All SEI GS13s are now set in High Analog Gain without Whitening except HAM6 and BS (Stage2.)  This standard High Gain configuration is with both FM4 & 5 Off in the GS13 INF module, H1:ISI-HAM5_GS13INF_H1 for example.

For HAM6, because of the shutter hit to the ISI, the GS13s are run with Low Analog Gain without Whitening.  This configuration is with FM4 On and FM5 Off.

For BS, because of the hit to the ISI when the MICH acquires, we run the GS13s in the standard low Gain configuration of Analog Low Gain and Whitening.  This has both FM4 & 5 On.

These configurations are set in SDF.

Here are the PSL DBB/ISS scans for this week.  No significant change from last week.

One of the ISCT6 enclosure handle could not be locked and it was guarded with an yellow caution tape.

Corey brought a new handle, but when we assessed the situation it turns out that the new one and the old one were identical, it was just that the old one was installed at a wrong angle. We removed the old one and re-installed after rotating 90 degrees, and voila, it can be locked when the door is closed and the handle becomes horizontal. Only  caveat is that the handle tip points up, not down, when the door is open.

We locked the doors and removed the yellow caution tape.

Here are the past 10 days trends:

The computer that generates web-accessible MEDM screen shots and model simlink captures is not running well since about March 11, 17:59 PDT.

It will hopefully be repaired soon.

Today we have spent most of the day trying to lock. We have locked, but only after some diifictulties. 

•  We saw that even with winds of only around 10-20mph, we are better off with high blends.  
• We moved the RF DARM transition earlier in the CARM offset reduction procedure, to an arm build up of about 10 times the single arm, which is what Den says they had at LLO before reducing the modulation depth. We are also engaging the DETM WFS right after transitioning to RF DARM.  
  • The hope is that these two things will make the lock acquisition sequence more robust if we start with a bad alingment.  In that case we are at a smaller CARM offset than we should nominally be at, and we can see that the ALS DIFF noise is large and the misalingments on the AS camera become large before we turn on the DETM WFS.  Hopefully this will prevent the type of lockloss we have been having in the guardian state switch to QPDs.  
• We saw that the CARM gain was not right when we are on TR carm, because of the IMC gain chage I made on monday.  (alog 17150)  Now the gain in the IMC refl servo board input two is increased from -4 to -2dB. 
• We've had some difficulty engaging DRMI ASC loops, especially PRC1, mainly because we end up with a spot on POP A that is different enough from our reference after doing the inital alingment that we saturate M3 of PRM.  Stefan working on solving this by engaging the loop with an offset which is slowly ramped down.  

Chris, Alexa

Loop Gains

The first two attachments show the OLTFs of the various length DOFs. In these plots, the model is the blue trace and the red trace is measured data. The DARM TF agrees pretty well. The PRCL and SRCL loops appear to have a gain missing. The CARM and MICH model loops are not correct. 

Noise Budget Overview (***Rough Estimates***)

The fourth attachment depicts the noise budget produced by the model for the 8W lock on March 04, 2015 15:30 UTC. This roughly agrees with the conclusions Evan has made with his NB (LHO#17101). At high frequencies we are dominated by shot noise. At around 300 Hz we suspect intensity noise (or maybe beam jitter), as Gabriele noticed. From 30-100 Hz we are limited by DAC noise. And below 10 Hz we see some angular fluctuations. 

Noise Budget Details

• Sensing Noise: The OMC dark noise was measured previously (LHO 16656) in mA/rtHz. We use the measurement with two whitening stages engaged and propagate this to darm. We find the conversion 1.56e12mA/m below the cavity pole.
• Intensity Noise: We use the second ISS loop out-of-loop PDs (currently PDs 5-8) to measure the RIN. We then measured the OMCPDSUM/ISS_PDSUM58 TF to determine the calibration from RIN to W. The third attachment shows the model (blue) optickle TF and the measured (green) TF. During this TF we only had coherence between 200-300 Hz. At this point we see that the model is -20dB relative to the measured data. This explains why the intensity noise looks too low in the NB plot. When the IFO is locked we should take this TF (/ligo/svncommon/NbSVN/aligonoisebudget/trunk/Dev/DRFPMI/Validation/H1Data/RIN2OMCDCPD.xml). Then the optickle model TF can be replaced with the actual measurement.  
• Angular Noise: The model uses live parts to measure the spectra in cts at the PUM stage of the quads. We have used an undamped model to convert these counts into displacement in P and Y of the test mass. We assume no coupling of P2Y and Y2P. Our cailibration from m to radians also needs to be checked. This produces a very rough estimate of angular noise. 
• We are using an ESD strength of 4.2e-10 [N/V^2], which is different than what Kiwamu uses for the calibration (2.8e-10 [N/V^2] LHO# 17206). The spectra agree within about 20%, which seems better than what one would expect with the differences in ESD strength.

SudarshanK, RickS

Today we had a quick look at our calibration data from Yend, taken after installing a polarizing beamsplitter downstream of the AOM (see aLOG 17145).

We will post a more detailed log after we have fully digested the data, but the preliminary result is that the new calibration of the Tx PD signal is within 6% of the previously reported number (see aLOG 16718).

This is about what we expected from our recent measurements of the signal drifts resulting from depolarization in the AOM.

Added 689 channels. Removed 123 channels.

The X direction at end X and the Y direction at the Y end are blended at 90mHz.  Sensor correction is in the normal conifugration (no BRS).  This was done at around 22:58 because we have had several lock losses due to large motions in the arms that ALS cannot handle. 

This was at about -30 minutes on this screenshot, as you can see the arm control signals are reduced with the higher blends.  

There is nothing that look like high ground motion on the seismic FOMs, although the winds are a little elevated (gusty 10-25 mph)

Corner station to X-1-5 double doors of the beam tube has been cleaned. Lights were relocated, support tubes vacuumed and moving north towards mid station from X-1-5 double doors. 
Looking into purchasing a suitable generator for this operation, the previous one not necessarily designed for this type of duty. We are still able to use site power for this section of cleaning.

Beam tube pressures continually monitored by control room operator during cleaning operations. 

Times in PST

07:00 Karen and Cris to LVEA

08:49 Richard to EY electronics bay

09:11 Peter King to Mid X

09:17 Richard back, Fil to EX electronics bay

09:30 Peter back

09:37 Fil back

09:39 Peter to Mid X

09:48 Corey to squeezer bay

10:10 Peter and Richard back from MX

10:26 Kyle to LVEA checking pumps

11:56 Corey out

13:38 Corey to squeezer bay for 20 min.

15:33 Dave/Ryan Fisher restarting OCD Master model

I'm posting some plots of the performance of the BSC-ISI's. The attached pdf has 18 plots, the first 12 show the contributions of each control path to the performance of the ISI, shown against aligo requirements, sensor noises and ground motion. The order is St1 X (p. 1), St2 X(p. 2), St1 Y(p. 3),...  for x, y, z, rx, ry, rz. The configurations measured were offline, damped ISI, St1 ISI isolated / St2 damped, isolated (both stages), isolated with tilt decoupling, isolated with tilt decoupling and sensor correction, isolated with tilt, sensor correction and feedforward from HEPI. HEPI was off for the offline measurment as well. The blend filters used were the normal blend filters (the rdr compliment of filters with the T750 blend on St1 RZ). Please note that on the rotational plots, I used "paralell" ground direction (Y for RX, X for RY, Z for RZ). No, it doesn't make perfect sense, but X can be injected to RY or vice versa, and the BSC's have a coupling from Z to RZ, that we need to be aware of.

The last 6 plots show the final performance (i.e. our current configuration with damping, isolation, tilt decoupling, sensor correction and feedforward) for each dof for both stages.

Similar plots for the HAM's are next.

Alexa, Sheila, Evan, Chris, Stefan

We implemented Peter's DARM 'SUScomp' from alog  16728. Since we can't lock with that filter directly (see alog 16840), deleted the old 'LLO' filter, but instead loaded a difference filter called 'acqLP' that makes the 'SUScomp' look like the old 'LLO' filter:
  zpk([80;500-800i;500+800i],[50;70;200],1,"n")

Guardian was updated to turn off acqLP' in FM8 instead of turning on a lead.



A note on the previous filter is also found in alog 16381.

In response to Evan's alog (alog 17065), I took a look at the DARM spectra. Here are conclusions at the moment:

• In the 2.8 W configuration, the optical gain seems to have decreased by approximately 9% compared with the noise curve from Feb. 26th (alog 16982) with the assumption that the high frequency band is limited by shot noise. This resulted in a too-good noise curve last night.

• The origins of this discrepancy is not clear.
  • Note that the arm build up (e.g. ASC_TR_X(Y)_B_QPD_SUM) were lower than that of Feb. 26 th only by 1-2% which is not big enough to explain the discrepancy. See the attached trends for more details.
  • One possible factor can be different sensing gain in the digital system such as OMC-READOUT_SCALE and LSC input matrix which the midnight lockers change every time they are transitioning to DC readout. I did not get chance to carefully go through these values yet.

• In the 8 W configuration, the 9% discrepancy was inherited and hence too good noise again by 9% above 1 kHz. On the other hand the power scaling from 2.8 to 8 W seems to have been done precisely.

• A strange thing is that the noise curve at around 2.8 kHz became further too low for some reason in the 8 W configuration. This can not be explained by the 9% overall discrepancy factor. The noise in this region seems lower by 10-ish% than the GWINC curve.

(Noise spectra)

The data sets that I used are from:

• 2015-02-26 10:2:50 (at 2.8 W)
• 2015-03-04 10:08:55 (at 2.8 W)
• 2015-03-04 14:03:55 (at 8 W)

Here is a comparison of all three curves with the GWINC theoretical curves above 400 Hz up to 7600 Hz.

As Evan reported, indeed the measured curves from last night are lower than the GWINC curve in 1 - 4 kHz band while the one from Feb-26 looks fine.

(Discrepancies between the curves)

Now, I want to answer how much the Mar-4 data differed from the one from Feb-26th by taking the ratio between them. I divided the Feb-26th by Mar-4th spectra in 400-7600 Hz band. Then I convert it into a histogram to see how they differ on average. Since there were many peaks whose amplitude varied as a function to time, I excluded them by limiting the histogram range from 0 to 2. The ratio is shown as red bars in the below plot.

Note that I could have done a fancy Gaussian fit for it, but for now I picked the highest bar in the histogram in order to coarsely estimate the ratio. As shown in the plot, the Feb-26 data had a higher noise level by a factor of 1.09 on average.

Then I did the same ratio analysis for the 2.8 W and 8 W data of Mar-4th. It is shown as blue bars in the same histogram plot. Picking the highest bar, I measured the ratio to be 0.58 which agrees with what we expected i.e. sqrt( 2.8W / 8W) = 0.59. So the power scaling from 2.8 W to 8 W seems to have been done correctly last night.

(Unexplainable dip at around 2.8 kHz in the 8 W data)

However, it is not the end of the story yet. The noise curve of the Mar-4 at 8 W had a funny feature at around 2.8 kHz where the noise go down below the GWINC curve even if i apply the 9 % correction.

The below plot shows "normalized" spectra of all the three data sets. In order to line up all the spectra at the same level, I "normalized" the Mar-4th-2.8W data by multiplying a factor of 1.09. In a similar manner, I "normalized" the Mar-4th-8W data by a factor of 1.09/0.59. In this way I checked the shape of all the spectra.

The Mar-4th-8W data was lower by the rest of the two curves by 10-ish %. I did not do a serious histogram analysis.

Finally , if I apply only the 1.09 correction factor to the data from last night, they look like this:

Apparently the Mar-4-8W data is lower at around 2.8 kHz than the GWINC curve.