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ID Date Authorup Type Category Subject
  11764   Sat Nov 14 00:52:25 2015 KojiSummaryCDSInvestion on EPICS freeze

[Yutaro, Koji]

Recently "EPICS Freeze" is so frequent and the normal work on the MEDM screen became almost impossible.

As a part of the investigation, all 19 realtime processes were stopped in order to see any effect on the probem.

IN FACT, when the realtime processes were absent (still slow machines were running), frequency of EPICS Freeze
became much less. This might mean that the issue is related to the data collection of the slow channels. We need more investigation.

After the testing, all the processes were restored although it was not so straghtforward. Particularly, c1sus DAC had an error which was
not visible from the CDS Status screen. We noticed it as suspension damping was not effective on any of the vertex suspensions.
This has been solved by restarting c1x02 process.

  11765   Sun Nov 15 22:43:48 2015 KojiSummaryPSLPMC LO degraded, usual ERA-5 replacement, LO recovered

I think the IMC locking was somewhat improved. Still it is not solid as long time before.

Before the PMC fix (attachment 1)
After the PMC fix (attachment 2)

To do
- PMC loop inspection / phase check / spectral measurements
- PMC / IMC interaction
- IMC loop check
 

  11768   Mon Nov 16 19:05:59 2015 KojiSummaryPSLPMC servo circuit review, follow up measurements

PMC follow up measurements have been done. The servo circuit was reviewed.

Now the PMC, IMC, X/Y arms are locked and aligned waiting for the IFO work although I still think something is moving (ITMX?)
as the FPMI fringe is quite fast.

  11769   Mon Nov 16 21:32:49 2015 KojiSummaryPSLPMC servo circuit review, follow up measurements

The result of the precise inspection for the PMC servo board for the 40m was done.

The record, including the photo of the board, can be found at https://dcc.ligo.org/D1400221-v2

- I found some ceramic 1uF caps are used in the signal path. They have been replaced with film caps by WIMA.

- In later measurements with the openloop TF measurement, it was found that the notch frequency (14.6kHz) was off from the a sharp PZT resonance at 12.2kHz.
I replaced the combined caps of 1220pF to 1742pF. This resulted nice agreement of the notch freq with the PZT resonant freq.


Past related elogs:

SRA-3MH mixer installed in 2009: http://nodus.ligo.caltech.edu:8080/40m/1502

R20 increased for more LO Mon gain: http://nodus.ligo.caltech.edu:8080/40m/10172

  11773   Tue Nov 17 15:49:23 2015 KojiConfigurationIOOMC Autolocker modified

/opt/rtcds/caltech/c1/scripts/MC/AutoLockMC.csh  was modified last night.

1. Autolocker sometimes forget to turn off the MC2Tickle. I added the following lines to make sure to turn it off.

    echo autolockMCmain: MC locked, nothing for me to do >> ${lfnam}
    echo just in case turn off MC2 tickle >> ${lfnam}
    ${SCRIPTS}/MC/MC2tickleOFF

2. During the lock acquisition, Autolocker frequently stuck on a weak mode. So the following lines were added
so that the Autolocker toggles the servo switch while waiting for the lock.

    echo autolockMCmain: Mon=$mclockstatus, Waiting for MC to lock .. >> ${lfnam}
    # Turn off MC Servo Input button
    ezcawrite C1:IOO-MC_SW1 1
    date >> ${lfnam}
    sleep 0.5;
    # Turn on MC Servo Input button
    ezcawrite C1:IOO-MC_SW1 0
    sleep 0.5;

  11775   Tue Nov 17 16:21:10 2015 KojiSummaryPSLPMC servo circuit review, follow up measurements

I'm still analyzing the open loop TF data. Here I report some nominal settings of the PMC servo

Nominal phase setting: 5.7
Nominal gain setting: 3dB

After the tuning of the notch frequency, I thought I could increase the gain from 5dB to 9dB.
However, after several hours of the modification, the PMC servo gradually started to have oscillation.
This seemed to be mitigated by reducing the gain down to 4dB. This may mean that the notch freq got drifted away
due to themperature rise in the module. PA85 produce significant amount of heat.

(The notch frequency did not change. Just the 22kHz peak was causing the oscillation.)

  11780   Wed Nov 18 16:51:58 2015 KojiSummaryPSLPMC servo calibration

Summary

The PMC servo error (MIX OUT MON on the panel) and actuation (HV OUT MON) have been calibrated using the swept cavity.

Error signal slope in round-trip displacement: 2.93e9 +/- 0.05e9 [V/m]
HV OUT calibration (round-trip displacement): 5.36e-7 +/- 0.17e-7 [m/V]
PZT calibration (round-trip displacement): 10.8 +/- 0.3 [nm/V]
=> corresponds to ~2.5 fringes for 0~250V full range => not crazy

Measurement condition

The transmission level: 0.743V (on the PMC MEDM screen)
LO level: ~13dBm (after 3dB attenuation)
Phase setting: 5.7
PMC Servo gain: 7dB during the measurement (nominal 3dB)

Method

- Chose PMC actuation "BLANK" to disable servo
- Connect DS345 function generator to EXT DC input on the panel
- Monitor "MIX OUT MON" and "HV OUT MON" with an oscilloscope
- Inject a triangular wave with ~1Vpp@1 or 2Hz with appropriate offset to see the cavity resonance at about the middle of the sweep.
  The frequency of the sweep was decided considering the LPF corner freq formed by the output impedance and the capacitance of the PZT. (i.e. 11.3Hz, see next entry)

Result

- 4 sweep was taken (one 2Hz seep, three 1Hz sweep)
- The example of the sweep is shown in the attachment.
- The input triangular wave and the PDH slopes were fitted by linear lines.
- Spacing between the sideband zero crossing corresponds to twice of the modulation frequency (2x35.5MHz = 71MHz)
- The error signal slope was calibrated as V/MHz
- FSR of the PMC is given by google https://www.google.com/search?q=LIGO+pmc.m
  => Cavity round trip length is 0.4095m, FSR is 732.2MHz
- Convert frequency into round-trip displacement

- Convert HV OUT MON signal into displacement in the same way.
- The voltage applied to the PZT element is obtained considering the ratio of 49.6 between the actual HV and the HV OUT MON voltage.

  11781   Wed Nov 18 16:53:17 2015 KojiSummaryPSLPMC PZT capacitance

The PMC PZT capacitance was measured.
- Turn off the HV supplies. Disconnect HV OUT cable.
- Make sure the cable is discharged.
- Measure the capacity at the cable end with an impedance meter.
=> The PMC PZT capacitance at the cable end was measured to be 222nF
Combined with the output impedance of 63.3kOhm, the LPF pole is at 11.3Hz

  11782   Wed Nov 18 17:09:22 2015 KojiSummaryPSLPMC Servo analysis

Summary

The PMC servo was analysed. OLTF was measured and modeled by ZPK (Attachment 1). The error and actuator signals were calibrated in m/rtHz (Attachment 2)

Measurement methods

OLTF:

- The PMC servo board does not have dedicated summing/monitor points for the OLTF measurement. Moreover the PZT HV output voltage is monitored with 1/49.6 attenuation.
  Therefore we need a bit of consideration.

- The noise injection can be done at EXT DC.
- Quantity (A): Transfer function between HV OUT MON and MIX OUT MON with the injection.
  We can measure the transfer function between the HV OUT (virtual) and the MIX OUT. (HV OUT->MIX OUT). In reality, HV OUT is attenuated by factor of 49.6.
  i.e. A = (HV_OUT->MIX_OUT)*49.6
- Quantity (B): Transfer function between HV OUT MON and MIX OUT MON without the injection.
 
This is related to the transfer function between the MIX OUT and HV OUT. In reality, HV OUT is attenuated. 
  i.e. B = 1/((MIX_OUT->HV_OUT)/49.6)

- What we want to know is HV_OUT->MIX_OUT->HV_OUT. i.e. A/B = (HV_OUT->MIX_OUT*49.6)*((MIX_OUT->HV_OUT)/49.6) = HV_OUT->MIX_OUT->HV_OUT

PSD:

- The MIX OUT and HV OUT spectra have been measured. The MIX OUT was calibrated with the calibration factor in the previous entry. This is the inloop stability estimation.
  From the calibrated MIX OUT and HV OUT, the free running stability of the cavity was estimated, by mutiplying with |1-OLTF| and |1-1/(1-OLTF)|, respectively, in order to recover
  the free running motion.

OLTF Modeling

Here is the model function for the open loop TF. The first line comes from the circuit diagram. The overall factor was determined by eye-fit.
The second and third lines are to reproduce the peak/notch feature at 12kHz. The fourth line is to reproduce 28kHz feature.
The LPF right after the mixer was analyzed by a circuit simulation (Circuit Lab). It can be approximated as 150kHz LPF as the second pole
seems to come at 1.5MHz.

The sixth line comes from the LPF formed by the output resistance and the PZT capacitance.

The seventh line is to reproduce the limit by the GBW product of OP27. As the gain is 101 in one of the stages,
it yields the pole freq of ~80kHz. But it is not enough to explain the phase delay at low frequency. Therefore this
discrepancy was compensated by empirical LPF at 30kHz.

function cmpOLTFc = PMC_OLTF_model(freqOLTFc)

cmpOLTFc = -7e5*pole1(freqOLTFc,0.162).*zero1(freqOLTFc,491)... % from the circuit diagram
    .*zero2(freqOLTFc,12.5e3,100)... % eye-fit
    .*pole2(freqOLTFc,12.2e3,6)... % eye-fit
    .*pole2(freqOLTFc,27.8e3, 12)... % eye-fit
    .*pole1(freqOLTFc,150e3)... % Mixer LPF estimated from Circuit Lab Simulation
    .*pole1(freqOLTFc,11.3)... % Output Impedance + PZT LPF
    .*pole1(freqOLTFc,8e6/101)... % GBW OP27
    .*pole1(freqOLTFc,3e4); % Unknown

end

Result

Attachment 1:

The nominal OLTF (Nov 17 data) shows the nominal UGF is ~1.7kHz and the phase margin of ~60deg.

The measured OLTF was compared with the modelled OLTF. In the end they show very sufficient agreement for further calibration.
The servo is about to be instable at 28kHz due to unknown series resonance. Later in the same day, the gain of the PMC loop had to be
reduced from 7dB to 3dB to mitigate servo oscillation. It is likely that this peak caused the oscillation. The notch frequency was measured
next day and it showed no sign of frequncy drift. That's good.

We still have some phase to reduce the high freq peaks by an LPF in order to increase the over all gain.

Attachment 2:

The red curve shows the residual floor displacement of 2~10x10-15 m/rtHz. Below 4Hz there is a big peak. I suspect that I forgot to close
the PSL shutter and the IMC was locked during the measurement. Then does this mean the measured noise corresponds to the residual laser
freq noise or the PMC cavity displacement? This is interesting to see.

The estimated free running motion from the error and actuation signals agrees very well. This ensures the precision of the caibration in the precious entries.
 

 

  11791   Thu Nov 19 17:06:57 2015 KojiConfigurationCDSDisabled auto-launching RT processes upon FE booting

We want to startup the RT processes one by one on boot of FE machines.

Therefore /diskless/root/etc/rc.local on FB was modified as follows. The last sudo line was commented out.

for sys in $(/etc/rt.sh); do
    #sudo -u controls sh -c ". /opt/rtapps/rtapps-user-env.sh && /opt/rtcds/cal\
tech/c1/scripts/start${sys}"

    # NOTE: we need epics stuff AND iniChk.pl in PATH
    # we use -i here so that the .bashrc is sourced, which should also
    # source rtapps and rtcds user env (for epics and scripts paths)

    # commented out Nov 19, 2015, KA
    # see ELOG 11791 http://nodus.ligo.caltech.edu:8080/40m/11791
    # sudo -u controls -i /opt/rtcds/caltech/c1/scripts/start${sys}
done

  11793   Fri Nov 20 15:44:12 2015 KojiSummaryPSLAdded 17.5kHz LPF to the PMC servo

As a final tune of the PMC servo, I've added 1nF cap at the error signal amplification stage. The diagram has been updated and uploaded to DCC. https://dcc.ligo.org/D1400221

It should be noted that this modification yielded the error signal to have 17.5kHz roll off.


The openloop TF after the modification has been measured. (Attachment 1)

With the new nominal gain of 9dB, almost the same gain margin for the 28kHz peak has been realized.
=> We have 6dB (factor of 2) more gain at low frequency. Currently, the feature at 8kHz causes the oscillation when the gain is further increased.
 

Here is the model function for the OLTF.

function cmpOLTFc = PMC_OLTF_model(freqOLTFc)

cmpOLTFc = -9.5e5*pole1(freqOLTFc,0.162).*zero1(freqOLTFc,491)... % from the circuit diagram
    .*pole1(freqOLTFc,17.5e3)... % Newly implemented input filter => GBW pole was replaced with this
    .*zero2(freqOLTFc,12.5e3,100)... % eye-fit
    .*pole2(freqOLTFc,12.2e3,6)... % eye-fit
    .*pole2(freqOLTFc,28.8e3, 12)... % eye-fit
    .*pole1(freqOLTFc,150e3)... % Mixer LPF estimated from Circuit Lab Simulation
    .*pole1(freqOLTFc,11.3)... % Output Impedance + PZT LPF
    .*pole1(freqOLTFc,3e4); % Unknown
   
end


The free-running round-trip displacement (roundtrip) / frequency noise is shown in Attachments. There we compare the spectra with and without IMC locked.

i.e. When the IMC is not locked, we are measuring the laser frequency noise with the sensor (PMC cavity) that is noisy due to the PMC displacement.
When the IMC is locked, the laser frequency is further stabilized while the sensor (PMC) noise is not changed.

- Without IMC locked

Can we see the laser freq noise? It seems that it is visible above 100Hz.
The red curve is the measured noise level. The NPRO (although it is LWE NPRO) noise level from S. Nagano's thesis (see our wiki) is shown there.

- With IMC locked

When the IC is locked, we see the increase of the noise between 1~4Hz. It means that the IMC is not only noisier than the laser, but also noisier than the PMC cavity.
Sounds reasonable. And the PMC is capable to handle this motion.

The reduction of the frequency noise is seen from 100Hz to 30kHz.

The interesting point is that we can see the noise increase above 30kHz when the IMC is locked.
I believe that the phase correction EOM is shared with the PMC modulation. i.e. PMC sees the corrected laser frequency.

We expect that the frequency noise is reduced at this frequency. But in reality not.

In addition, there is a sharp peak at ~35kHz. I wonder If this is caused by the IMC servo. It is worse to investigate.

  11794   Sat Nov 21 00:45:30 2015 KojiUpdateIOOIMC fix

Based on the observation of the PMC error signal, I started measuring the IMC OLTF. Immediately, it was found that the overall IMC loop gain was too low.
The UGF was ~40kHz, which was really marginal. It had been >100kHz when I have adjusted it about a year ago. (Next entry for the detail)

The first obvious thing was that the SMA cables around the IMC servo have visible degradation (Attatched photos).
I jiggled the signal cable from the demodulator Q_out to the MC servo. The openloop gain seemed fluctuating (increased) based on the cabling.
I decided to repair these cables by adding solder on the shield.

Even after the repair, the open loop TF didn't show any improvement. I checked the LO level and found that it was -16.7dBm.

I traced the problem down to the frequency generator unit (T1000461). The front panel of the unit indicates the output power for the 29.5MHz output is 13dBm,
while measurement showed it was 6~8dBm (fluctuating). The T1000461 document describes that there is only a wenzel oscillator inside. Does this mean the oscillatorwas degraded??? We need to open the box.

I was not sure what was the LO level. I naively assumed the input is 0dBm. Reducing the attenuation of the dial on the AM Stabilizer unit from 12dB attn to 0dB.
This made the LO level -3.3dBm.


Later at home, I thought this nominal LO level of 0dBm could have been wrong.

The demodulator circuit (D990511) has the amplifier ERA-5 (G=~20dB) at the input. Between the input and the ERA-5 there is a pattern for an attenuator.
Assuming we have no attenuator, the ERA-5 has to spit out 20dBm. That is too much for this chip. I need to pull out the box to see how much is the nominal LO for this box using an active probe.

This decrease/increase of the LO level affects the WFS demod too. According to D980233-B, the input stage has the comparator chip AD96687, which can handle differential voltage of 5.5V.
Therefore the effect is minimal.

  11795   Sat Nov 21 00:46:33 2015 KojiUpdateIOOIMC OLTF

Here is the comparison before and after the fix.

Before the work, the UGF was ~40kHz. The phase margin was ~5deg. This caused huge bump of the frequency noise.

After the LO power increase, I had to reduce the MC loop gain (VCO Gain) from 18dB to 6dB. This resulted 4dB (x2.5) increase of the OLTF. This means that my fix increased the optical gain by 16dB (x6.3). The resulting UGF and phase mergin were measured to be 117kHz and 31deg, respectively.

 

Now I was curious to see if the PMC err shows reasonable improvement when the IMC is locked. Attachment 2 shows the latest comparison of the PMC err with and without the IMC locked. The PMC error has been taken up to 500kHz. The errors were divided by 17.5kHz LPF and 150kHz LPF to compensate the sensing response. The PMC cavity pole was ignored in this calculation. T990025 saids the PMC finesse is 4400 and the cavity pole is 174kHz. If this is true, this also needs to be applied.

Observations:

1. Now we can see improvement of the PMC error in the region between 10kHz to 70kHz.

2. The sharp peak at 8kHz is due to the marginally stable PMC servo. We should implement another notch there. T990025 suggests that the body resonance of the PMC spacer is somewhere around there. We might be able to damp it by placing a lossy material on it.

3. Similarly, the features at 12kHz and 28kHz is coming from the PMC. They are seen in the OLTF of the PMC loop.

4. The large peak at 36kHz does not change with the IMC state. This does mean that it is coming from the laser itself, or anything high-Q of the PMC. This signal is seen in the IMC error too.

5. 72kHz, 108kHz, 144kHz: Harmonics of 36kHz?

6. Broad feature from 40kHz to 200kHz. The IMC loop is adding the noise. This is the frequency range of the PC drive. Is something in the PC drive noisy???
 

7. The feature at 130kHz. Unknown. Seems not related to IMC. The laser noise or the PMC noise.


Remaining IMC issues:

Done (Nov 23, 2015) - 29.5MHz oscillator output degraded. Possibly unstable and noisy. Do we have any replacement? Can we take a Marconi back from one of the labs?

Done (Nov 23, 2015) - Too high LO?

- Large 36kHz peak in the IMC

- IMC loop shape optimization

- IMC locking issue. The lock streatch is not long.

- IMC PC drive issue. Could be related to the above issue.

Maybe not relevant - PC drive noise?

  11797   Sun Nov 22 12:07:09 2015 KojiUpdateIOOIMC fix

TO DO

Done (Nov 23, 2015) - Check if the attenuator is still there in the input chain

Done (Nov 23, 2015) - Check if the actual LO levels at the 17dBm mixers are reasonable.

- Check if the actual LO levels for the LSC demods are OK too

  11798   Sun Nov 22 12:12:17 2015 KojiUpdateIOOIMC OLTF

Well. I thought a bit more and now I think it is likely that this is just the servo bump as you can see in the closed-loop TF.

Quote:

6. Broad feature from 40kHz to 200kHz. The IMC loop is adding the noise. This is the frequency range of the PC drive. Is something in the PC drive noisy???

  11800   Mon Nov 23 20:32:43 2015 KojiUpdateLSCFrequency source fixed, IMC LO level adjusted

The frequency source was fixed. The IMC LO level was adjusted.

IMC is locked => OLTF measured UGF 144kHz PM 30deg.

  11801   Mon Nov 23 21:48:49 2015 KojiUpdateLSCFrequency source fixed, IMC LO level adjusted

The trouble we had: the 29.5 MHz source had an output of 6 dBm instead of 13 dBm.

The cause of the issue: A short cable inside had its shield cut and had no connection of the return.


- The frequency source box was dismantled.
- The power supply voltages of +28 and +18 were provided from bench supplies.
- The 29.5 MHz output of 5~6 dBm was confirmed on the work bench.
- The 11 MHz OCXO out (unused) had an output of 13 dBm.

- Once the lid was opened, it was immediately found that the output cable for the 29.5 MHz source had a sharp cut of the shield (Attachment1).
- OK. This cable was replaced. The output of 13 dBm was recovered.

- But wait. Why is the decoupling capacitor on the 29.5 MHz OCXO bulging? The polarity of the electrolytic capacitor was wrong!
- OK. This capacitor was replaced. It was 100 uF 35 V but now it is 100 uF 50 V.

- I further found some cables which had flaky shields. Some of them were twisted. When the panel cable s connected, the feedthroughs were rotated. This twists internally connected cables. Solder balls were added to the connector to reinforce the cable end.

- When the box was dismantled, it was already noticed that some of the plastic screws to mount the internal copper heat sinks for ZHL-2's were broken.
They seemed to be degraded because of the silicone grease. I didn't try to replace all as it was expected to take too much time, so only the broken screws
were replaced with steel screws with shoulder washers
at the both side of the box.

- After confirming the circuit diagram, the box was returned to the rack. The 29.5 MHz output of 13 dBm there was confirmed.

  11802   Mon Nov 23 22:12:10 2015 KojiUpdateIOOLO level check for the IMC demod board

In order to check the proper LO level, the IMC demod board was checked. As a short summary, -8dBm is the proper input for the IMC demod board. This was realized when the variable attenuator of the RF AM Stabilizer was set up be -7dB.


Initially, I tried to do the measurement using the extender board. But every board had the issue of +15V not working. After several extender boards were tried, I noticed that the current draw of the demod board burned the 15V line of the extender board.

Then I moved to the work bench. The signals were checked with the 10:1 probe. It's not properly the 50Ohm system, exactly to say.

I found that the LO signals at the mixers have huge distortion as it reaches the nominal 17dBm, and I wondered if ERA-5s were gone. Just in case I replaced the ERA-5s but didn't see any significant change. Then I thought it is due to the mixer itself. The mixer was removed and replaced with a 50Ohm SMD resister. Then the output of the last ERA-5 became sinusoidal, and the level was adjusted to be ~17dBm (4.52 Vpp) when the input power was measured to be -7.7dBm with the RF power meter. Once the mixer was reinstalled, it was confirmed that the waveform becase rectangular like, with the similar amplitude (4.42Vpp).

Now the module was returned to the rack. The RF level at the LO input was adjusted to be -8dBm by setting the attenuator level to be 7dBm.

Once the IMC is locked with this setting, the open loop transfer function was measured. The optical gain seemed almost unchanged compared with the recent nominal. The UGF and PM were measured to be 144kHz and 30deg.

  11804   Tue Nov 24 01:14:23 2015 KojiUpdateLSCALSY recovered

Sorry, I completely forgot to turn the Marconi on...

  11808   Wed Nov 25 10:07:10 2015 KojiUpdateIOOLO level check for the IMC demod board

I didn't finish making the DCC entry for this module yet.

But the attenuators are
- AT1: 10dB. There is a sign that it was 3dB before ---  a 3dB chip was also attached on the boardnext to 10dB.
- AT2/3: Removed. They were replaced with 0Ohm resistors.

Currently the input is -8dBm. The input and output of the first ERA-5 are -17dBm and +7dBm, respectively.
Then the input and output of the second ERA-5 are -2dBm and 17dB, respectively.

In order to remove the second amplification stage, the first stage has to produce 26dBm. This is too much for either ERA-5 or any chips that fits on the foot print. If we use low gain but high output amp like GVA-81 (G=10dB, DF782 package), it is doable

Input 0dBm - [ATTN 3] - -3dBm - [ERA-5 G=20dB] - +16~+17dBm - [Circuits -9dB] - +7dBm - [Attn 0dB] - +7dBm - [GVA-81 G=10dB] - +17dBm

I think we should check the conditions of all the LSC demods.

  11811   Wed Nov 25 16:46:10 2015 KojiUpdateIOOLO level check for the IMC demod board

Awwww. I found that the demod board has the power splitter (PSCJ-2-1) with one output unterminated.
This power splitter should be removed.

https://dcc.ligo.org/D1500443

  11817   Thu Nov 26 19:39:27 2015 KojiUpdateLSCCurrent state of the frequency source, and possible improvement

Uploaded on T1000461 too.

  11822   Sun Nov 29 12:32:26 2015 KojiUpdateLSCCurrent state of the frequency source, and possible improvement

I'm not claiming we need to modify the frequency source immediately as we are not limited by the oscillator amplitude or phase noise.
I just wanted to note something in mind before it goes away quickly.

Alberto's T1000461 tells us that the oscillator and phase noise are degraded by factor of ~3 and ~5 due to the RF chanin.
My diagram is possible removal of up-down situation of the chain.

Maybe more direct improvement would be:

- Removal of two amplifiers out of four. The heat condition of the box is touch thought it is not critical.

- The modification will allow us to have a spare 11MHz channel at 1X2 rack that would be useful for 3f modulation.

  11826   Mon Nov 30 15:17:57 2015 KojiUpdateLSCLO level check for the LSC RF distribution box

T1000461 tells us that the nominal LO input is 2dBm although we don't know what's the LO level is at the mixers in the demod boards.

  11829   Mon Nov 30 18:27:30 2015 KojiUpdateLSCstrange behavior of ASDC

It wasn't fully mentioned in ELOG 11814.
We checked the PD first and this behavior didn't change after the realignment of the AS55PD.
Yutaro confirmed that this effect is happening in the vacuum chamber.

  11834   Tue Dec 1 17:26:14 2015 KojiUpdateGeneralMegatron maitenence

SLOWDC servo was dead. I followed EricQ's instruction.

  11835   Tue Dec 1 20:20:16 2015 KojiUpdateGeneralMegatron maitenence

MC Autolocker got stack somewhere. I had to go to megatron and kill MC Autolocker.

init relaunched the autolocker automatically, and now it started properly.

  11852   Sat Dec 5 21:28:33 2015 KojiHowToCamerasWhen image capture does not work...

Do we need "make" everytime? Do you mean just running "modprobe" didn't work?

  11867   Wed Dec 9 18:45:58 2015 KojiSummaryGeneralNetwork Topology Check

[Eric Q, Gautam, Koji]

We went through the network connections to produce the mapping of the instruments.
Gautam summarized the notes into a spread sheet. See attachments.

We didn't find any irregular connections except for the connection of NETMGR port of c1ioo to Martian Network.
This cable was removed.

  11873   Fri Dec 11 13:28:36 2015 KojiUpdateLSCPower recycling gain estimation from arm loss measurement

Can I ask you to make a plot of the power recycling gain as a function of the average arm loss, indicating the current loss value?

  11876   Fri Dec 11 23:12:09 2015 KojiSummaryCOCLoss map measurement document

Yutaro left detailed slides for his loss map measurement

https://dcc.ligo.org/LIGO-G1501547

  11920   Thu Jan 7 19:04:25 2016 KojiUpdateLSCAUX X Freq Noise measured

The next step is to compare this data with the same measurement with the PSL and the AUX laser on the PSL table (or the end Y laser). If these show a lot lower noise level, we can say 1) the x-end laser is malfunctioning and 2) the y-end and AUX laser on the PSL are well low noise.

  11923   Fri Jan 8 22:37:17 2016 KojiUpdateGeneralNew WiFi router

I configured a new wifi bridge for a GPIB Instruments.

The some facts are described on https://wiki-40m.ligo.caltech.edu/Network

The setting up wasn't so straight forward. I added more details there as a linked page.
One thing I had to do with the martian wifi router was that I had to separate the name of SSIDs for 2GHz and 5GHz networks.


Now the data download from Agilent is super fast!
The first establishing the connection takes the most of the time, and the data transfer takes literary nothing.

controls@pianosa|netgpibdata > time ./netgpibdata -i 192.168.113.167 -d AG4395A -a 10 -f meas01
Connecting to host 192.168.113.167, GPIB 10...
done.
Data will be written into meas01.dat.
Parameters will be written into meas01.par.
Writing measurement data to file...
Writing to the parameter file.

real    0m4.056s
user    0m0.068s
sys    0m0.020s

 

  11941   Thu Jan 21 00:02:11 2016 KojiUpdateLSCHopeful signs

That's a good news. Only quantitative analysis will tell us if it is true or not.

Also we still want to analyze the traffic with the new switch.

Quote:

On a brighter note, I've only noticed one brief EPICS freeze all night. In addition, the wall StripTools seem totally contiuous since ~4pm, whereas I'm used to seeing some blocky shapes particularly in the seismic rainbow. Could this possibly mean that the old WiFi router was somehow involved in all this? 

 

  11964   Sat Jan 30 09:56:24 2016 KojiUpdateGreen LockingInnolight laser is 10 years old

It is strange that there is no difference between with and without NE, isn't it?

  11968   Mon Feb 1 15:43:18 2016 KojiUpdateGreen LockingInnolight laser is 10 years old

This is the same one as what you got from Steve. But you can find full pages.

https://wiki-40m.ligo.caltech.edu/PSL/NPRO

  11971   Tue Feb 2 18:54:02 2016 KojiUpdateGreen LockingLightwave NPRO moved from PSL table to SP table

jiIn fact, it is one of the most difficult type mode profiling to measure a beam directly out from a laser source.

If you reduce the power by ADJ, this significantly changes the output mode as the pumping power varies temperature gradient of the laser crystal and thus thermal lensing in it. I'd recommend you to keep the nominal power.

If you use a PBS for power reduction, you should increase the transmission ~x10 from the minimum so that you are not dominated by possible junk polarization.

Any transmissive BK7 components where the beam is small can cause thermal lensing. In order to avoid this issue, I usually use two noncoated (or one AR coated) optical windows made of UV fused silica to pick off the beam. Once the beam power is reduced I suppose it is OK to use an additional ND filter in front of the CCD.

Another more reliable method is an old-good knife edge measurement.

  11974   Thu Feb 4 09:16:46 2016 KojiUpdateGreen LockingLightwave NPRO moved from PSL table to SP table

I don't think the discrepancy is a serious issue as long as the mode is clean. The mode is determined by the NPRO crystal and is hard to change by anything except for the thermal lensing in the crystal.

And I never succeeded to reproduce the mode listed in the manual.

One thing you'd better to take care is that clipping of the beam produces diffraction. The diffracted beam spreads faster than the nominal TEM00 mode. Therefore the power meter should to be placed right after the razor blade. i.e. As you move the longitudinal position of the razor blade, you need to move the power meter.

  11989   Fri Feb 12 19:07:52 2016 KojiUpdateGreen LockingLaser swap - green light recovered but no flashes in the arm

800e-6 / 0.225^2 = 0.016

=> 1.6%/W

I thought Kiwamu had roughtly 2%/W.

 

  11991   Mon Feb 15 13:09:33 2016 KojiUpdateGeneralSomething has gone wrong - was there a power outage?

Looks like that's the case. LIGO GC also sent an e-mail that there was a popwer glitch.

  12000   Fri Feb 19 15:12:38 2016 KojiSummaryPEMGuralp Health Check

I measured the guralp raw outputs and the TFs using the handheld unit and an FFT analyzer.

[Setup]

The handheld unit was connected to each guralp with the same cable which is confirmed t be functional with the Yend Guralp.

The signal for Z, N, and E directions are obtained from the banana connectors on the handheld unit. Each direction has mass, low gain velocity, and high gain velocity output. The PSDs of the signals were measured with an FFT analyzer. The transfer function from the mass signal to the low/high gain signals were also measured for each direction.

The adjustment screw for the E output of the Xend does not work. I had to tilt the Xend Guralp using the leg screws to bring the E signal to zero.

[Result]

Attachment 1: Raw voltage PSD for all outputs
Attachment 2: Comparison of the low gain vel outputs

- All of the mass output show similar PSDs.
- Low gain velocity outputs shows somewhat similar levels. I still need to check if the output is really the ground velocity or not.
- High gain velocity outputs are either not high gain, broken, or not implemented.

- We need to calibrate the low gain output using signal injection, huddle test, or something else.

Attachment 3: TFs between each mass output and the low or high gain outputs

- TFs between the mass signal and the low vel signals show the similar transfer functions between the channels.
- The high gain outputs show low or no transfer function with regard to the mass signals.
 

  12037   Wed Mar 16 16:02:40 2016 KojiUpdateSUSwire standoff test cut

It looks almost OK, but we need a bit sharper picture for both the groove and thw wire.

  12042   Tue Mar 22 21:30:15 2016 KojiUpdateIOOPMCIMC aligned, WFS offset adjusted

The alignment of the PMC adjusted on the PSL table: Trans 0.737->0.749

The alignment of the IMC adjusrted on the sliders: Trans 14300->15300

WFS offset has been reset by /opt/rtcds/caltech/c1/scripts/MC/WFS/WFSoffsets

  12049   Sat Mar 26 18:28:24 2016 KojiUpdateelogelogd flakiness

Elogd have been restarted several times today because it died everytime I submit something.
Here is the copy of the log.


GET /OMC_Lab/255?cmd=loc&value=Submit HTTP/1.1
Returned 6 bytes
GET /40m/elog.rdf HTTP/1.1
Returned 17109 bytes
TCP connection #1 on socket 5 closed
POST /OMC_Lab/ HTTP/1.1
Returned 20 bytes
GET /OMC_Lab/255 HTTP/1.1
Returned 53721 bytes
GET /ckeditor/skins/moono/images/arrow.png HTTP/1.1
Returned 489 bytes
POST /OMC_Lab/ HTTP/1.1
*** buffer overflow detected ***: /export/home/elog/elog/elogd terminated
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(__fortify_fail+0x37)[0x7f1435639e57]
/lib/x86_64-linux-gnu/libc.so.6(+0x108d50)[0x7f1435638d50]
/lib/x86_64-linux-gnu/libc.so.6(+0x1081b9)[0x7f14356381b9]
/lib/x86_64-linux-gnu/libc.so.6(_IO_default_xsputn+0xdd)[0x7f14355ab0cd]
/lib/x86_64-linux-gnu/libc.so.6(_IO_vfprintf+0x25a8)[0x7f143557ac18]
/lib/x86_64-linux-gnu/libc.so.6(__vsprintf_chk+0x94)[0x7f1435638254]
/lib/x86_64-linux-gnu/libc.so.6(__sprintf_chk+0x7d)[0x7f143563819d]
/export/home/elog/elog/elogd[0x426405]
/export/home/elog/elog/elogd[0x473b7f]
/export/home/elog/elog/elogd[0x4abfb2]
/export/home/elog/elog/elogd[0x4ad7fb]
/export/home/elog/elog/elogd[0x4b0af5]
/export/home/elog/elog/elogd[0x4b1eb9]
/export/home/elog/elog/elogd[0x403568]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xed)[0x7f143555176d]
/export/home/elog/elog/elogd[0x404299]
======= Memory map: ========
00400000-004e6000 r-xp 00000000 fc:00 10361276                           /export/home/elog/elog-3.0.d/elogd
006e5000-006e6000 r--p 000e5000 fc:00 10361276                           /export/home/elog/elog-3.0.d/elogd
006e6000-007c6000 rw-p 000e6000 fc:00 10361276                           /export/home/elog/elog-3.0.d/elogd
007c6000-0173d000 rw-p 00000000 00:00 0
0214d000-02656000 rw-p 00000000 00:00 0                                  [heap]
7f14342f8000-7f143430d000 r-xp 00000000 fc:00 2883628                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7f143430d000-7f143450c000 ---p 00015000 fc:00 2883628                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7f143450c000-7f143450d000 r--p 00014000 fc:00 2883628                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7f143450d000-7f143450e000 rw-p 00015000 fc:00 2883628                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7f143450e000-7f14348cd000 rw-p 00000000 00:00 0
7f1434a34000-7f1434d39000 r--p 00000000 fc:00 530477                     /usr/lib/locale/locale-archive
7f1434d39000-7f1434d4f000 r-xp 00000000 fc:00 655527                     /usr/local/lib/libz.so.1.2.8
7f1434d4f000-7f1434f4e000 ---p 00016000 fc:00 655527                     /usr/local/lib/libz.so.1.2.8
7f1434f4e000-7f1434f4f000 r--p 00015000 fc:00 655527                     /usr/local/lib/libz.so.1.2.8
7f1434f4f000-7f1434f50000 rw-p 00016000 fc:00 655527                     /usr/local/lib/libz.so.1.2.8
7f1434f50000-7f1434f52000 r-xp 00000000 fc:00 2883655                    /lib/x86_64-linux-gnu/libdl-2.15.so
7f1434f52000-7f1435152000 ---p 00002000 fc:00 2883655                    /lib/x86_64-linux-gnu/libdl-2.15.so
7f1435152000-7f1435153000 r--p 00002000 fc:00 2883655                    /lib/x86_64-linux-gnu/libdl-2.15.so
7f1435153000-7f1435154000 rw-p 00003000 fc:00 2883655                    /lib/x86_64-linux-gnu/libdl-2.15.so
7f1435154000-7f1435307000 r-xp 00000000 fc:00 2883609                    /lib/x86_64-linux-gnu/libcrypto.so.1.0.0
7f1435307000-7f1435506000 ---p 001b3000 fc:00 2883609                    /lib/x86_64-linux-gnu/libcrypto.so.1.0.0
7f1435506000-7f1435521000 r--p 001b2000 fc:00 2883609                    /lib/x86_64-linux-gnu/libcrypto.so.1.0.0
7f1435521000-7f143552c000 rw-p 001cd000 fc:00 2883609                    /lib/x86_64-linux-gnu/libcrypto.so.1.0.0
7f143552c000-7f1435530000 rw-p 00000000 00:00 0
7f1435530000-7f14356e4000 r-xp 00000000 fc:00 2884139                    /lib/x86_64-linux-gnu/libc-2.15.so
7f14356e4000-7f14358e3000 ---p 001b4000 fc:00 2884139                    /lib/x86_64-linux-gnu/libc-2.15.so
7f14358e3000-7f14358e7000 r--p 001b3000 fc:00 2884139                    /lib/x86_64-linux-gnu/libc-2.15.so
7f14358e7000-7f14358e9000 rw-p 001b7000 fc:00 2884139                    /lib/x86_64-linux-gnu/libc-2.15.so
7f14358e9000-7f14358ee000 rw-p 00000000 00:00 0
7f14358ee000-7f1435943000 r-xp 00000000 fc:00 2884155                    /lib/x86_64-linux-gnu/libssl.so.1.0.0
7f1435943000-7f1435b42000 ---p 00055000 fc:00 2884155                    /lib/x86_64-linux-gnu/libssl.so.1.0.0
7f1435b42000-7f1435b45000 r--p 00054000 fc:00 2884155                    /lib/x86_64-linux-gnu/libssl.so.1.0.0
7f1435b45000-7f1435b4c000 rw-p 00057000 fc:00 2884155                    /lib/x86_64-linux-gnu/libssl.so.1.0.0
7f1435b4c000-7f1435b6e000 r-xp 00000000 fc:00 2884145                    /lib/x86_64-linux-gnu/ld-2.15.so
7f1435d57000-7f1435d5c000 rw-p 00000000 00:00 0
7f1435d6a000-7f1435d6e000 rw-p 00000000 00:00 0
7f1435d6e000-7f1435d6f000 r--p 00022000 fc:00 2884145                    /lib/x86_64-linux-gnu/ld-2.15.so
7f1435d6f000-7f1435d71000 rw-p 00023000 fc:00 2884145                    /lib/x86_64-linux-gnu/ld-2.15.so
7ffd85795000-7ffd85997000 rw-p 00000000 00:00 0                          [stack]
7ffd859b2000-7ffd859b4000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
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Received unknown cookie "__utma"
Received unknown cookie "_ga"
Received unknown cookie "__unam"
Received unknown cookie "__utma"
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Received unknown cookie "ajs_user_id"
Received unknown cookie "ajs_group_id"
Received unknown cookie "ajs_anonymous_id"
Received unknown cookie "__utma"
Received unknown cookie "_ga"
Received unknown cookie "__unam"
Received unknown cookie "__utma"
Received unknown cookie "tk_ni"
Received unknown cookie "ajs_user_id"
Received unknown cookie "ajs_group_id"
Received unknown cookie "ajs_anonymous_id"
Received unknown cookie "__utma"
Received unknown cookie "_ga"
Received unknown cookie "__unam"
Received unknown cookie "__utma"
Received unknown cookie "tk_ni"
Received unknown cookie "ajs_user_id"
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  12052   Mon Mar 28 22:16:44 2016 KojiUpdateGeneralNew WiFi router

I configured three more mini wifi extender. They are ready to use.

We should add these to the host table (I forgot where it is)

192.168.113.233 NETGEAR_EX3700_1
192.168.113.234 NETGEAR_EX3700_2
192.168.113.235 NETGEAR_EX3700_3
192.168.113.236 NETGEAR_EX3700_4

  12072   Tue Apr 12 22:41:00 2016 KojiUpdateIOOPMC/IMC aligned, WFS offset adjusted

Did it again.

PMC Trans ~0.739
IMC Trans ~15000

  12146   Thu Jun 2 16:35:44 2016 KojiUpdateSUS wire standoffs update

Gap of the prism from the mirror

Sag: s = R(1-Cos[ArcSin[d/2/R]])

- Mirror curvature sag for 2mm prism (R=37.75mm): s=13um

- Minimum gap: 20um => s=33um => R=15mm

- Nominal gap: 35um => s=48um => R=10mm

- Maximum gap: 50um => s=63um => R=8mm


The second figure shows somewhat realistic arrangement of the pieces

  12223   Tue Jun 28 20:43:23 2016 KojiSummaryCOCFirst Contact cleaning practice

Made a dry run of the in-situ cleaning for a 3inch optic.

Attachment 1: The Al dummy mass is clamped in the suspension cage.
Attachment 2: The front surface was painted. The nominal brush with the FC bottle was used.
Attachment 3: Zoom in of the front surface.
Attachment 4: The back surface was painted.
Attachment 5: The back surface was peeled.
Attachment 6: The front surface was peeled too.
Attachment 7: The peeled layers.

Findings:

1. To paint a thick layer (particlarly on the rim) is the key to peel it nicely.

2. It was helpful for easier peeling to have mutiple peek tabs. Two tabs were sufficient for ~1" circle.

3. The nominal brush with the bottle was OK although one has to apply the liquid many times to cover such a large area. A larger brush may cause dripping.

4. The nominal brush was sufficiently long once the OSEMs are removed. In any case it is better to remove the OSEMs.

  12255   Wed Jul 6 19:36:45 2016 KojiUpdateGeneralSUS Vmon

I wanted to know what this Vmon exactly is. D010001 is telling us that the Vmon channels are HPFed with fc=30Hz (Attachment 1). Is this true?


I checked the quiscent noise spectrum of the ITMX UL coil output (C1:SUS-ITMX_ULCOIL_OUT) and the corresponding VMON (C1:SUS-ITMX_ULVmon). (Attachment 2 Ref curves). I did not find any good coherence. So the nominal quiscent Vmon output is carrying no useful information. 

Question: How much do we need to excite the coil output in order to see any meaningful signal?

As I excite the ITMX UL coil (C1:SUS-ITMX_ULCOIL_EXC) with uniform noise of 100-300 counts below 0.3Hz, I eventually could see the increase of the power spectrum and the coherence (Attachment 2). Below 0.1 Hz the coherence was ~1 and the transfer function was measured to be -75dB and flat. But wait, why is the transfer function flat?

In fact, if I inject broadband noise to the coil, I could increase the coil output and Vmon at the same time without gaining the coherence. (Attachment 3). After some more investigation, I suspect that this HPF is diabled (= bypassed) and aliasing of the high freq signal is causing the noise in Vmon.

In order to check this hypothesis, we need to visit the board.

  12256   Wed Jul 6 20:51:00 2016 KojiUpdateGeneralSeismometer Enclosure Development | SURF 2016

Circuit1: It is nice to receive the voltage across the transimpedance resistor with a high impedance buffer (or amplifier), as close to the resister as possible. This amplifier needs to have low numbers for input bias current, input offset current, and input current noise. These current noise becomes the noise of the temperature reading. On the top of that, the input voltage noise of the buffer will be added to the output. The typical noise model can be found in http://www.analog.com/media/en/technical-documentation/application-notes/AN-940.pdf

The good candidates for the buffer is LT1128, ADA4004, OPA140, and LT1012. If the application is not too sensitive to the total noise, OPA604 is a good choise with easier handling.

Circuit2: With the same reason, AD741 is an old generic amp that is not a great choise for this purpose. The current noise is more significant because of the higher transimpedance here. The same noise model as above can be used to analyze the performance.

ELOG V3.1.3-