All automated except HEPI watchdogs.

Peter, Sudarshan, Gabriele

Today we installed the ISS second loop servo board and connected all the cables to the board itself and to the photodiodes. 
After some tweaks, we could get all the eight photodiodes showing some reasonable signals.

The attached plot shows the signals measured on the eight photodiodes, still calibrated in counts. PD1-4 shows similar signals, although the gains seem to be different up to a factor 2. The same is true for PD5-8: they are quite similar one to the other. However, it seems that the signals on PD1-4 are a bit different from the signals on PD5-8. 

We also checked that the ISS QPD is cabled and working. As shown in the attached file, the QPD signals show some resonances at 1, 3.4 and 16 Hz, which are likely coming from motion of some optics. It is interesting to note that the same peaks are very well visible in all eight photodiodes. We don't know yet if the beam entering the ISS box is already intensity modulated at those frequencies, or if we have some jitter to intensity coupling at the ISS level. It seems that all PDs see the jitter peaks at a similar level, so the coupling should be in the common path.

There is also very good coherence of all PDs with the QPD signals, at all frequencies below 10 Hz.

We started investigating the transfer function of the transimpedance and whitening, to properly calibrate the signals in terms of dP/P. To be continued.

In preparation of opening the X-arm tomorrow

Restarted X-end rotating pumps -> John W. says that Richard M. had an indication of a power "blip" at the X-end at the time the pumps shut down

J. Kissel, J. Warner

Now that Jim has discovered and fixed my blunder at ETMY recovering the missing factor of ~10 (see 14066), all STSs on site* are functional, well-calibrated, and stored correctly in the frames. Indeed, with the knowledge of the sensor noise (from T0900450) and the plethora of sensitive instruments at End X telling us ground rotation (see LHO aLOG 14047), I think we understand the signals over the entire frequency band where we intend to use them (~10 [mHz] - 10 [Hz]). Well, at least at the X-end.

*used for ISI sensor correction. The vault STS2 which is still out for repair (c.f. )

Several interesting points along the way:
(1) ETMX T240 X and ETMX BRS RY are coherent between 20-80 [mHz], as expected. ETMX T240 Y and Z are *not* coherent, also as expected. This implies that we've well-aligned the X axis of the T240 with the sensitive axis of BRS. Good.
(2) Comparing the coherence between EX RY ground motion with the corner and EY stations' translation DOFS show no coherence. It's not totally crazy to interpret this as meaning the source of ground *tilt* is entirely local to each building. The only way to tell for sure, of course, is to build more BRSs (*hint*hint*).
(3) Each station also varies in the Z DOF, therefore obviously not tilt. Another potential source of noise that might explain this at these low-frequencies is the aging STS2s. Remember EX has a brand new T240, and the remaining GND seismometers are > 10 yr old STS2s. Of course, this could also be thermal drifts, as none of the translational ground motion sensors are as thermally well-isolated as the BRS (HAM2 and HAM5 aren't even a T240 Igloo).
(4) Jim has warned me that, in the corner station, each front-end model reads out HAM2 STSA, Beer-Garden STSB, and HAM5 STSC differently. Further, comparing coherence between each of the corner station STSs, it looks like each could use an alignment tweak-up.

I spent today trying to sort out more sensor correction issues. Over the weekend I realized that sensor correction not working could be explained by bad blends. I looked at ETMY and sure enough, there are 2 T750 blends, one of which is an old version, not to be used. Additionally I found that the calibration filters for the STS weren't turned on. I also noticed that the 8hz peak that comes from HEPI looks a bit bigger than the same peak at ETMX, something Hugh had noticed in August(?) and we thought had been addressed. I tried a number of configurations, shown in the attached pictures. The first is how I found the chamber this morning, with bad blends, HEPI running and basically no sensor correction (there was a gain of .5, with the cal filter off that becomes  ~.05). The second is how I'm leaving it tonight, with the right blends, STS cal filters engaged and sensor correction on. I wouldn't really call it better. The sensor correction seems to be re-injecting noise at ~1 hz, but cutting some at .1-.2 hz. This is not what I've found on E/ITMX, where sensor correction seems to cut more noise between .1-1hz and reinjects some below. Not sure what is going on there.

B. Weaver, T. Sadecki, D. Sellers

Today we laced reaction chain cables and plugged in UIM and PenRe OSEMs.  We then began another round of R0 TFs.  TF results pending.  Offsets and gains for the lower stages are as follows:

L1UL 19173 1.565  -9586
L1LL 27412 1.094 -13706
L1UR 24370 1.231 -12185
L1LR 23612 1.271 -11806
L2UL 22949 1.307 -11474
L2LL 24546 1.222 -12273
L2UR 24855 1.207 -12428
L2LR 23608 1.271 -11804

These have been loaded to MEDM.

9:09 Heading to End to search for parts in TMS lab – Travis
9:13 Working on all Mid/End station fans – Bubba
9:55 Heading into the LVEA - Aidan
9:58 Opening GV-15 at Mid X – Kyle
10:09 Going to work in the LVEA (West Bay) – Betsy/Danny
11:08 HEPI work on HAM6 – Hugh
12:05 Taking measurements at End X – Gerardo
12:46 Back from End X – Gerardo
13:05 Returning to the LVEA to work on Test Stand – Danny/Travis
13:18 Back to work in the LVEA – Aidan
13:57 Searching for cables (LVEA) – Corey
14:05 Valve operation on IP1/2/3/4/6 and YBM/XBM turbos – Kyle
14:59 Finished working in the LVEA – Travis/ Danny
15:42 Removing RGA from PT-346 at MidX - Kyle

J. Kissel

Remembering that we may need to re-balance the recycling-cavity HSTS drives after having replaced the lower stage drivers with increased-range, modified, coil drivers (PRM, PR2, SR2, SRM; see Integration Issue 936 for links log entries), I began to balance SRM M3 this morning. 

I used the same pringle-drive, demodulation-of-the-OSEM-sensors, balancing technique that we've used in the past (see e.g., LHO aLOGs 11392, or 9453). 

I was able to confirm that the balancing *is* now worse by a factor of ~6 (by not changing the previous COILOUTF gains and simply comparing the new results with the balanced old), but was unable to balance to many better than this newly bad value. My time was limited because of priority DRMI work, but I'll continue to investigate as time allows. For now, I've left the COILOUTF gains as they were balanced to the unmodified driver, 
 
H1:SUS-SRM_M3_COILOUTF_UL_GAIN  0.972
H1:SUS-SRM_M3_COILOUTF_LL_GAIN -1.014
H1:SUS-SRM_M3_COILOUTF_UR_GAIN -0.972
H1:SUS-SRM_M3_COILOUTF_LR_GAIN  0.964

See attached for plots.

Plots, Data, and Diary live in and have been committed to
/ligo/svncommon/SusSVN/sus/trunk/HSTS/H1/SRM/Common/Data/

I finished preparing the online calibration filters for the DRMI which I started in the last week (see alog 14030). The output spectra are now monitored on projector1 (see alog 14042) in the control room as shown in the above pitcture.

I checked the HSTS and BS suspension filters in the calibration paths in h1oaf. While the HSTS suspensions looked good to me, the BS suspension did not look similar to the suspension model. In particular, the location of resonances did not look correct in the first place. So I changed the BS model by running the BS design Matlab script in the SVN and, copying and pasting the result in foton. The DC gain was then re-adjusted by hand such that it is at 8.85 x 10^-5 um/cnts (= 46.40 um / (4 x 2¹⁷ counts)). Note that this 46.4 um came from DCC-T1100602-v2. And the factor of 4 in the denominator compensates to the Euler matrix in the suspension realtime controller.

Saw the HAM6 HEPI was tripped this morning.  It tripped on a large Actuator spike Saturday about 4pm, just a few hours after I go it fixed.  Attached are the IPS spectra for HAM6 like I've plotted before--obviously V2 is back to its old ways.  Also attached are all the local IPS sensors when it tripped.  Again, V2 is not like the others and it is a bit hard to be sure but it looks like the big glitch on the V2 channels preceeds the other sensors moving off their previous values.

What to do?

Wiggle the cable some more and/or look closer at thecable going into the Pier Pod?

Change the sensor?--Requires changing both V2 & H2 sensors as these are matched to the Kaman Box within the Pier Pod--And yes you guessed it, pull the Pier Pod box and mount the matching Kaman box within.

Last week with Seb here, I started playing with sensor correction on the ETM ISI's. ETMX turned on and did good things around a half hz, as it should. ETMY so far has not done as well, so I'm still investigating there. This morning I looked at the ITM's, just seeing if filters were installed. ITMX seems to have had it's filters modified, so I used foton and gedit to fix the IIR and FIR filters. That did not happen as transparently as I would have hoped, so, my apologies to the ISC crew. After talking to Kiwamu and Sheila, they let me try to turn sensor correction on on ITMX this morning. Looks like it's working so far, only on Z ,see attached plots. The upper right plot on each picture shows most of the action, but there does seem to be a reduction in the low frequency motion on RX and RY as well, that is probably just an artifact of only having 20 minutes of data. We can't use sensor correction on other DOF's, as the blends are too low.

Over the weekend I ran a transfer function on the BS with optical lever damping filters off, and FM2 of both L2P and L2Y filters on. These two filters were installed last week (alog 14046 and alog 14022). This transfer function was taken to determine the residual motion of the BS in yaw and pit given a drive in length on the M2 stage. We can compare this to the previous rediula motion with FM1 filters on for both L2Y and L2P as measured by Stefan alog 9394.  The attach screen shot shows a side by side comparion. The red traces are all YAW/L and the blue traces are all PIT/L. And the left most windows, or the traces with square symbols are the TF with FM2 (current version), while the right most windows, or the traces with the circle symbols are the TF with FM1 on (old version). The L1Y coupling improved by about 16dB at low frequency, and 24dB at high frequency. Meanwhile, in L2P the high frequency magnitude is about the same (it's actually slightly worse by about 2dB), but at low frequency we have imporoved by a factor of about 19dB. The new filter for L2P was intended to mostly correct the low frequency motion, so this result is about as expected. Also, in the process of creating the new filters, we did not concern ourselves with any of the resonances, which is why you don't see much of a change (and it may be a bit worse) compared to the older values. Jeff and I also checked that the BS coil balancing did not change between Stefan's measurement and mine, indicating that the improvement clearly came from the coupling filter change. I was unsure why the phase between the new and old version are no longer the same, given the that old and new filters have the same phase. Kiwamu explained to me that this came from whether we were pushing too much or too little to compensate for the L2Y/P coupling. The phase can change by 180 when we adjust for this.

Next, I plan on inspecting the power spectrum of the BS oplev with the PRMI locked on the sideband. One question we have though, is what constitutes good enough residual motion?

Kiwamu, Rana, Sheila

On Friday, we measured the spot position on PR2 using the A2L technique:  vertical / horizontal   ~   5mm / 3 mm.

We wonder if the spots are far off center and might explain the low recycling gain that we see. The camera images are not detailed enough to tell us about positions better than a couple cm.

The concept of the A2L measurement is that we drive the optic angle and measure the response in the cavity length sensor (REFL 45, in this case). We assume that the LSC photodiode has a very small angle sensitivity (which is true as long as the cavity is non-degenerate and has a high finesse and the beam on the photodiode is a few times smaller than the diode active area and that the photodiode has a small non-uniformity). We also assume that the mechanical coupling from torque to longitudinal motion is smaller than the centering precision we want. I don't know if all of these assumptions are true, but we proceed as if they are.

To make the measurement robust, we want to avoid the GDS testpoint dropouts, and so we use the front end digital lockins. Unfortunately, the LSC does not have capability to drive mirror angles and the SUS/ASC do not have capability to demodulate the LSC signals. So we make a temporary workaround in the SUS DRIVEALIGN matrix by routing the L drive to P or Y**. Then the LSC drive can drive apply torque on PR2-M3 and demodulate REFL45_I. We then null the demodulated signal by also sending some of the torque to the L2L path. By taking into account the size of the optic (R = 8 cm from T0900435-v9), we can use the ratio of L2L/L2A gains to determine the beam position on the optic (we also take into account the non-unity gains in the EULER2OSEM matrix: L=0.25, P/Y=5.3).

For PR2, we used a drive frequency of 9.57 Hz and amplitude 555 counts. Since we do not have WFS feedback yet, there were large beam spot motions. The 9.57 Hz digital lockin we use to demodulate the 45 MHz demod outputs have I and Q outputs. The I-phase corrresponds to the the steady beam spot position and the Q-phase gives us information of how much the beam is moving (?).

** This hacky technique won't work for the optics being used for LSC feedback, so we need to come up with a better hack or make some model rewiring. Now that we have larger range coil drivers, we can swap the control from PRM to PR2 to allow us to measure the spots all over the DRMI. And, of course, we can use the front end dither system to automatically center the spots as well.

J. Kissel

The Message: I've cross-checked the calibration of all the ground sensors at the X End-Station, and used that knowledge to gain further confidence in their assessment of ground motion and ground tilt (second attachment). With these confirmed sensors, I tried to figure out why no one can find coherence between the ISI T240 X and either the GND BRS RY or GND T240 X (first attachment). My conclusion is that the ISI ST1 X DOF is limited by re-injected noise from ISI ST1 RY DOF between 20 and 200 [mHz], because we've copied and pasted our X T240 blend filter to RY without being conscious of this tilt-horizontal-coupling path (fourth attachment). I *think* this noise, is T240 sensor noise in this 20 to 200 [mHz] frequency band (see fifth attachment). This can be solved by sacrificing unneeded higher-frequency performance in RY (say between 1-10 [Hz]), and moving the RY blend up a bit, and making the T240 high-pass roll-off more aggressive, or "faster," as a function of frequency (third attachment is current X / RY blends).

%%%%%%%%
% The Deets %
%%%%%%%%
Calibration:
------------
In the second attachment, 2014-09-18_H1EXGND.pdf, I've calibrated everything into translational acceleration units. I summarize here, then explain the details after.
Summary: 
(1) H1:ISI-GND_STS_ETMX_X_DQ                 1e-9 [(m/s) / ct] --> Let DTT differentiate once to acceleration units
(2) H1:ISI-ETMX_ST1_BLND_X_T240_CUR_IN1_DQ   1e-9 [(m/s) / ct] --> Let DTT differentiate once to acceleration units
(3) H1:ISI-GND_BRS_ETMX_RY_OUT_DQ            1.568e-8 [(m/s^{2}) / ct]
(4) H1:PEM-EX_SEIS_VEA_FLOOR_X_DQ            7.9e-9   [(m/s) / ct] --> Let DTT differentiate once to acceleration units
(5) H1:PEM-EX_TILT_VEA_FLOOR_X_DQ            5.5e-8   [(m/s^{2}) / ct]
(6) H1:PEM-EX_TILT_VEA_FLOOR_T_DQ            5.39e-7  [(m/s^{2}) / ct]

For (1) and (2), myself and the SEI group have graciously calibrated these channels into 1 [(nm/s) / ct] in the front end, following the electronics chain as described in D1001575. So I merely have to convert to (m/s), and let DTT handle the differentiation by requesting m/s^{2} / Hz^{1/2} on the units menu.
For (3), Krishna and I have installed a similarly dead-reckoned calibration that we believe is in 1 [nrad/ct]. However, converting to translational acceleration by multiplying by g = 9.8 [m/s^{2}/rad] and by 1e-9 [m/nm], leaves a discrepant factor of 1.6 between the GND T240 and the GND BRS (see pg 1 of 
2014-09-18_H1EXGND.pdf), where there is great coherence, between 10 and 100 [mHz] and we expect the signals to be the same. Also notice the how the harmonics is the 8 [mHz] resonance pollute the spectrum (the BRS has been rung up to +/- 200 [ct] during this measurement period). That's when I invoked the PEM sensors, hoping they would be coherent enough between the sensors to cross-check, but alas, in the 10 to 100 [mHz] region, they're too noisy to really tell if the GND BRS or GND T240 are "right," so I added in the extra factor of 1.6 assuming the T240s were correct, hence 1.6 * 9.8 * 1e-9 = 1.568e-8 [(m/s^{2}) / ct]
For (4), I used the pem.ligo.org prescribed 7.6e-9 [(m/s) / ct], it matched the GND T240 very well (within the 22% quoted precision) in the frequency region where we expect them both to be sensitive to translation, i.e. above 100 [mHz].
For (5) and (6), since the instrument has not yet been successfully calibrated (see LHO aLOG 13623) I assumed the that GND T240 and GND PEM Guralp were correct, and simply scaled the PEM TILT X channel to match them above 100 [mHz], ending up with 5.5e-8 [(m/s) / ct] (and let DTT do the differentiation). I then blindly assumed that the Tilt channel uses the same calibration value, but for rotational displacement, i.e. 5.5e-8 [rad/ct]. Scaling by g = 9.8 [m/s^{2} / rad] that yeilds the above 5.39e-7  [(m/s^{2}) / ct]. It seems to match up reasonably well, and it's not hard to imagine that the electronics chain is the same for both channels, but the sensor appears to be limited by some noise incoherent with the GND BRS in the 10 to 100 [mHz] region.

The Tilt-Horizontal Coupling Model:
-----------------------------------
On the final page of 2014-09-18_H1EXGND.pdf, I plotted the ISI performance against all of the ground sensors, and noted the hump between 10 and 100 [Hz] that looked suspiciously like a blend filter bump. Going on a hunch I've had for a while Similar to what I did in my thesis, knowing that we've thus far only copied and pasted our X blend filters to the RY DOF, I used the same 1-stage, MISO model (e.q. 5.3 on pg 80) to predict how much the residual platform tilt (RY) motion is coupling into the X DOF,
                     G_x         g        x
x              =  -------   *  ----- *  F          * res RY
  from res RY      1 + G_x      w^2       T240 HP
Thankfully, at these low frequencies (f < 1 [Hz]), the ISIs have loop gain, G_x, much much greater than 1, the closed loop gain (the first term) is well-approximated by unity, and I only have to know the blend filter F^{X}_{T240 HP}.

This model shows varying degrees of success.
(1) Between 50 and 300 [mHz], this predicts the X ST1 motion exactly. ISI T240 RY doesn't show coherence, however, but I'm confident that's because it's incoherent sensor noise of the RY loop in this band -- at least up until 100 [mHz]. I'm still confused why the double-peaked microseism (100-200 [mHz]) in ISI X is very coherent with GND X, but (a) doesn't show up in nor is it coherent with the GND RY spectrum, and (b) perfectly matches the shape of the ISI RY motion projected into ISI X. 
(2) The model WAY over predicts the X displacement between 10 and 60 [mHz]. I've triple-checked my blend-filter-multiplication-via-DTT-calibration, and I'm confident I'm doing it right -- see third attachment. Steps:
    - Grab a matlab version of the blend filter from ${SeiSVN}/seismic/BSC-ISI/Common/Complementary_Filters_BSC-ISI/aLIGO/TSheila.mat
    - Ask matlab for its poles and zeros via [Z,P,K]=zpkdata(High_Pass_Filters(1)), where X is the first DOF
    - Turn them from [rad/s] into [Hz], by dividing by -2*pi
    - Copy them into foton, bode plot, and find the correct normalization factor such that the filter asymptotes to 1 at high-frequency (-160.202 [dB])
    - Copy the normalization gain, poles and zeros into DTT and multiply the correct displacement calibration, 
         gain: 1/(2*pi) [rad / (rad/s)] * 1e-9 [rad/nrad] * 9.8 [(m/s^2) / rad] * 1 / (2*pi)^2 [m / (m/s^2)]
         poles: 0, 0, 0
         zeros: [none]
(3) Independent of the model's confusion, at least it shows lots of room for improvement with GND X to ISI X in this region (100 - 700 [mHz]).