(Not Dan)

An accidental INDENTING change in the ISC_LOCK guardian affected a "return True" statement. Result:

- CARM_ON_TR returned true without actually ramping H1:LSC-REFL_SERVO_IN2GAIN to -32dB.
- This resulted in random lock losses later on in the lock sequence.
- This resulted in 6h of head scratching of the assembled commissioning team.

There is a long an ongoing discussion about the python indentation convention. No need to state which side the author of this log is on.

We've been stably locked with a recycling gain of 38 at 23.3 Watts for almost 2 hours (I intentionally broke the lock).   There were some of the slow (20 second) oscillations that cause some of our locklosses durring ER7.  

When I first came in I had some trouble with locklosses durring ENGAGE_ASC.  One problem was just a typo, the other one seems to be when the gain is increased for the SRC2 loop.  I think this caused the increase in POP90 we were seeing last night, which went away.  This morning it kept increasing until the lockl dropped. I moved the transmon QPD offsets back to the pre-vent offsets, powered up to 18 Watts, turned off the ITM loops and adjusted the ITMY alingments slightly to get a decent recycling gain.    The green alignment in the arm was OK here, and the camera positions not off by more than 4 counts so I did not update the references. 

The offsets where we are stable with recycling gain of 38 and 23.3 Watts are:  

Before ER7 we noticed that we have a better signal for damping the ETMX roll mode in AS 45Q yaw than in pitch. Durring the vent we added a matrix to the ASC model to allow switching.  On Friday Nic found that the old settings for damping ETMX roll (using AS45Q PIT) were not working, so he found some settings that worked using DARM err alog 19561.  

Today I needed to damp ETMX roll again, so I tried using AS45 Yaw, this worked well, with a phase of -90 degrees relative to the settings we had for pitch (so we use bp 13.9, -60degrees, -30 degrees, -100dB and a gain of 60).  I also attempted to damp ITMX and ETMY using AS 45 Yaw (which has better SNR for these as well).    

While these settings seemed to work for each individual optic, when I turned all three on and left them on simultaneously for several minutes, they rang up all the modes.  

Reminder, the nominal settings for bounce and roll damping (with AS pit) can be found in alog18614.  

We've tracked down a few settings which became wrong durring our down time.  

BS OpLev yaw limit was set to 0, so we were not using yaw damping while trying to acquired DRMI (it has been working OK).

ITMY violin mode damping for mode6 had the wrong filters engaged.  This rang up the mode, meaning that we had to reduce the whitening gain for the DCPDs.  Now that the right filters are engaged the mode is coming down.  I went through and made sure that the handfull of violin mode damping settings that were not monitored are.  We use guardian to set the gains for these filterbanks, but not to choose the switch status.  

Sheila, Evan, Stefan,
With information for Sheila on Sun morning

We tried to operate the ASC system at full power (24W), using two different sets of QPD offsets (I'll call them pre-vent and post-vent, see burt files below).

With the pre-vent offsets we
 - The ASC system was stable at full input power
 - We had a recycling gain of about 36. (Based on transmitted power.)
 - These QPD offsets are not compatible with the current initial alignment (i.e. the Guardian will drop lock during ENGAGE_ASC - however a slow 2-min offset ramp from post-vent to pre-vent, with 20dB lower gains on the ITM loops worked)

With the post-vent offsets we
 - Get a recycling gain of 40. (Based on transmitted power.)
 - These QPD offsets are compatible with the current initial alignment. The ENGAGE_ASC step works fine.
 - Assuming the higher recycling gain is real (and not due to a difference in QPD clipping), we'd like to keep those QPD offsets because of the higher recycling gain.
 - However we get a 0.41Hz oscillation which starts at about 20W or 21W.


About this 0.41Hz oscillation:
 - It shows up in arm build-up's as 0.41Hz modulation (i.e. 1-f).
 - It is CSOFT PITCH, i.e. all 4 test mass optical levers show it exactly in phase.
 - The arm powers are exactly out-of-phase with the optical level pitch signals, i.e. when all optics point downward (highest OL value), the arm power is at a minimum. (see plot)
 - 

To deal with this mode, we switched the ITM ASC loops for PITCH to the common/differential basis (i.e. DSOFT is now DITM, and CSOFT is now CITM). At the time of this elog we were still designing a filter to stabilize the oscillation.



========================================================================================
Pre-vent QPD offsets (in /ligo/home/evan.hall/Public/Burt/ItmQPDsPre.snap burt file):
H1:ASC-X_TR_A_PIT_OFFSET 1 -2.900000000000000e-02
H1:ASC-X_TR_B_PIT_OFFSET 1 -1.580000000000000e-01
H1:ASC-X_TR_A_YAW_OFFSET 1 -7.000000000000000e-03
H1:ASC-X_TR_B_YAW_OFFSET 1 1.050000000000000e-01
H1:ASC-Y_TR_A_PIT_OFFSET 1 1.010000000000000e-01
H1:ASC-Y_TR_B_PIT_OFFSET 1 -5.600000000000000e-02
H1:ASC-Y_TR_A_YAW_OFFSET 1 -1.270000000000000e-01
H1:ASC-Y_TR_B_YAW_OFFSET 1 5.500000000000000e-02

Post-vent QPD offsets (in /ligo/home/evan.hall/Public/Burt/ItmQPDsPost.snap burt file):
H1:ASC-X_TR_A_PIT_OFFSET 1 -4.800000000000000e-02
H1:ASC-X_TR_B_PIT_OFFSET 1 -1.480000000000000e-01
H1:ASC-X_TR_A_YAW_OFFSET 1 -4.000000000000000e-03
H1:ASC-X_TR_B_YAW_OFFSET 1 7.800000000000000e-02
H1:ASC-Y_TR_A_PIT_OFFSET 1 -1.180000000000000e-01
H1:ASC-Y_TR_B_PIT_OFFSET 1 -3.690000000000000e-01
H1:ASC-Y_TR_A_YAW_OFFSET 1 -2.420000000000000e-01
H1:ASC-Y_TR_B_YAW_OFFSET 1 -3.180000000000000e-01

Sheila, Evan

Bat control is among the most challenging of control problems. In this case, some patience and a cardboard box were all that was needed to solve the problem.

Evan, Stefan

When we came in the winds were relatively high, so we decided to take another loock at the AS_A_36 phasing. We did so in DRMI.

- To take out the effect of WFS centering and the otherASC loops, we lowered the total ASC gain by a factor 10, and increased the WFS centering gain from 1 to 200 (raising the centering gain by a factor of 20).
- We then drove the SRM at 0.3Hz in PIT and YAW.
- Interestingly PIT and YAW totaly disagree on the phase, by about 125deg...
- Attached are screen shots for the old phases (picture 1), phased for PIT (picture 2), and phased for YAW (picture 3)
- Additionally, while all 4 quadrants show a reasonable signal for PIT, the YAW signal is weak in quadrant 1 and not present in quadrant 2
- We decided to make a pragmatic choice:
  - For PIT AS_B_36_I is already a fine signal - only for YAW it doesn't work
  - Thus we decided to phase AS_A_36_I for YAW...
  - ... and only use quadrants 3 and 4 (the lower two quadrants).
  - Quadrants 3 & 4 also have a similar strength signal (with opposite sign) and similar RF offset (with the same sign)
  - So: this new YAW signal AS_A_36_I should be fine now.

YAW Input matrix for I and Q now is:
H1:ASC-AS_A_RF36_I_MTRX_2_1    0
H1:ASC-AS_A_RF36_I_MTRX_2_2    0
H1:ASC-AS_A_RF36_I_MTRX_2_3    -2
H1:ASC-AS_A_RF36_I_MTRX_2_4    2

With this new YAW sensor we updated the ASC sensing matrix (pictures 3 and 4).

This sensor seemed to do a good job at 17W and at 24W. However at 24W we still saw a 0.4Hz instability - see next alog.

Nutsinee, Elli

When we arrived the IMC was not locking so we changed some settings to get it to lock.  Changed PSL differacted power to 7% up from 3% by changing H1:PSL-ISS_REFSIGNAL to -1.96V.PSL.  The PSL power was 1W when 2W  was requested at the rotation stage.  So we searched for home, and now requested power matches again.

We tried to lock the arms in green without success.  The X-arm PLL was not locked, we changed Crystal frequency to 100MHz and now it is locking, however the ALS_XARM and Y_ARM guardian still report faults "PLL; PHD", and "Ref. Cav. Power", which we couldn't fix.  We noticed the reference cavitytTPD has dropped from 0.85 to 0.7 V in the last 24 hours (see plot.)

We aligned the corner station optics using the oplev trend to where they were last night in order to do the HWS alignment.  We noticed BS oplev Yaw is showing zero as output.  Without the green from the arms this alignment was difficult.  in any case, we are starting to think that this HWSY alignment is proving too difficult with the current (wrong) in-vacuum lens installed-  the beam return beam is the same size as the mirrors we are using, and we have never been able to get rid of clipping patterns on the beam.

Nic, Sheila, Evan, Stefan

- Turned on ITMX PIT oplev (ITMY PIT OPLEV was already on)
- DC coupled SRM PIT oplev turned on.
- Tried new SRCL input matrix YAW:
   AS 36    AI    AQ     BI    BQ         
   OLD:   -0.6   0.3    0.3   0
   NEW:    0     1.0    0     0
- This seemed better at higher power for RF offsets, but is too early for judgement.
- Also tried new SRCL input matrix PIT:
   AS 36    AI    AQ     BI    BQ         
   OLD:    0     0      2     0
   NEW:   -0.5  -0.5    0     0
- We didn't keep this one though because it seemed worse at low power.

- Attempts later tonight were hampered by winds up to 30MpH in the corner.

We've noticed two more examples of epics channels freezing for a few seconds.  Yesterday (July 9 16:25:09 UTC) and tonight (0:22:49 UTC July 11)

Evan, Kiwamu, Jenne, Stefan

- DRMI alignment is back to the old-good one: strategy: Used old slider values for everything but large optics. Tweaked SR3 (for instance) to get the beam spot centred on ASPD. Aligned PRX using PRM and PR2.
- DRMI ASC worked except PRC2 loop (didn't further investigate because we didn't care without the arms)
- Then we focused on MICH freeze:
  - We fine-tweaked the transfer function using a zpk([0.03],[0.054],1,"n")gain(0.555556) filter.
  - This made the gain roughly 1 below 0.1Hz. Plot 1 shows that - if measured coherently - we win up to a factor of 10 reduction at 0.01Hz. (Blue: no MICH freeze, red: MICH freeze)
  - In terms of RMS reduction (position) of the power spectrum, we gain a factor of 2, at the cost of significant noise injection at 8Hz. (Plot 2)

Interestingly, this RMS is now small enough that we spend most of the time in about 1/3 for the whole simple Michelson fringe. Unfortunately there is still slow drift, so parking at a "good" position isn't quite possible. But we are definitely in a regime where simple "fringe velocity" isn't a good parameter by itself. Fringe position must matter too. In our brief attempt to see locking performance changes we didn't notice anything significant though.

However, the next time we have high winds, we should definitely re-evaluate MICH freeze.

Calibration Team

Sign of h(t):

The gravitational wave strain h(t) is given by  h(t) = Delta L/L where Delta L  is is computed using

                         Delta L = ± (Lx - Ly)

The sign of Delta L can be determined using Pcal actuation on the test mass. Pcal only introduces a push force  so pcal readout signal (truly pcal excitation) is minimum when the testmass is away from the corner station (closer to pcal laser). From the first plot the phase between DARM/PCAL is ~ -180 degrees (DARM lags PCAL) which suggests that DARM signal from ETMX will be maximum when pcal is minimum (ETMX further away from corner station). Similarly, from second plot, since DARM and PCAL have a phase difference of ~-360 degrees (essentially 0 degrees), the  DARM signal from ETMY is minimum when the pcal is minimum. This shows that the sign convention for the Delta L is '+'

Time Delay between Pcal and DARM:

Also the slope of the curve gives the time delay between Pcal and DARM signal chain. The time delay is about 125±20 us. This time delay can be accounted for, within the uncertainity, from the difference in signal readout chain outlined in Figure 3 attached.

Refer to LLO alog #18406 for the detailed explanation behind this  conclusion.