As we recently confirmed, the coil driver analog circuits are not accurately compensated in the suspension front end model (see alog 21189 for EY L3 stage, alog 21189 for EY L1 stage, and Darkhan is making alog about the EY L2 stage). This results in an extra frequency dependent response in the actuators which would be flat if the compensation was perfect. Since we will run the interferometer in this way without accurately compensating the coil driver responses, we need a correction filter to take this into account in CAL-CS. So I made a matlab script to pick up the latest DARMOLGTF model, which already includes the precise measurement of the analog coil drivers, and then install them in CAL-CS_DARM_ANALOG_ETMY filters.

The script can be found at:

aligocalibration/trunk/Runs/ER8/H1/Scripts/CALCS/quack_coilmismatch_into_calcs.m

The script simply loads the latest DARM open loop model by calling a matlab function, H1DARMOLGTFmodel_ER8, and then processes the mismatch into one digital filter for each stage by combining the digital compensation filter and corresponding analog responses. Currently it handles only L2 and L3 stages since we are still working on the L1 stage. Using autoquack, it is going to install the mismatch filters into CALCS. I have ran this code multiple times and seemed to run without an issue so far. The filters are already installed at the end of the actuator chain as seen in the attached plot -- FM6 of each stage is the one. Note that they are not enabled yet since we need to install the latest suspension model in CAL-CS in order to be accurate.

We did not get the factor of 5 reduction in jitter coupling from second loop ISS and PZT servos that I had hoped for, and resonances of the top mirror mount on the periscope are visible in DARM near 300 Hz. Jason and I altered PSL crystal chiller flow rates to see if they affected PSL periscope motion. Figure 1 shows that, indeed, a 2% decrease in flow rate (as low as we could go using the bypass valve) dropped the periscope motion by 8%. Also, a 10% increase in flow gave a 29% increase in periscope motion.

The great majority of the flow is through the unused HPO. A small fraction of the flow is needed for the front-end laser that we are using. We could reduce the flow and probably remove the peaks from DARM if we turn down the total flow while increasing the fraction to the front-end laser.

Robert, Jason

Ed, Sheila, Jeff K.

23:20UTC Observation Intent Bit set. This is following some debate as to the  "wait" time for the IFO to "cool" down before setting the bit.

ALL TIMES IN UTC

ACTIVITY LOG:

• 17:30 Kissel on site

• 18:44 ETMY Saturation

• 19:00 Kiwamu on site

• 19:45  Sheila on site

• 20:22  Sudarshan on site

• 21:02 ETMY Saturation

• 21:13  Wind picked up from 5 to about 15 in the last couple of minutes. No biggie.

• 21:18  Looks like another quake from the same New Zealand area is shaking us causing SRM saturations.

• 21:39  Sheila taking advantage of this Lockloss to try a different PRM offload to be able to ride out earthquakes better.

• 22:36 Jeff B on site for evening shift

• 22:46 Darkham on site

• Handing off to Jeff - Undisturbed

LOCK LOG:

• 16:58 DRMI finally able to lock

• 17:06 Lockloss at SWITCH_TO_QPDS

• 17:21 DRMI locked

• 17:24 Lockloss  @ DRMI_ON_POP

• 17:43  DRMI locked

• 17:56 Locked @ NOMINAL_LOW_NOISE 66Mpc

• 21:33 Lockloss - New Zealand quake

Summary:

• Not too much to summarize. The time logs tell the story.

21:33UTC

18:02UTC Intent Bit set

ER8 days 20,21. No restarts reported.

After the Earth settled down, I ran through an initial alignment (including dither alignment of TMSy) since the green alignment wasn't very good.  Lots of locklosses on the way up at various places.

11:48 Dan leaves for Italy

12:00 Begin initial alignment

12:08 I notice that ALS_-Y_WFS_DOF_3_P_GAIN and ALS_-Y_WFS_DOF_3_Y_GAIN are flagged in SDF.  I assume this is a result of the dither alignment of TMSy.  I revert them.

13:12 lockloss @ SWITCH_TO_QPDS

13:25 lockloss @ RF_DARM

13:36 lockloss @ DRMI_ON_POP, possibly due to PRM saturation

13:43 lockloss @ SWITCH_TO_QPDS

13:46 lockloss @ FIND_IR

13:54 lockloss @ SWITCH_TO_QPDS

14:13 ISC_LOCK is stalled at DC_READOUT_TRANSITION.  Looking at the code and OMC_LOCK log, I try re-requesting READY_FOR_HANDOFF in OMC_LOCK.  It works, and ISC_LOCK carries on.

14:16 lockloss at ENGAGE_ISS_2ND_LOOP, conicident ETMy saturation

14:18 Seismos start showing more activity.  USGS site reports another 6.2 EQ in New Zealand.  The thunder from down under does us in again.

14:47 Observatory mode set to Earthquake

15:00 Good luck Ed!

Dan, Travis

During the earthquake tonight we finally closed the loop on the HAM6 power budget measurements.  This is something Koji had asked for many, many months ago.  orz

With IMC-PWR_IN at 2.2388 +/- 0.0004 watts (not sure about the calibration for this channel) and a single bounce off ITMY, we collected the following data (30 seconds of slow channels, uncertainties are stdevs) with the OMC locked & unlocked:

AS_C has 36dB of whitening gain.  The OMCRs and DCPDs have no DC whitening.  I'm not sure about AS_A and AS_B (I think they have zero whitening, but I haven't looked at the electronics chain for the WFS DC signals so I'm not sure of the transimpedance, etc).  Since AS_C gets 400ppm of the light entering HAM6, the total light into the chamber is:

289 counts / (1638.4 counts/V * 0.8 A/W * 1000 V/A * 2 * 36dB * 400ppm) = 4.38 mW

(PD responsivity = 0.8, QPD transimpedance = 1000 ohms, differential output = 2x, whitening gain = 36dB)

The alignment into the OMC is probably not perfect in this state, but the mode-matching for the carrier should be better than 90% -- same as here, since we apply central heating to ITMX.  The modulation depths are also the same; the power in the carrier should be 94.3% of the total.

Dan, Travis

Following up on the measurement of the tip-tilt response at high frequencies, I've moved the OMC alignment dither lines up above 2kHz.  The new frequencies are [2125.1, 2150.1, 2175.1, 2200.1] Hz.  The amplitudes were slightly increased to maintain the same line height after the reduction in the tip-tilt response at high frequency.  In the filter banks following the demodulation, I changed the frequencies of the elliptic filters that are used to notch the line frequencies post-demodulation.

To update the control scheme, I adjusted the phase rotation of the demodulated signals such that offsets in the alignment loops only showed up in the I phase signals.  Striptools are the best way to do this.  Then, I reran the ditherDCsense script to calculate a new sensing matrix, and closed the loops.  Things looked pretty stable, so let's stick with this new arrangement.  I attach a screenshot of the new sensing matrix.

If for some reason people get spooked and want to revert, do the following:

 - set the frequencies back to what they were before: [P1, P2, Y1, Y2] --> [1675.1, 1700.1, 1725.1, 1750.1]

 - set the oscillator CLK_GAINs to 100.  The current CLK_GAINs are [150, 120, 100, 130].

 - in the dither demodulation, for filter banks {P,Y}{1,2}_X_{SIN,COS}, switch from FM7,9 to FM8,10.  These are pairs of ELPs that notch the dither line in the demodulated signal.  They're used to squash high-frequency stuff from the control signal.  It's probably excessive.

 - set the R demod phases to 90.  They are currently 135, 150, 150, and zero.

 - use conlog to revert the sensing matrix.  Look for changes to channels of the form "H1:OMC-ASC_DACTMAT*".

The SDF table has been updated with these new settings.  We were all set to go back to science mode when the IFO lost lock, after 28 hours of good data.  The lockloss was due to PRM M3 hitting the rails (see second plot), maybe because of a 6.4 earthquake, although the lockloss was about twenty minutes before the arrival time of the P-waves according to terramon.

Nutsinee handed over an IFO that had been locked for over 28 hours.  Unfortunately, an EQ in New Zealand took us down.  It appears that PRM had saturated, taking down DRMI a few minutes before the EQ arrived, but the EQ has prevented us from relocking for over an hour now as the Earth calms back down. 

7:30 LLO dropped lock, went to commissioning mode for a few minutes so Nutsinee and Dan could look at a few things

9:08 Lockloss (Guardian reports that the OMC SW watchdog has tripped and that DRMI has unlocked)

9:40 I begin initial alignment after seeing that ALS isn't well aligned post lockloss

9:44 After noticing that the alignment is wavering, Dan notices that TerraMon is reporting an EQ in New Zealand.  Site seismos start reporting the same things soon after.  Initial alignment is paused to wait for calmer conditions.

9:44 I notice a timing error on the CDS overview for ETMx.  ETMy already has one which a note from Ed says should be reset after lockloss.

10:53 ETMy timing error reset (as per Ed's note).  ETMx timing error is NOT reset (not sure if I should, emailed DaveB for advice).

(All time in UTC)

23:00 Take over from Ed. IFO has been locking and observing. Dick's inside optics lab.

01:21 Dick out of the lab.

05:00 Dan's on site. Will be here for the rest of the night.

07:00 The ifo has been locking over 26 hours now! Handing off to Travis.

- Quiet shift. Wind still below 20 mph. No seismic activity. Saturation alarm hasn't been complaining about anything else other than ETMY, which has been the only source of big glitches on the DMT Omega.

- Camera 3 control was very slow. At one point I thought it was busted. Seems to be working fine again.

The interferometer is still locking and going strong. Wind below 20 mph. Quiet seismic activity. No one on site but me. I'm hoping for another record breaking lock stretch!

LLO has been locking and observing over the past two hours.

I worked a bit more on the analysis codes that Jeff has written (alog 21015 and alog 21049). I was not able to finish deriving the suspension scale factors. Tomorrow, Jeff and Darkhan will pick up them at the point where I left and will continue working on it.

Major updates:

• DARMOLGTFmodel now incorporates not only each ESD driver circuit measurement but also each PUM coil driver measurement.
  • Darkhan is going to alog some detail of the PUM driver measurement and fitting.
• The ALS Diff measurements are now analyzed using the latest DARMOLGTF model.
• Also, the Pcal measurements are now analyzed using the latest DARMOLGTF model.
  • By eyeballing the resultant plots, I see that the inclusion of the ESD driver and PUM coil driver circuits made the model more accurate. This is encouraging.

Next steps:

• We need to include the latest DARMOLGTF model in the free-swinging Michelson analysis.
• UIM driver circuit needs to be updated. DARMOLGTF still assumes a perfect cancelation between the digital and analog filters.

Some notes:

In the course of the code update, I changed the file organization structure of the ALS diff and Pcal scripts so that they have only one analysis code which can be invoked by specifying a set of data parameters. This organization approach is the same as those for the DARM open loop analysis.

As for ALS diff, the core analysis code is

aligocalibration/trunk/Runs/ER8/H1/Scripts/ALSDiff/Matlab/analyze_alsdiff.m

and the parameter files are in the same directory and named as

H1ALSDIFFparams_20150826.m

H1ALSDIFFparams_20150828.m

H1ALSDIFFparams_20150829.m

As for Pcal, the core analysis code is

aligocalibration/trunk/Runs/ER8/H1/Scripts/PCAL/analyze_pcal.m

and the parameter files are in the same directory and named as

H1PCALparams_20150826.m

H1PCALparams_20150828.m

H1PCALparams_20150829.m

Each parameter file loads H1DARMOLGTFmodel_ER8 with the latest electronics information and subsequently returns the parameter structure, or the familiar variable "par". As usual the parameter structure can be then fed to the analysis code (e.g. analyze_alsdiff.m or analyze_pcal.m) as an input argument. I have not carefully thought about the final return variables from the core analysis codes, but in principle we can write them such that they return the calibrated suspension transfer functions in meters/counts together with some error bars and also perhaps some statistical values. In this way, the final step of performing apple-to-apple comparison between various measurements from various dates can be less painful.

I tried propagating the same file organization structure to the free-swinging Michelson codes, but apparently I am running out my energy for the night and did not finish it yet.

Stefan, Evan

This is an analysis that Daniel suggested a while ago.

When we increase the interferometer power from 3 W to 24 W, we increase the common-mode radiation force on the test masses. Since the suspensions are compliant, this produces an extra displacement in the test masses along the beamline relative to their suspension points. The CARM loop senses this common-mode displacement and compensates by applying a slow control voltage to the IMC VCO. This control voltage is offloaded to the UIMs of the end station suspensions, and then subsequently to the endstation HEPIs, thereby moving the suspension points of the ETMs forward so as to cancel the radiation-induced displacement. Therefore, an appropriately calibrated HEPI tidal signal can be used to estimate the amount of power circulating in the arms.

We looked at a data stretch from 2015-08-07, when we had been sitting at 3 W for a while and then powered up cleanly to 24 W, and found the following:

• The HEPI tidal signals show a nice, linear trend for the hour preceding and the hour following the power-up [first attachment].
• By fitting the linear trend [second attachment] and subtracting it off [third attachment], we can get an estimate of the HEPI displacement due to the radiation pressure alone. The displacements are 2.9 µm each for X and Y.
• During power up, the change in the force on the test mass due to the change in radiation pressure is ΔF = 2 ΔP / c. The dc compliance of each test mass is H = Δd/ΔF = 2.6×10⁻³ m/N, where Δd is the change in displacement of the end-station HEPI. Therefore, the power change is given by ΔP = c Δd / (4 H) [there is an extra factor of two here because there are two suspended masses per arm]. From this, the power change per arm is 85 kW.
• From the IMC input PD we know that the power ratio before and after powering up is P₂/P₁ = 10.3. This can be combined with the above power change to arrive at an absolute number for the circulating power: 94 kW.

On the other hand, when we make a similar estimate from the end-station QPDs, we have something like 24 W × 0.88 × 1/2 × 40 W/W × 283 W/W = 120 kW. [The factor of 0.88 is the modecleaner transmission.]

The calibration of the HEPI tidal signals into nanometers is sort of loose [to within 10%?], according to Hugh. Similarly, there is some spread in the power inferred from the endstation QPDs, which gives an uncertainty that is also on the order of 10%. With a more precise HEPI calibration, perhaps we could use this method to better constrain the optical calibration.