Sheila, Thomas, Elli, Evan

We locked the Y arm in IR, and then turned on WFS loops which feed back to IM4 and PR2 in order to keep the buildup in the arm maximized. We measured the dc counts on ASAIR_A_LF. Then we unlocked the arm and measured ASAIR_A_LF again. The results are as follows:

• ASAIR_A_LF_OUT, locked: P_on = 1205(5) ct
• ASAIR_A_LF_OUT, unlocked: P_off = 1300(10) ct
• LSC-Y_TR_A_LF_OUT, locked: 11.4(1) ct

Using the formula in LHO#15470, the locked and unlocked values of ASAIR give an equivalent loss of 267(31) ppm on ETMY.

To account for the power in the sidebands, we use the modulation depths given in LHO#15674: Γ₉ = 0.219(12) and Γ₄₅ = 0.277(16). Then the power in the sidebands is P_SB = P_off × (Γ₉²+Γ₄₅²)/2 = 81(7) ct. Then using our new value for the power fraction, A² = (P_on − P_SB)/(P_off − P_SB), we get an equivalent loss of 286(33) ppm on ETMY, not accounting for mode mismatch.

FYI, here is a 45 day Temperature trend of the End-X VEA.  Note, the temperature of the VEA ran away during our vent to clean the ETMx test mass likely due to the energized cleanrooms.  However, the Ex station is 2 deg hotter than it was before the vent.  That said, we probably set the EQ stops during the heat spike of ~70 deg C...

R Savage, P King, J Bartlett, Ed Merilh

This morning we went into the PSL to make some adjustments. The reference cavity transmission was down by quite a lot (~1.5V to ~0.4V) which normally would

have prompted an alignment session and we also noticed that the PMC POWERREFL was about 20% of the POWERTRAN rather than the desired10% or less. The following adjustments were made: 

1. the PMC was aligned by adjusting the light into the PMC using M6 & M7 mirrors. Vertical adjustments only were made bringing the POWERREFL from ~3.1w  to ~1.9w

2. The power level of the 80MHz RF level to AOM02 in the FSS loop was adjusted.

•    started at 1.515w now 1.22w after add 1db atten at PSL rack. (30.87dBm gives 1.22 w)

3.Power measurements were taken at different points in the FSS chain 

• power at AOM = 67mW
• single pass power upstream of M25 51.6mW (77%)
• double pass upstream of EOM 33.8mW (66%, 50%)

• RF PD 290 unlocked and 70 locked
• Adjustment of M25 
• Horz - start 34.8mW now 35.9mW
• Vert - start 34.8mW now 38.5mW
• after locking 37.4mW
• Power after top periscope mirror 32mW

4. PSL FSS TPD DC output at 1.602V 

5. The FE watchdog was reset

Last year, we thought we had found a configuration using sensor correction on HEPI that worked on HAM3. I was looking (Krishna was, too, he saw it first) at the summary pages over break and noticed that HAM3 still looked like it had the .6hz peak. I came in this morning, checked the configuration and did an on/off measurement, and HAM3 still has the same issue, even when we correct to HEPI instead of the ISI, contrary to what we found last time. See attached plot. Solids are measurement taken with sensor correction off, dashed are with HEPI sensor correction.

The HV voltage for the ESD in EX was turned on this afternoon ~3:00PM. Richard spoke to Kyle regarding the vacuum pressure before enabling the HV.

Filiberto C, Richard M.

Kyle, Gerardo 

Y-end turbo+QDP80 pumps valved-out but left running for now

The temperature sensor box for the reference cavity temperature stabilisation was swapped out.

old: S1400577
new: S1107831

The old one had a suspected blown regulator.

The two uncontrolled degrees of freedom in the mode cleaner ( MC1 - MC3 in pitch and MC1 + MC3 in yaw) are now under control.   These two degrees of freedom result in motion of beam spots on the ASC_IMC WFS sensors.   The beam spot on the WFS_B_DC sensor is now controlled with the DOF_4 servo loop in the ASC_IMC model. 

This scheme avoids two potential problems which could arise if we use IM4_TRANS as the sensor of choice for controlling these two degrees of freedom.  

a) IM4 TRANS QPD is affected by the longterm drifts of IM1,2 and 3. We would be folding these drifts back into IMC alignment if we use this sensor.

b) These drifts could further result in a drift of the spots on the WFS (since this is not a controlled parameter) and that could generate RIN due to spurious offsets in RF WFS signals.

During the course of this work I have made the following changes:

1) Offloaded the servo loop outputs using the Offload_WFS script

2) unlocked the mode cleaner and misaligned the MC2_PIT (to prevent flashing of the IMC)

3) centered the prompt reflection on the IMC WFS

4) realigned the MC2 and relocked the mode cleaner

5) the extinguished field landing on the IMC_WFS QPD generates a random offset due to the wierd pattern of the HOM.  This was zeroed out using offsets in the WFS A and B, DC  (PIT and YAW) sensors.  (Had to fix some macro entries in medm screens of the PIT and YAW filter banks so that we can get at the offsets)

6) adjusted the output matrices to  0.5*(MC1-MC3) in Pitch and 0.5*(MC1+MC3) in Yaw.  Attached screen shots show the situation before and after these changes to the input and output matrices.

7)  Checked the stability of the servos.

8) There has been no significant shift of the beam on pointing into the IFO as a result of this work.  Attached pic shows the time trends of IM4_TRANS_PIT and YAW

9) The UGF of these loops is about 100 mHz (a factor three lower than other loops in the ASC_IMC)

10) Next I will look into determining the DC offsets which minimise the jitter to RIN coupling.

11) I have modified some of the indicators in WFS_MASTER medm screen so that the switching on and off  of the servo loops by IMC Guardian is apparent on the screen. 

Havent had a chance to see the effects of some of these changes since the mode cleaner has not been locking in the past couple of hours due to ongoing work in the PSL ref cavity alignment.

Hugh and I were concerned that safe.snaps were not current for all the chambers, so I took the disruptions caused by the PSL work as an opportunity to update I/ETMX, and HAMs 4,5&6, ISI's and HEPI's. HAM5 ISI has some weird masterswitch/dackill coupling, which we've seen before, but I paid more attention to what I had to do to make it work this time. Closing the master switch trips the dackill and the rogue excitation wd. The only way to recover the ISI is to turn on the masterswitch, reset the rogue excitation wd, then reset the dackill. Then guardian can take over and bring the chamber up. None of the other chambers I did required this. Very weird.

Clean up after Dec. 24 power glitch:

Restarted 3 front end computers that rebooted before the boot server was ready (they couldn't find the PXE boot image), restarted 2 other computers that had bad DAQ and timing status on all models.  All restarted normally.  Checked status of frame writer/data concentrator, it was OK.

The DTS should be functional at this point.

no restarts reported

I was in the Control Room Sat, Sunday 2 - 7 PM    reading ALOGS  full screen.
Alone; all quiet; no obvious pblms.
Main gate refused to operate  till wiggled, persuaded.   DickG

no restarts, both days

Heard report of EQ in Idaho and checking the systems sure enough one of the SEIs had a trip.  Just the one though.  See the attached: The GS13 shows the arrival but didn't exceed trip limits until some secondary waves.  The vertical sensors are noticably much quieter than the horizontals.  The trip was 2 minutes after the event so this seems the reasonable cause.  ITMX back to fully isolated no problems.

1305 - 1310 hrs. local -> In and out of Y-end VEA 

1320 - 1325 hrs. local -> In and out of X-end VEA

Elli, Evan

For the past week or so I've noticed that initial alignment of the corner optics has become much more painful:

• With PRX locked in order to align PRM, the WFS loops seem to do nothing to improve the POP buildup.
• When locking MICH on a dark fringe in order to align BS, the two spots on the AS camera appear to escape from each other, as if there is some integrator feeding back to the BS pitch. This prevents MICH from locking.

The second of these problems was traced to the LSC_CONFIGS guardian: the threshold for LSC-ASAIR_A_LF_NORM_MON was too high (300 ct), so that even if the lock was broken, the guardian would not register it. This would leave the MICH loop trying to acquire lock with two integrators on and no limiter on BS-M3_ISCINF_L. I've turned the threshold down to 30 ct. The MICH locking seems more sluggish than it did a few weeks ago, but now it locks instead of wandering off.

Elli and I tried for a while to fix the first problem, but nothing we tried seem to work. Turning up the gain only made the PRX lock oscillate. Turning off the slow pitch/yaw bleed to the M1 stage seemed to have no effect. Different combinations of REFL_A and REFL_B WFS seemed to have no effect. So this will require some more attention.

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].

Jim, Hugh, Krishna, Jeff, Fabrice:

We keep investigating the sensor corrction issue on HAM3. What we found yesterday is that it depends on which blends are engaged. We can't explain why yet. We did additional tests today:

- we turned off all CPSs of all HAM-ISI and BSC-ISI in the corner station. No change.

- we checked the jumpers of all HAM3 CPS boards. All good.

- we tried to apply large offset in case it would reduce some kind of cable touching/rubbing (+/-400 um in HEPI Z, and +/-400 um in ISI X,Y, Z). No change.

Finally, we tried to do the Z sensor correction to HEPI. In the plot attached:

- Red curves is HAM3 ISI isolated, no sensor correction

- Green Curve, we turn ON the sensor correction in X and Y to the HAM-ISI

- Blue Curve, we also turn on Z sensor correction to ISI. The 0.6 HZ peak shows up. For some reason it also reduces X at the microseism.

- Brown, we do the Z sensor correction to HEPI instada of ISI. The peak is still there in the CPS, but not in the GS13. It's unclear why.

The last configuration looks good from the GS13s,  but it's unclear yet how good it is for the cavity. More info on that is coming.