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  15482   Wed Jul 15 17:46:05 2020 anchalSummaryALSNoise budget for ALS

I started my attempt on noise budgeting of ALS by going back to how Kiwamu did it and adding as many sources as I could find up till now. This calculation is present in ALS_Noise_Budget notebook. I intend to collect data for noise sources and all future work on ALS in the ALS repo.

The noise budget runs simulink through matlab.engine inside python and remaining calculations including the pygwinc ones are done in python. Please point out any errors that I might have done here. I still need to add noise due to DFD and the ADC after it. For the residual frequency noise of AUX laser, I have currently used an upper limit of 1kHz/rt Hz at 10 Hz free-running frequency noise of an NPRO laser.

Attachment 1: ALS_nb.pdf
ALS_nb.pdf
  15496   Mon Jul 20 19:21:16 2020 anchalSummaryALSFew proposals for Voyager ALS

I've added 4 proposed schemes for implementing ALS in voyager. Major thing to figure out is what AUX laser would be and how we would compare the different PSL and AUX lasers to create an error signal for ALS. Everywhere below, 2um would mean wavelengths near 2 um including the proposed 2128nm. Since it is not fixed, I'm using a categorical name. Same is the case for 1um which actually would mean half of whatever 2 um carries.


Higher Harmonic Generation:

  • We can follow the current system of ALS with using 1.5 times PSL frequency as AUX instead of second harmonic as 1 um is strongly absorbed in Si.
  • To generate 1.5 times PSL frequency, three stages would be required.
    • SHG: Second Harmonic Generation mode matched to convert 2um to 1um. If we are instead making 2 um from 1um to start with, this stage will not be required.
    • SFG: Sum Frequency Generation mode matched to sum 2um photon and 1um photon to give 0.65 um photon.
    • DPDC: Degenerate Parametric Down Conversion mode matched to convert 0.65 um to 1.3 um (which would be 1.5 times PSL frequency).
  • To compare, we can either convert pick-off from PSL to AUX frequency by doing the above 3 stages (Scheme II).
  • Or we can just do SHG and SFG at PSL pick-off and do another SHG at AUX end (Scheme I) to compare the AUX and PSL both converted to 0.65 um (which would be 2 times AUX and 3 times PSL frequency).
  • This method would have added noise from SHG, SFG and DPDC processes along with issues to be inefficiency of conversion.

Arbitrary AUX frequency:

  • We can get away with using some standard laser near 1.5 um region directly as AUX. Most probably this would be 1550 nm.
  • What's left is to devise a method of comparing 1.5 um and 2um frequencies. Following are two possible ways I could think of:

Using a frequency comb:

  • Good stable frequency combs covering the wavelength region from 1.5 um to 2 um are available of the shelf.
  • We would beat PSL and transmitted AUX separately with the frequency comb. The two beat note frequencies would be:
    \Delta_\text{PSL} = \nu_\text{PSL} - \nu_{CEO} - m_1 \nu_\text{Rep}
    \Delta_\text{AUX} = \nu_\text{AUX} - \nu_{CEO} - m_2 \nu_\text{Rep}
  • Here, m1 and m2 represent the nearest modes (comb teeth) of frequency comb to PSL and AUX respectively.
  • Carrier Envelope Offset frequency (\nu_{CEO}) can be easily generated by using an SHG crystal in front of the Frequency comb. This step is not really required since most of the modern frequency combs now comb with inbuilt zero \nu_{CEO} stabilization.
  • Mixing above beatnotes with \nu_{CEO} would remove \nu_{CEO} from them along with any noise associated with \nu_{CEO}.
  • Further, a Direct Digital Synthesis IC is required to multiply the AUX side RF signal by m1/m2. This finally makes the two RF signals to be:
    \nu_{A} = \nu_\text{PSL} - m_1 \nu_{Rep}
    \nu_{B} = \frac{m_1}{m_2}\nu_\text{AUX} - m_1 \nu_{Rep}
  • Which on mixing would give desired error signal for DFD as :
    \nu_\text{PSL} - \frac{m_1}{m_2}\nu_\text{AUX}
  • This method is described in Stenger et al. PRL. 88, 073601 and is useful in comparing two different optical frequencies with a frequency comb with effective cancellation of all noise due to the frequency comb itself. Only extra noise is from the DDS IC which is minimal.
  • This method, however, might be an overkill and expensive. But in case (for whatever reason) we want to send in another AUX at another frequency down the 40m cavity, this method allows the same setup to be used for multiple AUX frequencies at once.

Using a Transfer Cavity:

  • We can make another more easily controlled and higher finesse cavity with a PZT actuator on one of the mirrors.
  • In the schematic, I have imagined it has a triangular cavity with a back end mirror driven by PZT.
  • Shining PSL from one side of the transfer cavity and employing the usual PDH, we can lock the cavity to PSL.
  • This lock would require to be strong and wide bandwidth. If PZT can't provide enough bandwidth, we can also put an EOM inside the cavity! (See this poster from Simon group at UChicago)
  • Another laser at AUX frequency, called AUX2 would be sent from the other side of the cavity and usual PDH is employed to lock AUX2 to the transfer cavity.
  • So clearly, this cavity also requires coatings and coarse length such that it is resonant with both PSL and AUX frequencies simultaneously.
  • And, the FSS for AUX2 needs to be good and high bandwidth as well.
  • The transmitted AUX2 from the transfer cavity now would carry stability of PSL at the frequency of AUX and can be directly beaten with transmitted AUX from the 40m cavity to generate an error signal for DFD.
  • I believe this is a more doable and cheaper option. Even if we want to do a frequency comb scheme, this could be a precursor to it.

_________________________

EditTue Jul 21 17:24:09 2020: (Jamie's suggestion)

Using Mode Cleaner cavity as Transfer Cavity:

  • If we coat the mode cleaner cavity mirrors appropriately, we can use it to lock AUX2 laser (mentioned above).
  • This will get rid of all extra optics. The only requirement is for FSS to be good on AUX2 to transfer PSL (MC) stability to AUX frequency.
  • I've added suggested schematic for this scheme at the bottom.

 

Attachment 1: VoyagerALSSchemes.pdf
VoyagerALSSchemes.pdf VoyagerALSSchemes.pdf VoyagerALSSchemes.pdf VoyagerALSSchemes.pdf VoyagerALSSchemes.pdf
  15587   Sat Sep 19 23:59:22 2020 anchalSummaryALSALS noise budget update

Setting the record straight

I found out an error I did in copying some control model values from Kiwamu's matlab code. On fixing those, we get a considerably reduced amount of total noise. However, there was still an unstable region around the unity gain frequency because of a very small phase margin. Attachment 3 shows the noise budget, ALS open-loop transfer function, and AUX PDH open-loop transfer function with ALS disengaged. Attachment 4 is the yaml file containing all required zpk values for the control model used. Note that the noise budget shows out-of-loop residual arm length fluctuations with respect to PSL frequency. The RMS curve on this plot is integrated for the shown frequency region.


Trying to fix the unstable region

Adding two more poles at 100 Hz in the ALS digital filter seems to work in making the ALS loop stable everywhere and additionally provides a steeper roll-off after 100 Hz. Attachment 1 shows the noise budget, ALS open-loop transfer function, and AUX PDH open-loop transfer function with ALS disengaged. Attachment 2 is the yaml file containing all required zpk values for the control model used. Note that the noise budget shows out-of-loop residual arm length fluctuations with respect to PSL frequency. The RMS curve on this plot is integrated for the shown frequency region.

But is it really more stable?

  • I tried to think about it from different aspects. One thing is sure that  1+G_{OL} remains greater than 1 in all of the frequency region plotted for. This is also evident in the common-mode to residual noise transfer function which shows no oscillation peaks and is a clean mirror image of the open-loop transfer function (See Attachment 1, page 2).
  • Another way is to look for the phase margin. This is a little controversial way of checking stability. For clarity, the open-loop transfer function I'm plotting does not contain the '-1' feedback in it. So the bad phase value at unity gain frequency is -180 degrees (or 180 degrees) for us. I've taken the difference from the closest side and got 76.2 degrees of phase margin.
  • Another way I checked was by plotting a Nyquist plot for the open-loop transfer function. It is said that if the contour does not encircle the point '-1' in the real axis, then the loop would be stable even if the f_{180} < f_{UGF} where f_{180} is the frequency where phase lag becomes -180 degrees at the lowest frequency. For us, f_{180} is at 1 Hz because of the test mass actuator pole. But I have verified that the Nyquist contour of the open-loop transfer function does not encircle '-1' point. I have not uploaded the Nyquist plot as it is not straight forward to plot. Because of large dc gain, it covers a large region and one needs to zoom in and out to properly follow what the contour is really doing. I didn't get time to make insets for it.

Is this close to reality?

For that, we'll have to take present noise source estimates but Gautum vaguely confirmed that this looked more realistic now 'shape-wise'. If I remember correctly, he mentioned that we currently can achieve 8 pm of residual rms motion in the arm cavity with respect to the PSL frequency. So we might be overestimating our loop's capability or underestimating some noise source. More feedback on this welcome and required.


Additional Info:

The code used to calculate the transfer functions and plot them is in the repo 40m/ALS/noiseBudget

Attachment 5 here shows a block diagram for the control loop model used. Output port 'Res_Disp' is used for referring all the noise sources at the residual arm length fluctuation in the noise budget. The open-loop transfer function for ALS is calculated by -(ALS_DAC->ALS_Out1 / ALS_DAC->ALS_Out2) (removing the -1 negative feedback by putting in the negative sign.) While the AUX PDH open-loop transfer function is calculated by python controls package with simple series cascading of all the loop elements.

 

 

Attachment 1: ALS_nb_ExtraPoles.pdf
ALS_nb_ExtraPoles.pdf ALS_nb_ExtraPoles.pdf ALS_nb_ExtraPoles.pdf
Attachment 2: ALS_controls.yaml
# -----------------------------------------------------------------------------
# AUX
# -----------------------------------------------------------------------------
## Cavity Pole
C_AUX:
  p: 1.8883e+04
  k: 1.1865e+05

H_AUX:
  z: 0
... 109 more lines ...
Attachment 3: ALS_nb_Kiwamus_Values.pdf
ALS_nb_Kiwamus_Values.pdf ALS_nb_Kiwamus_Values.pdf ALS_nb_Kiwamus_Values.pdf
Attachment 4: ALS_controls_Kiwamus_Values.yaml
# -----------------------------------------------------------------------------
# AUX
# -----------------------------------------------------------------------------
## Cavity Pole
C_AUX:
  p: 1.8883e+04
  k: 1.1865e+05

H_AUX:
  z: 0
... 107 more lines ...
Attachment 5: ALS_simulink_model.svg
ALS_simulink_model.svg
  15593   Tue Sep 22 00:14:43 2020 anchalSummaryALSALS noise budget update

This is not a reply to comments given to the last post; Still working on incorporating those suggestions.


Trying out a better filter from scratch

Rana suggested looking first at what needs to be suppressed and then create a filter suited for the noise from scratch. So I discarded all earlier poles and zeros and just kept the resonant gains in the digital filter. With that, I found that all we need is three poles at 1 Hz and a gain of 8.1e5 gives the lowest RMS noise value I could get.

Now there can be some practical reasons unknown to me because of which this filter is not possible, but I just wanted to put it here as I'll add the actual noise spectra into this model now.


Few questions:

  • What anti-aliasing filters are used in ALS?
  • Is the digital delay fixed to a constant upper limit or is it left to change as per filters? I have already used a 470 us delay (modeled with Pade 4th order approximation).
  • I could not find a good place where channel names are listed with corresponding meaning. Where can I find them?
  • Is there a channel which keeps a record of lock status? In short, how do I find the in-lock times
Attachment 1: ALS_NoiseBudgetUpdate.pdf
ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf
Attachment 2: ALS_controls.yaml
# -----------------------------------------------------------------------------
# AUX
# -----------------------------------------------------------------------------
## Cavity Pole
C_AUX:
  p: 1.8883e+04
  k: 1.1865e+05

H_AUX:
  z: 0
... 106 more lines ...
  15601   Wed Sep 23 11:13:49 2020 anchalSummaryALSALS noise budget update

Yes, that loop was unstable. I started using the time domain response to check for the stability of loops now. I have been able to improve the filter slightly with more suppression below 20 Hz but still poor phase margin as before. This removes the lower frequency region bump due to seismic noise. The RMS noise improved only slightly with the bump near UGF still the main contributor to the noise.


For inclusion of real spectra, time delays and the anti-aliasing filters, I still need some more information.

Few questions:

  • What anti-aliasing filters are used in ALS?
  • Is the digital delay fixed to a constant upper limit or is it left to change as per filters? I have already used a 470 us delay (modeled with Pade 4th order approximation).
  • I could not find a good place where channel names are listed with corresponding meaning. Where can I find them?
  • Is there a channel which keeps record of lock status? In short, how do I find the in-lock times

Additional Info:

The code used to calculate the transfer functions and plot them is in the repo 40m/ALS/noiseBudget

Related Elog post with more details: 40m/15587

Attachment 1: ALS_NoiseBudgetUpdate.pdf
ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf
Attachment 2: ALS_controls.yaml
# -----------------------------------------------------------------------------
# AUX
# -----------------------------------------------------------------------------
## Cavity Pole
C_AUX:
  p: 1.8883e+04
  k: 1.1865e+05

H_AUX:
  z: 0
... 113 more lines ...
  15622   Fri Oct 9 18:32:14 2020 anchalSummaryALSALS noise budget update - Updated AUX PDH Loop values

The only two PZT Phase modulation transfer function measurements I could find are 40m/15206 and 40m/12077. Both these measurements were made to find a good modulation frequency and do not go below 50 kHz. So I don't think these will help us. We'll have to do a frequency transfer function measurement at lower frequencies.
I'm still looking for ALS PDH loop measurements to verify the model. I found this 40m/15059 but it is only near the UGF. The UGF measured here though looks very similar to the model prediction. A bit older measurement in 2017 was this 40m/13238 where I assume by ALS OLTF gautum meant the green laser PDH OLTF. It had similar UGF but the model I have has more phase lag, probably because of a 31.5 kHz pole which comes at U7 through the input low pass coupling through R28, C20 and R29 (See D1400293)

If the green laser is not being used, can I go and take some of these measurements myself?

  15626   Wed Oct 14 17:03:55 2020 anchalSummaryALSALS noise budget update - Added whitening filter for ADC

Koji recommended that I can add whitening filters to suppress ADC noise easily. I added a filter before ADC in ALS loop with 4 zeros at 1.5 Hz and 4 poles at 100 Hz and added a reversed filter in the digital filter of ALS. This did not change the performance of the loop but significantly reduced the contribution of ADC noise above 1 Hz. One can see ALS_controls.yaml for the filter description. Please let me know if this does not make sense or there is something that I have overlooked.

Now, the dominant noise source is DFD noise below 100 Hz and green laser frequency noise above that. For DFD noise, I used data dating back to Kiwamu's paper. The noise contribution from DFD in the model is lower than the latest measured ALS noise budget post on elog. I'll look further into design details and noise of DFD.


Code, data, and schematics

Attachment 1: ALS_NoiseBudgetUpdate.pdf
ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf
  15629   Thu Oct 15 13:48:58 2020 anchalSummaryGeneralLab Entry Notification

I entered 40m today at around 1:20 pm and left by 1:45 pm. I entered 104 through the machine shop entry. I did the following:

  • I took photos and videos of the PSL table with lights on.
  • I uncovered the AP table, took photos and video, and covered it back.
  • I went to the X End table and took a video without opening the enclosure.
  • Apart from flipping light switches, nothing else should have changed.
  15632   Fri Oct 16 19:44:41 2020 anchalSummaryGeneralLab Entry Notification

I entered 40m today at around 1:10 pm and left by 1:50 pm. I entered 104 through the machine shop entry. I took top view single picture photos of ITMY, BS, AP, ITMX, ETMX and ETMY tables. The latest photos will be put here on the wiki soon.

  15640   Fri Oct 23 09:03:43 2020 anchalUpdateElectronicsHV coil driver packaged into 2U chassis

Andrew made a battery-powered 0.7 nVrtHz input-referred noise pre-amplifier for gain of 200. That might help you.

Quote:

we'd need a preamp with better than 1nV/rtHz to directly measure the noise I guess.

RXA: 0.7 nV is OK if you're not interested in low noise measurements. Otherwise, we have the transformer coupled pre-amp from SRS which does 0.15 nV/rHz and the Rai Weiss FET amp which has 0.35 nV for high impedance sources.

  15650   Thu Oct 29 09:50:12 2020 anchalSummaryCalibrationPreliminary calibration measurement taken

I went to 40m yesterday at around 2:30 pm and Koji showed me how to acquire lock in different arms and for different lasers. Finally, we took a preliminary measurement of shaking the ETMX at some discrete frequencies and looking at the beatnote frequency spectrum of X-end laser's fiber-coupled IR and Main laser's IR pick-off.


Basic controls and measurement 101 at 40m

  • I learned a few things from Koji about how to align the cavity mirrors for green laser or IR laser.
  • I learned how to use ASS and how to align the green end laser to the cavity. I also found out about the window at ETMX chamber where we can directly see the cavity mode, cool stuff.
  • Koji also showed me around on how to use diaggui and awggui for taking measurements with any of the channels.

Preliminary measurement for calibration scheme

We verified that we can send discrete frequency excitation signals to ETMX actuators directly and see a corresponding peak in the spectrum of beatnote frequency between fiber-coupled X-end IR laser and main laser IR pickoff.

  • I sent excitation signal at 200 Hz, 250 Hz and 270 Hz at C1:SUS-ETMX_LSC_EXC channel using awggui with an amplitude of 100 cts and gain of 2.
  • I measured corresponding peaks in the beatnote spectrum using diaggui.
  • Page 1 shows the ASD data for the 4 measurements taken with Hanning window and averaging of 10.
  • Page 2 shows close up Spectrum data for the 4 measurements taken with flattop window and averaging of 10.
  • I converted this frequency signal into displacement by using conversion factor \nu_{FSR}/\frac{\lambda}{2} or \frac{L \lambda}{c}.

If full interferometer had been locked, we could have used the DARM error signal output to calibrate it against this measurement.

Data

Attachment 1: PreliminaryCalibrationData.pdf
PreliminaryCalibrationData.pdf PreliminaryCalibrationData.pdf
  15760   Tue Jan 12 08:21:47 2021 anchalHowToCDSAcromag wiring investigation

I used an Acromag XT1221 in CTN to play around with different wiring and see what works.  Following are my findings:


Referenced Single Ended Source (Attachment 1):

  • If the source signal is referenced single ended, i.e. the signal is only on the positive output and the negative side is tied to GND on the source side AND this GND is also shared by the power supply powering the Acromag, then no additional wiring is required.
  • The GND common to the power supply and the source is not required to be Earth GND but if done so, it should be at one point only.
  • RTN terminal on Acromag can be left floating or tied to IN- terminal.

Floating Single Ended Source (Attachment 2):

  • If the source signal is floating single-ended i.e. the signal is only on the positive output and the negative output is a floating GND on the source, the the IN- should be connected to RTN.
  • This is the case for handheld calibrators or battery powered devices.
  • Note that there is no need to connect GND of power supply to the floating GND on the source.

Differential Source (Attachment 3):

  • If the source is differential output i.e. the signal is on both the positive output and the negative output, then connect one of the RTN terminals on Acromag to Earth GND. It has to be Earth GND for this to work.
  • Note that you can no longer tie the IN- of different signals to RTN as they are all carrying different negative output from the source.
  • Earth GND at RTN gives acromag a stable voltage reference to measure against the signals coming in IN+ and IN-. And the most stable voltage reference is of course Earth GND.

Conclusion:

  • We might have a mix of these three types of signals coming to a single Acromag box. In that case, we have to make sure we are not connecting the different IN- to each other (maybe through RTN) as the differential negative inputs carry signal, not a constant voltage value.
  • In this case, I think it would be fine to always use differential signal wiring diagram with the RTN  connected to Earth GND.
  • There's no difference in software configuration for the two types of inputs, differential or single-ended.
  • For cases in which we install the acromag box inside a rack mount chasis with an associated board (example: CTN/2248), it is ok and maybe the best to use the Attachment 1 wiring diagram.

Comments and suggestions are welcome.


Related elog posts:

40m/14841    40m/15134


Edit Tue Jan 26 12:44:19 2021 :

Note that the third wiring diagram mentioned actually does not work. It is an error in judgement. See 40m/15762 for seeing what happens during this.

Attachment 1: SingleEndedNonFloatingWiring.pdf
SingleEndedNonFloatingWiring.pdf
Attachment 2: SingleEndedFloatingWiring.pdf
SingleEndedFloatingWiring.pdf
Attachment 3: DifferentialSignalWiring.pdf
DifferentialSignalWiring.pdf
  10424   Fri Aug 22 15:11:55 2014 andres, nicolasSummaryIOOMC WFS activity

1. Before doing anything, we centered the IOO QPDs.
2. With the WFS enabled, we offloaded the control signals onto the bias sliders. Then we saved the slider values. The MC LSC diode had a DC value of ~0.5
3. Turned down power with half wave plate before PMC.  Power injected to vacuum ~ 100mW.
4. We did a beam scan of MC REFL, it looks smaller than what Andres predicted based on the MC eigenmode by 10-20%.
5. We made many changes on the table, pictures to be added by Andres.
6. We didn't have the 80% reflector we wanted to increase the WFS power, so it's still a 98%.
6. Beams were aligned on MC REFL PL, camera, beam dumps, WFSs.
7. Clean up
8. PSL power increased to 1.2W, MC locked right away.
9 We didn't change the IOO WFS output matrix, but we changed some signs and gains to make everything stable. MC autolocker brings it back from cold just fine.
10. All time bombs that we've left will be E.Q.'s to clean up. Sorry.\
11. Yay

  74   Wed Nov 7 00:51:33 2007 andrey, rob, tobinConfigurationIOOMC ringdowns
We completed several ringdown measurements this afternoon; Andrey is currently processing the data.
  8892   Mon Jul 22 17:17:30 2013 annalisaUpdateendtable upgradeEnd table picture
Attachment 1: YendTable.jpg
YendTable.jpg
  13711   Tue Mar 27 19:32:03 2018 arijitUpdateIOOPSL noise eater was off

Kevin, Gautam and Arijit

We made a measurement of the MC_REFL photodiode transfer function using the network analyzer. We did it for two different power input (0dB and -10dB) to the test measurement point of the MC_REFL photodiode. This was important to ensure the measurements of the transfer function of the MC_REFL photodiode was in the linear regime. The measurements are shown in attachment 1. We corrected for phase noise for the length of cable (50cm) used for the measurement. With reference to ELOG 10406, in comparison to the transimpedance measurement performed by Riju and Koji, there is a much stronger peak around 290MHz as observed by our measurement.


We also did a noise measurement for the MC_REFL photodiode. We did it for three scenarios: 1. Without any light falling on the photodiode 2. With light falling on the photodiode, the MC misaligned and the NPRO noise eater was OFF 3. With light falling on the photodiode, the MC misaligned and the NPRO noise eater was ON. We observed that the noise eater does reduce the noise being observed from 80kHz to 20MHz. This is shown in attachment 2.


We did the noise modelling of the MC_REFL photodiode using LISO and tried matching the expected noise from the model with the noise measurements we made earlier. The modeled noise is in good agreement with the measured noise with 10Ohms in the output resistance. The schematic for the MC_REFL photodiode however reveals a 50Ohm resistance being used. The measured noise shows excess noise ~ 290MHz. This is not predicted from the simplied LISO model of the photodiode we took.


Discussion with Koji and Gautam revealed that we do not have the exact circuit diagram for the MC_REFL photodiode. Hence the simplified model that was assumed earlier is not able to predict the excess noise at high frequencies. One thing to note however, is that the excess noise is measured with the same amplitude even with no light falling on the MC_REFL photodiode. This means that there is a positive feedback and oscillation in the op-amp (MAX4107) at high frequencies. One way to refine the LISO model would be to physically examine the photodiode circuit.

We also recorded the POX and POY RF monitor photodiode outputs when the interferometer arms are independently stabilized to the laser. Given the noise outputs from the RF photodiodes were similar, we have only plotted the POY RF monitor output for the sake of clarity and convenience.

Quote:

While Kevin and Arijit were doing their MC_REFL PD noise measurements (which they will elog about separately shortly), I noticed a feature around 600kHz that reminded me of the NPRO noise eater feature. This is supposed to suppress the relaxation oscillation induced peak in the RIN of the PSL. Surprisingly, the noise eater switch on the NPRO front panel was set to "OFF". Is this the normal operating state? I thought we want the noise eater to be "ON"? Have to measure the RIN on the PSL table itself with one of the many available pick off PDs. In any case, as Attachment #1 showed, turning the noise eater back on did not improve the excess IMC frequency noise.

 

Attachment 1: MCREFL_TF.pdf
MCREFL_TF.pdf
Attachment 2: MCREFL_SPECTRUM.pdf
MCREFL_SPECTRUM.pdf
  13716   Wed Mar 28 21:47:37 2018 arijitUpdateIOOMCREFL_PD Optical response measurement

Kevin, Gautam and Arijit

We did a optical measurement of the MCREFL_PD transimpedance using the Jenny Laser set-up. We used 0.56mW @1064nm on the NewFocus 1611 Photodiode as reference and 0.475mW @1064nm on the MCREFL_PD. Transfer function was measured using the AG4395 network analyzer. We also fit the data using the refined LISO model. From the optical measurement, we can see that we do not have a prominent peak at about 300MHz like the one we had from the electrical transimpedence measurement. We also put in the electrical transimpedence measurement as reference. RMS contribution of 300MHz peak to follow.

 

As per Rana`s advice I have updated the entry with information on the LISO fit quality and parameters used. I have put all the relevant files concerning the above measurement as well as the LISO fit and output files as a zip file "LISO_fit" . I also added a note describing what each file represents. I have also updated the plot with fit parameters and errors as in elog 10406.

Attachment 1: LISO_fit_with_info.pdf
LISO_fit_with_info.pdf
Attachment 2: LISO_fit.zip
  13719   Thu Mar 29 17:57:36 2018 arijitUpdateIOOMCREFL_PD Optical response measurement

Kevin, Gautam and Arijit

Today we performed the in-loop noise measurements of the MCREFL-PD using the SR785 to ascertain the effect of the Noise Eater on the laser. We took the measurements at the demodulated output channel from the MCREFL-PD. We performed a series of 6 measurements with the Noise Eater ''ON'' and ''OFF''. The first data set is an outlier probably, due to some transient effects. The remaining data sets were recorded in succession with a time interval of 5 minutes each between the Noise Eater in the ''ON'' and ''OFF'' state. We used the calibration factor of 13kHz/Vrms from elog 13696 to convert the V_rms to Hz-scale.

The conclusion is that the NOISE EATER does not have any noticeable effect on the noise measurements.

ALS beat spectrum and also the arm control signal look as they did before. coherence between arm control signals (in POX/POY lock) is high between 10-100Hz, so looks like there is still excess frequency noise in the MC transmitted light. Looking at POX as an OOL sensor with the arm under ALS control shows ~10x the noise at 100 Hz compared to the "nominal" level, consistent with what Koji and I observed ~3weeks ago.

We tried swapping out Marconis. Problem persists. So Marconi is not to blame. I wanted to rule this out as in Jan, Steve and I had installed a 10MHz reference to the rear of the Marconi.

Attachment 1: NOISE_EATER_On_OFF.pdf
NOISE_EATER_On_OFF.pdf
  12628   Sun Nov 20 23:53:38 2016 awadeUpdatePSLFSS Slow control -> Python, WFS re-engaged

I made a very slighly updated version of Yinzi's script that pulls the channel names and actuator hardstop limits from an external .ini config file. The idea was to avoid having as many versions of the script as there are implimentations of it. Seems like slighly better practice, but maybe I'm wrong. The config files are also easier to read. Its posted on the elog (PSL:1758) with lastest on the 40mSVN .../trunk/CTNLab/current/computing/scripts . 

If you're working off her first implimentation 'RCAV_thermalPID.py' then there is an indent issue after the if statement on line 88: only line 89 should be indended. If you deactivate the debug flag then the script fails to read in PID factors and dies.

Quote:

[yinzi, craig, gautam]

Yinzi had translated the Perl PID script used to implement the discrete-time PID control, and had implemented it with Andrew at the PSL lab. Today afternoon we made some minor edits to make this suitable for the FSS Slow loop (essentially just putting the right channel names into her Python script). I then made an init file to run this script on megatron, and it looks to be working fine over the last half hour of observation or so. I am going to leave things in this state over the weekend to see how it performs.


We have been running with just the MC2 Transmission QPD for angular control of the IMC for a couple of months now because the WFS loops seemed to drag the alignment away from the optimum. We did the following to try and re-engage the WFS feedback:

  • Close the PSL shutter, turned off all the lights in the lab and ran the WFS DC offsets script
  • Locked the IMC, optimized alignment by hand (WFS feedback turned off)
  • Unlocked the IMC, went to the AS table and centered the spots on the WFS
  • Ran WFS RF offsets script
  • Re-engaged WFS servo

 

 

  13456   Tue Nov 28 17:27:57 2017 awadeBureaucracyCalibration-RepairSR560 return, still not charging

I brought a bunch of SR560s over for repair from Bridge labs. This unit, picture attached (SN 49698), appears to still not be retaining charge. I’ve brought it back. 

Attachment 1: 96B6ABE6-CC5C-4636-902A-2E5DF553653D.jpeg
96B6ABE6-CC5C-4636-902A-2E5DF553653D.jpeg
Attachment 2: image.jpg
image.jpg
  13500   Wed Jan 3 16:25:32 2018 awadeUpdateOptimal ControlOplev loop tuning

Another cool feature is client side pre-commit hooks. They can be used to run checks on the local version at the time of commit and refuses to push until the pass/fail exits 0.

Can be the same as the Gitlab CI or just basic code quality checks.  I use them to prevent jupyter notebooks being commited with uncleared cells. It needs to be set up on the user's computer manually and is not automatically cloned with the directory: a script can be included in the repo to do this and run manually on first time clone.

Quote:

When putting code into git.ligo.org, one way to have automated testing is to use the Gitlab CI. This is an automated 'checker', much like the 'Travis' system used in GitHub. Essentially, you give it a make files which it runs somewhere and your GIT repo web page gets a little 'failed/passing' badge telling you if its working. You can also browse the logs to see in detail what happened. This avoids the 'but it works on my computer!' thing that we usually hear.

 

  14174   Tue Aug 21 17:32:51 2018 awadeBureaucracyEquipment loanOne P-810.10 Piezo Actuators element removed

I've taken a PI Piezo Actuator (P-810.10) from the 40m collection. I forgot to note it on the equipment checklist by the door, will do so when I next drop by.

  14555   Fri Apr 19 12:06:31 2019 awadeBureaucracyElectronicsBorrowed Busby Box May 19th 2019

I've borrowed the Busby Box for a day or so.  Location: QIL lab at Bridge West.

Edit  Sat Apr 20 21:16:46 2019 (awade): returned.

  14565   Wed Apr 24 11:22:59 2019 awadeBureaucracyEquipment loanBorrowed Zurich HF2LI Lock in Amplifer to QIL

Borrowed Zurich HF2LI Lock in Amplifer to QIL lab Wed Apr 24 11:25:11 2019.

  12385   Tue Aug 9 13:53:57 2016 babbottUpdateSEIlong Guralp EX cable repaired on the D-sub side

I checked out the cable that I took from you, and all of the connections looked right.  The only thing I did notice was that some of the soldered wires on the 37-pin connector had gotten hot enough to melt their insulation, and potentially short together.  I cut off that connector, and left it on your desk to check out.  I put on a new connector, and checked the pinout.  If the Guralps still doesn't work, we'll have to check out other possibilities.

  13934   Fri Jun 8 14:40:55 2018 c1lscUpdateCDSi am dead
Attachment 1: 31.png
31.png
  1102   Thu Oct 30 20:39:47 2008 carynConfigurationPEMtemperature sensor
We attached the temperature sensor box to the MC1/MC3 chamber with a C-clamp. We connected the temp sensor to a 2nd box with a short BNC. Bob set up a power cable coming from the X-end towards the MC1/MC3 chamber(Thanks, Bob!) We soldered the end of Bob's power cable to a plug and attached it to the 2nd box (The power supply enters through the 2nd box). A ~20ft BNC cable connects the output signal of the 2nd box to the tall thing by the PSL where all the signals go labeled 1Y2. Once we had everything connected, we put in the fuses for the power supply. So, now the temperature sensor is receiving power. We checked that the power supply was working (we measured +15.08V and -14.95V, and we wanted 15V and -15V so it's OK for now). Tomorrow we will modify C1IOOF.INI file and reboot the frame builder.

About sensor-
There is an LM34 (looks like a transistor) glued w/ epoxy and thermal paste to the inside of a Pomona box ~1"x"1.5"x2". The lid to the box is covered with a 1-2mm thick piece of copper and a little thermal paste is sandwiched between the Pomona lid and the copper piece. A C-clamp attaches the copper piece to the chamber. A BNC is connected to one side of the box (the side with less copper)

About power supply box-
There is a power regulator and an op-amp inside a Pomona box ~2.5"x4"x2". The power regulator is attached to the center of lid of the pomona box with a screw and washer. There's a power plug on the front of the box
Left:+15V:red wire
Center:GND:white wire
Right:-15V:black wire
There are 2 BNC connections on the sides of the box. The left BNC connection is for the output signal and the right BNC connection is for the temperature sensor (if the power plug is coming out of the box towards you).

Sensor location-
Chamber which contains MC1/MC3. On the door facing towards the Y-end. On the bottom-left side. Behind the door. Attached with a C-clamp.

Power supply box location-
Chamber which contains MC1/MC3. On some metal leg thing near the floor facing towards the Y-end. Attached with a zip-tie

Power supply-
Coming from the X-end from a tall thing with all the fuses labeled 1X1
Fuse 160:+15V:red wire
Fuse 171:GND:white wire
Fuse 172:-15V:black wire

Signal-
Going towards the PSL to the tall thing labeled 1Y1 on the rack labeled SN208
ICS-110B
J12 (which we believe corresponds to 50-51 and channel number 13650)
Temperature sensor is connected to J12 with a ~20ft BNC attached to a BNC2LEMO connector we found lying around
  1176   Thu Dec 4 17:42:23 2008 carynUpdateIOOdrum modes observable without excitation
So, the mode cleaner was evidently aligned better and now the drum modes are observable using DTT.
The Lock-In was set to 27.8kHz and the drum mode frequencies were previously observed to be 28.039kHz(MC2), 28.222kHz(MC3) and 28.221kHz(MC1). So, we might expect peaks at ~239Hz,421Hz,422Hz.
Peaks have been observed around the expected frequencies in channel IOO-MC-DRUM1.
Note that it is possible to resolve the separate MC1 and MC3 peaks which are so close together.
(sorry these are pdf's and not png's)
Attachment 1: drum_modes.pdf
drum_modes.pdf
Attachment 2: drum_modes2.pdf
drum_modes2.pdf
  1185   Mon Dec 8 00:10:42 2008 carynSummaryGeneralcalibrating the jenne laser
I apologize in advance for the long list of numbers in the attachment. I can't seem to make them hide for some reason.

So, since Jenne's laser will probably be used for the Stoch mon calibration, Alberto and I took some measurements to calibrate Jenne's laser.
We focused the beam onto the New Focus RF 1GHz photodetector that we stole from rana's lab (powered with NewFocus power 0901). Measured the DC output of the photodetector with scope. Aligned the beam so DC went up (also tried modulating laser at 33MHz and aligning so 33MHz peak went up). Hooked up the 4395a Spectrum/Network Analyzer to the laser and to the AC out of the photodetector (after calibrating Network analyzer with the cables) so that the frequency response of the laser*photodetector could be measured.
(Note: for a while, we were using a splitter, but for the measurements here, I got rid of the splitter and just sent the RFout through the cables to channel A for the calibration, sent RFout to the laser and photodetector to channel A for the measurement)

Measured the frequency response. At first, we got this weird thing with a dip around 290MHz (see jcal_dip_2_norm.png below).
After much fiddling, it appeared that the dip was from the laser itself. And if you pull up just right on the corner of this little metal flap on the laser (see picture), then the dip in the frequency response seems to go away and the frequency response is pretty flat(see jcal_flat_3_norm below). If you press down on the flap, the dip returns. This at least happened a couple of times.
Note that despite dividing the magnitude by the DC, the frequency responses don't all line up. I'm not sure why. In some cases the DC was drifting a bit(I presume the laser was coming out of alignment or decided to align itself better) and maybe with avgfactor=16, and measuring mean DC on the scope, it made the DC meas not match up the the frequ resp meas...
I've attached the data for the measurements made (I'm so sorry for all the #'s. I can't figure out how to hide them)
name/lasercurrent/DC/analyzer SourcePower/analyzer avgfactor
jcal7_1/I=31.7mA/DC=-4.41/SourcePower=0dBm/avgfactor=16
jcal7_2/I=31.7mA/DC=-1.56/SourcePower=0dBm/avgfactor=none
jcal8_1/I=31.7mA/DC=-4.58/SourcePower=0dBm/avgfactor=16
jcal8_2/I=31.7mA/DC=-2.02/SourcePower=0dBm/avgfactor=16
jcal8_3/I=31.7mA/DC=-3.37/SourcePower=0dBm/avgfactor=16
Note also that the data from the 4395a seems to have column1-frequency, column2-real part, column3-imaginary part...I think. So, to calculate the magnitude, I just took (column2)^2+(column3)^2.


To get sort of an upper-bound on the DC, I measured how DCmax varied with laser current, where DCmax is the DC for the best alignment I could get. After setting the current, the laser was modulated at 33MHz and the beam was aligned such that the 33MHz peak in the photodetector output was as tall as I could manage. Then DC was measured. See IvsDCmax.png. Note the DC is negative. I don't know why.

Also, the TV's don't look normal, the alarm's going off and I don't think the mode cleaner's locked.
Attachment 1: IvsDCmax.png
IvsDCmax.png
Attachment 2: data.tar.gz
Attachment 3: jcal_dip_2_norm_log.png
jcal_dip_2_norm_log.png
Attachment 4: jcal_flat_3_norm_log.png
jcal_flat_3_norm_log.png
  1246   Thu Jan 22 14:38:41 2009 carynDAQPSLMC temperature sensor

Quote:

Quote:
I added a channel for the temperature sensor on the MC1/MC3 chamber: C1:PSL-MC_TEMP_SEN.
To do that I had to reboot the frame builder. The slow servo of the FSS had to get restarted, the reference cavity locked and so the PMC and MZ.


Where is this channel?


That's not the name of the channel anymore. The channel name is PEM-MC1_TEMPS. It's written in a later entry.
  1290   Wed Feb 11 00:50:24 2009 carynUpdateGeneralants?

So, near 2 of the trashcans in the control room and underneath a desk there are hundrends of ants. Is this normal?

  1331   Sun Feb 22 23:43:07 2009 carynSummaryGeneraltemperature sensor

Comparing  PSL-FSS-RMTEMP and PEM-MC1-TEMPS

So, to compare temp channels, I made a plot of PSL-FSS_RMTEMP and PEM-MC1_TEMPS(the test temp sensor channel after converting from cts to degC). This plot begins about 2 months ago t_initial=911805130. The temperature channels look kinda similar but MC1-TEMPS (the temp sensor clamped to MC1,3 chamber) is consistently higher in temperature than FSS_RMTEMP. See compare_temperature_channels.png.

MC1-TEMPS isn't exactly consistent with FSS-RMTEMP. I attached a few plots where I've zoomed in on a few hours or a few days. See compare_temperature_channels_zoom1.pdf & compare_temperature_channels_zoom2.pdf

Change the room temperature, see what happens to the chamber temperature

A while ago, somebody was fiddling around with the room temperature.  See compare_temperature_channels_zoom4.pdf.  This is a plot of PEM-MC1_TEMPS and PSL-FSS_RMTEMP at t0=911805130. You can see the chamber heating up and cooling down in happy-capacitory-fashion. Although, the PSL-FSS_RMTEMP and the PEM-MC1_TEMPS don't really line up so well. Maybe, the air in the location of the MC1,3 chamber is just warmer than the air in the PSL or maybe there's an offset in my calibration equation.

Calibration equation for PEM-MC1-TEMPS

For the calibration (cts to degC) I used the following equation based on the data-sheet for the LM34 and some measurements of the circuit:

TEMPERATURE[degC]=5/9*(((-CTS/16384/451.9/1.04094)-(.0499*10^-3))/(20*10^-6)-35);

How does the chamber temperature compare with the air temperature?

It looks like the chamber may be warmer than the air around it sometimes.

I wanted to check the temperature of the air and compare it with the temperature the sensor had been measuring. So, at t=918855087 gps, I took the temp sensor off of the mc1-mc3 chamber and let it hang freely, close to the chamber but not touching anything. See compare_temperature_chamber_air.png. MC1_TEMPS increases in temperature when I am handling the temp-sensor and then cools down to below the chamber temperature, close to FSS_RMTEMP, indicating the air temperature was less than the chamber temperature.

 When, I reattached temp sensor to the chamber at t=919011131 gps, the the temperature of the chamber was again higher than the temperature of the air. See compare_temperature_air2chamber.pdf.

Also, as one might expect, when the temp-sensor is clamped to the chamber, the temperature varies less, & when it's detached from the chamber, the temperature varies more. See compare_temperature_air_1day.pdf & compare_temperature_chamber_1day.pdf.

New temp-sensor power supply vs old temp-sensor power supply

The new temp-sensor is less noisy and seems to work OK. It's not completely consistent with PSL-FSS_RMTEMP, but neither was the old temp-sensor. And even the air just outside the chamber isn't the same temperature as the chamber. So, the channels shouldn't line up perfectly anyways.

I unplugged the 'old' temp-sensor power supply for a few hours and plugged in the 'new' one, which doesn't have a box but has some capacitors and and 2 more voltage regulators. The MC1_TEMPS channel became less noisy. See noisetime.png & noisefreq.pdf. For that time, the minute trend shows that with the old temp-sensor power supply the temp sensor varies +/-30cts and with the new power supply, it is more like +/-5cts (and Volt/16,384cts * 1degF/10mV -->  apprx +/-0.03degF). So, it's less noisy. 

I kept the new temp-sensor power supply plugged in for about 8 hours, checking if new temp sensor power supply worked ok. Compared it with PSL-FSS_RMTEMP after applying an approximate calibration equation. See ver2_mc1_rmtemp_8hr_appxcal.png.

Just for kicks

Measuring time constant of temp sensor when detached from chamber. At 918858981, I heated up the temp sensor on of the mc1-mc3 chamber with my hand. Took hand off sensor at  918859253 and let it cool down to the room temperature. See temperature_sensor_tau.pdf. 

Attachment 1: compare_temperature_channels.png
compare_temperature_channels.png
Attachment 2: compare_temperature_channels_zoom1.pdf
compare_temperature_channels_zoom1.pdf
Attachment 3: compare_temperature_channels_zoom2.pdf
compare_temperature_channels_zoom2.pdf
Attachment 4: compare_temperature_channels_zoom4.pdf
compare_temperature_channels_zoom4.pdf
Attachment 5: compare_temperature_chamber_air.png
compare_temperature_chamber_air.png
Attachment 6: compare_temperature_air2chamber.pdf
compare_temperature_air2chamber.pdf
Attachment 7: compare_temperature_air_1day.pdf
compare_temperature_air_1day.pdf
Attachment 8: compare_temperature_chamber_1day.pdf
compare_temperature_chamber_1day.pdf
Attachment 9: noisetime.pdf
noisetime.pdf
Attachment 10: noisefreq.pdf
noisefreq.pdf
Attachment 11: ver2_mc1_rmtemp_8hr_appxcal.pdf
ver2_mc1_rmtemp_8hr_appxcal.pdf
Attachment 12: temperature_sensor_tau.pdf
temperature_sensor_tau.pdf
  1540   Sat May 2 16:34:31 2009 carynDAQPEMGuralp channels plugged back in

I plugged the Guralp cables back into the PEM ADCU

       Guralp NS1b ---> #11

       Guralp Vert1b --->#10

       Guralp EW1b --->#12

  1546   Tue May 5 09:22:46 2009 carynUpdatePEMzeros

For several of the channels on the PEM ADCU, zeros are occuring at the same time. Does anyone know why that might happen or how to fix it?

Attachment 1: zerotest2.png
zerotest2.png
Attachment 2: zerotest.png
zerotest.png
  1571   Sun May 10 13:34:32 2009 carynUpdatePEMUnplugged Guralp channels

I unplugged Guralp EW1b and Guralp Vert1b and plugged in temp sensors temporarily. Guralp NS1b is still plugged in.

  1599   Mon May 18 10:06:56 2009 carynUpdatePEMTemp sensor

Quote:
To see if Caryn's data dropouts were happening, I looked at a trend of all of our temperature channels. Looks OK now.

Although you can't see it because I zoomed in, there's a ~24 hour relaxation happening before Caryn's sensors equilibrate.
I guess that's the insulating action of the cooler? We need a picture of the cooler in the elog for posterity.[/quote


Dropouts can't been seen with a minute trend, only a second trend. No big deal, but they are still occurring. See plot below.

The 24hr relaxation period is due to the cooler and some metal blocks that were cooled in the freezer and then put in the cooler to see if the relationship between the temp sensors changed with temperature. The relationship is not linear, which probably means there is some non-linearity in each temperature sensor's relationship to temperature. So, when calibrating them with Bob's temp sensor, more than 2 data points need to be collected.

Picture of cooler for posterity is attached
Attachment 1: datadropout.png
datadropout.png
Attachment 2: coolerpic1.jpg
coolerpic1.jpg
Attachment 3: coolerpic2.jpg
coolerpic2.jpg
  1624   Mon May 25 21:31:47 2009 carynUpdatePEMplugged in Guralp channels

Guralp Vert1b and Guralp EW1b are plugged back in to PEM ADCU #10 and #12 respectively. Guralp NS1b remains plugged in. So,  PEM-SEIS_MC1_X,Y,Z should now corrsp to seismometer as before.

  1647   Wed Jun 3 11:28:01 2009 carynUpdatePEMUnplugged Guralp channels
  1648   Wed Jun 3 12:31:13 2009 carynUpdatePEMplugged in guralp channels
  3308   Wed Jul 28 12:53:32 2010 channaUpdateComputersnds data listener

For the sake of writing it down: /cvs/cds/caltech/apps/linux64/rockNDS

  3310   Wed Jul 28 14:34:29 2010 channaUpdateComputersinstallation on allegra

I have done the following on allegra and rosalba:

[root@allegra caltech]# yum install glade2

On rosalba the matplotlib was out of date with respect to allegra.  I have no idea how the version 0.98 on allegra got there, but I left it.  However I updated rosalba to the epel version

  1 yum remove python-numpy
  2 yum install python-matplotlib numpy scipy --enablerepo=epel --disablerepo=rpmforge

 

This is all to support the LIGO data listener which now has a shortcut on rosalba and allegra's desktop.  It seems to work for (live mode) right now.
 

 

  14435   Tue Feb 5 10:22:03 2019 chubUpdate oil added to RP-1 & 3

I added lubricating oil to roughing pumps RP1 and RP3 yesterday and this morning.  Also, I found a nearly full 5 gallon jug of grade 19 oil in the lab.  This should set us up for quite a while.  If you need to add oil the the roughing pumps, use the oil in the quart bottle in the flammables cabinet.  It is labeled as Leybold HE-175 Vacuum Pump Oil.  This bottle is small enough to fill the pumps in close quarters.

  48   Thu Nov 1 16:51:33 2007 d40AoGGeneralD40
If you vant see D40 againn, you leave one plate goulash by N2 tank in morning.

Vit the good paprikash this time!!!
Attachment 1: PB010001.JPG
PB010001.JPG
  2709   Wed Mar 24 12:40:25 2010 daisukeConfigurationGeneralPeriscope for green laser delivery from the BSC to PSL table

The periscope design for beam elevation of the green beams is posted. The design for the 90 deg steering version is also coming.

(2010-03-29: update drawings by daisuke)

90deg version: http://nodus.ligo.caltech.edu:8080/40m/2725

40m_periscope.png

Attachment 2: 40m_periscope_A_100329.pdf
40m_periscope_A_100329.pdf 40m_periscope_A_100329.pdf 40m_periscope_A_100329.pdf 40m_periscope_A_100329.pdf
Attachment 3: 40m_periscope_A_dwg_100329.zip
  2725   Mon Mar 29 01:45:26 2010 daisukeConfigurationGeneralPeriscope version B for green laser ...

Here the design of the periscope for the 90 deg steering version is posted.

straight version http://nodus.ligo.caltech.edu:8080/40m/2709

Attachment 1: 40m_periscope_B.png
40m_periscope_B.png
Attachment 2: 40m_periscope_B_100329.pdf
40m_periscope_B_100329.pdf 40m_periscope_B_100329.pdf 40m_periscope_B_100329.pdf 40m_periscope_B_100329.pdf
Attachment 3: 40m_periscope_B_dwg_100329.zip
  11109   Fri Mar 6 13:48:17 2015 dark kiwamuSummaryIOOtriple resonance circuit

I was asked by Koji to point out where a schematic of the triple resonant circuit is.
It seems that I had posted a schematic of what currently is installed (see elog 4562 from almost 4 yrs ago!).

(Some transfomer story)
Then I immediately noticed that it did not show two components which were wideband RF transformers. In order to get an effective turns ratio of 1:9.8 (as indicated in the schematic) from a CoilCrfat's transformer kit in the electronics table, I had put two more transformers in series to a PWB1040L which is shown in the schematic. If I am not mistaken, this PWB1040L must be followed by a PWB1015L and PWB-16-AL in the order from the input side to the EOM side. This gives an impedance ratio of 96 or an effective turns ratio of sqrt(96) = 9.8.

(An upgrade plan document)

Also, if one wants to review and/or upgrade the circuit, this document may be helpful:
https://wiki-40m.ligo.caltech.edu/Electronics/Multi_Resonant_EOM?action=AttachFile&do=get&target=design_EOM.pdf
This is a document that I wrote some time ago describing how I wanted to make the circuit better. Apparently I did not get a chance to do it.

  9715   Tue Mar 11 15:14:34 2014 denSummaryLSCComposite Error Signal for ARms (1)

Quote:

The composite error signal


 

 Very nice error signal. Still, I think we need to take into account the frequency shape of the transfer function TR -> CARM. 

  9967   Sat May 17 14:48:06 2014 denUpdatePEMyend sei isolation kit is set

Yend seismometer isolation kit (elog 8461) hosts Guralp seismometer. I made a cable for inside connection, assembled the kit and relocated the instrument from its previous position at the yend inside the kit.

Seismometer is connected to the readout box and running.

IMG_1405.JPG    IMG_1406.JPG

  9968   Sun May 18 14:36:04 2014 denUpdateLSCoffsets in 3f and drmi stable lock on 1f

Eric, Den

We noticed that PRMI RIN is high when the cavity is locked on RELF33 I&Q signals. We compared the level of power fluctuations when PRMI was locked using REFL11, REFL55 and REFL 33. Attached plot "prmi_rin" shows the spectra.

Then we excited PRM and measured length to RIN coupling when PRMI was locked on REFL33 I&Q. DC offset of PRCL is only 3%. But MICH offset seems to be ~nm. When we gave offset of -15 cnts to the servo, power fluctuations improved by a factor of few.

Then we looked at DRMI. It seems that SRC macroscopic length is off but we still could lock it stably. To account for macroscopic length detuning we had to rotate REFL55 phase from 25 degrees to 50 degrees. Power at AS port increased by factor of ~2 compared to PRMI configuration. SPOP18 is decreased only by 30%. Attached plot "drmi_power" shows POP18, POP90, POPDC and ASDC in PRMI and DRMI configurations.

Plot "src_ol" shows srcl OL transfer function. UGF is 70 Hz. We have also centered SRM OL and copied the servo filters from PRM, gains are set to keep UGF at ~0.1 Hz and 7 Hz

This is a more detailed procedure:

1. Phase: REFL11: 19 degree, REFL55: 50 degrees (25 degrees for PRMI configuration)

2. Input matrix:

PRCL   0.15 0 0 REFL11I
MICH = 0 0.15 0 REFL55Q
SRCL   -0.09 0 1 REFL55I

3. Servo parameters:

PRCL: gain = -0.02, FM4,5 + trigger FM2,3,6,9

MICH: gain = 0.8, FM4,5 + trigger FM2

SRCL: gain = 0.25, FM4,5 + trigger FM2,3

4. Triggering:

signal is SPOP22 , levels 40:25

Attachment 1: prmi_rin.pdf
prmi_rin.pdf
Attachment 2: drmi_power.png
drmi_power.png
Attachment 3: src_ol.pdf
src_ol.pdf
  9971   Mon May 19 22:44:21 2014 denUpdatePEMxend sei isolation kit is set

Quote:

Yend seismometer isolation kit (elog 8461) hosts Guralp seismometer. I made a cable for inside connection, assembled the kit and relocated the instrument from its previous position at the yend inside the kit.

Seismometer is connected to the readout box and running.

    

 Xend internal cabling and external connector is ready. We are waiting for seismometer from Gyro lab. We still need to fix the pot with clamps after we put the instrument in.

We also need a long cable from Xend to the guralp readout box.

ELOG V3.1.3-