40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log, Page 334 of 339  Not logged in ELOG logo
ID Date Author Type Category Subjectdown
  10233   Thu Jul 17 21:01:28 2014 ManasaUpdateGeneral1X2 Rack Changes

Quote:

 Purpose

 

Steve and I moved some things around in the 1X2 rack in order to make room (roughly 6") for the electronics box that will contain rf frequency counters, ADC, and Raspberry Pi's for use in the Frequency Offset Locking apparatus

Picture

1X2Changes.png

Occurrences

First, we killed power by removing the fuse that the boxes we were moving were running through.

Then, we moved the boxes. I dropped//lost a washer. It didn't seem to cause any problems, so no further attempts to locate it were made.

The fuse was reinstalled, and everything was reconnected.

Moving Forward

We are now working on putting together the electronics box, which will contain ADC, and raspberry pi's. The frequency counters will be mounted on the front of the box.

Once complete, it will be installed for use in FOL.

Additional comments:

This was done based on the earlier proposed setup plan for the frequency counters that will be used to measure the beat note frequencies [Akhil's elog]

I switched off the power supply to the green PDs so that we don't cause any damage while moving the amplifier panel for the beat signals and beatbox. 

  10234   Thu Jul 17 22:08:14 2014 KojiUpdateGeneral1X2 Rack Changes

It sounds like the work was done carefully. Even so, Jenne or Manasa have to run the ALS (X and Y) to check if they are still functional.

  7433   Mon Sep 24 17:03:39 2012 JenneUpdatePEM1X1 rack power

Quote:

I've installed Guralp readout box back and it turned out that it does not work with voltage provided from the rack (+13.76 0 -14.94).  +/-12 voltage regulators inside the box convert it to -0.9 0 -12. I've connected the box to +/-15 DC voltage supply to measure seismic motion at the ETMY table. Readout box works fine with +/- 15.

 I'm not sure what the problem is here.  Den and I looked at it for a few minutes, before I went back to helping with putting doors on.  The Sorensons are not supplying the rack power for 1X1.  There are some flat cables which go from the fuses on the side of the rack up to the cable tray, and go elsewhere.  Den is going to continue looking into this, but I think it's a moderately high priority, since lots of things should be getting served by that same power.

  15669   Tue Nov 10 12:41:23 2020 gautamUpdateIOO1W > IMC

Looking back through the elog, 1mtorr is the pressure at which it is deemed safe to send the full power beam into the IMC. After replacing the HR mirror in the MCREFL path with a 10% reflective BS, I just cranked the power back up. IMC is locked. With the increased exposure on the MC2T camera, lots of new scattered light has become visible.

  2804   Sat Apr 17 18:30:12 2010 ZachUpdateGreen Locking1W NPRO output profile

NOTE: This measurement is wrong and only remains for documentation purposes.

Koji asked me to take a profile of the output of the 1W NPRO that will be used for green locking. I used the razor-scan method, plotting the voltage output of a PD vs the position of the razor across the beam, both vertically and horizontally. This was done at 6 points along the beam path out of the laser box.

I determined the beam spot size at each point by doing a least-squares fit on the plots above in Matlab (using w as one of the fitting parameters) to the cumulative distribution functions (error functions) they should approximate.

I then did another least-squares fit, fitting the above "measured" beam profiles to the gaussian form for w vs z. Below is a summary.

It seems reasonable, though I know that M2 < 1 is fishy, as it implies less divergence than ideal for that waist size. Also, like Koji feared, the waist is inside the box and thus the scan is almost entirely in the linear regime.

profile_fit_4_17_10.png

  2807   Mon Apr 19 11:31:04 2010 AidanUpdateGreen Locking1W NPRO output profile

Quote:

 Koji asked me to take a profile of the output of the 1W NPRO that will be used for green locking. I used the razor-scan method, plotting the voltage output of a PD vs the position of the razor across the beam, both vertically and horizontally. This was done at 6 points along the beam path out of the laser box.

I determined the beam spot size at each point by doing a least-squares fit on the plots above in Matlab (using w as one of the fitting parameters) to the cumulative distribution functions (error functions) they should approximate.

I then did another least-squares fit, fitting the above "measured" beam profiles to the gaussian form for w vs z. Below is a summary.

It seems reasonable, though I know that M2 < 1 is fishy, as it implies less divergence than ideal for that waist size. Also, like Koji feared, the waist is inside the box and thus the scan is almost entirely in the linear regime.

profile_fit_4_17_10.png

There is a clearly a difference in the divergence angle of the x and y beams - maybe 10-20%. Since the measurements are outside the Rayleigh range and approximately in the linear regime, the slope of the divergence in this plot should be inversely proportional to the waists - meaning the x- and y- waist sizes should differ by about 10-20%. You should check your fitting program for the waist.

 

  2818   Tue Apr 20 13:02:14 2010 ZachUpdateGreen Locking1W NPRO output profile

EDIT: I used an IFIT (inverse fast idiot transform) to change the x-axis of the plot from Hz to m. I think xlabel('Frequency [Hz]') is in my muscle memory now..

I have redone the beam fit, this time omitting the M2, which I believe was superfluous. I have made the requested changes to the plot, save for the error analysis, which I am still trying to work out (the function I used for the least squares fit does not work out standard error in fit parameters). I will figure out a way to do this and amend the plot to have error bars.

 
profile_fit_4_19_10.png
  2819   Tue Apr 20 13:37:36 2010 JenneUpdateGreen Locking1W NPRO output profile

Quote:

I have redone the beam fit, this time omitting the M2, which I believe was superfluous. I have made the requested changes to the plot, save for the error analysis, which I am still trying to work out (the function I used for the least squares fit does not work out standard error in fit parameters). I will figure out a way to do this and amend the plot to have error bars.

 
profile_fit_4_19_10.png

 Are you sure about your x-axis label? 

  2821   Tue Apr 20 19:37:02 2010 KojiUpdateGreen Locking1W NPRO output profile

Beautiful fitting.

Quote:

EDIT: I used an IFIT (inverse fast idiot transform) to change the x-axis of the plot from Hz to m. I think xlabel('Frequency [Hz]') is in my muscle memory now..

I have redone the beam fit, this time omitting the M2, which I believe was superfluous. I have made the requested changes to the plot, save for the error analysis, which I am still trying to work out (the function I used for the least squares fit does not work out standard error in fit parameters). I will figure out a way to do this and amend the plot to have error bars.

 
profile_fit_4_19_10.png

 

  12070   Mon Apr 11 17:03:41 2016 SteveUpdateCalibration-Repair1W Innolight repair completed

The laser is back. Test report is in the 40m wiki as New Pump Diode Mephisto 1000

It will go on the PSL table.

  12040   Mon Mar 21 14:29:32 2016 SteveUpdateCalibration-Repair1W Innolight laser repair diagnoses

 

Quote:
Quote:

After adjusting the alignment of the two beams onto the PD, I managed to recover a stronger beatnote of ~ -10dBm. I managed to take some measurements with the PLL locked, and will put up a more detailed post later in the evening. I turned the IMC autolocker off, turned the 11MHz Marconi output off, and closed the PSL shutter for the duration of my work, but have reverted these to their nominal state now. The are a few extra cables running from the PSL table to the area near the IOO rack where I was doing the measurements from, I've left these as is for now in case I need to take some more data later in the evening...I

Innolight 1W 1064nm, sn 1634 was purchased in 9-18-2006 at CIT. It came to the 40m around 2010

It's diodes should be replaced, based on it's age and performance.

RIN and noise eater bad. I will get a quote on this job.

The Innolight Manual frequency noise plot is the same as Lightwave' elog 11956

Diagnoses from Glasglow:

“So far we have analyzed the laser. The pump diode is degraded. Next we would replace it with a new diode. We would realign the diode output beam into the laser crystal. We check all the relevant laser parameters over the whole tuning range. Parameters include single direction operation of the ring resonator, single frequency operation, beam profile and others. If one of them is out of spec, then we would take actions accordingly. We would also monitor the output power stability over one night. Then we repackage and ship the laser.”

  3751   Thu Oct 21 10:44:56 2010 steveMetaphysicsTreasure1987 supernova tapes plus....?

I'm cleaning out to make room for our new optical cabinet. Are we keeping these? There are  ~20  pieces of 10" od 1" wide tapes and large number of cassettes.

AJW,  Zucker,  Stuart A and Koji were notified in this matter.

Alan suggested to save data of Bruce Allen paper of observation of binary neutron stars in the 40m on 1994 November 14-20 and save back up tapes of his period in the 40m.

Mike: reels are not readable any more, it is time to let go

  16155   Mon May 24 08:38:26 2021 ChubUpdateElectronics18-bit AI, 16-bit AI and 16-bit AA

- High priority units: 2x 18AI / 1x 16AI / 3x 16AA

All six are reworked and on the electronics workbench. The rest should be ready by the end of the week.

Chub

  11772   Tue Nov 17 14:31:25 2015 ericqUpdateCDS16Hz frame writing temporarily disabled

To test the effect on EPICS latency, I've restarted daqd with modified ini files which disable all frame writing of 16Hz channels. 

This happened at GPS:1131835955 aka Nov 17 2015 22:52:18 UTC

Last night, I started running a script written by Dave Barker that monitors a specified EPICS channel (in this case C1:IOO-MC_TRANS_SUM), to look for seconds in which it does not update the expected number of times. This is still running, so I will be able to compare the rate of EPICS slowdowns before and after this change. 

I will revert back to the nominal state of things in a few hours, or until someone asks me to. 

  11777   Tue Nov 17 20:57:43 2015 ericqUpdateCDS16Hz frame writing running again

Back to nominal FB configuration at 1131857782, aka Nov 18 2015 04:56:05 UTC.

Weirdly, during this time, the script watching MC_TRANS_SUM from pianosa saw tons of freezes, but another instance  watching LSC-TRY_OUT16 on optimus saw no freezes. 

  1534   Thu Apr 30 05:49:06 2009 YoichiUpdateLocking166MHz LO phase changed
In order to optimize the REFL_2I demod phase, I changed the delay line setting for the 166MHz LO.
Right now, the delay is not yet optimal.
Since the AS166 shares the same LO, the digital demodulation phase of the AS166 had to be changed too.
The DD demod phases and the DD hand off script were also tweaked to improve the resonant condition of the central part.
Now we have more 166MHz coming out of the AS port and the SPOB is larger (more 33MHz resonant in PRC).

Since REFL166 and AS166 demodulation phases are not yet optimized, the cm_step script won't work at this moment.
  1536   Fri May 1 01:32:43 2009 YoichiUpdateLocking166MHz LO phase adjustment
I continued to adjust the REFL_2I demodulation phase.
I first optimized the demod phase for SRCL in the DRMI configuration (the error signals were DDs).
Then I restored the full IFO and offset locked it.
Before handing the DARM to RF, I adjusted the 166MHz delay line to maximize the SRCL signal at REFL_2I.
I did this before the DARM RF hand off because changing the delay line setting also changes the AS166 demodulation phase.
After this, I adjusted the digital phase shifter for AS166 to maximize the DARM signal for this port.

I also adjusted the digital demodulation phase of PD11 (REFL_2I) because the optimal demodulation phase for the initial lock acquisition is somewhat (15deg)
different from the optimal demodulation phase for the SRCL when the central part is locked with the DD signals.
This happens because the resonant condition of the central part (lock points of the recycling cavities) changes when the error signals are switched to the DD signals,
due to the offset in the DD signals. This is not good and should be fixed by the optimization of the DD demodulation phases.

Finally, I reduced the CARM offset to zero and tweaked the delay line a bit to maximize the arm power.

Right now, the locking script runs fine until the end.
At the end of the script, I was able to engage the boost on the CM board.
  1537   Fri May 1 10:04:10 2009 robUpdateLocking166MHz LO phase adjustment

Quote:
I continued to adjust the REFL_2I demodulation phase.
I first optimized the demod phase for SRCL in the DRMI configuration (the error signals were DDs).
Then I restored the full IFO and offset locked it.
Before handing the DARM to RF, I adjusted the 166MHz delay line to maximize the SRCL signal at REFL_2I.
I did this before the DARM RF hand off because changing the delay line setting also changes the AS166 demodulation phase.
After this, I adjusted the digital phase shifter for AS166 to maximize the DARM signal for this port.

I also adjusted the digital demodulation phase of PD11 (REFL_2I) because the optimal demodulation phase for the initial lock acquisition is somewhat (15deg)
different from the optimal demodulation phase for the SRCL when the central part is locked with the DD signals.
This happens because the resonant condition of the central part (lock points of the recycling cavities) changes when the error signals are switched to the DD signals,
due to the offset in the DD signals. This is not good and should be fixed by the optimization of the DD demodulation phases.

Finally, I reduced the CARM offset to zero and tweaked the delay line a bit to maximize the arm power.

Right now, the locking script runs fine until the end.
At the end of the script, I was able to engage the boost on the CM board.



Awesome. Up next: dewhitening.
  2552   Thu Jan 28 09:17:32 2010 AlbertoUpdateLSC166 Modulation turned off

I temporarily turned off the 166 modulation.

  2545   Mon Jan 25 16:30:37 2010 AlbertoUpdateABSL166 MHz sideband turned off

I turned off the modulation at 166MHZ becasue I don't need it if I'm only locking the PRC.

It was introducing extra amplitude modulations of the beam which interfered with the AbsL's PLL photodiode.

I'm going to turn it back on later on.

  2546   Mon Jan 25 16:46:33 2010 AlbertoUpdateABSL166 MHz sideband turned off

Quote:

I turned off the modulation at 166MHZ becasue I don't need it if I'm only locking the PRC.

It was introducing extra amplitude modulations of the beam which interfered with the AbsL's PLL photodiode.

I'm going to turn it back on later on.

 I turned back on the 166MHz modulation just a bit. I set the slider at 4.156.

When it was totally off the MZ seemd quite unhappy.

  2547   Tue Jan 26 03:28:56 2010 ranaUpdateABSL166 MHz sideband turned off

 

 You can turn the 166 off if you want. MZ is unhappy after its turned off, but that's just the thermal transient from removing the RF heat. After a several minutes, the heat goes away and the MZ can be relocked.

One of these days we should evaluate the beam distortion we get in EOMs because of the RF heat induced dn/dT. Beam steering, beam size, etc.

  2389   Thu Dec 10 17:05:21 2009 AlbertoConfigurationLSC166 MHz LO SMA-to-Heliax connection repaired

I replaced the SMA end connector for the 166 MHZ Local Oscillator signal that goes to the back of the flange in the 1Y2 rack. The connector had got damaged after it twisted when I was tigheting the N connector of the Heliax cable on the front panel.

  2384   Thu Dec 10 13:10:25 2009 AlbertoConfigurationLSC166 LO Disconnected

I temporarily disconnected the Heliax cable that brings the 166MHz LO to the LSC rack.

I'm doing a couple of measurement and I'll put it back in as soon as I'm done.

  2393   Thu Dec 10 18:31:44 2009 AlbertoConfigurationLSC166 LO Disconnected

Quote:

I temporarily disconnected the Heliax cable that brings the 166MHz LO to the LSC rack.

I'm doing a couple of measurement and I'll put it back in as soon as I'm done.

 These are the losses I measured on a RG-174 cable for the two frequencies that we're planning to use in the Upgrade:

@11MHz Loss=0.22dBm/meter

@55MHz Loss=0.41dBm/meter

(The cable was 2.07m long. The input signal was +10dBm and the output voltages at the oscilloscope where: Vpk-pk(11MHz)=1.90V, Vpk-pk(11MHz)=1.82V )

  2395   Fri Dec 11 09:30:09 2009 KojiConfigurationLSC166 LO Disconnected

They must not be dBm, must be dB

Quote:

Quote:

I temporarily disconnected the Heliax cable that brings the 166MHz LO to the LSC rack.

I'm doing a couple of measurement and I'll put it back in as soon as I'm done.

 These are the losses I measured on a RG-174 cable for the two frequencies that we're planning to use in the Upgrade:

@11MHz Loss=0.22dBm/meter

@55MHz Loss=0.41dBm/meter

(The cable was 2.07m long. The input signal was +10dBm and the output voltages at the oscilloscope where: Vpk-pk(11MHz)=1.90V, Vpk-pk(11MHz)=1.82V )

 

  2396   Fri Dec 11 11:42:26 2009 AlbertoConfigurationLSC166 LO Disconnected

Quote:

They must not be dBm, must be dB

Quote:

Quote:

I temporarily disconnected the Heliax cable that brings the 166MHz LO to the LSC rack.

I'm doing a couple of measurement and I'll put it back in as soon as I'm done.

 These are the losses I measured on a RG-174 cable for the two frequencies that we're planning to use in the Upgrade:

@11MHz Loss=0.22dBm/meter

@55MHz Loss=0.41dBm/meter

(The cable was 2.07m long. The input signal was +10dBm and the output voltages at the oscilloscope where: Vpk-pk(11MHz)=1.90V, Vpk-pk(11MHz)=1.82V )

 

I apologize for the lack of correctness on the units in yesterday's elog entry, but I wasn't very sharp last night.

I repeated the measurement today, this time also making sure that I had a 50ohm input impedance set in the scope. These the results for the losses.

RG-174 Cable 0.053 dB/m @ 11MHz  0.155 dB/m @ 55 MHz

 I also measured the losses in the Heliax cable going from the 166 MHz LO to the LSC rack:

166MHz LO Heliax 0.378 dB @ 11MHz  1.084 dB @ 55 MHz

 

  2398   Fri Dec 11 14:12:32 2009 ranaConfigurationLSC166 LO Disconnected

 

 Seems like very strange cable loss numbers. The Heliax is lossier than the RG-174? I wonder how these compare with the specs in the cable catalog?

  2402   Fri Dec 11 19:51:13 2009 AlbertoConfigurationLSC166 LO Disconnected

Quote:

 

 Seems like very strange cable loss numbers. The Heliax is lossier than the RG-174? I wonder how these compare with the specs in the cable catalog?

In my last entry there was a typo for the measurement of the Heliax at 55 MHz. I corrected it. It was 1.084 dB instead of 1.084 dB/m.
For the Heliax I don't have the measurement of the loss per meter since I don't know the cable actual length.
 
Except for that, I checked the values I found on the Internet.
My measurements for the RG-174 seem comparable to the loss specified in the catalog (here): 6.6dB in 100ft @ 55 MHz, that is 0.22 dB/m, that compare with 0.155 dB/m that I measured.

I did the measurement on a 4.33 meter long cable with SMA connectors at the ends.

  12948   Wed Apr 19 15:46:24 2017 gautamUpdateGeneral1611/1811 inventory check

I looked through the lab area to do a fast photodiode inventory check, as we may need to buy some for the higher order mode spectroscopy SURF project. I looked on the following optical tables: ETMY, ITMY, BS, AS, PSL, SP, ITMX, Jenne laser table, and ETMX, as well as the photodiode cabinet, and could only find two 1611s. Here is a summary of the inventory: 

  • Power supply 0901: 2x in photodiode cabinet (E6 along the Y arm), 1x on Jenne laser table
  • Newfocus 1611 S/N 7284-WX, labelled "REF DET" on ITMY optical table, currently unused
  • Newfocus 1611 S/N 57109 on Jenne laser table

I have not yet checked if these photodiodes are in working order.

 

  4351   Thu Feb 24 17:42:00 2011 AidanUpdateGreen Locking15% of end laser sideband power transmitted through cavity

I did a quick calculation to determine the amount of sideband transmission through the FP cavity.

The modulation frequency of the end PDH is 216kHz. The FSR of the cavity is about 3.9MHz. So the sidebands pick up about 0.17 radians extra phase on one round trip in the cavity compared to the carrier.

The ITM reflectance is r_ITM^2 = 98.5% of power, the ETM reflection is r_ETM^2 = 95%.

So the percentage of sideband power reflected from the cavity is R_SB = r_ITM*r_ETM*(exp(i*0.17) - 1)^2 / (1 - r_ETM*r_ITM exp(i*0.17) )^2 = 0.85 = 85%

So about 15% of the sideband power is transmitted through the cavity. The ratio of the sideband and carrier amplitudes at the ETM is 0.05

So, on the vertex PD, the power of the 80MHz +/-200kHz sidebands should be around sqrt(0.15)*0.05 = 0.02 = 2% of the 80MHz beatnote.

Once we get the green and IR locked to the arm again, we're going to look for the sidebands around the beatnote.

 

 

  9618   Mon Feb 10 18:03:41 2014 jamieUpdateCDS12 core c1sus replacement

I have configured one of the spare Supermicro X8DTU-F chassis as a dual-CPU, 12-core CDS front end machine.  This is meant to be a replacement for c1sus.  The extra cores are so we can split up c1rfm and reduce the over-cycle problems we've been seeing related to RFM IPC delays.

I pulled the machine fresh out of the box, and installed the second CPU and additional memory that Steve purchased.  The machine seems to be working fine.  After assigning it a temporary IP address, I can boot it from the front-end boot server on the martian network.  It comes up cleanly with both CPUs recognized, and /proc/cpustat showing all 12 cores, and free showing 12 GB memory.

The plan is:

  1. pull the old c1sus machine from the rack
  2. pull OneStop, Dolphin, RFM cards from c1sus chassis
  3. installed OneStop, Dolphin, RFM cards into new c1sus
  4. install new c1sus back in rack
  5. power everything on and have it start back up with no problems

Obviously the when of all this needs to be done when it won't interfere with locking work.  fwiw, I am around tomorrow (Tuesday, 2/11), but will likely be leaving for LHO on Wednesday.

  7513   Tue Oct 9 23:12:56 2012 JenneUpdateLSC11MHz reconnected to EOM

Riju hasn't been in the lab in a long time to do any measurements, so I put the signals back to how they should be. 

I turned off / confirmed off the things which were sending signal to the EOM:  the network analyzer, the RF generator box, and the Marconi which supplies the 11MHz. 

I removed the cavity scanning cable, and terminated it, and put the regular 11MHz cable back on the splitter.

I then turned on the RF gen box and the Marconi.  The Marconi had been off, so we were not getting any 11MHz or 55MHz out of the RF gen. box.  This is why I couldn't lock any cavities last night (duh). 

On to locking!

----------------- In other news,

While swapping out the EOM cable, I noticed that the DC power supply sitting under the POX table was supplying a weird value, 17 point something volts.  I checked on the table to remind myself why that power supply is there...it's powering an RF amplifier right after the commercial PD that is acting as POP22.  The amplifier wants +15 and GND, so I reset the power supply to 15V.  We should add this to the list of things to fix, because it's dumb.  Either we need to put in the real POP22 (long term goal), or we need to get this guy some rack power, and do the same for any amplifiers for the Beat setup.  It's a little hoakey to have power supplies littering the lab.

  4530   Fri Apr 15 12:17:39 2011 kiwamuUpdateLSC11MHz demod board : funny I-Q phase

During checking the 11MHz demod boards I found that the I-Q relative phase showed funny LO power dependence.

It is now under investigation.

relativephase.png

 In the plot above the green curve represents the I-Q phase of a 11MHz demod board (see here).

It showed a strong dependence on the LO power and it changes from -60 deg to -130 deg as the LO power changes.

This is not a good situation because any power modulation on the LO will cause a phase jitter.

For a comparison I also took I-Q relative phase of a 33MHz demod board, which hasn't been modified recently.

 It shows a nice flat curve up to 5 dBm although it looks like my rough measurement adds a systematic error of about -5 deg.

 

 - to do -

* check RF power in every point of LO path on the circuit

* check if there is saturation by looking at wave forms.

  4533   Fri Apr 15 15:15:08 2011 kiwamuUpdateLSC11MHz demod board : 90 degree splitter

[Rana, Koji, Kiwamu]

 Moreover the amplitude of the I and Q signals are highly unbalanced, depending on the LO power again.

This implies the coil for a 90 degree splitting won't work at 11 MHz since the coil is home made and used to be designed for a specific frequency (i.g. 24.5 MHz).

We decided to use a Mini circuit 90 deg splitter instead. Steve will order few of them soon and we will test it out.

Quote:

During checking the 11MHz demod boards I found that the I-Q relative phase showed funny LO power dependence.

It is now under investigation.

 

  4537   Sat Apr 16 02:00:14 2011 ranaUpdateLSC11MHz demod board : 90 degree splitter

One way to avoid some of the bad stuff in there is to take the 1 dBm input and amplify it to ~21 dBm before splitting and sending in to the Level 17 mixers.

One way to do this is by using the A3CP6025 from Teledyne-Cougar. Its an SMA connectorized amp which can put out 25 dBm and has a gain of 24 dB. We can just glue it onto the demod boards. Then we can remove the ERA-5 amplifiers and just use the broadband splitter as Kiwamu mentioned.

  2657   Thu Mar 4 22:07:21 2010 ranaUpdate40m Upgrading11MHz PD not yet designed

Use 10 Ohms for the resistance - I have never seen a diode with 25 Ohms.

p.s. PDFs can be joined together using the joinPDF command or a few command line options of 'gs'.

  2656   Thu Mar 4 19:53:56 2010 AlbertoUpdate40m Upgrading11MHz PD designed adjusted for diode's resistance; 55 MHz RFPD designed
After reading this study done at LIGO MIT in 1998 I understood why it is difficult to define an effective impedance for a photodiode.

I read a few datasheets of the C30642GH photodiode that we're going to use for the 11 and 55 MHz. Considering the  values listed for the resistance and the capacitance in what they define "typical conditions" (that is, specific values of bias voltage and DC photocurrent) I fixed Rd=25Ohms and Cd=175pF.

Then I picked the tunable components in the circuit so that we could adjust for the variability of those parameters.

Finally with LISO I simulated transfer functions and noise curves for both the 11 and the 55MHz photodiodes.

I'm attaching the results and the LISO source files.

 

  6590   Mon Apr 30 22:58:57 2012 JenneUpdateElectronics11MHz Marconi set to default after power outage

After a power outage, a Marconi comes back to it's defaults.  It needed to be reset to the values in elog 5530.  I'm putting a label on the Marconi so we don't have to look it up next time.

Before fixing the Marconi, POY11, AS11 and AS55 all looked like noise, no real signals, even though the arm is flashing.  Now they all look PDH-y, so things are better.

  11230   Tue Apr 21 11:55:05 2015 SteveUpdateOptical Levers1103P noise measurement

Manasa and Steve,

Is this what you want?  Dashed lines are dark.

BS and PRM oplevs are blocked for this measurement. I will restore to normal operation at 4pm today.
 

  11231   Tue Apr 21 15:03:27 2015 ranaUpdateOptical Levers1103P noise measurement

It doesn't work with the lens in there, but it seems pretty close. Please leave it as is and I'll play with it after 5 today.

  11232   Tue Apr 21 21:46:34 2015 ranaUpdateOptical Levers1103P noise measurement

To test what the inherent angular noise of the HeNe 1103P laser is, we're testing it on a table pointing into the BS OL QPD with only a few steering mirrors.

From the setup that I found today, I've removed the lens nearest to the laser (which was used for the BS and PRM) as well as the ND filter (what was this for?) and the lens placed just before the BS QPD.

With the ND filter removed, the quadrant signals are now ~15000 if we misalign it and ~9000 each with the beam centered.

In order to calibrate the OLPIT_IN1 and OLYAW_IN1 signals into mm of beam motion, I misaligned the mirror just before the QPD. The knobs on there actuate the 100 TPI screws and the knurling on the knob itself has 10 ridges, so that's 36 deg per bump.

Pit Knob (deg) OLPIT Yaw Knob (deg) OLYAW
0 29 0 -36
45 13 36 -16
90 -16 72 19
135 -39 108 36
       

PIT cal ~ 1.55 (knob deg / count) -->> 10 microns / count --->>> 10 urad / count

YAW cal ~ 1 (knob deg / count)  -->> 6.5 microns / count --->>> 6.5 urad / count

Distance from the 45 deg turning mirror to the QPD silicon surface is 23 cm. Distance between knob tip and fixed pivot point is ~4 cm. 1 knob turn = 0.01" = 0.254 mm = 0.254/40 radians of mirror angle.

So 360 deg of knob gives 2*0.254/40 = 0.012 radians of beam angle = 0.012 * 230 mm ~2.3 mm of beam spot motion. Or 6.4 microns of translation / deg of knob.

The distance from the face of the laser to the QPD is 96 cm.


The punchline is that the laser shows a level of noise which has a similar shape to what's seen at LLO, but 10x lower.

The noise at 0.05 - 0.2 Hz is ~2-3x worse than the PR3 at LLO. Not sure if this is inherent to the HeNe or the wind in our setup.

  9072   Tue Aug 27 18:21:35 2013 JenneConfigurationElectronics110 MHz LO options

As I see it, we have a few options for getting the 110 MHz LO to both the POP110 and AS110 demod boards.  

The current situation is described by Kiwamu in elog 5746.  The 55 MHz signal comes into the box, and is split 4 ways, with each path having 19.7 dBm.  One of these 4 is for 110.  It has a 2dB attenuator (giving us ~17.7 dBm), and then it goes to an MK-2 frequency multiplier.  I'm a little lost on why we're giving the MK-2 17 dBm, since it says that it can handle an input power between 1 - 15 dBm.  It has ~16 dB conversion loss, so the 110 output of the distribution board has (according to the drawing) 1.9 dBm.  The demod boards have a 10 dB attenuator as the first element on the LO path, so we're giving the ERA-5 -8 dBm. 

We can either amplify the 110 leaving the distribution box, split it, and then attenuate it to the appropriate level for the demod boards, or we can change the attenuators on the POP110 and AS110 demod boards. 

Since we seem to be over driving the 2x frequency multiplier, I think I should change the 2dB attenuator to a 5dB attenuator, so we're giving the 2x multiplier ~15 dBm.  The conversion loss of ~16 dB means we'll have -1 dBm of 110 MHz.  I want to amplify that by ~10 dB, to give 9 dBm.  Attenuate by 5 dB to get to 4 dBm, then split into 2, giving me 2 110 MHz spigots, each of ~1 dBm.  Since the demod boards expect between 0-2 dBm for the LO's, this should be just fine.

Thoughts, before I start scrounging parts, and pulling the RF distribution box?

  9073   Tue Aug 27 18:58:52 2013 KojiConfigurationElectronics110 MHz LO options

- Do we have an appropriate amplifier?

- True challenge could be to find a feedthrough for the new port. (or to find a space for the amplifier in the box)

- PDXXX channels is on the DC whitening filter module. There could be some modification on this module (like diabling the whitening gain selector).

- We don't have AS11 and AS165, and so far it is unlikely to use AS11. i.e. The feedthrough, the slot on the crate, the whitening, and the channels can be trasnsition from 11 to 110.

Quote:

I want to amplify that by ~10 dB, to give 9 dBm.  Attenuate by 5 dB to get to 4 dBm, then split into 2, giving me 2 110 MHz spigots, each of ~1 dBm. 

Thoughts, before I start scrounging parts, and pulling the RF distribution box?

 

  7360   Fri Sep 7 12:28:09 2012 KojiUpdateLSC11&55MHz modulations turned off

11MHz modulation source was turned off (disabled) at Marconi at 12:00.

  845   Mon Aug 18 09:19:55 2008 steveSummaryVAC11 days at atm
It took 11 days to fix earth quake triggered sus problems of ITMX, SRM and PRM
Only ITMX north and BSC north vac doors were removed.

The PRM sus had to be removed form the vac envelope for "hip replacement"-new wire stand off was
epoxied in place.
Note: the PRM has no guide rod on the other side

ITMX, SRM and BS osems were optimized in place.
No crosscoupling optimization was performed.
Beam block was removed from ITMXC, it was too close to the main beam.

POX pick off mirror and mount will be replaced next vent.

Vac viewports were inspected from the inside.
  7515   Wed Oct 10 02:15:14 2012 ranaUpdateLSC11 MHz reconnected to EOM

 Absolutely hokey. What are our requirements for this RFPD? What are the power levels and SNR that we want (I seem to remember that its for 22 as well as 110 MHz)? Perhaps we can test an aLIGO one if Rich has one sitting around, or if the aLIGO idea is to use a broadband PD I guess we can just keep using what we have.

  2653   Wed Mar 3 18:32:25 2010 AlbertoUpdate40m Upgrading11 MHz RFPD elctronics
** Please add LISO file w/ component values.
 
I designed the circuit for one of the 11 MHz photodiodes that we're going to install in the 40m Upgrade.

This is a simple representation of the schematic:

          gnd
#          |
#          Cw2
#          |
#          n23
#          |
#          Lw2
#          |
#           n22
#          |
#          Rw2                
#                 |                   |\            
#           n2- - - C2 - n3 -  - -  - |  \          
#            |    |      |   |        |4106>-- n5 - Rs -- no
# iinput    Rd   L1     L2 R24    n6- |  /     |           |
#      nin - |    |      |   |    |   |/       |         Rload    
#           Cd   n7     R22 gnd   |            |           |          
#            |    |      |        | - - - R8 - -          gnd              
#           gnd  R1     gnd      R7 
#                 |               |
#         gnd               gnd
#                 
#
#

I chose the values of the components in a realistic way, that is using part available from Coilcraft or Digikey.

Using LISO I simulated the Tranfer Function and the noise of the circuit.

I'm attaching the results.

I'll post the 55MHz rfpd later.

  2655   Thu Mar 4 08:43:35 2010 AlbertoUpdate40m Upgrading11 MHz RFPD elctronics

Quote:
** Please add LISO file w/ component values.

oops, forgotten the third attachment...

here it is

  12949   Fri Apr 21 13:59:47 2017 Eric GustafsonSummary 1064 nm Semiconductor Laser Fiber Distribution System and Mirror Tomography

1064 nm Semiconductor Laser Fiber Distribution System and Mirror Tomography

Below threshold these Semiconductor Fabry-Perot lasers have an axial mode structure with a spacing of about a THz. As you turn up the current to above threshold the first mode to oscillate saturates the gain down on all the modes and only it oscillates.  The laser I have here in my office (a backup for the one you have at the 40 meter) has a wavelength of 1064.9 nm at 70 Degrees C.  We should be able to temperature tune it down to 1064.3 nm although this could be a bit tedious the first time we do it. The specifications claim a "spectrum width" of 1.097 nm which I believe is the temperature tuning range.  I don’t know what the line width is but it will be single frequency and we shouldn’t have mode hoping problems.  So we should be able to use it in the “Mirror Tomography” experiment.  You might want to use some sort of polarization diversity to avoid the problems of fiber polarization drift.

There have been 2 student projects on using the fiber distributed PD frequency response at1064 nm laser.

“Automated Photodiode Frequency Response Measurement System,” Alexander Cole - T1300618

“Final Report: Automated Photodiode Frequency Response Measurement System for Caltech 40m lab,” Nichin Sreekantaswamy - P140021

I’ll look up a few more references and add include them in the next elog.

Eric

 

ELOG V3.1.3-