It occurred to me last night that instead of doing measurements, I could figure out the gains from comparing the results of one measurement I remembered the settings for (because it was recent, but wrong) to a more distant measurement that was "right"(or at least things work). The GS-13's have to be run in low gain, or the St1 actuators will saturate them, so they are known. Looking at my data from the 14th (or 4th) of Nov, 2013 (first 2 plots, with "unknown" but "correct" gains) and comparing the magnitudes with the measurement I took on the 6th of this month (plots 3 & 4, with L4C and T240 in low gain) indicates that the T240 should be in high gain, L4C and GS-13 in low gain. 

(Kiwamu, Alexa)

We adjusted the PRM M3 L2P drive align gain to -1.36. This reduces the coupling of length drive to pitch. We deduced this by driving PRM_M3_LOCK_L at several frequencies and seeing the effect in ASC_REFL_B_DC_PIT.

I have been checking the whole ASAIR_A and _B electronics chain all the way from the diodes to the ADCs.

In summary:

• ASAIR_A has a smaller transimpedance gain at 45.5 MHz than that of the test document.
• ASAIR_B looks healthy.

Note that I used the old calibration coefficient for estimating the amount of amplitude modulation in the AM laser (see alog 9630).

ASAIR_A_RF45 (S1300523)

Remarks:

The transimpedance seems smaller by a factor of two than that of the test sheet at 45.5 MHz. All the signal chain after the PD looks healthy.

According to the test sheet from Caltech (S1300523), the transimpedance of the high-rf output should be 803 Ohm. However, it seems that the AM signal I obtained was smaller than the expected by a factor of two. If I we blame the transimpedance for this discrepancy, the transimpedance is smaller by a factor of two.

• DC laser power = 120 mV / 100 Ohm / 0.67 A/W = 1.79 mW
• Expected AM signal when driven by 0.1 Vdrivepp = 5.13 mW x (1.79 mW / 1 mW) x 0.1 Vpp x 0.67 A/W x 803 Ohm = 494.0 mVpp
• Measured AM signal at the SMA jack of the RFPD enclosure = 248 mVpp
  • This is smaller by a factor of two.
  • If we blame the transimpedance, it must be 403 Ohm rather than 803 Ohm.
• Hereafter, I ignore the PD response and use the 248 mVpp signal to check the electronics chain in the downstream.
• Expected IF signal at I-mon = 248 mVpp x 10.9 x 1/2 (single-ended) = 1.35 Vpp
• Measured IF signal at I-mon = 1.42 Vpp
  • good agreement with a small discrepancy of 5%.
• Expected ADC counts = 248 mVpp x 10.9 x 2^16 counts /40 V = 4428 counts pp
• Measured ADC counts = 4060 counts pp
  • This is within 10% deviation. The signal chain after the PD is healthy.

ASAIR_B_RF18 (S1200242)

Remarks:

The signal chain looks OK. The demodulated signal at the ADC is bigger than the expected by 12%. Good enough.

The demod board has a special one where it has a diplexer upfront. According to the test sheet (S1001003), the conversion gain of the whole demodulation box for 18 MHz is 13.8.

• DC laser power = 823 mV / 2k Ohm / 0.4 A/W = 1.03 mW
• Expected AM signal when driven by 0.1 Vdrivepp = 5.13 mW x (1.03 mW / 1 mW) x 0.1 Vpp x 0.4 A/W x 1.6k Ohm (see the plot from alog 9719) = 338.0 mVpp
• Expected IF signal at I-mon = 338 mVpp x 13.8 x 1/2 (single-ended) = 2.33 Vpp
• Measured IF signal at I-mon = 2.8 Vpp
  • this is too big by 24 %.
• Expected ADC counts = 338 mVpp x 13.8 x 2^16 counts /40 V = 7642 counts pp
• Measured ADC counts = 8577 counts pp
  • This is bigger by 12%. Good enough.

ASAIR_B_RF90 (S1200242)

Remarks:

The signal chain looks OK. The demodulated signal at the ADC was smaller than the expected by 13%. Good enough.

According to the test sheet (S1001003), the conversion gain of the whole demodulation box for 91 MHz is 11.4.

• DC laser power = 1.03 mW
• Expected AM signal when driven by 0.1 Vdrivepp = 5.13 mW x (1.03 mW / 1 mW) x 0.1 Vpp x 0.4 A/W x 1.2k Ohm (see the plot from alog 9719)= 254 mVpp
• Expected IF signal at I-mon = 254 mVpp x 11.4 x 1/2 (single-ended) = 1.45 Vpp
• Measured IF signal at I-mon = 1.32 Vpp
  • this is 9% smaller.
• Expected ADC counts = 254 mVpp x 11.4 x 2^16 counts /40 V = 4744 counts pp
• Measured ADC counts = 4210 counts pp
  • This is smaller by 13%. Good enough.

Transimpedance measurement of resonant-type RFPDs

To investigate the too-low-transimpedance in REFL_A(S1300523). I measured the transimpedance of S1300523 and S1300526 (whic is a spare, ) to make a comparison. Of course this measurement relies on the AM laser calibration. I believe that the calibration of the AM laser calibration is better than a factor of two and therefore I claim that the transimpedance is actually lower than 803 Ohm as measured.

I used HP4395A and the AM laser. The calibration of the data was done such that the transimpedance of S1300523 becomes 403 Ohm at 45.50298 MHz. The same calibration coefficient was applied on S1300526. The plot below shows the results. The vertical and hrizontal line indicates 45.5 MHz and 403 Ohm respectively.

From this measurement, I conlude that S1300523 is behaving fine. Also the two RFPDs consistently showed lower transimpedance gain by roughly a factor of two than that reported in the test sheets at 45.50 MHz. A possible explanation I can thinkg of at this point is that the test sheets were somehow consistently overetimsted the transimpedance gains.

model restarts logged for Wed 10/Sep/2014
2014_09_10 10:24 h1hpiham2
2014_09_10 10:24 h1hpiham3
2014_09_10 10:24 h1iopseih23
2014_09_10 10:26 h1isiham2
2014_09_10 10:26 h1isiham3

no unexpected restarts. h1sieh23 was dac-locked and needed a restart.

Peter Bojtos, Robert S, Dave Barker

This was a test carried out on two microphones at CS and one at EY with three DAC Box associated with these microphone. I left EX untouched because that setup is working and I am using that as a baseline to check everything else.

 My initial conclusion after looking at the power spectrum and time series plot:

1. MIC S1400302 (at CS) seems to be working with every DAC Box (named B, G and Y). This was not the case when I tested it on Monday. I only tested with DAC B and G and it worked with DAC G but not B. Fishy.

2. MIC S1400299 (at CS) seems to be little arbitrary but may be still working. This was tested with all three DAC Box.

3. MIC S1400300 (at EY) is not working with any DAC Box.

4. Also, the AA chassis that takes the microphone at CS seems to have 10X additional gain compared to EY.

The power spectrum plot and time series plot are attached for comparison.

Lisa, Sheila, Rana, Kiwamu

One of the goals for tonight was to test out the PR3 low frequency oplev servo to see if it improves the long term locking stability. And it helped.

We could keep the carrier PRMI locked for more than 30 minutes which is long enough to perform some studies.

The highest recycling gain we obtained tonight was roughly 15. Still too low. The investigation continues.

(Angular drift)

The PR3 oplev was engaged all the time during the commissioning tonight. We used the pitch loop and left the yaw loop off all the time. This was good enough to keep the PRMI locked for a long time.

On the other hand, we did not have to pay attention to the BS oplevs -- the BS angular drift is not significant or maybe it is not drifting in the carrier lock condition. Indeed, we did not observe a significant long term degradation in the dark port beam pattern. I attach a vide of the dark port when the carrier PRMI was locked. Note that the BS oplev loops were engaged all time time, which take care of only damping. So there was no control at low frequencies via the opelv.

(Some attempt for a better alignment)

The highest build up we obtained tonight was about 3000 counts in POPAIR_A_LF. Compared with the simple MICH configuration, this is 500 times brighter light (it was about 6 counts when a simple MICH was locked with PRM misaligned.) If we ignore a mode-matching effect, this corresponds to a recycling gain of 15.

However, when the intracavity power was maximized, we noticed that the REFL beam had a terrible beam shape -- the prompt reflection from PRM and the leakage fields were far apart. I will post a video of the REFL beam later. So we suspected a large misalignment in IMs.

We then tried moving a combination of IM3 and IM4, and a combination of IM1 and IM4 to see if we can make both the build-up and refl beam better. This was not successful. We could not optimized both at the same time. Tomorrow, we will check out the ABCD matrix for the IMs to make sure we are moving the right degrees of freedom.

(Some loop studies)

In parallel to the low-recycling-gain study, we measured the open loop of the length loops. The UGF of PRCL was about 40 Hz and MICH was 8 Hz. The phase looked OK. We will quantitatively cross-check the loops with models tomorrow.

I readjusted the demodulation phase of all the REFL WFSs. This time, instead of using a IMC excitation techqnue, I simply used a free swinging PRX signal and minimized the q-signals. The phases were adjusted such that every segment has the same sign.

In the process, I found that five RF cables disconnected from the field rack. Bad. This explains why we did not have a good signal in REFL_A_RF9_SEG4. I plugged them back in. Now they can see reasonable signals.

=======

-Punchline: I screwed up the measurement settings. These are critical in the calculation of the blend filters. I have loaded new blends based on old data, so ITMX is running, but not in an ideal configuration, as the controllers were designed around a different data set. I will work on getting proper data (last time, I swear!) this weekend. 

-More detail: If you look at the first attached pdf, the second page shows what the complementary filters should more or less look like, the gain for the sum (say, for the X loop) should be ~1 all the way across and the phase for the sum should be zero. The same page on the second plot shows what was causing the problems at ITMX. The gain for the sum does not stay at 1 and there is a large loss of phase in the 1-10hz region. This was causing loops to go unstable. 

-I didn't notice this at the time, because the commissioning script that calculates the filter produces a plot of the complementary form of the filters (shown in the first png file, the sum is the thicker line at 0 dB) that looks complementary. Something is wrong, somewhere.

-The form that gets loaded into Foton (second png, produced by the same script) should have alerted me, but it's a much less straightforward plot. The third and fourth pngs shows the same plots of the "good" blends, currently installed. 

-The only clue I would have had before trying to run things at this point is that the T240 and L4C blend filters should have been closer together on the Foton plots. Maybe there were other clues, but that's all I can see right now.

-How I figured this out: 

-I worked through the seismic commissioning scripts, designed my isolation loops and installed everything. Damping turned on (although, the first time round the St1 outputs were low) but turning on loops was difficult. 

-When I took open loop measurements in DTT my UGF was lower than expected. The magnitude shown in png #5 (the different traces are different loop gains, blue is a gain of 1, so look at blue) shows the UGF is much lower than design, I designed for 30 hz. The 6th picture shows that the loop has 0 phase at 30 hz and the shape wasn't right, it looked tilted relative to my design. My loop design for St1-X is in the last picture.

-Looking at blends, isolation loops and every other filter I could think of loaded in Foton didn't really yield any help. It wasn't until I ran JeffK's plot_current_blends script (which really should be a function, it would be nice) which produced the attached pdf's that I could see that the blends weren't complementary. After a lot of deleting, reloading and other shenanigans, as well as hours on the phone with Rich and Hugo, I decided to try loading old (Nov of last year!) data and seeing what blends I got. 

-Problems fixed. 

-Head-desk.

H. Radkins, J. Warner, S. Biscans, J. Kissel

Here's a prioritized list of things the LHO SEI Team + Seb intends to tackle (or start tackling) over the next 10 days or so.

(1) Fix problems with ITMX ST1 [[DONE -- aLOG pending shortly]]

(2) (a) Add control of sensor gain and whitening settings to matlab transfer function scripts to ensure they're *always* in the right configuration. 
    (b) Fix blend filter design plots in commissioning scripts to show the blend design MUCH better than it currently does.

(3) Finish commissioning HAM4 and HAM5 ISIs and HEPIs

(4) Support commissioning efforts with "spot" improvements, if possible.

(5) Resurrect Fabrice's Standardized Commissioning Steps list

(6) Use (5) to assess all chambers, to see where we are -- at least with the "fixed" stuff

(7) Gather "current performance" plots for all chambers

(8) Gather HAM2 and HAM3 in-vac, HEPI unlocked, floating, with fluid TFs and HEPI-Position-controlled ISI TFs to help investigation with HAM4 and HAM5 results

(9) Resurrect plant comparison script and use it to compare in-vac transfer functions between HAM and BSC ISIs

(10) Teach Jim and Hugh how to commission sensor correction / feed forward.

(11) Play with Beam Rotation Sensor at EX -- try to get some performance improvements

(12) Think hard about HAM and BSC performance models.

We made two additional experiments with the unsuspended, isolated pilot (Corning ETM02) ITMY, in the west bay of the LVEA. (Moreno, Landry)

1) We applied FirstContact to the HR surface, let dry over 24h, measured no excess charge (no more than |3V| at 1" from HR surface, AR surface, and barrel), ripped the FirstContact off the HR face in ~20s *without* doing any TopGun ion gun blowing, and then measured the voltage 1" from the HR surface. We find the resultant charge negative, with a claimed voltage of ~-22kV, -22kV and -22kV at three points across the face of the optic.  Assessing the AR surface, we find a voltage 1" from the AR face of -12.1kV, -12.1kV and -11.3kV.  

2) We made another trial in which after FirstContacting, we removed the polymer film while TopGun blowing to neutralize the surface.  We followed the same basic procedures as outlined in alog 13104, with slightly different timings. The primary change in the experiment was the grounding of the optical table, and the addition of a grounded Al foil shield (see photo attached).  The addition of the shield and ground dramatically changed the behaviour seen in the prior experiment linked above: generally, individual measurements that took minutes to settle exponentially to some voltage now settled in seconds.  Furthermore, the apparent long time constants for which it seemed necessary to continue with the ion gun (~9min total) were not observed in this experiment. We took 2 minutes to pull the FirstContact, which included a coincident 2 minute TopGun blow, plus one additional minute of TopGun blowing, and measured +18 to +30V at several locations 1" from the surface of the HR side of the optic.  

We'll repeat experiment #2 one more time, with shorter intervals between electrometer measurements, to better understand the field sizes, signs, and time constants.

A new version of dataviewer has been built and installed for Ubuntu and OS X control room computers.  This version allows unsigned integer data to be viewed properly, fixes a bug where the mean value of integer data in minute trends was always 0 or close to it, and allows selection of short channel names from the channel menu.  WP 4837.

Following the recent replacement (generic maintenance) of PT120B, PT170B and PT180B Cold Cathode gauge sensor+electronics, there has been an apparent 25% discrepancy between the indicated pressures of the new PT170B and PT180B gauges -> Swapping the removable electronics between the two units has (surprisingly) resulted in both read backs being as expected in both absolute and relative pressure values 

As stated yesterday, I changed the ITMy oplev laser and saw no change in the sawtooth pattern in the oplev yaw.  I noticed that the curtains of the cleanroom that is still sitting over the Y manifold spool were resting on the oplev receiver pylon.  Today we moved that cleanroom and saw, once again, no change in the sawtooth pattern.  See the attached dataviewer screenshot, where the signal gets noisy is when we moved the cleanroom.  Will continue to investigate.

Changed location of ESD bias filter at ETMX and ETMY to before the 10kohm resistor instead of after.

J. Kissel, J. Rollins, S. Dwyer, A. Staley

While Sheila and Alexa began to lock PRMI on carrier, the HAM2 and HAM3 HEPI and ISIs tripped for an unknown reason. We'll leave this to people offline to figure out what happened. See attached actuator trip plots from the ISIs.