Den, Kiwamu, Evan

We continued investigations into locking robustness and low-frequency noise.

Notes on robustness:

>> Engaging the soft loops is still painful, particularly in yaw. When the loops are ramped up to their nominal gains (a few tens of millihertz bandwidth), the SRM yaw loop misaligns the SRM in yaw, which causes POP90 to rise and causes lockloss after about 1 minute. If the SRM yaw loop is turned off, this misalignment does not occur. So far, the most reliable way to engage the ASC is to (1) engage the soft loops with the −20 dB filters, and let them run for a few minutes, (2) turn off the SRM yaw loop, (3) turn off the −20 dB filters in the soft loops, and then (4) once the soft loop error points have reached 0, turn the SRM yaw loop back on. This has not been added to the guardian.

>> Den retuned the PR2 actuator feedforward which decouples MICH from PRCL, but this has not been added to the guardian yet.

Notes on noise:

>> Similar to yesterday's frequency noise test, we injected high-frequency noise into the ISS first-loop error point. We drove several volts (both sine waves and broadband noise) up to 10 MHz, but we did not see any nonlinear coupling.

>> As noted previously, the input jitter coupling into DARM is worse than before, particularly in pitch. Den opened the SRM angular loops and moved SRM to minimize the coupling. However, this seemed to make the noise worse in other places. In particular, the region from 35 Hz to 70 Hz swas dominated by some kind of nonstationary excess (perhaps scattering in HAM6). Also, there appeared to be a slight excess frequency noise above 5 kHz.

>> We drove the ITM ring heaters (upper and lower) in common-mode in order to measure the voltage-to-displacement coupling in DARM. By driving a few lines at 250 mVpk between 80 and 160 Hz, we could see that the coupling goes like 1/f². The levels at 160 Hz are as follows:

>> We flipped the sign of the DARM offset. Normally we run with the X arm shorter than the Y arm (i.e., a positive offset is applied at the DARM error point, and DARM is Lx − Ly); so here we are running with X arm longer than Y arm. This is achieved with the ISC_LOCK paramter lscparams.omc_sign that is applied at the appropriate points during the dc readout handoff. The sign of the SRCL feedforward also has to be flipped, and the SRCL FF filters that we normally use cause some 1 Hz instability that unlocks the interferometer. We installed a more aggressive AC coupling filter (FM8), and this solved the issue. DARM has a small amount of excess noise with this new offset, but the SRCL coherence does not seemed to have changed much after FF retuning. Good time to look at is 2016-02-21 21:44:40 (bruco).

Cao, Elli

To measure the SRC gouy phase, we need to move the BS and PR2 optics in yaw and know the angle we move them to at least 5% (but ideally more like 2%).  So today we checked the calibration of these optics' alignment sliders using the ETMY baffle PDs.  We have used the method which was previously used to calibrate the BS optic align sliders (alog 14321), although we have taken extra care to loacte the center of the baffle PDs, as we are particularly interested in understanding the accuracy of this measurement.  Just to be clear, we are not making any changes to the alignment slider gains, we are simply measuring how good the current ones are.

Method:

The BS was moved in pitch and yaw to direct the PSL beam onto each of the ETMY baffle PDs (PD1 and PD4).  PRM, SRM, ITMs, ETMs and TMSs were misaligned to prevent flashes from other optics from corrupting the baffle PD signal.  Once the PSL beam was directed onto a baffle PD, we moved the BS around and plotted BS location vs intensity.  We fit gaussian profile to this plot to pinpoint the BS slider values for when the beam is centered on each of the baffle PDs.  (Attached are the plots of slider value vs PD power and the fited gaussian, for the BS).

This procedure was repeated using the PR2 to direct the beam onto each baffle PD.

Results:

We can check the calibration of these sliders by comparing to the angle the beam moves through to move from PD1 to PD4, as calulated from the geometry of the interferometer.  Accordong to Jeff and Gerado (alog 14321, D1200296), the baffle PD locations are 11.329 [inches] = 0.288 [m] apart in vertical, and 11.313 [inches] = 0.287 [m] apart in horizontal.  With a 3994.5m long arm (LHO aLOG 11611),  and 4.986 [m] for the distance between the HR surface of the BS and the back of the ITMY CP, through the thin CP, through the ITMY to the HR surface of ITM, respectively (D0901920), that's a lever arm of 3999.5 [m]. Hence, a displacement of

BS P   0.288 [m] / 3999.5 [m] = 72.01 [urad]
BS Y   0.287 [m] / 3999.5 [m] = 71.76 [urad]

The alignment offset slider gains can therefore be corrected by
BS P  72.01 / 71.2 = 1.011 [urad/"urad"]
BS Y  71.76 /70.6   = 1.016  [urad/"urad"]
or
BS P 0.989["urad"/urad]
BS Y  0.984 ["urad"/urad]

Which means the BS calibration is pretty bloody good. Go team!

Checking the calibration of the PR2 alignment sliders can be done similarly, provided we take into account the extra distance from PR2 to PR3 to BS, and the ROC of the PR3.  This looks like a job for tomorrow.

We broke the lock this morning to do this measurement.  We have returned all optics to where they were and are leaving the interferometer in the down state (I had a shot at relocking but I've been away too long it appears :(  ).

Den, Kiwamu, Evan

Tonight we again made it to low noise, although the locking procedure is still not robust enough. In the end, it seems that the sensitivity degredation is not due to a new mystery noise, but rather is a consequence of a shift in the interferometer alignment and some left-over temporary equipment.

List of changes/observations for locking is as follows:

• We found that engaging true differential hard loops (instead of differential ETM loops) during the CARM reduction sequence causes the sideband powers to drop too much. So ITM feedback should only be turned on once resonance is achieved.
• We are still coming into resonance with middling recycling gain, sometimes too low to engage the Refl 45 MHz → PR3 loop. The procedure that works most of the time is to gently engage the soft yaw loops, which brings the recycling gain above 36 W/W. Then the soft pitch loops are engaged with error point offsets (0.1 ct for differential and −0.1 ct for common). The offsets in the QPD pitch/yaw filters have not been changed.
• With good recycling gain (>38 W/W) at 2 W, we adjusted the ALS Y camera offset setpoints. The ALS X setpoints didn't seem to need adjustment.
• Kiwamu found that the TMSX yaw OSEM readbacks had moved several days ago, coincident with the amplifier swap. We don't necessarily believe that this represents a real motion of the TMS.
• In the guardian we now engage 5 Hz low-pass filters in the beamsplitter angular loops, and a slight boost in the Michelson length loop. This prevents loop instability during power-up.
• Several times we saw the return of the 0.4 Hz angular instability when powering up with mediocre recycling gain.

Once we reached the low-noise state, we again saw the excess noise that has been bothering us for the past few days. We were able to partially mitigate this as follows:

• The dsub breakout board for OMC measurements was removed. This seems to have fixed the majority of the broadband excess noise from 20 to 100 Hz.
• We retuned the test-mass angle-to-length decoupling. At first we tried using the script, but it didn't do a good job. So we did it by hand. This fixed the excess noise below 20 Hz. Mistuned A2L is consistent with the interferometer being in a different alignment state.
• The SRCL feedforward had to be retuned. Again this is consistent with the interferometer being in a different alignment state. For now, we just retuned the gain. Den suggests using a flat FF filter (which will take care of the radiation pressure coupling) and not worrying about the junk coupling above 80 Hz.
• The jitter coupling into DARM is worse, particularly around 290 Hz. Again this is consistent with the interferometer being in a different alignment state. The 290 Hz peak is also visible in the pitch/yaw IM4 transmission signals, but it seems to have been there last week as well. So it seems the jitter exiting the IMC has not changed.

The sensitivity is now 70–76 Mpc.

Finally, we looked for high-frequency frequency noise downconverting into DARM. We didn't see anything, but here is what we did:

• We used an SR785 to drive a ~20 mVpk sine wave into the CARM error point. We swept the frequency from 30 kHz to 100 kHz while watching the DCPD sum. We didn't see anything.
• Then we used the 4396B to drive a ~20 mVpk sine wave from 100 kHz to 10 MHz. We didn't see anything.

Den, Evan, Sheila, Hang

We've spent some time on ASC today.  First of all we added yesterday's changes to the DRMI ASC (25630) to the guardian, but used the new AS36 A phasing from early this morning.  This seems to work fine.

We also measured the sensing matrix for the INP1, PR3, and CHARD in the refl WFS.  For pitch, in counts/counts

Den set this up using the locking oscillator, the excitation amplitude and demod phases used are for future reference.  For yaw:

Since Den noticed that the values of the sensing matrix we got for REFL45A were fluctuating (and small compared to the others), we did not use it. 

The POP offsets have changed, and right now we are using small offsets in the soft loop error points. 

To summarize the last few days, we had some kind of alignment problem perhaps because of a temperature swing in the lvea on tuesday.  We have fixed a few things that have been longstanding oddities in our ASC system:

• We now have phases for AS36 and REFL 45 that seem sensible (they mostly within a few degrees for all the quadrants on one head, except for SA36B with has a 20 degree spread.)
• We are now using normal matrices for all the WFS, no more random zeroed quadrants. 
• We are no longer switching our AS36 input matrix around as we power up. 

This seems like great progress, although we clearly have more work to do increasing gains, and getting rid of some cross couplings between loops.  Most of the new settings have been accepted into SDF, and we think all of them are in guardian, which we are about to test.

In the past 2 weeks, the crew cleaned 286 meters of Y beam tube ending at HSW-01-058. The support tubes in that same section were vacuumed and capped also.

Commissioners continue ASC commissioning.  It's been a bit of a windy afternoon.  I did some alarm handler work.

• 21:50 Returning from solar panel cable investigagation (fil)
• 23:33 -0:58 RF Glitch investigations (Dick)
• 0:04 Magnetometer check in CER (Vinny, Brynley)

.HIGH Alarm Levels Changed for FMCS Air Handlers

Had a few FMCS alarms this week due to warmer temps and changes to heaters.  The MAJOR alarms occured when H0:FMC-CS_LVEA_REHEAT_1B_DEGF went above 100degF.  John said we should bump this up to 110degF, so I went ahead and updated the burt.snap for h0fmcs.snap.  I changed all the H0:FMC-*_REHEAT*_DEGF.HIGH from 100 to 110.  To do this:

• cp /ligo/cds/lho/h0/burt/2016/02/19/14:00/h0fmcs.snap /ligo/home/corey.gray/h0fmcs.snap.copy
  • Made edits to this file in my home directory & saved it
• Dave did the following from my home directory:  burtwb -f h0fmcs.snap.copy
  • This wrote the new file to the running copy.
  • At the top of the hour we saw that my changes were used during the autoburt back-up.

Now, if we get an alarm, it's more serious, and we should notify Bubba.

Updated fmcs.alhConfig File

Mainly updated the Guidance windows to show Bubba as the primary contact.  Updated this file, tested, and committed to the svn per instructions, here.

I've written a python script called check_model_daq_configuration which is designed to run between the 'make' and 'make install' phases of model compilation. It reports on the DAQ changes of the new model. It can be used to verify a DAQ change is needed after the code is installed, and to check if an existing DAQ channel is changing its data rate or data type.

As an example, I have temporarily changed a H1PEMMX channel's name by adding a zero to the end of the name. The code reports:

david.barker@opsws16: check_model_daq_configuration h1pemmx
DAQ configuration is changed, processing...
 
Channel H1:FEC-121_ADC_OVERFLOW_ACC_0_40 will be added to the DAQ
Channel H1:FEC-121_ADC_OVERFLOW_ACC_0_4 has been removed from DAQ
Total number of DAQ changes = 2
 

in this example I added 384 to a 16Hz channel

david.barker@opsws16: check_model_daq_configuration h1pemmx
DAQ configuration is changed, processing...
 
Channel H1:FEC-121_ADC_OVERFLOW_ACC_0_4 datarate change from 16 to 16384
Total number of DAQ changes = 1
 

Had fairly calm skies with small winds and then were quickly overtaken by winds (below 10mph to 40+mph!)  & a bit of a torrent of rain (huge puddles and gushing rain gutters) all within a span of minutes (see winds attached).  

Some mentioned hail as well.  This occured right around 3pm local time.

This has been running for a couple weeks, but I've been lagging in my logging. I've installed inertial isolation on HAM1 HEPI, it seems to be working okay. The first 3 attached plots HAM1's L4Cs (in X, Z and RY, other dofs are similar) from earlier today versus HAM1's performance on Feb 9th, before I installed higher ugf loops and blend filters. On each plot solid is the currnet inertial set, dashed are from before. Red and blue are the L4Cs, green ad brow are the ground STS. Z shows quite a bit of improvement up to 9 hz, with some amplification above coming from isolation loop gain peaking. X looks pretty good, but not quite as nice. Below .1hz there is quite a bit of gain peaking from the Hua sensor correction, and more gain peaking above 10hz, similar to Z. RY doesn't get much benefit below 1hz and gets some gain peaking from  the blend filters, but it gets a nice suppression of ~50 at a few hz, over what the old configuration got  with 2hz loops, no inertial sensors, sensor correction only on Z.

I think it's possible the blend filters could be tuned a little better, all dofs are the same blend that I stole from LLO, so some more thought could be put in there. My last attached plot is the blend being used. When I get around to it, I'll post the complementary version, but for now suffer with the raw foton display. I haven't messed with this at all, but it's possible we are being limited by IPS noise. Similar blends on the ISI are limited by CPS noise, so it seems likely.

This morning, the IFO was locked and noone was around, so I took a look at how my endstation ISI configurations affected ASC. The two configurations I looked at are:  

O1 high microseism configuration, 45mhz blends, .46hz sensor correction to St1 X&Y

The current configuration, with 90mhz blends, useism sensor correction on St1 X&Y and .46hz sensor correction on St2 X,Y&Z.

The two attached plots show ASC D/C hard and soft pitch and yaw signals. The Common ASC signals are on the first plot, Differential are on the second plot. Dashed lines are the "O1" configuration, solid lines are the "current" configuration. I don't know ASC enough to say if what matters here, but the differences aren't dramatic.The main differences are where I would expect them: the current configuration does worse at the microseism, but better over 20-60mhz. The environment is not particularly difficult today, microseism is about .5 micron (90th percentile?) RMS and winds are low. It would be good to do this measurement again under different conditions (i.e. high winds, higher microseism). 

RF90 phase for ASC-AS_A was totally off this morning but AS_B was good, it turns out that somehow the whitening and awhitening  didn't match for AS_A (first attachment).

In the attached 2-days trend of analog whitener (ch1) and digital anti-whitener (ch2) (second attachment),  the second stage whitener/awhitener was turned off by me yesterday morning and it was good, was turned back on by me later and it was good for a while, but something turned off the digital quietly after that.

I wanted to see the guardian log but it's already in the maze of cryptic file names and it's a royal pain.

Yesterday, I switch the HAM3 ISI to use the "HAM5" STS (now, actually in the biergarten), did an initial measurement to make sure the ISI was performing okay, then left it overnight. This morning I compared it's performance to HAM2, and I think we should switch all of the ISIs to used this seismometer. Attached 3 spectra show the GS13 spectra for X,Y and Z over a ~1 hour period overnight. In all DOF's over most frequencies, HAM3 does better than HAM2 now, where previously they had performed similarly (excepting HAM3's transient .6hz mystery line). Most important, HAM3 does much better where sensor correction gets us most of our isolation (~.1-1hz). This is an easy change, and should be totally transparent.

J. Kissel, J. Warner

Excited to use the buried STS (see LHO aLOG 25574), Jim had switched over to using the recently-moved-to-20 [m]-from-the-building STS for sensor correction (coupled with some other new configuration changes he's trying out; see LHO aLOG 25623). He was getting poor results when comparing internal vs external sensor correction use, so I've compared the times yesterday when we had great coherence at 10 [m] and 0-5 mph winds against today, when the STS is at 20 [m] away and there are consistent 25-30 mph winds.

The message: both the internal and external ASDs, in X, Y, and Z, are comparable in amplitude and yet incoherent at this location and these 25-30 mph wind speeds. That means the buried STS is not so promising for sensor correction use at this level of wind.

One can compare this to results originally presented by Robert at the 40 [m] location in ~15 mph winds; see LHO aLOG 19210. 

You'll notice that in both of these data sets, the contrast in amplitude difference between windy and not windy is "better" in the X DOF (perpendicular to the arm) than in the Y DOF (parallel with the arm; what we're trying to improve). 

We shall continue to take a smattering of data points to gather statistics at all wind speeds in this location.

For the impatient and saddened -- recall that we have or will employ three different methods to attack wind at EY:
(1) This buried, external STS [in the testing phase now]
(2) A new BRS [scheduled for delivery in mid-March]
(3) A wind screen system [working on getting funding] 
We're trying all three just in case one actually works. Let's hope one does!