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ID Date Authorup Type Category Subject
  12337   Tue Jul 26 14:24:38 2016 KojiSummaryVACPurge compressed air system at LHO

I've visited the purge clean air system at LHO Yarm mid-station with John Worden.

The system is described C981637. There is a schematic in C981637-06-V (Vol.6).pdf although the schematic has some differences (or uncorrected mistakes).

This system is intended to provide positive pressure when a soft cover is attached to a chamber door. When the door is open, the purging does not help to keep the chamber clean because the flow is too slow. This protection has to be done with overhead HEPA filters (22x5000cfm). It may be possible that this purge air helps the tube not to allow dusts to come in. But before using this, the chambers and the tubes have to be cleaned, according to John.

- Here at the site, the purge air system is started up a day before the vent. This system is used for the vent air, the purge air, and turbo foreline filling.

- Air intake (attachment 1): At the site, the air is intaken from the VEA. We want to incorporate somewhat clean air instead of dirty, dusty, outside air.

- Initial filter (attachment 2): a high volume filter before the compressors.

- The compressors (attachment 3, 4) are 5x 6 horse power air compressor each goes up to 160 psi. They are turned on and off depending on the demand of the air. Which is turned on is revolved by the controller to equalize the compressor usage hours.

- The compressed air goes through the air cooler (heat exchanger) to remove the heat by the compressor work.

- This air goes through prefilters and accumulated in the air receiver (100psi) (attachment 5). This receiver tank has an automated vent valve for periodical water drainage at the bottom.

- The accumulated air is discharged to twin drier towers (attachment 6, blue). The tower is operated by the controller (attachment 7) alternately with a period of 4min (or 10min by setting). When one of the towers is working, a humid air comes from the bottom and the dry air is discharged from the top. A part of the dry air goes into the other tower from the top to the bottom and dries the tower. There is a vent at the bottom to discharge water periodically.

- The dried air goes through 4 types of filters. After the last filter, all of the plumbing should be made of stainless steel to keep cleanliness.

- The air goes to the pressure reducing regulator (attachment 8, gray). The final flow speed at the chamber side is 50cfm max, according to John.

- The lower pressure air goes through the final filter (attachment 8, blue). As the pressure is low, this filter is big in order to keep the volume of the air flow.

- The purge air is supplied to the chamber side with KF50 (attachment 9). There is a vent valve (attachment 10) for safety and also to run a dry air for at least a day before the use to clean up the supply line. The purge line is disconnected when no in use.

- The entire system (attachment 11) and size comparison (attachment 12).


Attachment 1: air_intake.jpg
Attachment 2: initial_filter.jpg
Attachment 3: compressors1.jpg
Attachment 4: compressors2.jpg
Attachment 5: air_receiver_dryer.jpg
Attachment 6: drier.jpg
Attachment 7: drier_controller2.jpg
Attachment 8: pressure_regulator_and_last_filter.jpg
Attachment 9: chamber_side_supply.jpg
Attachment 10: vent_valve_for_line_cleaning.jpg
Attachment 11: the_whole_system.jpg
Attachment 12: size_comparison.jpg
  12339   Tue Jul 26 17:41:59 2016 KojiSummaryVACPurge compressed air system

We have no number for the CFM without calculation. We can't assume a random number like 10-15

  12354   Fri Jul 29 13:17:34 2016 KojiUpdateGeneralOven

While the air bake oven situation is being improved, how about to buy a cheepo toaster oven at Target, BestBuy, or anywhere?

We don't need precise temp control for the glue cure test. At LLO I saw that they are using cooking grade oven for this purpose.
(Of course, we should not use this oven for foods once it is used for epoxy)

I have a fryer temp sensor in my office on the freezer stole from the 40m long time ago. You should be able to measure high temp.

If you have such an oven, I'd love to borrow it for the OMC lab later, as I expect to work on epoxy bonding later.

  12375   Thu Aug 4 17:41:53 2016 KojiUpdateComputer Scripts / ProgramsWeb things mostly back online

Sorry I was writting the elog, but I had to dive into the chamber (@LHO) before completion.

  12376   Thu Aug 4 17:57:09 2016 KojiConfigurationGeneralDon't restart apache2 - nodus /etc/apache2/sites-available/* accidentally deleted

Late coming elog about the deletion of the apahce config files

Thu Aug 4 8:50ish 2016

Please don't restart apache2

I accidentally deleted four files in /etc/apache2/sites-available / on nodus. The deleted files were

elog   nodus  public_html  svn

I believe public_html is not used as it is not linked from /etc/apache2/sites-enabled

They are the web server config files and need to be reconfigured manually. We have no backup.

Currently all the web services are running as it was. However, once apache2 is restarted, we'll lose the services.


  12378   Fri Aug 5 04:43:09 2016 KojiUpdateSUSETMX Ruby Wire Standoff Ready for Gluing

If only the LL magnet looks too low, doesn't this mean that the OSEMs are not arranged in a square shape?
If so, you can fix this misalignment by moving the OSEM holding plate rather than OSEM shimming, can't you?

  12398   Thu Aug 11 00:20:41 2016 KojiUpdateSUSETMY re-suspended

How much pitch bias do you need in order to correct this pitch misalignment?
That may give you the idea how bad this misalignment is.

  12418   Wed Aug 17 16:28:46 2016 KojiUpdateCOCRC folding mirrors - Numerical review

For the given range of the PR3/SR3 RoCs for both cases, all the resulting numbers such as TMSs/mode matching ratios look reasonable to me.

  12435   Tue Aug 23 22:58:16 2016 KojiUpdateElectronicsDecoupling capacitor 101

What I suggested was:
- For most cases, power decoupling capacitors for the regulators should be ~100nF "high-K ceramic capacitors" + 47uF~100uF "electrolytic capacitors".
- For opamps, 100nF high-K ceramic should be fine, but you should consult with datasheets.
- Usually, you don't need to use tantalum capacitors for this purpose unless specified.
- Don't use film capacitors for power decoupling.

79XXs are less stable compared to 78XXs, and tend to become unstable depending on the load capacitance.
One should consult with the datasheet of each chip in order to know the proper capacitors values.
But also, you may need to tweak the capacitor value when necessary. Above recipe works most of the case.

  12438   Wed Aug 24 19:37:55 2016 KojiUpdateElectronicsDecoupling capacitor 101


Interesting articles how they should only be used for power decoupling and not in the signal path.



  12539   Fri Oct 7 20:25:14 2016 KojiUpdateCDSPower-cycled c1psl and c1iool0

Found the MC autolocker kept failing, It turned out that c1iool0 and c1psl went bad and did not accept the epics commands.

Went to the rack and power cycled them. Burt resotred with the snapshot files at 5:07 today.

The PMC lock was restored, IMC was locked, WFS turned on, and WFS output offloaded to the bias sliders.

The PMC seemed highly misaligned, but I didn't bother myself to touch it this time.

  12540   Fri Oct 7 20:56:15 2016 KojiUpdateSUSOutput matrix diagonalization

I wanted to see what is the reason to have such large coupling between pitch and yaw motions.

The first test was to check orthogonality of the bias sliders. It was done by monitoring the suspension motion using the green beam.
The Y arm cavity was aligned to the green. The damping of ITMY was all turned off except for SD.
Then ITMY was misaligned by the bias sliders. The ITMY face CCD view shows that the beam is reasonably orthogonally responding to the pitch and yaw sliders.
I also confirmed that the OPLEV signals also showed reasonablly orthogonal responce to the pitch and yaw misalignment.

=> My intuition was that the coils (including the gain balance) are OK for a first approximation.

Then, I started to excite the resonant modes. I agree that it is difficult to excite a pure picth motion with the resonance.

So I wanted to see how the mixing is frequency dependent.

The transfer functions between ITMY_ASCPIT/YAW_EXC to ITMY_OPLEV_PERROR/YERROR were measured.

The attached PDFs basically shows that the transfer functions are basically orthogonal (i.e. pitch exc goes to pitch, yaw exc goes to yaw) except at the resonant frequency.

I think the problem is that the two modes are almost degenerate but not completely. This elog shows that the resonant freq of the ITMY modes are particularly close compared to the other suspensions.
If they are completely degenerate, the motion just obeys our excitation. However, they are slightly split. Therefore, we suffer from the coupled modes of P and Y at the resonant freq.
However, the mirror motion obeys the exitation at the off resonance as these two modes are similar enough.

This means that the problem exists only at the resonant frequencies. If the damping servos have 1/f slope around the resonant freqs (that's the usual case), the antiresonance due to the mode coupling does not cause servo instability thank to the sufficient phase margin.

In conclusion, unfortunately we can't diagnalize the sensors and actuators using the natural modes because our assumption of the mode purity is not valid.
We can leave the pitch/yaw modes undiagnalized or just believe the oplevs as a relatively reliable reference of pitch and yaw and set the output matrix accordingly.


The figures will be rotated later.

Attachment 1: 161007_P.pdf
Attachment 2: 161007_Y.pdf
  12555   Wed Oct 12 22:51:26 2016 KojiUpdateGeneralClipping could not be improved by the PZTs - NEED ANOTHER VENT

[Gautam Koji]

We engaged the HV driver to the output port PZTs, hoping to mitigate the AS port clipping. Basically, the range of the PZT is not enough to make the beam look clean. Also, our observation suggested there are possible multiple clipping in the chamber. We need another vent to make the things clearly right. Eric came in the lab and preparing the IFO for it.

1. Before the test, the test masses have been aligned with the dither servo.

2. We looked at the beam shape on the AS camera with a single bounce beam. We confirmed that the beam is hard-clipped at the upper and left sides of the beam on the video display. This clipping is not happening outside of the chamber.

3. We brought an HV power supply to the short OMC rack. There is a power supply cable with two spades. The red and black wires are +150V and GND respectively.

4. The voltage of +/-10V was applied on each of the four PZT drive inputs. We found that the motion of the beam on the camera is tiny and in any case, we could not improve the beam shape.

5. We wondered that if we are observing ANY improvement of the clipping. For this purpose, we aligned AS110 sensor every time we gave the misalignment with the PZTs. Basically, we are at the alignment to have the best power we can get. We thought this was weird.

6. Then we moved the AS port spot with the ITMX. We could clearly make the spot more round. However, this reduced the power at the AS port reduced by ~15%. When the beam was further clipped, the power went down again. Basically, the initial alignment gave us the max power we could get. As the max power was given with the clipped beam, we get confused and feel safer to check the situation with the chambers open.

During this investigation, we moved the AS port opitcs and the AS camera. So they are not too precise reference of the alignment. The PZT HV setup has been removed.

  12558   Thu Oct 13 14:49:57 2016 KojiConfigurationPEMXLR(F)-XLR(M) cable took from the fibox to the Blue microphone

[Gautam Koji]

XLR(F)-XLR(M) cable for the blue microphone is missing. Steve ordered one.

We found one in the fibox setup. As we don't use it during the vent, we use this cable for the microphone.
Once we get the new one, it will go to the fibox setup.


  12580   Tue Oct 25 18:07:28 2016 KojiUpdateGeneralPRFPMI locked, arms loss improved

Great to hear that we have the PRG of ~16 now!

Is this 150ppm an avg loss per mirror, or per arm?

  12584   Thu Oct 27 13:48:20 2016 KojiUpdateGeneralPRFPMI locked, arms loss improved

It is also difficult to have a high arm transmission without having high PRG.

What about to plot the arm trans and the REFL DC power in a timeseries?
Or even in a correlation plot (X: Arm Trans or PRG vs Y: REFL Reflectivity)

This tells you an approximate location of the critical coupling, and allows you to calibrate the PRG, hopefully.

  12641   Sat Nov 26 19:16:28 2016 KojiUpdateIOOIMC WFS Demod board measurement & analysis

[Rana, Koji]

1. The response of the IMC WFS board was measured. The LO signal with 0.3Vpp@29.5MHz on 50Ohm was supplied from DS345. I've confirmed that this signal is enough to trigger the comparator chip right next to the LO input. The RF signal with 0.1Vpp on the 50Ohm input impedance was provided from another DS345 to CH1 with a frequency offset of 20Hz~10kHz. Two DS345s were synced by the 10MHz RFreference at the rear of the units. The resulting low frequency signal from the 1st AF stage (AD797) and the 2nd AF stage (OP284) were checked.

Attachment 1 shows the measured and modelled response of the demodulator with various frequency offsets. The value shows the signal transfer (i.e. the output amplitude normalized by the input amplitude) from the input to the outputs of the 1st and 2nd stages. According to the datasheet, the demodulator chip provides a single pole cutoff of 340kHz with the 33nF caps between AP/AN and VP. The first stage is a broadband amplifier, but there is a passive LPF (fc=~1kHz). The second stage also provides the 2nd order LPF at fc~1kHz too. The measurement and the model show good agreement.

2. The output noise levels of the 1st and 2nd stages were meausred and compared with the noise model by LISO.
Attachment 2 shows the input referred noise of the demodulator circuit. The output noise is basically limited by the noise of the first stage. The noise of the 2nd stage make the significant contribution only above the cut off freq of the circuit (~1kHz). And the model supports this fact. The 6.65kOhm of the passive filter and the input current noise of AD797 cause the large (>30nV/rtHz) noise contribution below 100Hz. This completely spoils the low noiseness (~1nV/rtHz) of AD797. At lower frequency like 0.1Hz other component comes up above the modelled noise level.

3. Rana and I had a discussion about the modification of the circuit. Attachment 4 shows the possible improvement of the demod circuit and the 1st stage preamplifier. The demodulator chip can have a cut off by the attached capacitor. We will replace the 33nF caps with 1uF and the cut off will be pushed down to ~10kHz. Then the passive LPF will be removed. We don't need "rodeo horse" AD797 for this circuit, but op27 is just fine instead. The gain of the 1st stage can be increased from 9 to 21. This should give us >x10 improvement of the noise contribution from the demodualtor (Attachment 3). We also can replace some of the important resistors with the thin film low noise resistors.

Attachment 1: WFS_demod_response.pdf
Attachment 2: WFS_demod_noise.pdf
Attachment 3: WFS_demod_noise_plan.pdf
Attachment 4: Screen_shot_2011-07-01_at_11.13.01_AM.png
  12645   Tue Nov 29 17:45:06 2016 KojiUpdateIOOIMC WFS Demod board measurement & analysis

Summary: The demodulator input noise level was improved by a factor of more than 2. This was not as much as we expected from the preamp noise improvement, but is something. If this looks OK, I will implement this modification to all the 16 channels.

The modification shown in Attachment 1 has actually been applied to a channel.

  • The two 1.5uF capacitors between VP and AN/AP were added. This decreases the bandwidth of the demodulator down to 7.4kHz
  • The offset trimming circuit was disabled. i.e. Pin18 of AD831 was grounded.
  • The passive low pass at the demodulator output was removed. (R18, C34)
  • The stage1 (preamp) chip was changed from AD797 to OP27.
  • The gain of the preamp stage was changed from 9 to 21. Also the thin film resistors are used.

Attachment 2 shows the measured and expected output signal transfer of the demodulator. The actual behavior of the demodulator is as expected, and we still keep the over all LPF feature of 3rd order with fc=~1kHz.

Attachment 3 shows the improvement of the noise level with the signal reffered to the demodulator input. The improvement by a factor >2 was observed all over the frequency range. However, this noise level could not be explained by the preamp noise level. Actually this noise below 1kHz is present at the output of the demodulator. (Surprisingly, or as usual, the noise level of the previous preamp configuration was just right at the noise level of the demodulator below 100Hz.) The removal of the offset trimmer circuit contributed to the noise improvement below 0.3Hz.

Attachment 1: demod.pdf
Attachment 2: WFS_demod_response.pdf
Attachment 3: WFS_demod_noise.pdf
  12661   Fri Dec 2 18:02:37 2016 KojiUpdateIOOIMC WFS Demod board measurement & analysis

ELOG of the Wednesday work.

It turned out that the IMC WFS demod boards have the PCB board that has a different pattern for each of 8ch.
In addition, AD831 has a quite narrow leg pitch with legs that are not easily accessible.
Because of these, we (Koji and Rana) decided to leave the demodulator chip untouched.

I have plugged in the board with the WFS2-Q1 channel modified in order to check the significance of the modification.

WFS performance before the modification

Attachment 1 shows the PSD of WFS2-I1_OUT calibrated to be referred to the demodulator output. (i.e. Measured PSDs (cnt/rtHz) were divided by 8.9*2^16/20)
There are three curves: One is the output with the MC locked (WFS servos not engaged). The second is the PSD with the PSL beam blocked (i.e. dark noise). The third is the electronics noise with the RF input terminated and the nominal LO supplied.

This tells us that the measured PSD was dominated by the demodulator noise in the dark condition. And the WFS signal was also dominated by the demod noise below 0.1Hz and above 20Hz. There are annoying features at 0.7, 1.4, 2.1, ... Hz. They basically impose these noise peaks on the stabilized mirror motion.

WFS performance after the modification

Attachment 2 shows the PSD of WFS2-Q1_OUT calibrated to be referred to the demodulator output. (i.e. Measured PSDs (cnt/rtHz) were divided by 21.4*2^16/20)
There are three same curves as the other plot. In addition to these, the PSD of WFS2-I1_OUT with the MC locked is also shown as a red curve for comparison.

This figure tells us that the measured PSD below 20Hz was dominated by the demodulator noise in the dark condition. And the WFS signal is no longer dominated by the electronics noise. However, there still are the peaks at the harmonics of 0.7, 1.4, 2.1, ... Hz. I need further inspection of the FWS demod and whtening boards to track down the cause of these peaks.

Attachment 1: WFS_demod_noise_orig.pdf
Attachment 2: WFS_demod_noise_mod.pdf
  12662   Sat Dec 3 13:27:35 2016 KojiUpdateIOOIMC WFS Demod board measurement & analysis

ELOG of the work on Thursday

Gautam suggested looking at the preamplifier noise by shorting the input to the first stage. I thought it was a great idea.

To my surprise, the noise of the 2nd stage was really high compared to the model. I proceeded to investigate what was wrong.

It turned out that the resistors used in this sallen-key LPF were thick film resistors. I swapped them with thin film resistors and this gave the huge improvement of the preamplifier noise in the low frequency band.

Attachment 1 shows the summary of the results. Previously the input referred noise of the preamp was the curve in red. We the resistors replaced, it became the curve in magenta, which is pretty close to the expected noise level by LISO model above 3Hz (dashed curves). Unfortunately, the output of the unit with the demodulator connected showed no improvement (blue vs green), because the output is still limited by the demodulator noise. There were harmonic noise peaks at n x 10Hz before the resistor replacement. I wonder if this modification also removed the harmonic noise seen in the CDS signals. I will check this next week.

Attachment 2 shows the current schematic diagram of the demodulator board. The Q of the sallen key filter was adjusted by the gain to have 0.7 (butter worth). We can adjust the Q by the ratio of the capacitance. We can short 3.83K and remove 6.65K next to it. And use 22nF and 47nF for the capacitors at the positive input and the feedback, respectively. This reduces the number of the resistors.

Attachment 1: WFS_demod_noise.pdf
Attachment 2: demod.pdf
  12668   Tue Dec 6 13:37:02 2016 KojiUpdateIOOIMC WFS Demod board measurement & analysis

I have implemented the modification to the demod boards (Attachment 1).
Now, I am looking at the noise in the whitening board. Attachment 2 shows the comparison of the error signal with the input of the whitening filter shorted and with the 50ohm terminator on the demodulator board. The message is that the whitening filter dominates the noise below 3Hz.

I am looking at the schematic of the whitening board D990196-B. It has an VGA AD602 at the input. I could not find the gain setting for this chip.
If the gain input is fixed at 0V, AD602 has the gain of 10dB. The later stages are the filters. I presume they have the thick film resistors.
Then they may also cause the noise. Not sure which is the case yet.

Also it seems that 0.7Hz noise is still present. We can say that this is coming from the demod board but not on the work bench but in the eurocard crate.

Attachment 1: demod.pdf
Attachment 2: WFS_error_noise.pdf
  12669   Tue Dec 6 16:47:40 2016 KojiUpdateIOOIMC WFS whitening filter investigation

The whitening board saids it is Rev B, but the actual component values are more like Rev. C.

The input stage (AD602) has an input resistor of 909 Ohm.
This is causing a big attenuation of the signal (x1/10) because the input impedance of AD602 is not high. And this screws up the logarithm of the gain.
I don't think this is a right approach.

Attachment 1: D990196-C.pdf
  12670   Tue Dec 6 17:54:08 2016 KojiUpdateIOOIMC WFS whitening filter investigation

The input resistor 909Ohm of AD602 was shorted. I've confirmed that the gain (= attenuation by voltage division) was increased by a factor of 10.
This modification was done for WFS2-I1 and WFS2-Q1. Also the thick film resistors for the WFS2-I1 channel was all replaced with thin film resistors.

Attachment 1 shows the comparison of the noise levels. The curves were all calibrated referred to the response of the original whitening filter configuration.
(i.e. measurement done after the gain change was compensated by the factor of 10.)

Now the AF chain is not limited by the noise in the whitening filter board. (Brown)
In fact, this noise level was completely identical between I1 and Q1. Therefore, I don't think we need this resistor replacement for the whitening filter board.

We can observe the improvement of the overall noise level below 10Hz. (Comparison between green and red/blue)
As the signal level goes up, the noise above 100Hz was also improved.

Now we need to take care of the n x 0.7Hz feature which is in the demod board...

Attachment 1: 34.png
  12671   Tue Dec 6 22:41:49 2016 KojiUpdateIOOIMC WFS whitening filter investigation

I have implemented the same modification (shorting the input resistor of AD602) to the two whitening boards.

  12676   Tue Dec 13 17:26:42 2016 KojiUpdateIOOIMC WFS whitening filter investigation

Rana pointed out that this modification (removal of 900Ohm) leave the input impedance as low as 100Ohm.
As OP284 can drive up to 10mA, the input can span only +/-1V with some nonlinearity.

Rather than reinstalling the 900Ohms, Rana will investigate the old-days fix for the whitening filter that may involve the removal of AD602s.
Until the solution is supplied, the IMC WFS project is suspended.

  12679   Mon Dec 19 22:05:09 2016 KojiSummaryIOOPMC, IMC aligned. The ringdown PD/Lens removed.

PMC and IMC were aligned on Friday (16th) and Today (19th).

The PD and lens for the ringdown experiment were removed as they were blocking the WFS.

  12680   Wed Dec 21 21:03:06 2016 KojiSummaryIOOIMC WFS tuning

- Updated the circuit diagrams:

IMC WFS Demodulator Board, Rev. 40m https://dcc.ligo.org/LIGO-D1600503

IMC WFS Whitening Board, Rev. 40m https://dcc.ligo.org/LIGO-D1600504

- Measured the noise levels of the whitening board, demodboard, and nominal free running WFS signals.

- IMC WFS demod phases for 8ch adjusted

Injected an IMC PDH error point offset (@1kHz, 10mV, 10dB gain) and adjusted the phase to have no signal in the Q phase signals.

- The WFS2 PITCH/YAW matrix was fixed

It was found that the WFS heads were rotated by 45 deg (->OK) in CW and CCW for WFS1 and 2, respectively (oh!), while the input matrices were identical! This made the pitch and yaw swapped for WFS2. (See attachment)

- Measured the TFs MC1/2/3 P/Y actuation to the error signals

Attachment 1: DSC_0142.JPG
  12682   Thu Dec 22 18:39:09 2016 KojiSummaryIOOIMC WFS tuning

Noise analysis of the WFS error signals.

Attachment 1: All error signals compared with the noise contribution measured with the RF inputs or the whitening inputs terminated.

Attachment 2: Same plot for all the 16 channels. The first plot (WFS1 I1) shows the comparison of the current noise contributions and the original noise level measured with the RF terminated with the gain adjusted along with the circuit modification for the fair comparison. This plot is telling us that the electronics noise was really close to the error signal.

I wonder if we have the calibration of the IMC suspensions somewhere so that I can convert these plots in to rad/sqrtHz...?

Attachment 1: WFS_error_noise.pdf
Attachment 2: WFS_error_noise_chans.pdf
  12683   Fri Dec 23 20:53:44 2016 KojiSummaryIOOIMC WFS tuning

WFS1 / WFS2 demod phases and WFS signal matrix

Attachment 1: DSC_0144.JPG
Attachment 2: DSC_0145.JPG
  12684   Fri Dec 23 21:05:56 2016 KojiSummaryIOOIMC WFS tuning

Signal transfer function measurements

C1:SUS-MC*_ASCPIT_EXC channels were excited for swept sine measurements.

The TFs to WFS1-I1~4, Q1~4, WFS1/2_PIT/YAW, MC2TRANS_PIT/YAW signals were recorded.

The MC1 and MC3 actuation seems to have ~30Hz elliptic LPF somewhere in the electronics chain.
This effect was compensated by subtracting the approximated time delay of 0.022sec.

The TFs were devided by freq^2 to make the response flat and averaged between 7Hz to 15Hz.
The results have been summarized in Attachment 3&4.

Attachment 4 has the signal sensing matrix. Note that this matrix was measured with the input gain of 0.1.

Input matrix for diagonalizing the actuation/sensor response


\begin{pmatrix} -1.58983 & -0.901533 & -5592.53 \\ 0.961632 & -0.569662 & 1715.12 \\ 0.424609 & 1.60783 & -5157.38 \end{pmatrix}

e.g. To produce pure WFS1P reaction, => -1.59 MC1P + 0.962 MC2P + 0.425 MC3P


\begin{pmatrix} 1.461 & -0.895191 & -4647.9 \\ 0.0797164 & 0.0127339 & -1684.11 \\ 0.223054 & -1.31518 & -4101.14 \end{pmatrix}

Attachment 1: IMC_WFS_segment_TF.pdf
Attachment 2: IMC_WFS_channels_TF.pdf
Attachment 3: IMC_WFS_161221_table1.pdf
Attachment 4: IMC_WFS_161221_table2.pdf
Attachment 5: IMC_WFS_161221.xlsx.zip
  12685   Sun Dec 25 14:39:59 2016 KojiSummaryIOOIMC WFS tuning

Now, the output matrices in the previous entry were implemented.
The WFS servo loops have been engaged for several hours.
So far the REFL and TRANS look straight. Let's see how it goes.

  12686   Mon Dec 26 12:45:31 2016 KojiSummaryIOOIMC WFS tuning

It didn't go crazy at least for the past 24hours.

Attachment 1: IMC_REFL_TRANS_26hrs.png
Attachment 2: IMC_TRANS_P_Y_26hrs.png
  12689   Thu Dec 29 16:52:51 2016 KojiSummaryIOOIMC WFS tuning

Koji responding to Rana

> For the rough calibration below 10 Hz, we can use the SUS OSEM cal: the SUSPIT and SUSYAW error signals are in units of micro-radians.

I can believe the calibration for the individual OSEMs. But the input matrix looked pretty random, and I was not sure how it was normalized.
If we accept errors by a factor of 2~3, I can just naively believe the calibration factors.

> If the RF signals at the demod input are low enough, we can consider either increasing the light power on the WFS or increasing the IMC mod. depth.

The demod chip has the conversion factor of about the unity. We increased the gains of the AF stages in the demod and whitening boards. However, we only have the RMS of 1~20 counts. This means that we have really small RF signals. We should check what's happening at the RF outputs of the WFS units. Do we have any attenuators in the RF chain? Can we skip them without making the WFS units unstable?

  12715   Fri Jan 13 21:41:23 2017 KojiUpdateCDSDC errors

I think I fixed the DC error issue

1. I added the leap second (leapsecond ?) entry for 2016/12/31, 23:60:00 UTC to daqdrc

set gps_leaps = 820108813 914803214 1119744016;
set gps_leaps = 820108813 914803214 1119744016 1167264018;

2. Restarted FB and all realtime models

Now I don't see any RED light.

  12756   Wed Jan 25 17:30:03 2017 KojiUpdateIMC29.5 MHz modulation depth measurement plan

I'm afraid that the bidirectional coupler, designed to be 50ohm in/out, disturbs the resonant circuit designed for the EOM which is almost purely capacitive.

One possible way could be to measure the transfer function using the active FET probe from the triple resonant input to the output with the EOM attached.

Another way: How about to measure the reflection before the resonant circuit? Then, of course, there is the triple resonant interface circuit between the power combiner and the EOM. This case, we will see how much power is consumed in EOM and the resonant circuit. Then we can use the previous measurement to see the conversion factor between the power consumption to the modulation depth. Kiwamu may give us his measurement.

  12757   Wed Jan 25 18:18:08 2017 KojiSummaryIOOMCL / MCF / Calibration

jiSome notes on the FSS configuration: ELOG 10321

  12761   Fri Jan 27 15:36:17 2017 KojiUpdateSUS wire standoffs update

Very nice! I got excited.

  • Don't you ask Calum and co to check the groove size with their microscopes? Just give the samples and the wire.
  • Do we want to make a simple "guitar" setup to measure the vibration Qs with Al piece, glass prism, ungrooved Sapphire, this grooved sapphire, grooved ruby, etc?
  12783   Wed Feb 1 11:51:19 2017 KojiUpdateIMCRF AM stabilization box pulled out

For a comparison: OMC ELOG 238

  12805   Mon Feb 6 18:20:08 2017 KojiUpdateIMCMCL Feedback - simulink model updated

It is more accurate to model the physical frequency noises at various places.

cf. See also 40m ALS paper or Shigeo Nagano PDH thesis on https://wiki-40m.ligo.caltech.edu/40m_Library

- The output 4 should be "Laser frequency"

- Seismic path should be excluded from the summing node

- The output after the PMC: "Laser frequency after the PMC"

- "Laser frequency after the PMC" is compared (diffed) with the output 1 "mirror motion in Hz"

- The comparator output goes to the cav pole, the PD, and the PDH gain: This is the output named "PDH Error"

- Tap a new path from "Laser frequency after the PMC" and multiply with the cav pole (C_IMC)
- Tap a new path from "Mirror motion" and multiply with the cavity high pass  (s C_IMC/omega)
- Add these two: This is the output named "Frequency noise transmitted by IMC"

  12821   Fri Feb 10 19:32:15 2017 KojiUpdateIMCIMC Demod board

The input impedance of the mixer is not constant. As the diode switches, it changes dynamically. Because of this, the waveform of the LO at the mixer input (i.e. the amplifier output) is not sinusoidal. Some of the power goes away to harmonic frequencies. Also, your active probe is calibrated to measure the power across the exact 50Ohm load, which is not in this case. The real confirmation can be done by swapping the mixer with a 50Ohm resistor. But it is too much. Just confirm the power BEFORE the amp is fine. +/-1dB does not change the mixer function much.

Instead, we should measure
- Orthogonality
- Gain imbalance
of the I/Q output. This can be checked by supplying an RF signal that is 100~1kHz away from the LO frequency and observe I&Q outputs.

  12837   Fri Feb 17 20:04:43 2017 KojiUpdateGeneralProjector not functional / Zita partially working

Koji, Gautam, Johannes

We quickly checked the situation of the projector in the control room.

- We found that the proejctor was indicating "lamp error".
==> Steve, could you remove the projector from the ceiling and check if it still does not work?
If it still does not work, send it back to the vender. It should be covered by the previous service.

- Zita seemed happy with the DVI output. We tried the dual display configration and  VGA and DVI are active right now.
The DVI output (from RADEON something video card) is somewhat strange. We probably need to look into the video display situation.

  12846   Thu Feb 23 09:32:20 2017 KojiUpdateSUS wire standoffs update

Kyle took high quality images of  the three sapphire prisms using the microscope @Downs. He analyzed the images to see the radius of the groove.

They all look sufficiently sharp for a 46um steel wire. Thumbs up.
I am curious to see how the wire Q is with grooved sapphires, ungrooved sapphires, grooved ruby, grooved aluminum stand off, and so on.

Attachment 1: Sapphire_prism_1(A015).png
Attachment 2: Sapphire_prism_2(A016).png
Attachment 3: Sapphire_prism_3(A014).png
  12875   Thu Mar 9 15:25:12 2017 KojiUpdateGeneralIMC/XYarms aligned/locked

As per Steve's request, I've checked the alignment of the IMC and the arms. These three cavities are locked and aligned.

  12877   Thu Mar 9 20:11:04 2017 KojiUpdateGeneralattempted ETMY picture taking

The attached is the ETMY image with the single arm locked. This was the best I could do. Here is the recipe

  • Turn on SP570UZ
  • Switch to "M" mode (Manual aperture and exposure)
  • Set the aperture to be the widest (smallest F number) and the exposure to be maximum (15 second).
  • Switch to AF mode by the lens side switch
  • Use the lens dial to adjust the zoom until the OSEMs fill the central 1/3 box (i.e. 1/9 area of the field of view). If you zoom more, you can't focus the spot later.
  • Use menu button to switch to ISO1600 (You are now capable to see the beam spot)
  • Switch to MF mode by the lens side switch
  • Use the lens dial to adjust the focus to have the sharpest image of the spot. This can be achieved at the focal distance of ~1m
  • Use menu button to switch back to ISO64
  • Push the shutter (I didn't use it, but you should be able to use 2sec timer)
Attachment 1: P3090032.JPG
  12912   Mon Mar 27 22:40:44 2017 KojiSummaryIOOMCL / MCF / Calibration

In http://nodus.ligo.caltech.edu:8080/40m/11793 I posted the calibrated PMC free-running displcament with/without IMC locked. Unfortunately, this measurement was done with a part of the IMC electronics not perfect (https://nodus.ligo.caltech.edu:8081/40m/11794). I did the same measurement after the fix, but there is no low freq data http://nodus.ligo.caltech.edu:8080/40m/11795.

Assuming we have the similar error signal leve in the low freq band as The entry 11793, the IMC is considered to be noisier than the PMC between 0.8 and 4Hz. But we should do the same measurement with the current electronics.

The PMC calibration can be found in this entry http://nodus.ligo.caltech.edu:8080/40m/11780

  12966   Wed May 3 16:46:18 2017 KojiConfigurationComputerscatastrophic multiple monitor failures

- Is there any machine that can handle 4K? I have one 4K LCD for no use.
- I also can donate one 24" Dell

  12967   Wed May 3 16:47:45 2017 KojiUpdateGeneralPI pzt inventory check

I also have a functional one on my desk, which has one of the wires repaired.


One is broken, two are ready to steer green and 3 available in un known condition



  12992   Mon May 15 19:21:04 2017 KojiUpdateComputer Scripts / ProgramsFSSslow / MCautolocker restarted

It seems that FSS slow servo stopped working.

I found that megatron was restarted (by Rana, to finish an apt-get upgrade) on ~18:47 PDT today.

controls@megatron|~> last -5
controls pts/0  Mon May 15 19:15   still logged in   
controls pts/0  Mon May 15 19:14 - 19:15  (00:01)    
reboot   system boot  3.2.0-126-generi Mon May 15 18:50 - 19:19  (00:29)    
controls pts/0  Mon May 15 18:43 - down   (00:04)    
controls pts/0  Mon May 15 15:25 - 17:38  (02:12)

FSSslow / MCautolocker were restarted on megatron.

  13032   Fri Jun 2 00:54:08 2017 KojiUpdateASSXarm ASS restoration work

While Gautam is working the restoration of Yarm ASS, I worked on Xarm.

Basically, I have changed the oscillator freqs and amps so as to have linear signals to the misalignment of the mirrors.
Also reduced the complexity of the input/output matrices to avoid any confusion.

Now the ITM dither takes care of the ITM alignment, and the ETM dither takes care of the ETM alignment.
The cavity alignment servos (4dofs) are running fine although the control band widths are still low (<0.1Hz).
The ETM spot positions should be controlled by the BS alignment, but it seems that these loops have suspicion about the signal quality.

While Gautam wa stouching the input TTs, we occasionally saw anomalously high transmission of the arm cavities (~1.2).
We decided to use this beam as this could have indicated partial clipping of the beam somewhere in the input optics chain.

Then the arm cavity was aligned to have reasonably high transmission for the green beam. i.e. Use the green power mon PD as a part of the alignment reference.

This resulted very stable transmission of both the IR and green beams. We liked them. We decide to use this a reference beam at least for now.

Attachment1: GTRX image at the end of the work.

Attachment2: ASSX screen shot

Attachment3: ASSX servo screen shot

Attachment4: Green ASX servo screen shot

Attachment 5: Screen shot of the ASS X strip tool

Attachment 6: Screen shot of the ASS X input matrix

Attachment 7: Screen shot of the ASS X output matrix

Attachment 1: GTRX.jpeg
Attachment 2: 54.png
Attachment 3: 37.png
Attachment 4: 16.png
Attachment 5: 26.png
Attachment 6: 41.png
Attachment 7: 01.png
  13081   Mon Jun 26 22:01:08 2017 KojiUpdateGeneralc1iscex timing troubles

I tried a couple of things, but no fundamental improvement of the missing LED light on the timing board.

- The power supply cable to the timing board at c1iscex indicated +12.3V

- I swapped the timing fiber to the new one (orange) in the digital cabinet. It didn't help.

- I swapped the opto-electronic I/F for the timing fiber with the Y-end one. The X-end one worked at Y-end, and Y-end one didn't work at X-end.

- I suspected the timing board itself -> I brought a "spare" timing board from the digital cabinet and tried to swap the board. This didn't help.


Some ideas:

- Bring the X-end fiber to C1SUS or C1IOO to see if the fiber is OK or not.

- We checked the opto-electronic I/F is OK

- Try to swap the IO chassis with the Y-end one.

- If this helps, swap the timing board only to see this is the problem or not.

ELOG V3.1.3-