Peter, Stefan

We read up on alog # 20699, indicating that the main problem during power-up is a change of the MICH ASC error signal. That alog suggested mixing in A36I, but back then AS_A_RF36 was phased differently.

Thus we looked at the MICH_P signal in AS_A_RF36, and indeed confirmed that the signal is now in Q, as expected.

We thus set the following pitch matrix element for MICH:

        ISC_library.asc_intrix_pit['MICH', 'AS_B_RF36_Q'] = 1     # reduce from 2 to 1
        ISC_library.asc_intrix_pit['MICH', 'AS_A_RF36_Q'] = 0.666

With this setting we noticed that MICH_Y was unhappy - in particular the AS_A_RF36_Q_YAW signal grew tremendously during power-up. We confirmed my moving the BS that the same error signal combination as for MICH_P also made sense for MICH_Y, i.e. we used the following yaw matrix element for MICH:

        ISC_library.asc_intrix_yaw['MICH', 'AS_B_RF36_Q'] = 1     # reduce from 2 to 1
        ISC_library.asc_intrix_yaw['MICH', 'AS_A_RF36_Q'] = 0.666

These settings are now in the Guardian (including setting them to 0 in the DOWN state).

For reference, for SRCL we are using the following error signals:

        ezca['ASC-INMATRIX_P_6_3']=0 # off for now                        # AS_A_RF36_I
        ezca['ASC-INMATRIX_P_6_7']=1 # good enough for now    # AS_B_RF36_I
        ezca['ASC-INMATRIX_Y_6_3']=-1.5                                           # AS_A_RF36_I
        ezca['ASC-INMATRIX_Y_6_7']=1                                                # AS_B_RF36_I
 

We then noticed that the SRC1_Y top stage offloading resulted in a slow oscillation, indicating the the loop gain dropped enough to make the offloading oscillate. We have not fixed this in the Guardian yet.

We also used the TCS_ITMX_CO2_PWR and TCS_ITMY_CO2_PWR guardians to set the TCS power at 11W. This ramps the central heating down as the power comes up. This is currently only done in the guardian after the whole power-up is finished (i.e. in the COIL_DRIVER). For now, we did this by hand.

With this setting we were stably sitting at 11W until the 5.4 magnitude earthquate in Vanuatu hit.

=================================================================================

After the quake had settled down,  we went to 23W, and noticed that SRC1_Y now would prefer a different error signal:

ASA36_I to SRC1_Y: -1.5 (was -1.5) 
ASB36_I to SRC1_Y: 0.53 (was  1.0)   # (not in guardian yet)

We noticed that for large SRC1_Y offsets AS36_I seems to turn around - during one lock we even were able to keep it locked with opposite gain, al;though the sideband buildups were worse.

We also set

H1:TCS-ITMX_CO2_LSRPWR_MTR_OUTPUT = 0.2    # (not in guardian yet)
H1:TCS-ITMY_CO2_LSRPWR_MTR_OUTPUT = 0.0    # (not in guardian yet)

this slightly improved the sideband buildups.

We left it locked atr 25W to damp the violin modes out over night. Attached are screen shots of the ASC input matrix.

Last entry that I can read is from Saturday?

[Jenne, Peter]

Tonight we were able to get to DC Readout, and increase the power to 10W.  While there, we measured all of the ASC HARD loops.  In order to get to 10W, we kept SRC1 open (already was written into the guardian), and had to move SRM to keep POP90 low (Evan said he didn't have to do that last time he was increasing the power).

We determined that CHARD Pit really had too little gain (Sheila and Haocun saw this in alog 27617, but weren't sure if they belived the measurement).  We increased the gain of CHARD Pit by 10dB, so now it goes to -60 rather than -21 in EngageReflPopWFS. 

We found that the boosts were different for Pit versus Yaw, but the more aggressive one (can't remember which was which right now) was too aggressive, so we made all the boosts be gentle single pole, single zeros. 

We tried the boosts, and they worked well at 10W (no OLG measurement taken though...).  They are now in the IncreasePower state of the guardian, coming on after the laser power is above 10W.

We tried to increase the power further, but both times we lost lock fairly quickly (once at 20W, and the second time at 15W).  It looks like the MICH ASC loop's error signal is no good at higher powers - it looks like the BS is being misaligned by the loop.  For the 15W loop I opened the MICH ASC loop when it became clear that it wasn't going well, and that let us hold the lock for marginally longer, but not by much.  "Not going well" means here that POP90 was increasing, but POP18 and AS90 were starting to decrease significantly.

As a side note, while at 10W I noted that the AS36I signals are still responsive to SRM, although the combination is definitely different from the 2W input matrix combo.

At this point, we need to get a better MICH error signal so that we can hold lock at higher powers.  We should consider something like alog 20699, where we altered the SRC1 and MICH input matrix values to deal with this change as we increase the power.  The old version of the guardian in the svn (ISC_LOCK rev 12339) has the values that we used to use.  Daytime-us are going to look at this.

As of June 18, 7:22 UTC. See Violin mode table for details.

2:09 Robert to EY Ebay.

2:31 Robert back

3:05 Jenne and Keita powercycle OMC OSEM box

Stream images looks funny. Powercycled the camera and frame grabber solved the problem.

Conor, Jeff K

Summary:
- Conversion of ISI Suspoint motion into the DoF basis works for the arms, with limited fidelity.
- Corner station DoFs seem not to work, possibly some problem with inclusion of the Beamsplitter.
- IPC communication between ISI and SUS at ETMY is spoilt somehow.

The GS-13s on stage 2 are used as witnesses for residual motion. Their outputs are calibrated to nm, and converted to suspension point motion using Euler matrices (Cart2Eul). The output is in the local suspension coordinates. For example, the channel 'H1:ISI-ITMX_SUSPOINT_ITMX_EUL_L_DQ' is the longitudinal motion of ITMX, which is along the normal vector pointing outward from the HR surface, in the global +X direction.

These suspension point motions are IPC'd to the OAF model, and in the case of the ETMs this involves some multiplexing/AI-filtering for communication down the arm. In OAF they are combined into the IFO degrees of freedom based on  T1500610 .

As a sanity check, I fetched the ISI-model Suspoint channels and matrix'd them into the IFO DoFs in Matlab, for comparison with the OAF DoF channels. For the arms (XARM, YARM, CARM, DARM), things seem to be somewhat okay. I confirmed this by eye, and then took the spectrum of the subtraction (attachment 1, CARM_Spectrum). The residual is consistent with the dynamic range of single-precision floats (about 10^9), at least at high frequencies. A quick software-only transfer function using four poles at 0.1Hz and white-noise injection in a spare filter bank shows a similar total dynamic range (attachment 2, DTT_dynamic_range). The anti-imaging filters, for transmission of the ETM signals along the arm, should allow a considerably smaller residual than we see at low frequencies, and I don't really know what else might cause this.

The corner station DoFs are substantially wrong, visible directly in the time series' (eg attachment 3, MICH_time_series). Since MICH only uses the ITMs (confirmed to be 'okay') and the Beamsplitter, presumably the difference arises there. PRCL and SRCL are similarly incorrect.

Document T1500610 has some minor errors in the Suspoint->IFO-basis definitions, but the current matrix has correct values as far as I could see. It also points to the Suspension model versions of the Suspoint motion, eg 'H1:SUS-ITMX_M0_ISIWIT_L_DQ', but the model uses the ISI versions. Initial testing revealed discrepancies between:
    'H1:ISI-ETMY_SUSPOINT_ETMY_EUL_L_DQ'
    'H1:SUS-ETMY_M0_ISIWIT_L_DQ'
visible in attachment 4 (ETMY_IPC_issue). The other 3 test masses didn't show this gross level of disparity.

Wrote a a new guardian (VIOLIN_DAMPER.py in /opt/rtcds/userapps/release/isc/common/guardian/) that can figure out the best damping phase for the violin mode damper. (This automates a usually very boring task.)

The code relies on each modal damper filter module being set up the same way, with a narrowband filter in FM1, a -60deg filter in FM2 and a +60deg filter in FM3. This setup allows setting the feed-back phase in 60deg increments. E.g. 240deg = negative gain & +60deg filter.

The code loops through the 6 possible phase settings (0deg,180deg,60deg,240deg,120deg,300deg). For each setting it waits for the filter to settle, takes a peak reference value of the mode strength, then waits for a specified time and measures the mode strengh again, calculating the after/before ratio. If the mode grows too fast, the code stops earlier to avaoid a runaway, and procedes to the next phase setting.

After loopig through all settings, it sets the module to the best daming setting.

This seems to work reliably as long as we are not hampered by closely neighbouring modes, and should reduce the repetitive work in modal damping.

As example, I attached the output of the Guardian when it was applied to SUS-ITMY_L2_DAMP_MODE8. Plot 1 shows the violin mode strength over the 15min the code ran, screen shot 2 shows the Guardian message output.

We had an episode of really large beam motion at about 0.6Hz on OMC QPDs as well as OMCR QPDs but not on ASC_AS_C nor AS WFSs. It was very very slow to damp, and at some point it didn't damp further. It was clear that the OMC or OM3 was moving, but the motion didn't show up on none of OMC and OM3 OSEMs. But the OMC SD and RT OSEMs were super noisy.

On inspecting the spectrum of OSEMs, it was clear that the SD and RT OSEMs of OMC had a large broad band noise, the signature of the satellite amp oscillation. However, the difference is that we couldn't see the oscillation in kHz range even using the 16kHz channel (sorry no screen shot). Maybe the oscillation frequency got higher?

Anyway, apparently it has been like that since power outage (attached). Though it's not shown in the spectrum, we confirmed that the broadband noise was there every day after the power outage.

We disabled the OMC damping and the beam motion on OMC QPD immediately got quieter.

We went to the floor and power cycled the satellite amp for RT/SD of OMC (they're on the same box, everything else is on another one), and the noise went away.

Turned on the damping again and it worked fine, no excessive beam motion.

Apparently this happens even though all satellite amplifiers are "fixed". It's worth checking all OSEMs for all optics.

Sheila, Cheryl, Haocun

We re-centered the WFS A and B this afternoon to fix the misalignment (alog27792). Both of them are centered around (0,0) now and we took measurements on the IMC.

The spectrum (measured at test 1) and transfer function (with 20dB gain) of the IMC were taken both before and after re-centering, but there were nearly no differences between them.

For the spectrum, several peaks are:

-55.5 dBm/Hz @ 197.5kHz

-85 dBm/Hz @ 87.5kHz

-83.7 dBm/Hz @ 25kHz

For the Transfer Function:

UGF @150kHz, and we have a bump close to 0dBm at higher frequency.

Jenne, Nutsinee Sheila

We had trouble with locking the arm in IR for inital alingment, because PSL-POWER_SCALE_OFFSET was different from the input power.  We added a statement to the "IDLE" run state of LASER_PWR (the generator of states when not changing the power) that will adjust the normalization if it is more than 0.5Watts wrong. 

            if abs(ezca['PSL-POWER_SCALE_OFFSET'] - ezca['IMC-PWR_IN_OUTMON'])> 0.5:
                ezca['PSL-POWER_SCALE_OFFSET'] = ezca['IMC-PWR_IN_OUTMON']
 

Raised CP5 Dewar pressure (3/4 turn at pressure regulator + 1/4 turn yesterday). Will take days to read a pressure response. Current pressure is 17.5 psi in tank and 15 psi at exhaust. 

Also filled CP5 to 100% with 1/2 turn open on LLCV bypass valve. 

Peter, Sheila, Evan

We have been having trouble keeping the IMC locked when powering up (without the interferometer).

We found that the UGF of the loop was something like 110 kHz. During O1, we ran with a UGF that was more like 50 kHz. Recall also that the IMC loop at one point had some questionable resonance features above 100 kHz, so it is probably in our interest to keep the UGF on the low side (though we should confirm this with a high-frequency OLTF measurement).

We turned down the loop gain by 4 dB, giving a UGF that is more like 60 kHz. We were able to power up from 2 W to 23 W without lockloss.

Attached is an OLTF measurement after turning down the gain. As usual, the last point is garbage.

C. Cahillane

I have revamped the uncertainty budget to include covariances between all stages of actuation and all time-dependent parameters.
I computed each parameter's covariances in real and imaginary coordinates to provide a consistent basis.  I then compiled an 6 x 6 Actuation Covariance Matrix C_A, a 2 x 2 Sensing Covariance Matrix C_S, and an 8 x 8 Kappa Covariance Matrix C_K.  Then I compile them into a giant covariance matrix C:

     _             _
    |  C_A  0   0   |
C = |   0  C_S  0   |
    |_  0   0  C_K _|     

Then, I multiply by some conspicuous Jacobian vectors J(f) to get the final 2 x 2 uncertainty matrix σ_R^2(f):

σ_R^2 = J * C * J'

where J looks like:

        _                            _
       |  d Re(R)    d Im(R)          |
       | ---------  ---------   ....  |
       | d Re(p_i)  d Re(p_i)         |
J(f) = |                              |
       |  d Re(R)    d Im(R)          |
       | ---------  ---------   ....  |
       |_d Im(p_i)  d Im(p_i)        _|

(I was able to use complex differentiation and Cauchy-Riemann here to make the derivatives easier.  Recall that R = 1/C + D*A.  Now I can compute dR/dA = D and dR/dC = -1/C^2 to form J(f), thanks to 200 year old mathematics)

Finally, to make the uncertainties readable by humans, I divide σ_R^2(f) by |R(f)|^2, rotate σ_R^2(f) by angle(R(f)) via a rotation matrix, and read off the square roots of the diagonal of the rotated σ_R^2(f) to get the magnitude and phase uncertainties plotted below.

I have plotted the uncertainty at GPSTime = 1135136350, the time of the Boxing Day Event.

The plot shows an overall increase in magnitude uncertainty of about 1% at low frequency.
Phase uncertainty increased by about 0.5 degrees at low frequency.

The effects are more dramatic at Livingston.  Check out LLO aLOG 26542.  

Jenne, Peter, Jeff, Terra

We took charge measurements on the ITMs by driving 20.1 Hz into H1:SUS-ITMX/Y_L3_DRIVEALIGN_L2L_EXC with 100k cts and looked at the coupling to DARM. We stepped up and down the ESD bias voltage from zero and found the bias that gave zero coupling to get charge measurements, where V_charge= (20/2¹⁸) * bias * 40. ITMX zeroed with bias = 3k, ITMY zeroed with bias = 2.5k. See bias stepping ITMX and ITMY spectra attached. 

ITMX charge: 9.15 V,   ITMY charge: 7.6 V

ITMX: 

ITMY:

Approximating alpha: The first term in the expression for the force produced by the ESDs is the attractive force between the ESD fringe fields and the test mass: F = alpha(V_bias - V_signal)^2, where alpha is a constant of proportionality. With the known bias voltage V_b, signal drive voltage V_s, drive frequency f, and now the peak amplitude x_pp , we used the largest bias offset (100k) to approximate alpha for both ITMs. Work is attached. 

ITMX: alpha = 1.78 x 10^-11 N/V²,   ITMY: alpha = 1.85 x 10^-11 N/V²