no restarts reported

I spent some time today on the automation of our inital alingment steps. 

• There is now a new gaurdian called LSC_CONFIGS that manages suspensions and all of the length sensing and control for the various configurations that we are using for inital alingment, or comisioning (PRX, SRY, XARM locked on IR, ect).  This is just the code that was previously used for this purpose in the ISC DOF guardian.  This can now be used as a subordinate for intal alingment gaurdians. 
• I incorporated Dan's offloading script (alog 14195) in the the ISC_DOF guardian, at least for the INPUT alingment.  Right now there is no intelligent function that decides when the input alignment is good enough, the user just has to manually change the requested state to OFFLOAD_INPUT_ALINGMENT when they think it is good.   We can aslo use this for PRM and SRM, but that is not implemented yet.
• I have incorporated and combined Gabrielle's script for alinging the Y arm to the IR beam (alog 14296) into the ISC_DOF guardian.  It is working well.

Following Arnaud's work on the SRM M2 stage (alog 13558), I made a couple of modifications on the L2P filters that he implemented in this past August. It is now engaged, but I did not get a chance to evaluate the performance of it yet.

(Merging the two filters into one)

First, as he mentioned in the alog, a filter in FM2 that he installed was numerically unstable. It seemed that the FM2 filter had been meant for the inverse of the P2P response which grew up at high frequencies as f⁴. Therefore the filter was accidentally designed to return incredibly high values at the Nyquist frequency. In order to fix this issue, I decided to combine this filter with the other one, i.e. L2P such that the high frequency response becomes flat. Even though this idea of combining two or multiple aggressive filters into a moderate one is generally good, foton did not allow me to do this due to too many numbers of poles and zeros this time. I could have split the filters again into two moderate ones, but instead I decided to drop off some pairs of poles and zeros which are so similar to each other that dropping them did not change the overall response so much. Also, I took out a 2nd order zero at 20-ish Hz in order to let the L2P decoupling filter roll off at high frequencies because I was worried about saturation in DACs especially for the 3f locking. The attached is the transfer function of before and after the modification. Of course, now the filter is not unstable any more.

As seen in the attached, the modified version is accurate until 3 Hz or so and it completely deviates at high frequencies. I am hoping that this is OK because the M2-M3 cross-over is now as low as 4.5 Hz and therefore the discrepancy at high frequencies does not matter. I did not get a chance to see the performance of this filter yet.

no restarts reported

We noticed that in the past there were some long lags between turning the fans on in the Laser Room and turning the two airconditioners on. This led to temperature spikes because the fans rapidly heat the room if the AC is not on. The source of the problem is that the Mitsubishi air conditioners can not be turned on by the same Unitronics control system that controls the fans and must instead be turned on at the thermostats in the Laser Room. This might be hackable, but for now, the proceedure will be to turn on the Laser Room fans at the Unitronics box in the Ante Room instead of at the Unitronix box outside the PSL. The full proceedure is attached to this log and posted at both Unitronics boxes. 

Robert, Rick

The story made brief

In a previous alog entry I pointed out that most of the intensity nosie we see in transmission of the IMC is due to input beam jitter converted to RIN due to an IMC misalignment. Today, to prove this, I improved the IMC alignment in three steps:

1. First of all, I tuned the DC alignment by moving the beam on MC2_TRANS QPS. This improved significantly the power transmitted by the IMC, as visible in the first plot. The IMC transmission increased by 7%, from 2020 counts to 2160 counts (in IM4_TRANS_SUM). This re-alignment also reduced the intensity noise at the output of the IMC.
2. However, the RIN was still highly non stationary, as shown in the spectrogram attached as second plot. I used some non-stationary analysis technique (described later) to track down the RIN modulation to the residual motion of IMC_DOF_1 yaw. Measuring the loop, I found that the UGF was likely few mHz, so I increased the gain by a factor 20 (gain from -1 to -20). I applied the same cure to DOF_1_P and DOF_2_*. This reduced a lot the error signal residual RMS, and also the RIN.
3. I added two offsets to DOF_1_P and DOF_1_Y, both -20 counts. This reduced even further the RIN at the IMC transmission.

The third attached plot shows the improvement in RIN in transmission of the IMC. Now it is at a level of 1e-6 at 10 Hz and 2e-7 at 100 Hz. It's almost a factor 10 better everywhere.

It's interesting to note that the RIN is still non stationary, so we should improve further the IMC alignment accuracy. I could not increase more the gains of DOF1 and DOF2, since I got a 1 Hz instability (as expected from the open loop transfer function). However, my intuition is that the IMC mirrors are pretty much not moving, and instead the input beam pointing is moving a lot. So we should servo the input beam to the IMC cavity axis with some Hz of bandwidth. This is what we did at Livingston, where the input beam motion was limited by air currents in the PSL room. I believe a similar approach should be used here. This is much better than high bandwitdh loops on the mirrors, since they should be our best reference.

Some details

Non Stationarity analysis

To study the dependency of RIN on IMC angular fluctuation I used a code developed for a similar task at Livingston. See more details here. In brief, i compute the band-limited RMS of the IM4_TRANS_SUM signal between 50 and 10 Hz, and correlate this with the low frequency content of the IMC alignment error signals. The scatter plot in the 4th attachment shows the correlation between each IMC angular DOF and the BLRMS. There is a clear correlation with DOF1_Y. From the scatter plot we can also see that there is an offset on the error signal.

A more quantitative analysis can be obtained by fitting the BLRMS time series with a linear combination of a constant, the error signals and their squared values. The procedure I used is a slightly modified version of a LSQ fit, and it gives me a ranking of the signals as a function of their importance in improving the fit. The code is attached to this entry. Basically, the first step is to find which one of the channels (constant, error signals or their squares) can be best fit to the BLRMS. finding the minimum residual squared error. Typically a constant is the first winner. Then the procedure is repeated with the residual, looking for the single bets channel to furher reduce the rfit error. At each step I search for the channel that reduces the error the most. The procedure is repeated iteratively.

The 5th plot shows the result of the fit before any improvement on the IMC alignment. Most of the noise fluctuations could be explained by angular motions. The 6th plot shows the ranking of the channels (the bigger the bar, the most important the channel is), confirming that DOF_1_Y is our best candidate.

DOF_1 bandwidth

The 7th plot shows the measured open loop transfer function of IMC DOF 1 Y before and after my gain increase. The loop had a bandwidth of probably 3 mHz with the original gain of -1. The plot shows the OLTF with a gain of -100, giving a badwidth of 300 mHz. I did not measure the other DOF1 and DOF2 loops, but I could increase their gain in a similar fashion.

After some tweaking, I reduced the gains to -20, since the error signals were showing a large 1 Hz instability, which is consistent with the measure OLTF. However, we are clearly still limited by the residual motion of the beam with respect to the cavity axis.

I'm leaving this configuration running, as shown in the attached screenshot. In case there is any problem, revert back to the original configuration by reducing the gains to -1 and removing the two offsets. No other modification will be needed.

WFS offsets

Since I don't like much the idea of running WFS loops with offstes, I tried to zero them by moving the beam on the WFS using the picomotors, but I couldn't get any effect at all, no matter how big step I was moving.

model restarts logged for Fri 03/Oct/2014
2014_10_03 02:41 h1fw0
2014_10_03 14:26 h1fw1

unexpected restarts of fw's

Alexa, Sheila, Kiwamu

ALS COMM is robust, we can easily transition from green to IR lock. We measured the noise to be about 20 Hz RMS.

Meanwhile, we had a bit of trouble with ALS DIFF. First the DIFF VCO is railed. To handle this we used an ezca servo to feedback to ETMX. The ezca command we used is: ezcaservo -r H1:ALS-C_DIFF_PLL_CTRL_OUTPUT -g 100 H1:SUS-ETMX_M0_TEST_OFFSET. We also had to set the tune voltage to 5.526V in the Y VCO.  This technique would bring the DIFF VCO into range so we could engage the DARM feedback. We were able to close the loop with a lower gain (input matrix set to 0.05). We quickly leanred that the L2P  in both ETMX and ETMY are bad (ETMX was worse than ETMY). We need to examine these filters again, and do something similar to what was done with the BS.

The document attached shows the Yaw motion (first page, left) and Pitch motion (second page, left), Friday morning at 1 am PT, for all test masses.

All units were controlled with the blend configuration imported from LLO. The sensor correction was OFF.

Compared to the previous nights measurements, ITMY optical lever has been re-centered. Values look reasobable now. Also the combs in ETMY are gone.

ITMX does look higher than the others, as seen during the previous days by the commissioners in the time series, but it might be due to calibration error (see Jeff's alog).

In general:

- the Yaw rms values seem dominated by micro-seism (or sub-microseism for ETMY)

- the Pitch rms values seem dominated by the 0.5 Hz suspension resonances

Alexa, Sheila, Gabriele

We closed the servo  loops for the relf wfs IR  y-arm centering. The error signals are fed back to the test masses as follows:

The DC centering must be on; these were unchanged. I have also taken a screen shot just in case (the input/output matrices are the same for pitch and yaw).

J. Kissel, J. Driggers

There's been some confusion about why the ITM ISIs are performing so differently. This resurrected memories of mistrust in the optical lever calibration, that I'd talked to Thomas about in June (see LHO aLOG 12216). That aLOG leaves it at "we should confirm the calibrations once we have arms again." The idea will be to cross-check the calibration  using the alignment sliders, which can be precised calibrated using the green beam and baffle PDs as a 4 [km] optical lever. The details of the process are below, but in summary, the refined calibration of the sliders is
IX P = 15.589 [ct/urad]
IX Y = 43.835 [ct/urad]
IY P = 19.920 [ct/urad]
IY Y = 46.700 [ct/urad]
which, for IX P is a ~50% correction, but the rest is a ~10-20% correction.

We have updated both the OPTICALIGN [ct/urad] gains, and corrected the "cal" [ct/urad] FM0 in the M0 LOCK P and Y filter banks, saved the newly corrected alignment offsets, and confirmed that the refinement of gain and slider value brings the optic to the same place.

DETIALS
------------

Currently, the alignment slider calibration gains are
P  23.219 [ct/"urad"]
Y  51.689 [ct/"urad"]
based on dead-reckoned knowledge of the actuation chain (see LHO aLOG 4730).

Keita, Alexa, and Shiela recently went through the exercise of finding the green beam down the arms (see LHO aLOG 14201 for ITMX, and LHO aLOG 14161 for ITMY) using baffle PDs and the SUS alignment sliders. 

From these aLOGs, we know that the ETMY baffle PDs, and ETMX ERM Pattern are at the following ITM alignment slider values:
                 P ["urad"]     Y ["urad"]
ETMX Top Stop     65.2     
ETMX Bot Stop     84.2
ETMX Lef Stop               -20.2
ETMX Rig Stop                3.8
ETMY PD1          165      -105.3
ETMY PD4          197       -139
for displacement claimed by the sliders of
      delta ["urad"]
EX P   -19 * 2 = -38
EX Y   -24 * 2 = -48
EY P   -32 * 2 = -64
EY Y   33.7* 2 = 67.4 
where the factor of 2 comes from the single bounce, optical lever effect.

From an older aLOG when Keita had performed a similar calibration (see attachment to 9087), we know the ETMX baffle PDs are a distance 11.76 [inches] = 0.2987 [m] apart in vertical, and 11.77 [inches] = 0.29895 [m] in horizontal. From D0900949, we know the pattern has an inner-most diameter of 226 [mm] = 0.226 [m]. The length of the arms is 3994.5 [m], confirmed by older measurements during the HIFO days (see LHO aLOG 9635 and 11611).
That means the physical displacements are
EX P   0.226 [m] / 3994.5 [m] = 56.6 [urad]
EX Y   0.226 [m] / 3994.5 [m] = 56.6 [urad]
EX P   0.298 [m] / 3994.5 [m] = 74.6 [urad]
EX Y   0.298 [m] / 3994.5 [m] = 74.6 [urad]

Hence the slider gains should be corrected by
IX P   56.6 / 38   = 1.49 [urad / "urad"]
IX Y   56.6 / 48   = 1.18 [urad / "urad"]
IY P   74.6 / 64   = 1.17 [urad / "urad"]
IY Y   74.6 / 67.4 = 1.11 [urad / "urad"]
or
IX P  0.67138 ["urad"/urad]
IX Y  0.84806 ["urad"/urad] 
IY P  0.85791 ["urad"/urad]
IY Y  0.90349 ["urad"/urad]



The new slider gains are therefore
IX P   23.219 [ct/"urad"] * 0.67139 ["urad"/urad] = 15.589 [ct/urad]
IX Y   51.689 [ct/"urad"] * 0.84806 ["urad"/urad] = 43.835 [ct/urad]
IY P   23.219 [ct/"urad"] * 0.85791 ["urad"/urad] = 19.920 [ct/urad]
IY Y   51.689 [ct/"urad"] * 0.90349 ["urad"/urad] = 46.700 [ct/urad]

Which means the former alignment values, in ["urad"],
                     P               Y
IX Aligned         75.4            -7.6
IX Misaligned        0            -52.75
IY Aligned         182.4          -116.6
IY Misaligned        0               0
now become (["urad"] slider value * [urad/"urad"] = [urad] slider value)

                      P            Y
IX Aligned         112.35       -8.968
IX Misaligned        0         -62.245
IY Aligned         213.41     -129.43
IY Misaligned        0           0   

We have updated both the OPTICALIGN [ct/urad] gains, and corrected the "cal" [ct/urad] FM0 in the M0 LOCK P and Y filter banks, saved the newly corrected alignment offsets, and confirmed that the refinement of gain and slider value brings the optic to the same place.

After it was decided that the existing design for the TCS HWS table light pipes was insufficient to protect the vacuum envelope we decided to use what everyone else uses, some 10" self sealing flanges and the lexan viewport assemblies. Anyhoo, the commissioners should be happy I won't need to be thumping around on HAM4 any longer.

The rotation stage on ITMy had become unresponsive last week after some cable dressing was done. Restarting Beckhoff had proven ineffective and Fil was unable to find any lose cables. Unplugging and replugging the interlock bypass on the D1300131 box. This possibly had the effect of resetting the relay that blocks communication to the relay stage. Whatever happened the rotation stage is working again.

Andres covered from 10:00 - 11:00. Thank you Andres.

09:15 Betsy to LVEA West bay to work on 3IFO SUS
10:43 Aaron pulling cables between HAM1 and the PSL closet
11:17 Kiwamu to end Y to align optics on the ISCT table
11:56 Corey walking around IMC for ~ 5 minutes
12:00 Chris to end X to check on moth situation
12:04 Aaron pulling cables over HAM1 and HAM2
12:36 Sheila, Kiwamu at end Y
12:40 Aaron done pulling cables over HAM1 and HAM2
12:44 Chris back from end X
14:08 Andres to TMSX lab to look for parts
14:42 Andres back from TMSX lab

Peter K, Gabriele

Loop performance, excess sensing noise

As reported yesterday, the second loop servo didn't have enough gain, so this morning we modified one switchable stage of the board to include a x10 gain. Unfortunately, that stage is an inverting one, so we can't really switch it on and off with the ISS second loop closed. This stage is controlled by H1:PSL-ISS_SECONDLOOP_ADD_GAIN.

Using everything we have in the board (maximum gain at +40dB, x10 stage, integrator and boost) we could engage the second loop and get the performance shown in the first attached plot. The red and blue traces are the in-loop and out-of-loop signals, calibrated in RIN, when the second loop is open. The green and maroon traces are again the same signals, with the loop engaged with maximum gain. The cyan and magenta traces correspond to the integrator and boost switched on. We're getting a bandwith of about 1 kHz.

We can see that the out-of-loop signal shows an excess of noise with respect to the in-loop signal, up to about 60 Hz. The out-of-loop RIN is about 1e-6 at 10 Hz and 2e-7 at 60-70 Hz. We can conclude that our ISS second loop photodiodes are limited by sensing noise of some kind at this level.

The second plot shows a comparison of the error signals (sum of photodiodes 1-4 and sum of photodiodes 5-8) with one or the other in loop. The performance is very similar in the two cases, so the amouint of excess sensing noise is about the same in both sets of sensors.

The last plot shows that there is some coherence between the out-of-loop signal and the ISS QPDs. This is true at least at low frequency, below 10 Hz. The QPD signals show a structure at ~18 Hz which is very similar to the one visible in the out-of-loop signal, altough there is no coherence. It might be due to a highly non stationary coupling, but we're not sure of that. So it is likely that at least some of the excess sensing noise is due to beam jitter to intensity noise coupling at the ISS array. to imrpove this, we should try to move the beam using the picomotors and looking at the out-of-loop signal noise in the 10-60 Hz region.

How to switch on the ISS second loop

The medm screen of the second loop is wrong, in the sense that the buttons are connected to the wrong switches. I created a new screen for the second loop, which for the moment is living in /ligo/home/controls/gabriele/SecondLoop.adl. Once finalized, we should move it to the right place.

1. Switch off the connection between second loop and first loop (H1:PSL-ISS_SECONDLOOP_CLOSED to low level)
2. Ensure that the additional gain path is on (H1:PSL-ISS_SECONDLOOP_ADD_GAIN to high)
3. Move the loop gain to 0 dB (H1:PSL-ISS_SECONDLOOP_GAIN)
4. Engage the second loop servo (H1:PSL-ISS_SECONDLOOP_SERVO_ON to high) and tune the reference level (H1:PSL-ISS_SECONDLOOP_REF_SIGNAL_ANA) to move the sencond loop output signal (H1:PSL-ISS_SECONDLOOP_SIGNAL_OUTMON) as close as possible to zero. You won't be able to get zero, just ensure that it is oscillating with a rough zero mean. You might need to tune the reference signal at the mV level.
5. Switch on the connection between second loop and first loop (H1:PSL-ISS_SECONDLOOP_CLOSED to high level). Some times this kicks the first loop out of lock, but usually it is able to recover withtin few seconds. Watch the diffracted power, since any small error in the reference signal for the second loop will have a large impact. You might have to retune the reference signal
6. Increase the gain to the maximum (+40 dB) and engage boost (H1:PSL-ISS_SECONDLOOP_BOOST_ON) and integrator (H1:PSL-ISS_SECONDLOOP_INT_ON)

To do

1. automate the whole switch on procedure, including th zeroing of the second loop output tuning the reference signal
2. when the IMC drops lock, we should automatically switch off the ISS second loop
3. try to move the beam into the array using the picomotors, to minimize the out-of-loop noise

After fixing the not taking Damped TF problem and the channel list mismatch problem, we took a full set of transfer functions for 3IFO Quad-09. The results data are posted below and have been added to the SVN repository. There are a couple of anomalies in the data. 

(1). The last peak of the Damped M0 data in "Y", "R", and "L" are shifted up. 
(2). The R0 "Y" DOF appears to not be damped where as the other 5 DOFs are.  

Note: The staging building test stand hardware and software are somewhat down level to the H1 & L1 test stands.   

For those interested in looking closer at QUAD model parameters, attached are plots comparing all of the QUAD Main Chains when suspended with wires and also when suspended with fibers.   Note, if QUAD data is missing for one of these configurations it's because there was no clean data available.  Between the 2 plotted configurations, all 12 (H1, L1, and 3IFO) QUADs are represented.  Note, I tried to chose data sets that had the same or similar environmental conditions, but it was difficult due to the fact that some QUADs were reworked on test stands and some were reworked in chamber.  In all cases they were mounted on Solid Stack Test Stands or Locked ISIs and in-air.

Data is committed to the svn and can be found at:

/ligo/svncommon/SusSVN/sus/trunk/QUAD/Common/Data/

There does not seem to be a pattern in the data of the 2nd pitch mode peak which are clustered by a specific type of suspension (ETM vs ITM, or wire segment hang vs wire loop hang).

After consulting with Keita and TMS group, we finalized where we wanted the QPD cables to go [we have to be EXTREMELY careful with cabling the QPDs because if the wrong cable is connected to these guys we run the risk of frying the QPDs---several QPDs were damaged during the H2 TMS Installation].  Basically, we stuck with what the drawing (D1300007) calls out.  But I made sure to clearly label the external flanges to where the QPDs are connected (see photo).

Below is the latest cable run-thru with Flanges noted: