Cheryl, Evan

The 0.43 Hz pitch instability strikes again. I had to turn up the dHard pitch gain from 10 to 20 in order to prevent a runaway. Back into the guardian it goes!

It takes tens of minutes to ring up, and even after tweaking loops, it never exactly rings down (the fuzz in the attached striptool is almost all from this 0.43 Hz feature).

This is a report by Jenne.

[Sheila, Jenne, Cheryl, Evan]

We have (finally) recovered from the input pointing adventures of the day. 

In the end, I think all we did was some hand alignment to get the ASC error signals small-ish, so that the loops could take over without pulling down the power buildups.  We are now able to go all the way through the guardian states automatically.

This is the first low-noise lock since the EOM driver was replaced earlier today with the new box that can suppress amplitude noise of the sideband (20392).  From Lisa's log post (20131), we see that a useful comparison is the OMC DCPD Null stream with the Sum.  In the plot below, the dotted line references are from August 1st, when we still had the old 45 MHz driver. The solid lines are from tonight.  The null stream is the same then and now, (as it should be), but the sum has come down significantly. This means that our OMC DCPD is now closer to the shot noise limit, since we have better suppressed this RFAM noise.

[Edit: It's true that the coherent excess in the DCPD sum has been decreased, but there is still a broadband excess everywhere from 400 Hz to 7 kHz, and we still see broadband coherence between DCPDs A and B with AS C. See second attachment (the IOP channel is AS C segment 1). Might be worthwhile to try varying the modulation index. —Evan]

LVEA: Laser Hazard
IFO: Unlocked
Observation Bit: Commissioning  

All Times in UTC
23:00 Take over from Jim W. 
23:40 Sheila & Jenne – Going to IOT2L table to look for beam
23:55 Sheila & Jenne – Back in LVEA at IOT2L
00:45 Daniel & Sheila – Going into PSL enclosure to check PZTs
01:00 Daniel & Sheila – Out of PSL enclosure
01:10 Adjust ISS diffracted power to 8%
02:37 Evan & Daniel – Going into the LVEA to work on EOM drivers
03:00 Commissioners working on reestablishing lock

Initial alignment was redone following today's PSL work.

Attached is the whiteboard list of tomorrow's scheduled tuesday maintenance activites.

We'll start with some hardware related work, and follow up with an ASC model restart.  As usual, please let us know when you are coming and going to VEAs, whether for listed work or not, so we can ensure efficiency of everyone's work.

1st wave tasks:

Fix 1st loop ISS servo card

Install PI AA chassis (Ex, EY)

Install TCSx viewport temp sensor

Finish SEI "safe" .snaps

Stagger start in 1st wave task:

Pcal work at Ey

Sweep VEAs for test equipment that needs to come home

PEM injection setup

2nd wave tasks:

ASC model restart

REVERT EX FE computer to original machine

DAQ Restart

Kiwamu recently found, while trying to to use suspension model to calibrate Pcal, that the use of IIR filter in the front-end results in distortion of the filter response from its actual intended response. (G1501013). 

We decided to check all the whitening filters that are use in CAL-CS model to confirm (check) if we see similar effect. The following filters were analyzed:

CAL-DARM_CTRL_WHITEN

CAL-DARM_ERR_WHITEN

CAL-CS_DARM_DEALTAL_CTRL_SUM(L1/L2/L3/M0)

CAL-CS_DARM_RESIDUAL_WHITEN

CAL-CS_DARM_DELTAL_EXTERNAL_WHITEN

The frequency response of these filters deviate from the model by about 2.5% at its max in amplitude and about 8 degrees in phase (at around 5 KHz). Some filters are severe than the other but they produce this effect nonetheless.

I varied a pair of pole frequencies, keeping two zeros at 1 Hz, to see what the effect looks like. From the last plot, we can see that the distortion is more severe if the pole frequencies are higher. 

(Evan, Kiwamu. Daniel)

We installed the 45.5MHz EOM driver in the PSL room. It is located below the PSL table and replaces the RF amplifier at the same location. The drive power has been adjusted to be the same as before at 23.2dBm. This is now controlled remotly through medm.

Calibration:

• For the front panel BNC of Mon1 and Mon2 the calibration is 105V/V relative the output signal. The DAQ readbacks RF45_ERR and RF45_AC have an additional gain of 20.
• The DC output at the fron panels have a gain of 0.578V/V relative to the output signal. The DAQ readback RF45_DC has an additonal gain of 2.
• To caluclate the RF AM in dBc one has to divide the AC/ERR values by the DC value.

The RF phase shift was compensated by cable length to within 1°.

The RF phase has a slightl dependence on the RF level. At 45.5MHz with 23dBm output level the phase advance of the entire chassis is 121°. The relative phase shift at 17dBm is +4.8° (advance), +8° at 13dBm, and 12.8° at 5dBm—or –0.8°/dBm.

The attached plot shows the RF AM RIN in dBc/Hz for both the in-loop and out-of-loop sensor (double-sided). At 100Hz with 23dBm output we are achieving-170dBc/Hz.

[Sheila, Jenne, Kiwamu, Daniel]

It's not totally clear how or when this happened, but at some point today the input pointing PZT driver's power cable came loose.  This box is on the PSL table, in the PSL enclosure.  The failure seems to have happened before anyone went into the enclosure today, but after the fans were turned on (in preparation for going in). 

The big symptom was that we had no light at all on the IMC Refl camera, even though the PMC was locked.  There was no light reaching IOT2L, even at the top of the down-periscope.   We also found that we were unable to move the input beam with the PZT (moving very large steps had no effect on the spot position), and the beam was very low. 

Kiwamu and I confirmed that we were getting signals out of the DAC, so the problem was clearly downstream.

Sheila and Daniel went into the PSL and discovered that the power cable for the PZT driver was loose. The AC adapter for the cable was hanging, with its weight pulling on the power connection on the box.  Jiggling the cable caused the LED on the box to illuminate, and we immediately saw beam on the IMC Refl camera.  Sheila and Daniel moved the power cable, so hopefully this won't happen again.

A bit of alignment later, and the IMC is locked once again. 

Reed E., Erik K., Matt E.

In order to explore the possibility that the big glitches in DARM come from ambient dust events in the arms, we took a look at the transmitted power signals.  In a perfect world, these should dip if something falls trough the beam.

We found that that dust glitches also appear in the X and Y TR signals (e.g., ASC-{X,Y}_TR_{A,B}_NSUM_OUT_DQ) with large amplitude (see first 2 plots).  Interestingly, both arms are affected, though the arm where the dust is not falling appears to see a low-passed version of the disturbance (e.g., via the DARM cavity pole).

Some of the glitches looked at by Gabriele also seem to appear weakly in the TR signals, though a more sophisticated analysis will be needed to draw conclusions about the efficiency of these signals as a veto.

Sudarshan, Gabriele

Today when the IFO was locked in low noise, we could see the 300-400 Hz peaks in the sensitivity again. Those are know to be due beam jitter caused by the PSL periscope.

We looked into the performance of the ISS second loop, which was closed at the time. The first strange thing that we can't understand is that both the in-loop and out-of-loop signals are dominated by a flat  noise background at a level of 1e-8 /rHz. We would expect the out-of-loop to be at this level, but the in-loop should be squeezed down by the larg loop gain.

We changed the ISS gain, anmd discovered that if we turned down the gain at the minimun (-26-20 dB with respect to nominal), and disengage both boost and integrator, the in and out of loop ISS signals got worse, but the sensitivity got better at the 300-400 Hz peaks. So out guess is that beam jitter on the ISS array is actually causing an excess sensing noise on the ISS diodes, which is then re-injected into the laser beam as real intensity noise when the ISS second loop is closed with high gain.

We tried briefly to optimize the centering of the beam on the ISS array. We couldn't find any spot better than the initial one in terms of power on the diodes. One possible strategy would be to move the beam into the ISS array with the IFO in full lock, and use the coupling of a PZT jitter line to the sensitivity as a figure of merit.

Dan has identified all 8 frequencies that belong to ETMX here. So I added them to the monitor.

The conlog process on h1conlog1-master failed at 12:25PDT Saturday 8th August. The error is shown in the FRS report linked below. I restarted the process this afternoon. Conlog is reporting 412 disconnected channels which relate to the guardian and h1calcs work which was done last week, we will need to regenerate the conlog channel list tomorrow.

Fault Report 3433

After pulling the latest ASC_MASTER.mdl and talking to Adam at LLO, I added the following channels in ASC_MASTER to the science frame in addition to what Adam did:

ASC-DC1_P_OUT_DQ , (also Y, also DC2, DC3, DC4 and DC5): 512Hz

ASC-OMC_A_PIT_OUT_DQ (also YAW and SUM, also B): 2kHz

I then changed H1ASC.mdl to use the new ASC_MASTER. Dave compiled the model without an error. We'll install it tomorrow.

Some details:

0: Pzt outputs for new POPX thing is terminated at LHO.

At LLO this is connected to DAC, but here I simply terminated the output.

1: Initial Alignment system (obsolete, not used these days) are purged from h1 model.

This was purged from the latest ASC_MASTER. To accomodate this,  access to ALS_X_REFL_B_LF_RFM, and ALS_X_REFL_B_LF_RFM_IPC_ERR, and their Y-arm counterparts, were all deleted from the top level.

2: DARM_CTRL and IM4_TRANS_PIT and YAW input for the common block are terminated in h1 model

This is a part of LLO dither scheme, but I just terminated these input in h1 model.

3: Unused PZT[12][XY]_[PY] and QPD[12][XY]_[PY] are gone from ASC_MASTER.

These were already obsoleted by green WFS at LHO and were terminated at the top level at LHO. Now these signals are gone.

4: New dither outputs are connected to some masses in h1 model.

New ASC_MASTER has dither outputs to BS, ITMs and ETMs in addition to PRM, PR2 and PR3.

In the old h1 model, RFM sender to corresponding optics already existed but was sending 1 or 2 (constant). In the new h1 model these things are connected to the dither output even though we do not use dither these days.

There are unused RFM sender to SRM, SR2 and SR3, these are kept there.

5: Deleted some obolete text labels and an unused orphaned RFM receiver in h1 model.

JeffreyK, Darkhan

Overview

We found that some of the calculations in the recently implemented CAL_CS front-end model (see LHO alog #20360) do not produce expected results. We found this problem in the division block that takes input of significantly smaller number for denominator vs. number in the nominator.

Since this calculation is done on quantities that should change only as a result of manual input we've decided to calculate these quantities in Matlab and then export final results to EPICS. Tomorrow we will add these EPICS inputs into CAL_CS front-end model.

Details

In this section we show how this bug was identified.

Following EPICS input channels exist in the CAL_CS front-end model: REF_A_TST_REAL and REF_A_TST_IMAG. They form a complex quantity A_tst = Re{ A_tst } + i * Im{ A_tst } = REF_A_TST_REAL + i * REF_A_TST_IMAG.

We wanted to calculate Re{ -1/A_tst } and Im{ -1/A_tst } as

| A_tst |² = Re{ A_tst }² + Im{ A_tst }²

Re{ -1/A_tst } = - Re{ A_tst } / | A_tst |²

Im{ -1/A_tst } = Im{ A_tst } / | A_tst |²

When we provided both inputs (real and imaginary) with quantities their values, the quantity | A_tst |² came out to be about right, but the final values Re{ -1/A_tst } and Im{ -1/A_tst } were off by several orders of magnitude.

The finals values should have been

Re{ -1/A_tst } = 1.39199e+16

Re{ -1/A_tst } = -1.14388e+16

We don't know for sure, but it might be possible to avoid this bug by trying rearrange signals in simulink design (e.g. replace division by multiplication by inverse of the quantity or maybe some other way).

For this case we decided to calculate these final quantities in Matlab and into EPICS only final results.

Leonid.Prokhorov, Jeffrey.Kissel
Charge measurements was done on both ETMs.
Results are in attachments. For most quadrants we have follow trend: 

From June, 24 to July, 21 (from discharging to changing the bias sign) data are consistent with positive charging for ETMY and negative charging for ETMX.
ETMX Bias: +9.5V, Mean charging rate: -10 V/month (st. dev. +/- 3 V/mon)
ETMY Bias: -9.5V, Mean charging rate: +7 V/month (st. dev. +/- 3 V/mon)

From July, 22 to Aug, 10 (from changing the bias sign to today's measurements) data for most of quadrants are consistent with the changed sign of charging - negative for ETMY and positive for ETMX.
ETMX Bias: -9.5V, Mean charging rate: +17 V/month (st. dev. +/- 9 V/mon)
ETMY Bias: +9.5V, Mean charging rate: -20 V/month (st. dev. +/- 14 V/mon)
Note, because the standard deviation is less that the mean, it shows that the rate is roughly the same for each quadrant. However, there are outliers (see, e.g. Right quadrants of ETMY).

Now the effective bias voltage is about few volts for ETMX, and about 10 volts for most quadrants of ETMY, but ETMY UR shows as much as 15-20 Volts. 
Probably, it's a good time to reverse the bias sign at ETMY.


There are two sets of plots, each which show the same data in a different way:
(1) ETMX_Mean.png & ETMY_Mean.png shows both the mean and standard deviation, and weighted mean and sqrt(weighted variance) of the charge measurements for a given day (which can be from ~4 to ~15 of these 12 minute measurements per mean point). We believe this better shows the long-term trend of the charge.
(2) ETMX.png & ETMY.png show the "raw" data, where the result of each estimate of the effective bias voltage shown *since* the discharging. Each single data point is an estimate of the effective bias voltage, i.e. the charge, as determined by driving the test mass while varying the requested bias voltage and measuring the response with the optic's optical lever.

Related alogs: 19848, 19821