICH still trying to lock, impulses would still trip the watchdog before guardian had the chance to switch *all* of the GS13s gains. 
(4) This, trigger-happy watchdog resetting, and guardian half transitioning, caused a nasty loop of guardian sloshing the GS13 gains back and forth between high and low, which, with MICH impulses, continued to trip the watchdog.

I attach a plot of one of the WD trip, which clearly shows that the V3 GS13 had failed to have its gain switched to low. 

We should 
(a) look the new code to make sure there isn't a bad loophole regarding the GS13 gain switching when transitioning from "fully isolated" to "isolated damped"
(b) look for ways to increase the switching speed, or add a pause / check that the switch has occured on all GS13s before proceeding with the transition
(c) remember that these are physical, several thousand pound systems -- if you have to reset watchdogs repeatedly something is wrong and you don't know why, don't just blindly continue to mash the reset button, figure out what's wrong, or do what Kiwamu did and ask an expert!

#justwait