Sheila, Alexa

We aligned TMSX again using the baffle PDs. We noticed this gave a slightly different alighment than the 'TMSX Align' script.

The TMSX guardian now has a 'PD1 Aligned' and 'PD4 Aligned' states that are currently saved to the value listed above. We have also updated the centering on the GigE camera so that the script is consistent with above centering and no longer has such a discrepancy.

We have proceeded to lock IR to the x-arm using the ALS COMM handoff. Last week, we had noticed that the COMM VCO would rail if we enabled the servo, and would manually set the frequency by adjusting the tune offset. Today we noticed that the frequency monitor was sometimes giving bogus values. We checked that this was not coming from the timing comparator. Reconnecting the output of the COMM FDD seemed to have fixed the problem. Now we can enable the COMM VCO servo to search for the IR. The IR frequency offset had to be adjusted to 21620Hz (or  -15930 Hz). Now, the guardian script 'IR_FOUND" successfully finds the IR resonance in the x-arm.

PSL Status: 
SysStat: All Green, except VB program offline 
Output power: 33.6w  
Frontend Watch: Green
HPO Watch: Red

PMC:
Locked: 3 days, 4 hours, 37 minutes
Reflected power:    1.9w
Power Transmitted: 24.0w 
Total Power:       26.0w 

FSS:
Locked: 0 days, 0 hours, 6 minutes
Trans PD: 0.586v

ISS:
Diffracted power: 8.103%
Last saturation event: 1 days, 20 hours, 47 minutes  

J. Kissel

Following the refinement of the ITM alignment slider calibration (see LHO aLOG 14265), I used the sliders as a reference to refine the calibration of the optical levers. As suspected (see LHO aLOG 12216), the correction factor to the ITMX calibration is around a factor of two. The following new calibrations have been installed as of Oct 06 2014 19:00:00 UTC (12:00:00 PDT, GPS 1096657216):
IX P = 30.87 [urad/ct]
IX Y = 25.29 [urad/ct]
IY P = 23.94 [urad/ct]
IY Y = 24.01 [urad/ct]

I still need to capture new safe.snaps for both these suspensions to make sure both the refined slider and optical lever calibrations stick.

The process:
- Step through several alignment offset values (in [urad]), record DC optical lever output (in ["urad"], the quotes indicating the to-be-refined units). I chose to get a smattering of offsets between +/- 20 [urad] surrounding the currently saved "ALIGNED" values.
- Fit slope of data points to a line (see attached). The calibration corrections are
       ["urad"/urad]    [urad/"urad"]
IX P       1.578           0.6339
IX Y       2.233           0.4478
IY P       0.9767          1.024
IY Y       1.031           0.9703
- Correct calibration.

Previous Cal        * Correction           = New Cal
48.6954 ["urad"/ct] * 0.6339 [urad/"urad"] = 30.87 [urad/ct]
56.4889 ["urad"/ct] * 0.4478 [urad/"urad"] = 25.29 [urad/ct]
23.38 ["urad"/ct] * 1.024 [urad/"urad"] = 23.94 [urad/ct]
24.74 ["urad"/ct] * 0.9703 [urad/"urad"] = 24.01 [urad/ct]

Will decouple backing pump after turbo spins down (later today)

Richard:   Pulling power and camera cables along the input arm.
	       Working on PCal chassis at both end stations
	       Ken installing receptacles for vacuum pumps in LVEA and VEAs

Gerardo:   Testing optical path of 3IFO OFI in H2 enclosure

Corey: Taking photos of ISC tables
	    Bagging parts in cleanroom by Ham2-3

Betsy: Working on 3IFO Quad builds in LVEA west bay.       

Unless someone is running a configuration test, this state is not nominal and should be corrected.  Usually, we can switch this with out too much stirring up of the platform.

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).