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ID Date Author Typeup Category Subject
  2681   Thu Mar 18 13:40:35 2010 KojiUpdateABSLPLL reconstructed

We use the current PLL just now, but the renewal of the components are not immediate as it will take some time. Even so we need steady steps towards the better PLL. I appreciate your taking care of it.

Quote:

Quote:

Last night (Mar 17) I checked the PLL setup as Mott had some difficulty to get a clean lock of the PLL setting.

  • I firstly found that the NPRO beam is not going through the Faraday isolator well. This was fixed by aligning the steering mirrors before the Faraday.
     
  • The signal from the RF PD was send to the RF spectrum analyzer through a power splitter. This is a waist of the signal. It was replaced to a directional coupler.
  • Tee-ing the PZT feedback to the oscilloscope was producing the noise in the laser frequency. I put the oscilloscope to the 600Ohm output of the SR560, while connectiong the PZT output to the 50Ohm output.
  • In addition, 6dB+6dB attenuators have been added to the PZT feedback signal.

Now the beating signal is much cleaner and behave straight forward. I will add some numbers such as the PD DC output, RF levels, SR560 settings...

Now I am feeling that we definitely need the development of really clean PLL system as we use PLL everywhere! (i.e. wideband PD, nice electronics, summing amplifiers, stop poking SR560, customize/specialize PDH box, ...etc)

I also had noticed the progressive change of the aux NPRO alignment to the Farady.

I strongly agree about the need of a good and robust PLL.

By modifying the old PDH box (version 2008) eventually I was able to get a PLL robust enough for my purposes. At some point that wasn't good enough for me either.

I then decided to redisign it from scratch. I'm going to work on it. Also because of my other commitments, I'd need a few days/1 week for that. But I'd still like to take care of it. Is it more urgent than that?

 

  2684   Thu Mar 18 21:42:26 2010 KojiUpdateABSLPLL reconstructed

I checked the setup further more.

  • I replaced the PD from NewFocus 1GHz one to Thorlabs PDA255.
  • I macthed the power level of the each beam.

Now I have significant fraction of beating (30%) and have huge amplitude (~9dBm).
The PLL can be much more stable now.

Koji

  2685   Fri Mar 19 18:00:14 2010 jenneUpdatePEMGuralp2 centered again

[Jenne, Sanjit]

It looks like Steve used a GND-12V supply to power the Guralp through the little breakout box (the box is for checking the centering of the mass).  This is BAD.  The Guralps want +/- 12V.

We centered all of the channels on Gur2, and checked the channels on Gur1, so we'll see how they're feeling after a while.

  2686   Fri Mar 19 21:15:33 2010 ranaUpdatePEMGuralp2 centered again

This trend of the last 200 days shows that GUR2 has been bad forever...until now anyways.

  2687   Fri Mar 19 23:03:41 2010 ranaUpdatePEMGuralp2 centered again

I went and double-checked and aligned the styrofoam cooler at ~5:00 UTC. It was fine, but we really need a better huddling box. Where's that granite anyway?

Here's the new Huddle Test output. This time I show the X-axis since there's some coherence now below 0.1 Hz.

You'll also notice that the Wiener filter is now beating the FD subtraction. This happened when I increased the # of taps to 8000. Looks like the noise keeps getting lower as I increase the number of taps, but this is really a kind of cheat if you think about it carefully.

  2689   Sun Mar 21 19:25:29 2010 ranaUpdatePEMGuralp2 centered again

From this morning, now in calibrated units, and with the Güralp self noise spec from the Güralp manual.

  2690   Sun Mar 21 20:08:20 2010 kiwamu, ranaUpdatePSLEOM wasit size

We are going to set the waist size to 0.1 mm for the beam going through the triple resonant EOM on a new PSL setup.

When we were drawing a new PSL diagram, we just needed to know the waist size at the EOM in order to think about mode matching.

waist.png

This figure shows the relation between the waist size and the spot size at the aperture of the EOM.

The x-axis is the waist size, the y-axis is the spot size. It is clear that there is a big clearance at 0.1 mm waist size. This is good.

Also it is good because the waist size is much above the damage threshold of the EO crystal (assuming 1W input).

The attached file is the python code for making this plot.

  2691   Sun Mar 21 21:02:39 2010 KojiUpdatePSLEOM waist size
You don't need a lengthy code for this. It is obvious that the spot size at the distance L is minimum when L =
zR, where zR is the Rayleigh range. That's all.

Then compare the spot size and the aperture size whether it is enough or not.

It is not your case, but if the damage is the matter, just escape to the large zR side. If that is not possible
because of the aperture size, your EOM is not adequate for your purpose.
  2694   Mon Mar 22 11:37:09 2010 steveUpdatePEMjackhammering

There was more jackhammering this morning just about 20 ft north-west of the beamsplitter chamber, outside.

  2696   Mon Mar 22 22:11:26 2010 MottUpdateABSLPLL reconstructed

 

 It looks like the PLL drifted alot over the weekend, and we couldn't get it back to 9 dBm.  We switched back to the new focus wideband PD to make it easier to find the beat signal.  I replaced all the electronics with the newly fixed UPDH box (#17) and we aligned it to the biggest beat frequency we could get, which ended up being -27 dBm with a -6.3V DC signal from the PD.  

Locking was still elusive, so we calculated the loop gain and found the UGF is about 45 kHz, which is too high.  We added a 20 dB attenuator to the RF input to suppress the gain and we think we may have locked at 0 gain.  I am going to add another attenuator (~6 dB) so that we can tune the gain using the gain knob on the UPDH box.  

Finally, attached is a picture of the cable that served as the smb - BNC adaptor for the DC output of the PD.  The signal was dependent on the angle of the cable into the scope or multimeter.  It has been destroyed so that it can never harm another innocent experiment again!

  2697   Mon Mar 22 23:37:32 2010 MottUpdateABSLPLL reconstructed

 

We have managed to lock the PLL to reasonable stability. The RF input is attenuated by 26 dBm and the beat signal locks very close to the carrier of the marconi (the steps on the markers of the spectrum analyzer are coarse).  We can use the marconi and the local boost of the pdh box to catch the lock at 0 gain.  Once the lock is on, the gain can be increased to stabilize the lock.  The locked signals are shown in the first photo (the yellow is the output of the mixer and the blue is the output to the fast input of the laser.  If the gain is increased too high, the error signal enters an oscillatory regime, which probably indicates we are overloading the piezo.  This is shown in the second photo, the gain is being increased in time and we enter the non-constant regime around mid-way through.

Tomorrow I will use this locked system to measure the PZT response (finally!).

  2698   Tue Mar 23 00:31:51 2010 KojiUpdateIOOMC realigned

This is the first touch to the MC mirrors after the earthquake on 16th.

  • I made an aluminum access connector so that we can work on the MC even the door is open. We still can be able to open the aluminum tube. The photos are attached. Steve, could you please look it at a glance whether the seal is enough or not.
  • MC resonances were flashing. Align MC2 and MC3 so that we have many TEM00s.
  • Found c1vmesus2 gone mad. Restarted remotely according to the wiki entry. 
  • Reset the MC coil output matrix to 1. (Previously, balance was adjusted so that A2L was minimized.)
  • Excite MC2 Pitch/Yaw at 8 and 9 Hz, looking at the peaks in the MC-MCL output. Move MC2 Pitch/Yaw so that the peak
    is reduced. (*)
  • MC1/MC3 were aligned so that we get the maximum transmission (or minimum reflection). (**)
  • Repeat (*) and (**)

So far, I have aligned in Yaw such that the yaw peak is minimized.

  2699   Tue Mar 23 09:37:36 2010 steveUpdateIOOvac envelope has to be sealed as antproof for overnight

Quote:

This is the first touch to the MC mirrors after the earthquake on 16th.

  • I made an aluminum access connector so that we can work on the MC even the door is open. We still can be able to open the aluminum tube. The photos are attached. Steve, could you please look it at a glance whether the seal is enough or not.
  • MC resonances were flashing. Align MC2 and MC3 so that we have many TEM00s.
  • Found c1vmesus2 gone mad. Restarted remotely according to the wiki entry. 
  • Reset the MC coil output matrix to 1. (Previously, balance was adjusted so that A2L was minimized.)
  • Excite MC2 Pitch/Yaw at 8 and 9 Hz, looking at the peaks in the MC-MCL output. Move MC2 Pitch/Yaw so that the peak
    is reduced. (*)
  • MC1/MC3 were aligned so that we get the maximum transmission (or minimum reflection). (**)
  • Repeat (*) and (**)

So far, I have aligned in Yaw such that the yaw peak is minimized.

 This seal is good for daily use- operation only. The IFO has to be sealed  with light metal doors every night so ants and other bugs can not find their way in.

Our janitor Kevin is mopping the hole IFO room floor area with 5%  ant killing solution in water in order to discourage bugs getting close to our openings of the vented chamber.

You may be sensitive to this chemical too.  Do not open chamber till after lunch.

  2700   Tue Mar 23 09:55:20 2010 KojiUpdateIOOvac envelope has to be sealed as antproof for overnight

Roger.

Quote:

 This seal is good for daily use- operation only. The IFO has to be sealed  with light metal doors every night so ants and other bugs can not find their way in.

 

  2701   Tue Mar 23 10:11:13 2010 steveUpdatePEM small air cond unit failed yesterday

Old control room air condition failed yesterday around noon. It was blowing 80-85F hot air for about 2-3 hours at racks 1Y4-7 and the entry room 103

  2702   Tue Mar 23 15:38:26 2010 AlbertoUpdateelogelog just restarted

I found the elog down and I restarted it.

Then, after few seconds it was down again. Maybe someone else was messing with it. I restarted an other 5 times and eventually it came back up.

  2703   Tue Mar 23 18:44:46 2010 MottUpdateABSLPLL reconstructed

 

 After realigning and getting the lock today, I tried to add in the SR785 to measure the transfer function.  As soon as I turn on the piezo input on the PDH box, however, the lock breaks and I cannot reacquire it.  We are using an SR650 to add in the signal from the network analyzer and that has worked. We also swapped the 20 dB attenuator for a box which mimics the boost functionality (-20 dB above 100 Hz, 0 dB below 6Hz).  I took some spectra with the SR750, and will get some more with the network analyzer once Alberto has finished with it. 

The SR750 spectra is posted below.  The SR750 only goes up to 100 kHz, so I will have to use the network analyzer to get the full range. 

  2704   Tue Mar 23 22:46:43 2010 AlbertoUpdate40m UpgradingREFL11 upgraded
I modified REFL11 according to the changes lsited in this schematic (see wiki  / Upgrade 09 / RF System / Upgraded RF Photodiodes ).
I tuned it to be resonant at 11.06MHz and to have a notch at 22.12MHz.
These are the transfer functions that I measured compared with what I expected from the LISO model.

2010-03-23_REFL11_model_to_meas_comparison.png

The electronics transfer function is measured directily between the "Test Input" and the "RF Out" connector of the box. the optical transfer function is measured by means of a AM laser (the "Jenne laser") modulated by the network analyzer.
The AM laser's current was set at 20.0mA and the DC output of the photodiode box read about 40mV.
The LISO model has a different overall gain compared to the measured one, probably because it does not include the rest of the parts of the circuit other than the RF out path.

I spent some time trying to understand how touching the metal cage inside or bending the PCB board affected the photodiode response. It turned out that there was some weak soldering of one of the inductors.

  2705   Wed Mar 24 02:06:24 2010 KojiUpdateIOOvac envelope has to be sealed as antproof for overnight

Matt and Koji:

We closed the light doors of the chambers.

Quote:

Roger.

Quote:

 This seal is good for daily use- operation only. The IFO has to be sealed  with light metal doors every night so ants and other bugs can not find their way in.

 

 

  2706   Wed Mar 24 03:58:18 2010 kiwamu, matt, kojiUpdateGreen Lockingleave PLL locked

We are leaving the PLL as it is locked in order to see the long term stability. And we will check the results in early morning of tomorrow.

DO NOT disturb our PLL !!

  


(what we did)

After Mott left, Matt and I started to put feedback signals to the temperature control of NPRO.

During doing some trials Matt found that NPRO temperature control input has an input resistance of 10kOhm.

Then we put a flat filter ( just a voltage divider made by a resistor of ~300kOhm and the input impedance ) with a gain of 0.03 for the temperature control to inject a relatively small signal, and we could get the lock with the pzt feedback and it.

In addition, to obtain more stable lock we then also tried to put an integration filter which can have more gain below 0.5Hz.

After some iterations we finally made a right filter which is shown in the attached picture and succeeded in obtaining stable lock.

 

 

 

  2707   Wed Mar 24 04:22:51 2010 kiwamu, mattUpdateGreen Lockingtwo NPRO PLL

Now some pedestals, mirrors and lenses are left on the PSL table, since we are on the middle way to construct a PLL setup which employs two NPROs instead of use of PSL laser.

So Please Don't steal any of them.

  2710   Wed Mar 24 14:52:02 2010 AlbertoUpdateGreen Lockingtwo NPRO PLL

Quote:

Now some pedestals, mirrors and lenses are left on the PSL table, since we are on the middle way to construct a PLL setup which employs two NPROs instead of use of PSL laser.

So Please Don't steal any of them.

 Can I please get the network analyzer back?

  2711   Wed Mar 24 14:57:21 2010 AlbertoUpdate40m UpgradingREFL11 upgraded

 

 Hartmut suggested a possible explanation for the way the electronics transfer function starts picking up at ~50MHz. He said that the 10KOhm resistance in series with the Test Input connector of the box might have some parasitic capacitance that at high frequency lowers the input impedance.

Although Hartmut also admitted that considering the high frequency at which the effect is observed, anything can be happening with the electronics inside of the box.

  2712   Wed Mar 24 15:59:59 2010 kiwamu, mattUpdateGreen Lockingleave PLL locked

Matt checked it in this morning and he found it's been locked during the night.

 

 

  2713   Thu Mar 25 09:07:08 2010 steveUpdatePEMGuralp2 x problem is back

Quote:

I went and double-checked and aligned the styrofoam cooler at ~5:00 UTC. It was fine, but we really need a better huddling box. Where's that granite anyway?

Here's the new Huddle Test output. This time I show the X-axis since there's some coherence now below 0.1 Hz.

You'll also notice that the Wiener filter is now beating the FD subtraction. This happened when I increased the # of taps to 8000. Looks like the noise keeps getting lower as I increase the number of taps, but this is really a kind of cheat if you think about it carefully.

 The same thing happening again.  The intermittent offset upstream of the seismometer that never got fixed.

The granite plate and ball bearings are in. I will place seismometers on it.

  2714   Thu Mar 25 17:29:48 2010 kiwamu, mottUpdateGreen LockingPLL two NPROs

In this afternoon, Mott and I tried to find a beat note between two NPROs which are going to be set onto each end table for green locking.

At first time we could not find any beats. However Koji found that the current of innolight NPRO was set to half of the nominal.

Then we increased the current to the nominal of 2A, finally we succeeded in finding a beat note.

Now we are trying to lock the PLL.

P.S. we also succeeded in acquiring the lock

 

nominal setup
  innolight  lightwave
T [deg] 39.75 37.27
current [A] 2 2
laser power [mW] 950 700


  2715   Thu Mar 25 17:32:42 2010 AlbertoUpdate40m UpgradingREFL55 Upgraded

I upgraded the old REFL199 to the new REFL55.

To do that I had to replace the old photodiode inside, switching to a 2mm one.

Electronics and optical transfer functions, non normalized are shown in the attached plot.

2010-03-25_REFL55_model_to_meas_comparison.png

The details about the modifications are contained in this dedicated wiki page (Upgrade_09 / RF System / Upgraded RF Photodiodes)

  2716   Fri Mar 26 10:48:35 2010 steveUpdateSAFETYsafety glasses measured

Safety glasses 1064 nm transmission measured at ~200 mW level. They are all good.

  2717   Sat Mar 27 16:23:10 2010 KojiUpdateSUSanother SRM sidemagnet glued

Kiwamu and Koji

Last night we have released PRM from the gluing fixture. All of the six magnets are successfully released from the fixture.

We put SRM on the fixuture and glued a side magnet which we had failed at the last gluing.

We let it cure in the Al house. This should be the last magnet gluing until ETMs are delivered.

[Current status]

ITMX (ITMU03): all of magnets/guiderod/standoffs glued, mirror baked; balance to be confirmed
ITMY (ITMU04): all of magnets/guiderod/standoffs glued, balance confirmed, mirror baked
SRM  (SRMU03): magnets/guiderod/standoff glued; a side magnet gluing in process, balance to be confirmed, last stand off to be glued, mirror to be baked
PRM  (SRMU04): magnets/guiderod/standoff glued; balance to be confirmed, last stand off to be glued, mirror to be baked

TT:            magnets/guiderod/standoff glued; balance to be confirmed, last stand off to be glued, mirror to be baked

  2718   Sun Mar 28 17:28:26 2010 matt, kiwamuUpdateGreen Lockingfrequency discriminator for green PLL

Last Friday, Matt made a frequency discriminator circuit on a bread board in order to test the idea and study the noise level. I think it will work for phase lock acquisition of Green locking.

As a result a response of 100kHz/V and a noise level of 2uV/rtHz @ 10Hz are yielded. This corresponds to 0.2Hz/rtHz @ 10Hz.

The motivation of using frequency discriminators is that  it makes a frequency range wider and easier for lock acquisition of PLLs in green locking experiment.

For the other possibility to help phase lock acquisition, Rana suggested to use a commercial discriminator from Miteq.


(principle idea)

The diagram below shows a schematic of the circuit which Matt has built.

FD.png

Basically an input signal is split into two signals right after the input, then one signal goes through directly to a NAND comparator.

On the other hand another split signal goes through a delay line which composed by some RC filters, then arrive at the NAND comparator with a certain amount of delay.

After going through the NAND comparator, the signal looks like a periodic pulses (see below).

If we put a signal of higher frequency we get more number of pulses after passing through the NAND.

pulses.png

Finally the pulse-signal will be integrated at the low pass filter and converted to a DC signal.

Thus the amplitude of DC signal depends on the number of the pulses per unit time, so that the output DC signal is proportional to the frequency of an input signal.

 

 

(result)

By putting a TTL high-low signal, an output of the circuit shows 100kHz/V linear response.

It means we can get DC voltage of 1 V if a signal of 100kHz is injected into the input.

And the noise measurement has been done while injecting a input signal. The noise level of 0.2Hz/rtHz @ 10 Hz was yielded.

Therefore we can lock the green PLL by using an ordinary VCO loop after we roughly guide a beat note by using this kind of discriminator.

 FDnoise.png

  2719   Sun Mar 28 20:00:17 2010 ranaUpdateCamerasGigE camera no work from screen

Not that this is an urgent concern, just a data point which shows that it doesn't just not work at the sites.

  2727   Mon Mar 29 10:40:59 2010 josephbUpdateCamerasGigE camera no work from screen

Quote:

Not that this is an urgent concern, just a data point which shows that it doesn't just not work at the sites.

I had to restart the dhcpd server on Ottavia that allows us to talk to the camera.  I then also changed the configuration script on the camera so that it no longer thinks ottavia is 131.215.113.97, but correctly 192.168.113.97.  Overall took 5 minutes.

I also looked up services for Centos 5, and set it using the program serviceconf to start the DHCP server  when Ottavia is rebooted now.  That should head off future problems of that nature.  For reference, to start the dhcp server manually, become root and type "service dhcpd start".

 

  2728   Mon Mar 29 15:19:33 2010 mevansUpdateGreen Lockingfrequency discriminator for green PLL

Thanks for the great entry!

In order to make this work for higher frequencies, I would add Hartmut's suggestion of a frequency dividing input stage.  If we divide the input down by 100, the overall range will be about 200MHz, and the noise will be about 20Hz/rtHz.  That might be good enough... but we can hope that the commercial device is lower noise!

Quote:

Last Friday, Matt made a frequency discriminator circuit on a bread board in order to test the idea and study the noise level. I think it will work for phase lock acquisition of Green locking.

As a result a response of 100kHz/V and a noise level of 2uV/rtHz @ 10Hz are yielded. This corresponds to 0.2Hz/rtHz @ 10Hz.

The motivation of using frequency discriminators is that  it makes a frequency range wider and easier for lock acquisition of PLLs in green locking experiment.

FD.png

  2731   Mon Mar 29 18:50:14 2010 KojiUpdateSUSPRM sidemagnet glued

PRM was released from the fixuture without any trouble. This was the last magnet gluing until ETMs are delivered.

The below is the up-to-date Jenne stat table.

The clean room is getting too narrow. I am thinking that we should install ITMs to the chamber so that we can accommodate SRM/PRM suspensions.

  2737   Wed Mar 31 02:57:48 2010 kiwamuUpdateGreen Lockingfrequency counter for green PLL

Rana found that we had a frequency counter SR620 which might be helpful for lock acquisition of the green phase lock.

It has a response of 100MHz/V up to 350MHz which is wide range and good for our purpose. And it has a noise level of 200Hz/rtHz @ 10Hz which is 1000 times worse than that Matt made (see the entry).

The attached figure is the noise curve measured while I injected a signal of several 100kHz. In fact I made sure that the noise level doesn't depends on the frequency of an input signal.

The black curve represents the noise of the circuit Matt has made, the red curve represents that of SR620.

  2739   Wed Mar 31 10:34:02 2010 josephbUpdateelogElog not responding this morning

When I went to use the elog this morning, it wasn't responding.  I killed the process on nodus, and then restarted, per the 40m wiki instructions.

  2741   Wed Mar 31 12:30:31 2010 ranaUpdateGreen Lockingfrequency counter for green PLL

Its a good measurement - you should adjust the input range of the 620 using the front panel 'scale' buttons to see how the noise compares to Matt's circuit when the range is reduced to 1 MHz. In any case, we would use it in the 350 MHz range mode. What about the noise of the frequency discriminator from MITEQ?

  2742   Wed Mar 31 15:31:53 2010 steveUpdatePSLReference Cavity RF PD base upgraded

Quote:

Some more words about the RFAM: I noticed that there was an excess RFAM by unlocking the RC and just looking at the RF out with the 50 Ohm input of the scope. It was ~100 mVp-p! In the end our method to minimize the AM was not so sensible - we aligned the waveplate before the EOM so as to minimize the p-pol light transmitted by the PBS cube just ahead of the AOM. At first, this did not minimize the RFAM. But after I got angry at the bad plastic mounting of the EOM and re-aligned it, the AM seemed to be small with the polarization aligned to the cube. It was too small to measure on the scope and on the spectrum analyzer, the peak was hopping around by ~10-20 dB on a few second timescale. Further reduction would require some kind of active temperature stabilization of the EOM housing (maybe a good SURF project!).

For the EOM mount we (meaning Steve) should replace the lame 2-post system that's in there with one of the mounts of the type that is used in the Mach-Zucker EOMs. I think we have spare in the cabinet next to one of the arms.

After the RFAM monkeying, I aligned the beam to the RC using the standard, 2-mirror, beam-walking approach. You can see from the attached plot that the transmission went up by ~20% ! And the reflection went down by ~30%. I doubt that I have developed any new alignment technique beyond what Yoichi and I already did last time. Most likely there was some beam shape corruption in the EOM, or the RFAM was causing us to lock far off the fringe. Now the reflected beam from the reference cavity is a nice donut shape and we could even make it better by doing some mode matching! This finally solves the eternal mystery of the bad REFL beam (or at least sweeps it under the rug).

At the end, I also fixed the alignment of the RFPD. It should be set so the incident angle of the beam is ~20-40 deg, but it was instead set to be near normal incidence ?! Its also on flimsy plastic legs. Steve, can you please replace this with the new brass ones?

 Teflon feet removed and heavy brass-delrin pd base installed. Ref-cavity reflected light remains to be beautiful doughnut shape on camera.

  2743   Wed Mar 31 16:31:44 2010 steveUpdatePEMGuralp interface box turned off

Quote:

Quote:

I went and double-checked and aligned the styrofoam cooler at ~5:00 UTC. It was fine, but we really need a better huddling box. Where's that granite anyway?

Here's the new Huddle Test output. This time I show the X-axis since there's some coherence now below 0.1 Hz.

You'll also notice that the Wiener filter is now beating the FD subtraction. This happened when I increased the # of taps to 8000. Looks like the noise keeps getting lower as I increase the number of taps, but this is really a kind of cheat if you think about it carefully.

 The same thing happening again.  The intermittent offset upstream of the seismometer that never got fixed.

The granite plate and ball bearings are in. I will place seismometers on it.

 

  2744   Wed Mar 31 16:55:05 2010 josephbUpdateComputers2 computers from Alex and Rolf brought to 40m

I went over to Downs today and was able to secure two 8 core machines, along with mounting rails.  These are very thin looking 1U chassis computers. I was told by Rolf the big black box computers might be done tomorrow afternoon.  Alex also kept one of the 8 core machines since he needed to replace a hard drive on it, and also wanted to keep for some further testing, although he didn't specify how long.

I also put in a request with Alex and Rolf for the RCG system to produce code which includes memory location hooks for plant models automatically, along with a switch to flip from the real to simulated inputs/outputs.

 

  2745   Wed Mar 31 19:29:58 2010 HartmutUpdateElectronics(1cm-) Si PD transfer functions update

Recorded transfer functions for the 1cm Si-PD as described on p. 2708

for different biases. I put the plots in there, to keep the info in one place,

where the label on the PD case (which Steve made without asking him) points

to.

I talked to some people recently about the fact that the responsivity (A/W) of the PD

changes even at DC for different biases. I tested this again and should be more precise about this:

The first time I observed this was in the transfer functions as shown on p. 2708.

With 'DC' I meant 'low frequency' there, as you can still see an effect of the bias as low as 100kHz.

Then at one point I saw the responsivity changing with bias also at true DC.

However, it turned out that this is only the case if the photocurrent is too high.

If the photocurrent is 4mA, you need 400mV bias to get the max. responsivity.

For 2mA photocurrent, the responsivity is already maximal for 0V bias.

An effect for relative low frequencies remains however.

The DC check of responsivity was done with white light from a bulb.

 

 

  2746   Thu Apr 1 00:43:33 2010 MottUpdateGeneralPZT response for the innolight

Kiwamu and I measure the PZT response of the Innolight this evening from 24 kHz to 2MHz.  

We locked the PLL at ~50 MHz offset using the Lightwave NPRO and and swept the Innolight with the network analyzer (using the script I made; it has one peculiar property, but it does work correctly).  

We will post the plot of the Lightwave PZT response tomorrow morning.

 

**EDIT**: As Koji pointed out, the calibration factor on this plot is WRONG.  See my more recent update for the correctly calibrated plot.

  2747   Thu Apr 1 07:17:15 2010 KojiUpdateGeneralPZT response for the innolight

The shape of the TF looks nice but the calibration must be wrong.

Suppose 1/f slope with 10^-4 rad/V at 100kHz. i.e. m_pm = 10/f rad/V
This means m_fm = 10 Hz/V. This is 10^6 times smaller than that of LWE NPRO.

(Edit: Corrected some numbers but it is not significant)

Quote:

Kiwamu and I measure the PZT response of the Innolight this evening from 24 kHz to 2MHz.  

We locked the PLL at ~50 MHz offset using the Lightwave NPRO and and swept the Innolight with the network analyzer (using the script I made; it has one peculiar property, but it does work correctly).  

We will post the plot of the Lightwave PZT response tomorrow morning.

 

  2748   Thu Apr 1 10:21:58 2010 MottUpdateGeneralPZT response for the innolight

Quote:

The shape of the TF looks nice but the calibration must be wrong.

Suppose 1/f slope with 10^-4 rad/V at 10kHz. i.e. m_pm = 1/f rad/V
This means m_fm = 1 Hz/V. This is 10^7 times smaller than that of LWE NPRO.

Quote:

Kiwamu and I measure the PZT response of the Innolight this evening from 24 kHz to 2MHz.  

We locked the PLL at ~50 MHz offset using the Lightwave NPRO and and swept the Innolight with the network analyzer (using the script I made; it has one peculiar property, but it does work correctly).  

We will post the plot of the Lightwave PZT response tomorrow morning.

 

 Koji is absolutely right.  I just double checked my matlab code, and saw that I divided when I should have multiplied.  The correctly calibrated plots are attached here for the Innolight and the lightwave.  Kiwamu and I will measure the amplitude and the jitter today.

  2749   Thu Apr 1 10:47:48 2010 KojiUpdateGeneralPZT response for the innolight

Innolight: 100rad/V @ 100kHz  => 1e7/f rad/V => 10MHz/V

LWE: 500rad/V @ 100kHz =>  5e7/f rad/V => 50MHz/V

They sound little bit too big, aren't they?

  2750   Thu Apr 1 12:07:22 2010 ranaUpdateGeneralPZT response for the innolight

The Lightwave NPRO should be around 5 MHz/V. 

The Innolight PZT coefficient is ~1.1 MHz/V.

(both are from some Rick Savage LHO elog entries)

  2751   Thu Apr 1 15:21:12 2010 ranaUpdateGreen Lockingfrequency counter for green PLL

 

  2752   Thu Apr 1 16:34:29 2010 HartmutUpdateGreen LockingSilicon PDs

just a few infos on Silicon PDs I looked up.

If you want to go beyond the 100MHz achievable with the device I worked on,

the one thing to improve is the opamp, where Steve is trying to find OPA657.

This is a FET with 1.6GHz BWP, minimum stable gain of 7, and 4.8nV/rt(Hz) noise.

Should be ok with 750-1000 Ohm transimpedance.

The other thing you might want to change is the PD

(although it might be the 1cm PD with high bias is as fast as smaller ones with lower bias).

There are two types of other Si diodes at the 40m right now (~3mm):

-Rana and I found a Centronic OSD 15-5T in the old equipment

-Frank gave me a Hamamatsu S1223-01 on a Thorlabs pre-amp device (could be taken out).

 

The Centronic OSD 15-5T has up to 80pF with 12 V bias according to the datasheet.

The Hamamatsu S1223-01 is stated with 20pF only, but stated to have a max. frequency resp. of 20MHz ('-3db point').

I dont know what this means, as the corner freq. of 10pF into 50Ohm is still 160MHz.

In any case there are faster 3mm types to start with, as for example Hamamatsu S3399 (~ 90$),

which is stated to have the corner at 100MHz with 50 Ohm load.

For this type the stated capacity (20pF) looks consistent with ~100MHz corner into 50 Ohm.

So probably you can get higher BW with this one using much smaller load, as in transimpedance stage.

 

 

  2753   Thu Apr 1 17:35:24 2010 KojiUpdateSUSWorking on ITMX/Y

Steve and Koji

- We removed old ITMX/Y from the chambers. Now they are temporarily placed on the flow table at the end. Steve is looking for nice storages for the 5inch optics.

- We wiped new ITMX/Y by isopropanol as they were dusty.

- We put them into the corresponding towers. Checked the balancing and magnet arrangements with the OSEMs. They were totally fine.

- We clamped the mirrors by the EQ stops. Wrapped the towers by Al foils.

Tomorrow we will put them into the chambers.

 

  2754   Thu Apr 1 18:05:29 2010 MottUpdateGeneralPZT response for the innolight

 

 We realized that we had measured the wrong calibration value; we were using the free-running error signal with the marconi far from the beat frequency, which was very small.  When we put the Marconi right at the beat, the signal increased by a factor of ~12 (turning our original calibration of 10 mV/rad into 120 mV/rad).  The re-calibrated plots are attached. 

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