The noise during last night lock was much better and more stationary than what we had the night before that. Closing more ASC loop helped a lot.

The first attached plot compares the time series of the band-limited RMS in the 100-200 Hz region during the two lock stretches. Now the noise is lower and there is hardly any non stationary behavior.

The most nasty feature of the spectrum is likely related to violin modes. There is a forest of peaks around 500 Hz, together with all harmonics up to many kHz.

Here are the past 10 days trends.

model restarts logged for Tue 03/Mar/2015
2015_03_03 01:48 h1fw0
2015_03_03 07:14 h1lsc
2015_03_03 07:16 h1omc
2015_03_03 07:18 h1calcs
2015_03_03 07:22 h1susmc2
2015_03_03 07:24 h1calcs
2015_03_03 07:34 h1broadcast0
2015_03_03 07:34 h1dc0
2015_03_03 07:34 h1fw0
2015_03_03 07:34 h1fw1
2015_03_03 07:34 h1nds0
2015_03_03 07:34 h1nds1
2015_03_03 09:57 h1lsc
2015_03_03 12:05 h1broadcast0
2015_03_03 12:05 h1dc0
2015_03_03 12:05 h1fw0
2015_03_03 12:05 h1fw1
2015_03_03 12:05 h1nds0
2015_03_03 12:05 h1nds1

• C1PLC1 9:52 3/3 2015
• C1PLC2 9:52 3/3 2015
• C1PLC3 9:52 3/3 2015
• X1PLC1 11:40 3/3 2015
• X1PLC2 11:43 3/3 2015
• X1PLC3 11:43 3/3 2015
• Y1PLC1 11:25 3/3 2015
• Y1PLC2 11:25 3/3 2015
• Y1PLC3 11:27 3/3 2015

One unexpected restart. Maintenance day: ISC, SUS and CAL model changes with associated DAQ restarts. Beckhoff EX machine needed a reboot (fortnighly freeze), new Beckhoff PLC2 code went into all slow controls machines.

Alexa, Sheila, Dan, Gabriele, Evan

In full lock, we now have the following loops closed:

• ASA45Q → dETM
• REFLA9I + REFLB9I → cETM
• REFLA9I  − REFLB9I → IM4
• POPB → PRM
• −0.66 REFLA9I + REFLA45I → PR2
• ASB36Q → BS
• ASA36I → SRM pitch, ASB36I → SRM yaw

The first six of these are more or less identical to what we had last night (some of them have different gains). The SRM loops are new, and have bandwidths of 100 mHz or so, based on step response.

SRM pitch could also be accomplished with ASB36I; tonight it appeared identical to ASA36I except with opposite sign. For SRM yaw, only ASB36I was a good signal; ASA36I had a static offset which could not be affected by moving SRM. Perhaps for symmetry, we should use ASB36I for SRM pitch, as has been done in the past for DRMI+arms off resonance.

It was also possible to move SR2 and SRM so as to center the spot on AS_C. However, we have not yet tried to close a pointing loop from AS_C to SR2.

I reduced the amplitude of the OMC ASC dither lines today, to [33, 50, 100, 100] counts for the [P1, P2, Y1, Y2] error signals, which are injected at [575.1, 600.1, 625.1, 65.1] Hz.  Along with the ever-increasing ASC goodness, this reduced the noise around the lines.  The attached plot compares the sidebands

We didn't observe any ill effects from reducing the dither amplitude (the SIN and COS gains were increased to maintain the overall loop gain).  At some point we should measure the loops again to check that the bandwidths are still in the tenths-of-Hz range.

In other OMC news, someone merged the H1 OMC_CONTROL medm screen with the Livingston version last week; this change has been backed out.  It's not a bad idea per se, but there are some scripts and buttons used here that aren't used by L1, and vice versa, so things were a little confused.  Also, the DCPD gains had been reduced to 1, from 1000, around 2:30 in the afternoon today.  This change was also reverted (maybe from a bad burt restore?) to keep the DCPD SUM channel calibrated in milliamps (rather than amps).

For some reason the OMC-DCPD_SUM_OUT_DQ channel is no longer accessible via ezca read.  This caused problems in the OMC_LOCK Guardian.

I've posted an entry into the LLO log, comparing the audio of the 2 strain channels.

After maintence day this morning, the corner beckhoff was not restored.  The ALS SHG was not working because the temperature was not controlled.  Before we realized this we went to the table to investigate and tried to adjust the beat note alingment.  Once the SHG was back on, the beat note stregth was low.  Although this sounds impossible, the thing that seemed to fix the problem was unplugging the RF amplifier and plugging it back in.  

Sheila, Elli

This morning I noticed the IR buildup in the arms as meaured by LSC-TR_X/Y_QPD_B is read out as 10% lower in the x arm than in the y arm.  This is unexpected because we think the loss in the x-arm is lower than in the y-arm.  Because of this we wondered if the normalisation of these QPDs is a little off.  To check this, I adjusted the gains and offsets of these QPDs to get the single-arm buildup of these equal to one.

Firstly the dark offset on the LSC-TR_X/Y_QPD_B QPDs was not correct (LSC-TR_Y offsets were of by 15% of the single-arm buildup power).  It looks like there is a slow drift in these offsets, and it looks like they have been corrected multiple times in multiple places.  To remove the dark offset, we unlocked theIMC so there was no light on the arms and adjusted the LSC-TR_X/Y_QPD_SUM_SEG?_OFFSET for segment so that it read zero.    The changes to the X_TR_A_SEG?_OFFSETs are:

Once the QPD segment offsets were set to zero, we were able to remove a few rouge offsets from other places.  We turned off offsets on H1:ASC-X_TR_A_SUM_OFFSET (was 8), H1:ASC-Y_TR_A_SUM_OFFSET (was 1), H1:ASC-X_TR_A_SUM_OFFSET (was 4), H1:LSC-TR_X_QPD_B_SUM_OFFSET (was 0.5), H1:LSC-TR_Y_QPD_B_SUM_OFFSET (was -0.2).

We changed LSC-Y_TR_A_LF gain from 0.017 to 0.0188 and LSC-TR_Y_QPD gain from 0.219 to 0.231  so that the y-arm single arm buildup is equal to one.  The x-arm buildup was close to 1 so we didn't change it.

Sheila, Evan, Elli

We adjusted SR2, SR3 alignment sliders to center the beam going into the output faraday and to maximise light going into the OMC DCPDs.   This was done with a straight shot through the sorner sation with BS, ITMY aligned, SRM, PRM, ITMX misaligned.  The input laser power was 10W.  We used the ASC wfs DC centering servos and the OMC dither align.

We moved SR2 pitch, SR2 yaw, SR3 picth, SR3 yaw alignment offsets one at a time and located the alignments the power on the DCPDs started to drop off.  There is about 70 microradians of range for each degree of freedom where the power is high (see screenshot).  We picked alignment values in the center of these ranges where the OMC DCPD power is also maximised.  The maximum power on H1:OMC-DCPD_A_OUT_DQ was 7.7e-3 counts in this configuration.

Changed values are:

Sheila then used the picomotors to center ASC-AS_C qpd, so we can use this to check the alignment into the output faraday.  Afterwards, Evan and Sheila re-centered the beams on the ASAIR photodides and the ASAIR camera.

(Kyle, Gerardo)

We pumped the annulus system for 4 hours, we got down to 5.0X10^-5 torr at the pump cart.  Pumping will continue on Thursday.

Friday morning Jim and I unlocked WHAM1 HEPI and closed the position loops.  It looks like this reduces peaks at 2.5 & ~3.75hz, may have some gain peaking reinjection around 1hz and shows good pitch & yaw motion reduction below 1hz as seen by the RM1_M1_DAMP IN1s.

The attached ASD shows the RM1_M1_DAMP_L/Y/P_IN1_DQs.  The lower plot group has a couple HAM1 L4Cs.  The thicker light colored reference traces are from Thursday 0800utc and the dark thin current traces are from Saturday 0800utc.  There is a peak in the RMs at 6hz that may be amplified in the current traces; it is hard to tell but the ISI may be amplifying that peak.

Bottom Line--When using Guardian, engaging the RZ loop twists the MICH too far.  It may be doing the CPS Offset zeroing in a weird method.  When the loops are engaged with the old Command Scripts, the RZ input does not get driven off and no bad RZ twist occurs.

Further, with MICH locked, the X & Y ST2 ISO loops are not stable--they ring up and trip.  Without Mich Locked, the loops are stable.

Details: Let's start with the first attachment; it is 25 minutes of second trends.  The Guardian turns on the Z loop after first LOAD_CART_BIAS_FOR_ISOLATION so this is the first thing to do.  Manually one can do this on the CART_BIAS screen (Reset CPS offsets button.)  In outward appearances, there is a difference in how this button and Guardian perform this operation; however, Jamie says no it doesn't.  Maybe it is the slow ramping of the new setpoint.  Anyway, my observation is that the residuals for this platform are always small.  After the CPS offsets are Reset, the Guardian turns on the Z dof.  The gain steps and the ramp times are the same for the Command Scripts and Guardian.

Using the Command Scripts, engaging the Z dof ISO is seen at point 1.  Notice how at point 2, the RZ INMON is not doing anything awful while the Z loop is turned on and the RZ loop turns on (point 3) nicely and well behaved.  However, when Guardian does this...

When Guardian turns things on at point 4, look at what happens to the RZ INMON.  The Z_OUT16 is much larger when Guardian turns it on and the RZ_INMON is driven way off.  And, even though the RZ_INMON is much lower by the time the RZ loop comes on, turning on the RZ loop at point 5 produces a too large an output--The RZ_OUT16 looks just like the OpLev Yaw.

You can see that the manual turn on of the Z then RZ loop was repeated a few times with the same result; like wise the Guardian turn on was similarly consistent.  Of course, Guardian also turns on the X & Y DOFs when it engages the RZ loop and as I allude to in the summary above, these loops may be unstable.  However, at this point I return you to the point of how the Z_OUT is so different for Guardian and how that impacts RZ_INMON all before the X Y & RZ loops are engaged.

I left the ST2 in fully isolated and later Ellie locked the MICH.  After a minute or so, it didn't look stable and MICH was turned back off.  Shortly after that the ISI tripped.  So then we tested things.  Ellie locked MICH and then I engaged the ST2 ISO Loops.  Things were fine with the Command script turn on of Z and RZ but the ISI slowly rang up and tripped on either X or Y DOF even without the boost on.

Solution--Identify why the Command Script and Guardian do something different at the CPS Reset stage.  Identify the loop instability.

Gabriele, Sheila, Alexa, Evan

Summary

We have engaged the DHARD WFS Y (and P) at 3 Hz on resonance with a reduced oplev damping gain in the ETMs. Again, to start off we closed the DHARD Y WFS  with 3 Hz BW at 50pm CARM offset. Since this loop is also stable at low BW, we will leave it in the low BW configuration at this point, so that we are at a 3 Hz BW on resonance.

Details

We had tried engaging the new DHARD Y loops as described in LHO#17006. However, we quickly found that this configuration was unstable. So, we removed the partial plant inversion FM6 and took a plant TF. We found that the plant that Gabriele had measured with the oplevs was slighlty different than the @50pm plant (see Gabriele's comment). We adjusted FM6 accordingly to compenstate for the peaks seen between 1 and 5Hz. FM6 is now zpk([-0.3303+i*15.1459;-0.3303-i*15.1459;-1.9027+i*16.6711;-1.9027-i*16.6711; -0.2672+i*19.227;-0.2672-i*19.227],[-0.6659+i*18.7;-0.6659-i*18.7;-0.509+i*11.519; -0.509-i*11.519;-1.0404+i*15.4844; -1.0404-i*15.4844], 1)gain(0.469248).

To close the loop at low BW at 50pm CARM offset, we engage FM2, FM3, FM4, FM6, FM9 with a gain of 30. FM6 is described above, and the remaining filters are the same as in LHO#17006. With a gain of 360, this gives a UGF of 3 Hz and a phase margin of 36 deg.

On resoncance with a gain of 30, we measured that the UGF is 3.5 Hz with a phase margin of 36 deg.

This is in the guardian now.

I am concluding that the scale factor in the original calibration (alog 16698) was underestimated by a factor of about 2.4 in 2 - 20 Hz frequency band (meaning, the DARM spectra we had collected were too good). This was due to my inaccurate estimation of the ESD actuation response.

For the frequency region above 20 Hz, it has been underestimated by a factor of 3.2 when the PSL power stayed at 2.8 W and the same DARM offset was used. This was due to the inaccuracy in the ESD propagating into the sensing factor and also inaccuracy in the UGF location. I did not try to track how the sensing calibration should have been compensated as a function of the PSL power or the DARM offset (alog 16726).

I have updated the CAL-CS online calibration coefficients accordingly in both the sensing and actuation paths.

Pcal_Y seems to still indicate that the DARM spectrum is consistently too good by 40-65 %.

(ETMX response agreed the sus model by 40 %)

The day before yesterday, I had a chance to repeat the calibration of the ESD response of ETMX by locking the X arm with the IR laser. Comparison with ITMX at 13 Hz gave me an ESD response of 6.32 x 10^-16 m/cnts in ETMX at 13 Hz. This is 1.4 times larger than the expected than the suspension model. Since I used alpha of 2.0 x10^-10 N/V² in the model, the measured response corresponds to a slightly larger alpha of 2.8x10^-10 N/V². With the right force coefficient of -124518.4 cnts applied on ETMX, I tested both the linearized actuation and non-linearized. They showed almost same strength in a frequency band of 10 - 59 Hz as expected but with the linearized version somewhat stronger by 3-ish % (see the attached) presumably due to the charge on the test mass.

Since the change between the linearized and non-linerized actuations is so small, I neglected this effect and kept using the transfer coefficient of the non-linarized version at 13 Hz.

(Estimation of the DARM optical gain)

Using the measured data taken by Alexa (alog 16805), I estimated the optical gain of the DC read out to be 9.09x10^-7 cnts/m. To get this number, I first extrapolated the ESD response to some frequencies at around 20 Hz. Since the loop shape is already known, fitting of the open loop gives me the optical gain. I did eye-fitting this time. The UGF was at around 23 Hz in this particular data.

Since I was able to lock the interferometer at 2.8 W with the DC read out tonight, I cross-checked the DARM open loop. Running a swept sine, I confirmed that it sill kept the same UGF (see the attached below). Good.

(Comparison with Pcal)

First of all, one thing I have to mention is that, in an alog (alog 16781) describing the comparison between LSC-DARM_IN1 and PCAL is not a fair comparison because we know that LSC_DARM_IN1 was not well-calibrated. I checked the CAL-DELTAL_EXTERNAL_DQ at this particular time, but unfortunately the spectrum did not look reasonable probably because I was in the middle of changing some parameters in the CAL-CS. Instead, I looked into a different lock stretch at Feb-02, 5:13:11 UTC with the same IMC incident power of 2.8 W. The Pcal reported greater displacement by a factor of approximately 4.6 (see the attached below).

If I applied the new accurate sensing calibration, the discrepancy would have been a factor of 1.45 or 45% with the Pcal higher than the DARM spectrum.

To double check it, I checked the Pcal again during one of today's lock stretches at Feb-21, 10:04:05 UTC. One thing we have to pay attention is that the Pcal excitation frequency is now shifted to 540.7 Hz (alog 16815). I used the Pcal calibration formula that Sudartian posted in alog 16718 to get the displacement. The ratio between the Pcal and DARM spectrum was about 1.65 or 65% with the Pcal greater than the DARM spectrum. Even though the ratio is slightly different from 8 days ago or so, it still indicates that the DARM calibration is too good by several 10%.

The other excitation at 36.7 Hz (alog 16815) did not have signal-to-noise ratio more than 2 in the DARM spectrum due to high noise in this frequency region and therefore I did not use it this time. Nevertheless, the Pcal at this frequency was also greater as well. So the relation between Pcal and DARM spectrum is qualitatively consistent.

We made two additional experiments with the unsuspended, isolated pilot (Corning ETM02) ITMY, in the west bay of the LVEA. (Moreno, Landry)

1) We applied FirstContact to the HR surface, let dry over 24h, measured no excess charge (no more than |3V| at 1" from HR surface, AR surface, and barrel), ripped the FirstContact off the HR face in ~20s *without* doing any TopGun ion gun blowing, and then measured the voltage 1" from the HR surface. We find the resultant charge negative, with a claimed voltage of ~-22kV, -22kV and -22kV at three points across the face of the optic.  Assessing the AR surface, we find a voltage 1" from the AR face of -12.1kV, -12.1kV and -11.3kV.  

2) We made another trial in which after FirstContacting, we removed the polymer film while TopGun blowing to neutralize the surface.  We followed the same basic procedures as outlined in alog 13104, with slightly different timings. The primary change in the experiment was the grounding of the optical table, and the addition of a grounded Al foil shield (see photo attached).  The addition of the shield and ground dramatically changed the behaviour seen in the prior experiment linked above: generally, individual measurements that took minutes to settle exponentially to some voltage now settled in seconds.  Furthermore, the apparent long time constants for which it seemed necessary to continue with the ion gun (~9min total) were not observed in this experiment. We took 2 minutes to pull the FirstContact, which included a coincident 2 minute TopGun blow, plus one additional minute of TopGun blowing, and measured +18 to +30V at several locations 1" from the surface of the HR side of the optic.  

We'll repeat experiment #2 one more time, with shorter intervals between electrometer measurements, to better understand the field sizes, signs, and time constants.