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  8   Thu Nov 12 18:01:10 2009 FrankThings to BuyRefCavheaters for the other two chambers

in order to improve the stability of the chamber temperature the current plan is to add a heater and insulation for the second chamber. room temperature changes were about 2Kpp over the last couple of days. I already ordered flexible insulating foam for the chamber (the round parts). What we need is one or more heaters. We could somehow add half of the original heater to that chamber but i would like to go for a more final solution as we need one for the other chamber in the ATF as well. The plan is to buy standard heaters with adhesive backside and stick them to the chamber.  Price is about $70 for a 10"x10" heater (MINCO). The chamber surface is about 22"x25" in total, cut into smaller areas by the 4 vaccum tubes and 2 legs. I think we can cover most of it with a total amount of 4 to 6 heaters of different sizes.

  9   Thu Nov 12 20:56:38 2009 ranaThings to BuyRefCavheaters for the other two chambers

I think its important to think of a good solution, since we may want to retrofit some other chambers.

For the electronics to drive the heater, let's make sure not to use the power supply solution that is in use now in LIGO and at the 40m. We should make sure to make the design such that the residual temperature noise from the heater is below what we expect for coating thermal noise, assuming we use Fused Silica spacer of 1m length.

This should be quite easy in principle, especially with the radiative shields on the inside.

 

  10   Fri Nov 13 10:56:32 2009 FrankThings to BuyRefCavheaters for the other two chambers

Quote:

I think its important to think of a good solution, since we may want to retrofit some other chambers.

For the electronics to drive the heater, let's make sure not to use the power supply solution that is in use now in LIGO and at the 40m. We should make sure to make the design such that the residual temperature noise from the heater is below what we expect for coating thermal noise, assuming we use Fused Silica spacer of 1m length.

This should be quite easy in principle, especially with the radiative shields on the inside.

 

 What is a "good" solution for you? A custom-made heater fitting the whole thing like the ones at the sites? They are expensive and it will take several weeks/month  to get them. The only advantage i see is that you can remove them from the chamber but do we need this feature? The other heaters are standard parts and you just stick them to the chamber, so you have a good thermal contact to it. As we only have two of the "other" chambers with a different layout for the small CF flanges i think this is good enough for our tests. For a new super-cavity chamber we can choose a different design. I think it does not make a big difference in stability. The design of the insulation is more important..

Yeah, i'm currently thinking off designing a first prototype for such a low-noise driver. As i think we will use the DAQ for temp controll thats the only part we need (and the power supply for the supply, but we have one of those). The current heaters i want to use have enough heating power when used with up to 24V, which is a good value as easy to buy. The noise can be easy as low as a couple of 10nV/sqrt(Hz) with standard parts..

  198   Wed Jul 7 10:44:39 2010 MeganSummaryVCOVCO Output vs Input

I redid one of the graphs for the output of the VCO vs the input voltage to make sure I didn't miscalculate. I got the same graph when accounting for the 19dBm attenuation at the output of the VCO. I also made a graph of the output RMS voltage ignoring the attenuation - the total output ranged from 13mV to 918mV, while the voltage added by taking the attenuation into account is 1.9929V.

I used the equation N dBm = 10*log(Vrms2/50/0.001) to solve for the voltage associated with 19 dBm.

Attachment 1: VCOOutputvsInput.png
VCOOutputvsInput.png
  200   Wed Jul 7 16:08:40 2010 MeganSummaryVCOUpdate on VCO offset

I realized I was doing the calculations incorrectly - this should make more sense.

Attachment 1: VCO_Output_Input.png
VCO_Output_Input.png
  205   Fri Jul 9 11:45:05 2010 MeganSummaryVCOPhase Noise of Marconis and VCO

I used the data for the phase noise of the marconis to calculate the individual phase noise of each marconi. The noise of the three are roughly the same. The noise increases with frequency and input range, with the maximum variation in our measurements about 1 order of magnitude. This shows the noise is fairly consistent, but does change with different frequencies used and different input ranges.

We also have some data for the phase noise of the VCO compared with Marconi 2 (with the feedback going to the Marconi). The VCO is currently much noisier than the Marconis, so hopefully we can reduce the noise by modifying the current VCO.

We used swept sine to find the gain of the feedback loop, with a UGF of roughly 2.8 KHz with a gain of 1. With a gain of 100, the UGF is roughly 280 kHz and a peak to peak voltage when unlocked of 438mV.

The gain (for calibration) with the poles and zeroes can be calculated as:

(4V/216)(pi/Vp-p)(1/1000)(0.03)(UGF)

where 4/216 is the resolution of the ADC, pi/Vp-p gives the number of radians per volt, 1000 is the amplification of the signal into the ADC, 0.03 is the first zero (to compensate for the amplifier, which diminishes the signal below 0.03 Hz), and the UGF is the other zero. Multiplication by the zeros ensures the signal above the zeros will not be affected by the transfer function.

As a note - when the signals are calibrated in the DTT, the calibrated data can be saved by exporting the trace, not the signal itself, by exporting win0_pad0_trace1 or whichever trace it is saved under. This removes a need to calibrate the original data outside the DTT.

Attachment 1: IndividualNoise_80MHz_160MHz_10Hz_100HzRanges.png
IndividualNoise_80MHz_160MHz_10Hz_100HzRanges.png
Attachment 2: Separate_Individual_Noise.png
Separate_Individual_Noise.png
Attachment 3: VCONoise_Gain1_100.png
VCONoise_Gain1_100.png
  206   Sat Jul 10 05:31:15 2010 ranaSummaryNoiseBudgetfrom the SVN today

I modified the photo-thermal part of the NB to use the Alnis et. al. number of 25 Hz / uW  (frequency shift per input power noise). I adjusted it for the ratio of the cavity lengths between theirs and ours, and also for the ratio of the Finesses (400000 : 10000).

Tara should now grab this code and replace my guess at the RC RIN with his real measurements and also add the previously measured RC/AC frequency noise to this plot.

The punchline is that the this thermo-refractive noise is significant and we must control the low frequency RIN.

Attachment 1: psl_refcav_sio2_300K.png
psl_refcav_sio2_300K.png
  207   Sun Jul 11 00:52:14 2010 MeganSummaryVCOVCO Noise

I graphed the VCO phase noise with the previously measured data - the data I have seems to be a bit higher. I also converted the phase noise into frequency noise for both VCOs and the previous measurement. Just for reference, "VCO 1" is the one that we were measuring the noise of the different parts of the VCO and that has its lid off.  "VCO 2" is the one we brought over from the PSL lab that is currently still in one piece.

Attachment 1: PhaseNoisePreviousMeasure.png
PhaseNoisePreviousMeasure.png
Attachment 2: FrequencyNoisePreviousMeasure.png
FrequencyNoisePreviousMeasure.png
  208   Mon Jul 12 11:04:16 2010 MeganSummaryVCONoise of 2023B and Electronic Noise of VCO

I got the measurements locking the 2023B (from the PSL lab) to one of the 2023As in 40m. I have one graph showing the calibrated data compared to the calibrated data of one of the other 2023As locked to the one I used. Another has the individual phase noise of the 2023A and the 2023B (by removing the noise of the 2023A). The individual noise of the 2023B can be found by using the equation

S2023B = sqrt(S2023A2 - SCombined2)

The individual noise looks very close to that of the other Marconis (previous graphs show all 3 2023As are almost identical), so I'm not going to test the 2023B at all frequency combinations.

I also measured the electronic noise of the VCO, only accounting for the gain of 1000 in the feedback loop.

Attachment 1: NoiseBothTypes.png
NoiseBothTypes.png
Attachment 2: IndividualNoiseBothTypes.png
IndividualNoiseBothTypes.png
Attachment 3: ElectronicNoise.png
ElectronicNoise.png
  209   Mon Jul 12 11:49:17 2010 MeganSummaryVCONoise of 2023B and Electronic Noise of VCO (correct graphs)

The previous graphs are wrong. Here are the correct ones and the electronic noise is plotted compared to the total noise of the VCO.

Attachment 1: NoiseBothTypes.png
NoiseBothTypes.png
Attachment 2: IndividualNoiseBothTypes.png
IndividualNoiseBothTypes.png
Attachment 3: VCOElectronicNoise.png
VCOElectronicNoise.png
  210   Mon Jul 12 14:32:49 2010 taracSummaryRefCavRCTRANSPD RIN

Before, when we tried to lock the cavity, it seemed that the gain was too high, and the power output

from RefCav(C3:PSL-FSS_RCTRANSPD) fluctuated when both PC and Fast feedback were connected, and the data was measured when only Fast feedback was on.

So I try to change RF power to reduce the modulation index (hence, the gain.)

The value before was 6.5V, This time I tried 5.5 and 5.8 V.

At each RF power setting, I lock the cavity with

1) Fast feedback alone, and

2) both Fast and PC feedback

and measure the transmitted beam's RIN. The gain for each setup was readjust (see the values for each setup below)

so that the transmitted beam power was most stable as seen on an oscilloscope, then the data was taken.

The results are plotted below. It turns out that

when the PC feedback is connect, RIN becomes noisier. I don't no where 

it comes from. It might be that the setting still has too high gain, or RFAM from broadband EOM due to misalignment,

or broken opamp in FSS PC path.

 


 I'm still not sure why there are jumps at 100 Hz and 1k Hz. The sr785 is set at 4 different spans

which are, 0-100Hz, 0-1kHz,0-10kHz, and 0- 100kHz. Each span contains 800 FFT lines. The auto range is on.

 

The setting are [this will be updated soon]

1)RF5.5

 Fast feedback: on

 PC feedback: off

 CG

 FG

 

2) RF5.5

  Fast: on

  PC: on

 CG:

 FG:

 

3 RF 5.8

Fast: on

  PC: off

 CG:

 FG:

 

 

4 RF 5.8

Fast: on

  PC: on

 CG:

 FG:

 

 

 

 

 

 

Attachment 1: RIN.png
RIN.png
  211   Tue Jul 13 11:35:12 2010 MeganSummaryVCOVCO Frequency Response

We measured the frequency response of the VCO and fit it with a linear curve to give an idea of the frequency response around 80MHz. This shows that the general trend is not linear, but can be approximated within 1V applied to the VCO.

Attachment 1: VCOFreqResponse.png
VCOFreqResponse.png
  213   Tue Jul 13 18:40:56 2010 MeganSummaryVCOComparison of Modeled and Measured VCO Noise

I modeled the VCO using LISO to find a model of the electronic noise entering the actual VCO. I will double-check all the resistor and capacitor values with the actual VCO to make sure I'm modeling what I actually measured and post the file I used. I also converted the electronic noise into frequency noise of the VCO assuming the conversion factor of 680 kHz/V (found by measuring the frequency response around 80MHz - previous post).

I will work on replacing resistors tomorrow, after looking at my model to see which have the greatest impact on noise, and see if that decreases the measured electronic noise.

Attachment 1: Electronic_and_Frequency_Noise.png
Electronic_and_Frequency_Noise.png
  216   Thu Jul 15 11:43:36 2010 MeganSummaryVCOMeasured and Modeled Noise with Instrumentation Noise

I created a very rough model of the LM336 (emailed to Frank and Jan to try to improve) to see if the noise of the LM336 might explain the noise at lower frequencies. I think from this rough sketch that might be the case, but again, it was a very rough model. This shows the new model with the instrumentation noise and measured noise. The instrumentation noise probably explains the higher frequency discrepancy - I will test that later today - and there's a chance that the LM336 explains the lower frequency discrepancy.

Attachment 1: MeasModelInstNoise.png
MeasModelInstNoise.png
  234   Mon Jul 19 18:21:50 2010 taraSummaryNoiseBudgetLaser intensity noise & pointing

I checked the noise budget code psl_refcav_sio2_300K.m on Laser intensity noise.

The value for df/dp, which is intensity dependence of the cavity resonance frequency, from Alnis et al. is 70 Hz/uW (page 6, just before section 3)

for the light coupled into the cavity. I'm not sure where the original value, 25 Hz/uW, in the code came from. I'll ask Rana about this.

 df/dp already incorporates both effects from photo elastic and photo refractive noise in the coatings + substrate,

so we don't have to worry about dn/dT, or

thermal expansion coeff of the material.

Their coating materials are SiO2, Ta2O5, 38 layers. Our coating materials are similar, but only 17 layers thick.

So we should be able to rescale their df/dp for our cavity.

                                        | Alnis etal|    PSL   |

cavity length [mm]        |  77.5      |  203.5  |

Finesse                          | 4e5         |  1e4     |

wavelength [nm]           |  972        |   1064  |    

If we have dp (the power fluctuation of the coupled power, coupling efficiency * input power * RIN,),df can be calculated.

However, df should depend on the cavity length, and the nominal frequency of the beam. 

df ~  f dL / L, where f = nominal frequency, L = cavity length.

And dP should depend on the circulating power inside the cavity which truly tells the value of absorbed power on the coatings.

dp ~ Pcirculating/ Finesse.

Thus, our df/dp should be rescaled to

70e6 * (203.5  /  77.5 ) * (1e4 / 4e5) = 4.6e6 Hz/W.

=========================================================

About Pointing noise. The instability of laser pointing will cause power fluctuation coupled into the cavity.

  This power fluctuation will induce frequency noise. If we know

how the beam moves, power coupled into the cavity and fluctuation can be calculated.

I'm thinking about using 2 QPDs to measure the beam position. A beam splitter will split the beam between 2 QPDs, the difference between

two readouts should tell us about angular and tranlational motion, and the power will be

P = Po Exp [ - (dx/w0)2 - (dtheta/ div angle)2]

where dx = translational motion

w0 = beam's waist

dtheta = angular motion

div angle = beam divergence angle.

  236   Mon Jul 26 20:43:30 2010 FrankSummaryComputersnew workstation

i got an old workstation and have converted it into a new linux workstation for the PSL lab.
It's like one of the usual workstation but with only a single screen due to space limitations.

Name: WS5
IP-address: 10.0.0.25

users are root and controls. passwords the usual ones...

  245   Thu Jul 29 02:55:15 2010 DmassSummaryComputersboth cavities individually locked

I noticed that root built the last ATF model and this screwed some things up. I am not sure if this was also done with the PSL model, and if it might somehow cause network problems.

  247   Fri Jul 30 13:17:05 2010 FrankSummaryComputersRT code built using wrong user
i deleted the PSL compiled stuff and rebuilt it with the controls user. Someone wants to do this for the ATF
model as well...

<p>
<table width="98%" cellspacing="1" align="center" style="border: 1px solid rgb(72, 96, 144);">
    <tbody>
        <tr>
            <td style="background-color: rgb(72, 96, 144); color: white;" cellpadding="3px">Quote:</td>
        </tr>
        <tr>
            <td style="background-color: rgb(255, 255, 176);" cellpadding="10px">
            <p>I noticed that root built the last ATF model and this screwed some things up. I am not sure if
this was also done with the PSL model, and if it might somehow cause network problems.</p>
            </td>
        </tr>
    </tbody>
</table>
</p>
<p>&nbsp;</p>
  257   Fri Aug 6 00:43:09 2010 FrankSummaryComputerswifi bridges configured

as Mott can't finish the installation of the wifi bridges for the gpib-to-ethernet adapters a configured 4 devices today.
Username and password are clearly labeled on each device, they are the usual ones for administrator rights.

The 4 new devices have the following IP adresses:

10.0.1.6
10.0.1.7
10.0.1.8
10.0.1.9

i will finish configuring the gpib-to-ethernet adapters on Friday, one for each instrument in the labs.

i will update the network diagram as soon i decided which ip addresses the will get

  261   Fri Aug 6 23:41:36 2010 ranaSummaryRefCavThe low UGF on Frank's temperature servo

Dear Frank,

I think basically you're right about the foam and the RC can's temperature servo. Although the impulse response of the can to heat is fast, the cool down time must be slow as its dominated by the conduction through the foam. Since this makes the servo asymmetric, it cannot have a high gain at the 24-hour period, unlike the system at the 40m.

So, what's the answer? We need to be able to keep the 24-hour period to be less than 5 MHz in the relative frequency shift. Ignoring the effects from the coating we ought to get ~150 MHz / K. At the 40m, we actually see more like 110 MHz / K at DC.

Assuming that you will always have 3 deg p-p fluctuations down there, we need a gain of 60 at 24 hours. This means that the UGF should be ~24 hours / 60 = 20 minutes. So that sets the maximum amount of foam that we are allowed to have on the can.

That ought to allow us to make the measurement for the first phase (the one with the double AOM setup).


For the second stage, we ought to use your Aluminum box idea. Put a 2 mm thick Al box completely enclosing the RC can leaving 4-5 inches of space. Layer the outside of the Al box with a 2-3 cm thick sheet of foam to keep the heating power low. In that setup, we ought to be able to go wild with the RC foam since the DC control will all be done with the faster Aluminum heater.

Rana

  263   Mon Aug 9 00:21:39 2010 FrankSummaryRefCavThe low UGF on Frank's temperature servo

What about the idea of putting both cavities in one chamber? Then we don't have to worry about the temp stability anymore.

Quote:

Dear Frank,

I think basically you're right about the foam and the RC can's temperature servo. Although the impulse response of the can to heat is fast, the cool down time must be slow as its dominated by the conduction through the foam. Since this makes the servo asymmetric, it cannot have a high gain at the 24-hour period, unlike the system at the 40m.

So, what's the answer? We need to be able to keep the 24-hour period to be less than 5 MHz in the relative frequency shift. Ignoring the effects from the coating we ought to get ~150 MHz / K. At the 40m, we actually see more like 110 MHz / K at DC.

Assuming that you will always have 3 deg p-p fluctuations down there, we need a gain of 60 at 24 hours. This means that the UGF should be ~24 hours / 60 = 20 minutes. So that sets the maximum amount of foam that we are allowed to have on the can.

That ought to allow us to make the measurement for the first phase (the one with the double AOM setup).


For the second stage, we ought to use your Aluminum box idea. Put a 2 mm thick Al box completely enclosing the RC can leaving 4-5 inches of space. Layer the outside of the Al box with a 2-3 cm thick sheet of foam to keep the heating power low. In that setup, we ought to be able to go wild with the RC foam since the DC control will all be done with the faster Aluminum heater.

Rana

  265   Mon Aug 9 17:34:43 2010 FrankSummaryRefCavtemperature jumps

the temperature in some of the cavity channels jumps about 5mK if you kick the table hard enough, so there is some problem with the d-sub connections on the table connecting the sensor readout box with the DAQ.

 tempsteps.png

  267   Tue Aug 10 01:10:35 2010 FrankSummaryRefCavupdated schematics of the setup

entire setup (simplified version):

refcav-setup_v1.png

 

beat signal generation in more detail:

refcav-beat_v2.png

  272   Thu Aug 12 00:10:44 2010 FrankSummaryRefCavboth cavities locked ~24h

this afternoon both cavities were locked since 24h. The initial problem was to find the right temperature for one of the cavities if we keep the other one fixed at 35 degrees. So now the reference cavity is held at 35 degrees, (because the time constant it needs to settle is much higher), while the analyzer cavity is at 35.3 degrees. With those setting the VCO input signal is almost at zero, having about +/-10MHz of tuning range.

  273   Thu Aug 12 00:15:59 2010 Frank, MeganSummaryComputersnetgpib scripts working

Megan tested the gpib scripts today and they are working except that the plotting of the data doesn't work as some packages are still missing.
Unfortunately i couldn't install them with yum so i will do it later.
Anyway, taking data without the plot function is working ...

  276   Thu Aug 12 17:34:37 2010 MeganSummaryNoiseBudgetNoise Budget

Sorry, here's a prettier graph! I think the strange bumps in the low frequencies is from very few samples in that region and the interpolation matlab is trying to do. Once I have more data to compare it to, I'll try to figure out how to get rid of them.

Attachment 1: NoiseBudget.fig
Attachment 2: NoiseBudget.png
NoiseBudget.png
  279   Fri Aug 13 15:10:33 2010 ranaSummaryNoiseBudgetNoise Budget

Quote:

Sorry, here's a prettier graph! I think the strange bumps in the low frequencies is from very few samples in that region and the interpolation matlab is trying to do. Once I have more data to compare it to, I'll try to figure out how to get rid of them.

 It looks a little like the FFT was done wrong here. How about uploading some more details, e.g. what is the channel names used? Is this in the DAQ or just using the SR785? How about a diagram showing what the transmission PD is, what the range of the Marconi is, how the signal goes to the DAQ, etc, etc, etc.....

Don't we need a whitening filter to put the PLL control signal into the DAQ? Or I guess we can use a DC channel and an AC coupled, high gain channel.

  280   Fri Aug 13 15:47:36 2010 MeganSummaryNoiseBudgetNoise Budget

Quote:

Quote:

Sorry, here's a prettier graph! I think the strange bumps in the low frequencies is from very few samples in that region and the interpolation matlab is trying to do. Once I have more data to compare it to, I'll try to figure out how to get rid of them.

 It looks a little like the FFT was done wrong here. How about uploading some more details, e.g. what is the channel names used? Is this in the DAQ or just using the SR785? How about a diagram showing what the transmission PD is, what the range of the Marconi is, how the signal goes to the DAQ, etc, etc, etc.....

Don't we need a whitening filter to put the PLL control signal into the DAQ? Or I guess we can use a DC channel and an AC coupled, high gain channel.

 This was directly from the SR785, where I saved the data using the GPIB scripts. This is the data with the 1MHz input range of the Marconi with the New Focus photodiode signal. The two signals go into a mixer, through a 1.9MHz LPF, then to the Stanford SR560 with a gain of 2000 and a break frequency of 0.03Hz on the low pass filter (the values necessary for it to actually lock). This feeds back to the input of the Marconi. We looked at data from the error point and the feedback loop with an input range of 100kHz to compare, calibrating the error point by pi/Vp-p*UGF (compensated for the gain by multiplying by 1/f, but then also multiplied by f to give the frequency noise) where Vp-p was 836mV and UGF was 16.2kHz as measured by taking a transfer function with the SR785. The feedback loop was calibrated by multiplying by 71kHz/V, the measured range of the Marconi (measured by applying 0V and 1V and finding the frequency difference). The 1MHz data was from the feedback loop and calibrated by multiplying by 715kHz/V (measured range at 1MHz setting). All the curves showed the same features and were at roughly the same level (within a factor of 2). I chose to plot the 1MHz data because it extended to lower frequencies (possibly a poor choice). We could not get lock with 100kHz input range for long enough to measure the lower frequencies because the cavities were drifting too much in temperature. We looked at the channels for temperature, and it looks like a 1K step in room temperature was causing the cavities to drift quite a bit. So our goal is to restabilize the cavities and take another measurement to verify the ones we already took.

*EDIT* Frank pointed out a concern with the lower frequencies. I attached a graph with the actual data. The strange spikes in low frequencies is from the interpolation of data that isn't real to begin with because of the measurement process. I'm working to figure out how to fix the interpolation and will hopefully have a graph of something less confusing soon. Also, the flat line at higher frequencies is electronic noise, we believe from the demodulation setup, because the line is always present, but higher with higher input ranges.

*EDIT2* The noise budget is back! I just deleted the low frequencies that aren't accurate and the high frequencies that weren't measured because I haven't figured out how to accurately extrapolate what we have.

Attachment 1: BeatSignal.png
BeatSignal.png
Attachment 2: NoiseBudget.png
NoiseBudget.png
Attachment 3: NoiseBudget.fig
  283   Mon Aug 16 16:36:35 2010 FrankSummaryLaserlaser, PMC, refcav re-characterization and recent changes

laser & PMC:

re-characterized the laser and PMC

new laser temp setpoint : 44.1 C  - almost centered between mode hops,
also PMC resonance close to that with centered PZT offset

  • PMC PZT OFFSET (PMC_RAMP) = -2.7V = 145V @ PZT (300V max)
  • PMC PZT tuning: 2.24V / FSR (714MHz)  for EXT DC INPUT
  • PMC TRANSPD close to limit: changed gain, now 3.32V=24.6mW  (7.41mW/V)

current values for TEM00:
RCAV resonant at 0.0182V
ACAV resonant at 0.0566V

ACAV:

  • re-aligned and re-modematched ACAV as old mode matching was only 47%
  • now DC voltage in reflection is 359mV if not locked and 42mV if locked. -> now 88% coupled into cavity
  • position of lenses very sensitive -> changing position a millimeter makes huge difference but no space for different mode matching
  • changed position of RF photodiode a little bit
  • beam size on PD now a little bit smaller
  • beam dump added for reflected beam from RF photodiode
  • changed setpt temp to 36.5 C, since the box changed the difference between both cavities. So the actual temp read and stabilized is not the (only) one seen by the cavity. The gradient seems to be important too.
  285   Tue Aug 17 14:35:34 2010 FrankSummaryRefCavACAV re-aligned

re-aligned the ACAV once more, now about 91% are coupled into the cavity

  292   Wed Aug 18 16:33:52 2010 FrankSummaryDAQ3123 card broken ?

the 3123 card (16bit input) seems to be broken. That's the card which also samples the PMC transmitted light which fluctuates periodically since a couple of days...
I changed the database to read the temp sensors for both cavities and when testing the inputs i figured out that it's reading only 8.97V of the 10 i put in, same for other values...
soft and hard resetting the crate doesn't change anything...

gonna replace the card...

  293   Wed Aug 18 20:04:53 2010 FrankSummaryDAQVME 3123 card NOT broken

it turned out that the ADC card is not broken. Instead it's a common-mode range problem of the inputs.
As we are using several PDs on the table powered by individual (non-grounded) power supplies (Thorlabs photodiodes), these signals are floating around.
And turns out that for some reason since a couple of days the common-mode voltage was sometimes larger than the input can handle (+/-12V) and so strange things happen to the signals from time to time.
In order to fix that i added 1MOhm resistors from the negative input to analog ground of the adc-card to prevent that input from floating around. The negative input is usually ground as all our signal are single-ended referred-to-ground signals; there are no differential transmitted signals for those devices) and so this should work fine. I only added one resistor per device connected to the DAQ, meaning the temp box with four signals has only one (the first one) connected to ground as all other ones have the same ground and so they can't floaf different anymore.

That fixed all problems...

  294   Wed Aug 18 20:11:44 2010 FrankSummaryDAQsome signals moved to VME DAQ system

moved the first 8 signals, the 4 individual sensors for each cavity, to the VME DAQ system.
Because i would have to open the foam box in order change the cables, i extended the existing ones for now to see if everything is working.
Once all channels are configured and everything is working i will open the box and make all the changes.
I also have to add the voltage reference for the second board and add the averaged channel from that board to the DAQ as well.
I need two more of the 9-pin D-SUB connector blocks or i have to make breakout cables instead.

Also added the VCO input monitor signal to the DAQ: channel name is C3:PSL-ACAV_VCOMON.
This channel can be used to keep the VCO signal centered in the range by feeding back to the temp setpoint of the cavity or the laser temp if locked alone (to match resonance of both cavities)

  297   Thu Aug 19 18:56:29 2010 Megan, FrankSummaryDAQmoved PD channel to 12bit card (VMIC 3113A)

moved PD channel to 12bit card (VMIC 3113A)

C3:PSL-PMC_PMCTRANSPD now connected to CH63, pins 64(HI)/63(LO) on block J3 (J3-3113A-P3)

C3:PSL-ACAV_RCTRANSPD now connected to CH62, pins 62(HI)/61(LO) on block J3 (J3-3113A-P3)

C3:PSL-RCAV_RCTRANSPD now connected to CH61, pins 60(HI)/59(LO) on block J3 (J3-3113A-P3)

  298   Thu Aug 19 19:17:44 2010 FrankSummaryDAQremoved connecting blocks J21 & J22

removed both 9-pin D-SUB blocks (blocks J21 & J22) which were used for the RF photodiodes (PMC, RCAV) before (only to power them).
As we hooked them up to individual power supplies a long time ago they are free to use for the temp readout of the cavities.

  300   Fri Aug 20 00:00:42 2010 FrankSummaryDAQnew/old channels for transmitted light of refcav

as we moved the channels from the 16bit card to the 12bit card we also changed the channel name for the transmitted light of the reference cavity.
The original (historic) channel name was C3:PSL-FSS_RCTRANSPD, but since we have two cavities now we started to separate both systems by using the subsystem names RCAV and ACAV quite some time ago.

So far we still use some of the old channel names like the ones for the VCO as "FSS" channels, even if they belong to the other cavity since some while.
As it is quite a lot of work to change everything (you have to change all screens, scripts etc too) we didn't change those yet.

As we moved the PD channels today, we renamed the C3:PSL-FSS_RCTRANSPD into C3:PSL-RCAV_RCTRANSPD.
So plz use the new name from now on. We created a calc record entry for the old channel name which basically copies the value from the new, physical channel.
So all the old screens and scripts are still working. Once we changed all things and if we find the time we disable that channel and check if everything is still working.
Right now i don't see a problem in having both in parallel and use the new channel name wherever me make changes....

  301   Fri Aug 20 00:04:14 2010 FrankSummaryDAQchannels from PSL RT system

i disconnected all signal from the PSL RT system running on fb0 this afternoon, so this model doesn't have to run anymore.
They are all hooked up to the VME system now.

I will remove the configuration file for those channels from the fb0 framebuilder the next day. Right now it's still running but not used anymore...

  302   Fri Aug 20 00:14:09 2010 FrankSummaryDAQchanges at VCO connecting block at x-connect

i replaced some cables going from the 9-pin D-SUB connection block connecting the VCO with the DAQ by bi-colored, twisted ones.
Someone used yellow cables for everything when he set this up. Now the ADC and DAC channels are bi-colored (black-LO, yellow-HI).

I also removed one connection from ground to the rack frame, so protective earth. I don't see why we need that as we have one at the power supply already. There ground=earth.

  303   Fri Aug 20 00:54:48 2010 FrankSummaryDAQPSL RT fronend code shut down

i've killed the PSL RT frontend. Everything else should be ok, so plz check if everything is working.

  305   Fri Aug 20 21:03:16 2010 FrankSummaryDAQchannel list for fb1 updated and framebuilder restarted

i updated the database for epics channels for the PSL lab and restarted the framebuilder on fb1.
I didn't restart the framebuilder on fb0, but once it will be restarted it' will load the new channel list too.

I saw that something seems to be wrong with the network as we have several lost packets which also shows up in the saved data.
I will investigate this later as it seems to be a problem for the slow channels from the PSL lab only.

  317   Mon Aug 30 23:25:06 2010 taraSummaryRefCavRIN comparison between PMC and RCAV

 I measured RIN from beam behind PMC and RCAV. Photodiodes are connected to SR785 and measured at the same time. 

DC level from PMC and RCAV are 3.56 V and 1.58 V, respectively.

The HEPA filters above the table were turned off during one measurement to see how much it would effect the RIN (turn out to be not that much)

Only PMC and RCAV were locked during the measurement.

The results are plotted together with RIN from 40m's RCAV ( 40m elog. ) PSL has lower noise at lower frequency f< 50Hz, and about 1.5 order of magnitude higher

between 50Hz to 10 kHz. 

I haven't tried to optimize any cavities yet. This is just walk-in,plug-in and measure as a reference for the current setup.

if I try to re-center the beam into the cavities, the result might be better (or worse).

Attachment 1: RINcompare.png
RINcompare.png
  335   Tue Aug 31 21:59:19 2010 FrankSummaryComputersstill network problems

i tried to figure out where the network problems come from. Looks like it's the fiber connection between fb1 and the switch in the PSL lab.

Here a result from a simple ping between fb1 and the other computers. It acrually doesn't matter which one.

--- 10.0.0.1 ping statistics ---
1000 packets transmitted, 817 received, 18% packet loss, time 201397ms
rtt min/avg/max/mdev = 0.169/0.233/0.381/0.025 ms

--- 10.0.0.2 ping statistics ---
1000 packets transmitted, 786 received, 21% packet loss, time 202036ms
rtt min/avg/max/mdev = 0.617/0.694/2.658/0.152 ms

--- 10.0.0.3 ping statistics ---
1000 packets transmitted, 796 received, 20% packet loss, time 201696ms
rtt min/avg/max/mdev = 0.410/0.453/2.655/0.081 ms

Pings between computers within the PSL lab but connected to the same switch are OK:

--- 10.0.0.1 ping statistics ---
1000 packets transmitted, 1000 received, 0% packet loss, time 202998ms
rtt min/avg/max/mdev = 0.000/1.092/13.755/1.340 ms

--- 10.0.0.2 ping statistics ---
1000 packets transmitted, 1000 received, 0% packet loss, time 203161ms
rtt min/avg/max/mdev = 0.200/1.719/13.230/1.545 ms

So i think it's the fiber connection.

 

  341   Fri Sep 3 01:45:54 2010 taraSummaryLaserRIN comparison between PMC and RCAV

 When both cavities are locked, I measured

1) power fluctuation behind ACAV (DC@0.55V) and RCAV (DC@2.2V)

2) power fluctuation behind PMC (DC@3.17V)and RCAV (DC@2.2V)

the HEPA filter was on, the SLOWDC loop was engaged.

SR785 is set to AC couple mode, auto range on both channels.

 

The level of RIN from RCAV from two measurements are a bit different,see fig2.

RIN from ACAV is not significantly higher than that of RCAV. This is good news, I thought AOM might pose more pointing instability to the system.

Attachment 1: all_compare.png
all_compare.png
Attachment 2: RCAV_compare_.png
RCAV_compare_.png
  351   Thu Sep 9 23:03:40 2010 taraSummaryRefCavreduced back reflection

    After PBS is rotated to the right position (yesterday I made a mistake by minimizing the split beam.

The split beam is minimized. This guarantees that the beam passing through is highly linearly polarized.

The reflection back to PMC is reduced from 1.9 mW to ~1.1 mW.

The cross correlation between the beat measurement and RIN is measured before and after the reduction of back reflection.

The plot shows certain correlation between RCAV's RIN and beat measurement when there is back reflection to PMC.

  352   Thu Sep 9 23:20:19 2010 FrankSummaryComputersMAC address overview for PSL lab
IP-ADDRESS MAC-ADDRESS
VENDOR DESCRIPTION
10.0.0.1 00:03:ba:04:b6:2f Sun Microsystems Inc. SUN
10.0.0.2 00:01:af:03:a3:76 Emerson Network Power PSL-CRATE
10.0.0.3 00:80:f9:75:04:5c HEURIKON CORPORATION ACAV-CRATE
10.0.0.12 00:a0:d1:e5:5a:3e (Unknown) FB2
10.0.0.24 00:1a:a0:1b:08:42 Dell Inc DELL WS (WS4)
10.0.0.32 00:91:00:00:85:d2 (Unknown) VIDEO SERVER
10.0.0.251 00:11:6b:f0:0a:c1 Digital Data Communications Asia Co.,Ltd 3COM SWITCH


 

  355   Fri Sep 10 12:32:04 2010 FrankSummaryComputersPSL crate rebooted

rebooted the PSL crate to see if it fixes the problem with some of the channels inaccessible from external computers

  356   Fri Sep 10 14:37:37 2010 FrankSummaryDAQPSL crate reboot fixed channel problems

all channels are working now

  365   Sat Sep 18 01:12:03 2010 taraSummaryPMCLISO model of the PMC servo

I started work on a LISO model of the PMC servo - it does not yet agree with reality.

Yesterday, I measured the open loop gain (OLG) of the PMC loop.

It consists of two parts, which are the PMC servo's OLG and the rest, i.e. OLG of photodiode, PMC, PZT actuator.

Knowing each part's OLG is useful for modification.

Since we are going to do most modification on the PMC's servo, we want to know what is its TF. 

 

This is where LISO comes in. I use it to simulate the TF of the PMC servo.

I don't know how to model AD602, because it is not actually an opamp and therefore not in the LISO opamp library.

The datasheet says it has -3db at 35MHz. Thus, for our region of interest, it probably has a flat response. It is just an

adjustable gain amplifier.

 

I'm not sure how to use LISO to calculate poles and zeros of my model yet. I'm reading the manual.

This simulation will be compared with the measurement.

Once we verify that all the parts behave the way they should, we can think about the modification.

We want to modify the TF because even though we maximize the gain slider, the system is still stable

( no sign of oscillaltion from too much gain.) It means we can still optimize our TF for better stability.


 Lastly, knowing the servo's OLG and the whole loop OLG,

we can compute what is the OLG of the rest of the system by simple subtraction.

 

I hope the quality of this elog entry is improved, however slightly it might be. It has motivation why I do what I do, details, and people who want to reproduce my work should be able to follow it.

Thanks Koji for a useful discussion on how to elog properly.

 

The attached plot shows modeled transfer function of the PMC Servo card + PZT capacitance.

Components' names in LISO code are taken from the schematic

Attachment 1: 2010-09-18_01-06-08.png
2010-09-18_01-06-08.png
Attachment 2: pmc.fil
#  Noise sim for pmc servo
# Tara C, 2010_09_17
#
#
#

r   R41  49.9   n0   gnd
l   L1   20u    n0   n1
r   R42  470    n1   n2 
c   C4   82p    n2   gnd
... 56 more lines ...
  385   Tue Nov 9 15:05:00 2010 taraSummaryPMCTF plot for each stage in PMC loop

I plot the TF from each stage in the PMC loop and plot below.

 

1)  Servo (+ gain slider)[V/V], From the mixer output to the output of PA85. The amplitude can be added upto 30.5 dB by the gain slider setup

 

2) PZT [V/V]. From PA85 V output to V at PZT. This includes the last R in the servo (R44 = 64.3k Ohm) and C_pzt (0.23 uF). 

 

 3) Opt [V/V]. This includes the PMC and the frequency discriminator part up to the signal to the mixer.

The PMC converts V -> Hz [1.36 MHz/V]. The PMC pole is 1.9 MHz, so I

assume that it is flat at the region of interest (1-100kHz). The frequency discriminator convert Hz->V, and assuming flat response for now.

Thus the total unit of this part is [V/V] too. I'll separate this part into PMC and+ RFPD later.

 

 

Attachment 1: TF_stage.png
TF_stage.png
Attachment 2: forplot.mat.zip
Attachment 3: TF_each_stage.m.zip
  387   Wed Nov 10 01:06:40 2010 taraSummaryPMCPMC OLG TF with different RF/gain settings

I measure the OLG TF of the PMC with 3 different RF and gain slider settings. I plot the OLG TF of each setup and identify their UGF.

 

 I increase the RF as a first step to optimize PMC loop w/o modifying the circuit. This will increase the TF of the optical path.

The setting are

      

set RF V Gain slider (read out/acutal) UGF [Hz]
b 5.6 15 / 17.5 775
c 5.7 11 / 11.5 520
d 5.7 13 / 14 630

 

 

 

First I  adjust the RF power to reach where I can adjust the stability by changing the gain slider.

RF V above (6 or 7) the gain is too large, even with smallest gain slider, the signal is not stable and the PMC_RCTRANSPD drops from maximum.

So RF V ends up around 5.5 V. this makes the gain slider sit around 10 -15 where I obtain maximum stability. 

The gain slider should not to be set too low because of stability problem. The voltage supply for the opamp should be > +10V.

The gain slider setups are chosen to obtain the maximum stability and maximum power out put (PMC_RCTRANSPD.)

\

c and d have the same RF V, I change the gain to see if there would be any significant change in the performance, and

the data will be used for RF V calibration (how much gain we got from RF V adj).

 

Now we have some room to increase the gain once we lower the power, but

I have to understand why increasing the gain slider makes signal unstable.

The phase margin seems to be ok.  It might be the slope of the TF at UGF that causes instability.

Attachment 1: OLGTF_2010_11_05.png
OLGTF_2010_11_05.png
Attachment 2: TF_bcd.mat
ELOG V3.1.3-