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ID Date Authorup Type Category Subject
  192   Wed Jun 30 12:39:17 2010 FrankHowToPMCPMC fixed

Quote:

Quote:

the reason why you had this flickering problem was that you had too much power on the RFPD in reflection of the PMC. You already saturated it.
I also reduced the RF power as the error signals were not signals anymore, just spikes.

my new settings are:

RF power : 3.0
Phase : 2.5
PMC Gain: 14dB

reduced laser power to 40mW. Transmitted power is 32mW .You have to exchange the output coupler mirror in front of the RFPD in order to increase the power. I think 32mW is enough, it's something like 13mW per cavity.

 

 

 Ok, I'll find another output coupler mirror and replace the current one, and make sure that it will not saturate the RFPD.

 the saturating power seems to be much to low. it saturates at .5V DC, usually you can have something like 2V or so. So we should propably fix the PD even if it is working with lower power levels.

For now it's much more important to connect all the signals to the DAQ and lock the refcav. You still have to make a lot of cables, like the ones going to the laser (fast & slow), RFPD DC, PMC and refcav transmitted light, refcav RFPD DC etc.

  193   Wed Jun 30 15:51:05 2010 FrankHowToNoiseBudgetview factor for two cylinders to calculate heat transfer via radiation

view factor for two cylinders to calculate heat transfer to and from cavity via radiation

from Michael F. Modest  "Radiative Heat Transfer", Second Edition
ISBN: 0-12-503163-7

view_factor.png
 

  196   Fri Jul 2 13:45:55 2010 FrankNotesEnvironmentchanged lab temperature

lowered the lab temperature avout 1K to get some data for the time constant from the environment to the chamber over the weekend which i can compare with my theoretical model.

current heater voltage for revcav is 14.5V @37Ohm resistance, so heater power is currently 5.68W.
current chamber temp is ~29C
current RT is 21.3C

  202   Thu Jul 8 15:20:24 2010 FrankNotesRefCavtemp sensor calibration

PT1000 value (chamber temp):

1083.9 Ohm

 

AD590 values:

RT:20.6
S1: 20.8
S2: 21.55
S3: 21.76
S4: 20.77

  218   Thu Jul 15 13:47:04 2010 FrankNotesVCOLM 336 Noise

you can model voltage references like this:

use an ideal opamp and add the parameters for the voltage noise manually: un=flat noise level, uc=1/f corner frequency

op LM336 op0 nii no no un=205e-9 uc=80   # simulate noise of LM336-5 reference

can you post the whole vco model plz. I would like to check the whole model. you might use the wrong opamps as your schematic is not the one for the vco you are debugging...

Quote:

I had forgotten to include the noise of the LM336 in the noise model because it cannot be easily modeled by LISO. So I thought I would look up its noise to see if I could make an approximation just to see if it will affect the noise levels coming from the model. I found this on a data sheet and will try to find a way to include it in the model.

 

  220   Thu Jul 15 15:08:46 2010 FrankNotesPMCcurrent values to lock system

personal notes to lock system remotely:

for PMC:
PMC voltage 203.5V --> DC offset -3.258
slow DC value : 0.15
PMC transmission value: 0.291V

  221   Thu Jul 15 15:46:20 2010 FrankNotesVCOMatching Model and Measurement

we replaced U9 by an OP27 instead of AD797. The replacement AD797 and AD829 were oscillating at 12MHz and larger.
So if you replace U9 by an OP27in your model the noise will be slightly higher at high frequencies.

Did you subtract the instrumentation noise from your measurement @TP7?
If not then do it.
As far as i remember the noise level of the DAQ/preamp is/was about 4nV/sqrt(Hz). I guess the simulation will then match your measurement

Quote:

Thanks, I modeled the LM336 and get almost the same measured curve at low frequencies. I'm on my way over to 40m in a matter of minutes to remeasure the noise with a lower noise amplifier to see if the entire curve can fit. I also have the model attached - the strange graphing frequencies were to match the ones I got with the measured data. I am also going to double-check the opamps used in the circuit currently. I already verified the resistor values - only R18 was incorrect (1k instead of 390).

 

  224   Thu Jul 15 19:04:45 2010 FrankDailyProgressVCOVCO Noise Update

looks quite good.

You can take the two new batteries out of the FET preamp box if you can't find more (the ones we replaced last week).

i had a quick look onto your new data. If you subtract the busby box noise floor from the new data you are almost there...

Quote:

I re-measured the noise at TP7 using the Busby Low Noise Box and measured the instrument noise of the box - the noise is lower at high frequencies, but much higher at low frequencies. There is a possibility some of this came from old batteries - they measured 7.4 V, but we were 2 short in 40m so I couldn't replace them. I will try to get new batteries tomorrow and see if that affects it at all.

I also changed the couple of things that were wrong with the model and have the revised model as well as its resultant graph attached.

I subtracted the noise of the other amplifier from the previous measurement of the noise at TP7 and compared it with the new model and they line up almost perfectly except around 10 Hz, where they're a little off.

 

  225   Thu Jul 15 19:23:51 2010 FrankNotesPEMtemp sensor calibration using PT1000

platinum temp sensor (PT1000) used for calibration of AD590 on PSL table:

Callendar-Van Dusen Equation:
RT = R0(1+AT+BT2-100CT3+CT4)
RT = Resistance at temperature T (°C)
R0 = Resistance at 0°C
T = Temperature in °C

 

CALLENDAR-VAN DUSEN CONSTANTS
Alpha, a (°C-1) .003750 ± .00003 .003850 ± .0001
Delta, d (°C) 1.605 ± 0.009 1.4999 ± 0.007
Beta, b* (°C) 0.16 0.10863
A (°C-1) 3.81*10e-3 3.908*10e-3
B (°C-2) -6.02 *10e-7 -5.775*10e-7
C (°C-4)* -6.0*10e-12 -4.183*10e-12

*Both b =0 and C=0 for T>0°C

source:  http://content.honeywell.com/sensing/prodinfo/temperature/technical/c15_136.pdf
online calculator: http://www.isotech.co.uk/prtcalc-web.html

 

measured resistance: 1083.9Ohm = 21.55C

calibration offsets for chamber sensors:
S1: +0.75K
S2: 0
S3: -0.11
S4: +0.88

room temp sensors:

ACAV_AMB1 : +0.2
ACAV_AMB2:  -0.3

  226   Thu Jul 15 20:30:30 2010 FrankNotesPMCPMC scan

PMC scanned using slow actuator (NPRO temp)

pmc-scan.png

pmc-scan2.png

  228   Fri Jul 16 15:18:55 2010 FrankDailyProgressVCOBusby box

there are 0 Ohm resistors, but you can also make a simple short between those two pads

i don't understand the third graph.  Looks like the blue data is the frequency noise calculated from the electronic noise with your 680KHz/V coefficient. The green one looks like phase noise, so i think you have to convert one of those into other units

Quote:

I replaced the batteries of the Busby box today to see if that reduced noise. It did not. Measuring the instrument noise and TP7 noise gave exactly what I got yesterday with the old batteries. I subtracted the instrument noise to plot against the model again and got basically the same graph as yesterday.

I also tried comparing the phase noise coming from the electronic noise against the total noise of the VCO. The total noise of the VCO was apparently below that of the electronic noise. I'm wondering if it could have been the fault of all the ground loops, since removing almost every cable changed the graph of the electronic noise so much. So at some point soon I would like to re-connect the entire VCO and measure the phase noise again, making sure I remove every unnecessary cable. This part confuses me though - all the schematics label the connecting resistor as 0, so I'm not sure if there is a 0 resistor or if it's a value that I don't know?

 

  230   Fri Jul 16 16:58:02 2010 FrankNotesRefCavlatest values for locking refcav

 - personal notes -

PMC voltage : 212V
PMC transPD : 0.291V

slow actuator : 0.1500V
RCTransPD : 0.796V

  231   Sun Jul 18 18:32:08 2010 FrankDailyProgressComputersMaster MEDM screen for RefCav experiment

i prepared a master screen for the refcav experiment.
This main screen contains all important numbers to figure out what the status of the experiment is.
It also contains several stripcharts which monitor important values like temperatures of the cavities, transmitted power levels etc over time.
It also has several buttons which link to the individual sub-screens which already exist for our subsystems.

medmScreen.png

  235   Wed Jul 21 10:39:10 2010 FrankDailyProgressComputersMaster MEDM screen for RefCav experiment

i don't know the units for the strength, but it's showing how good the reception of the signal is.I can't be dBm or something like that, so i don't know what units they use for that kind of quality signal.

The success rate is basically percent. Same situation here, there is no explanation for this signal, but it goes from 0 to 100 so it's percent.
If the value drops below 100 that basically means that the sensor is close to the range limit or the batteries are empty and so the communication is bad and we are loosing some data points...

the reason for some funny numbers like getting energy out of the PMC is that most of those channels are not connected or not calibrated yet. The PMC refl power is an open input

Quote:

While I guess it's a nice idea to put a Success = 100 meter on all of our MEDM screens for motivational purposes, what are the units on this one / the meaning of it?  Everything else makes sense (except maybe for the strength....are strength and success related?), but the success is confusing.

Quote:

i prepared a master screen for the refcav experiment.
This main screen contains all important numbers to figure out what the status of the experiment is.
It also contains several stripcharts which monitor important values like temperatures of the cavities, transmitted power levels etc over time.
It also has several buttons which link to the individual sub-screens which already exist for our subsystems.

 

 

  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...

  240   Wed Jul 28 21:53:10 2010 FrankNotesDAQconfusing cross-connect panel connections

the documents we have in the PSL lab about the connection made in the PSL rack cross-connect panel are not consistent with the current wiring.
A couple of channels are labeled to be connected to the VMIC3123 card (16bit) , but are connected to the VMIC3113A card (12bit).
One of these channels is  PSL-FSS_RCTRANSPD. I will reconfigure some of those channels.
Documentation will be provided in the elog and changes marked in the existing, printed version of cross-connect panel document.

  241   Wed Jul 28 22:11:11 2010 FrankNotesDAQold channel connections - blocks TB2 and TB4

- personal notes -

current cross-connect connections

PMC_RFPDDC:
block TB4
1 - LO
2 - HI
connected to ?

------------------------------------------------------------------------------

FSS_RFPD_DC:
block TB2
1 - LO
2 - HI
connected to J2-3113A  43/44 (CH21)

------------------------------------------------------------------------------

FSS_RCTRANSPD:
block TB2
5 - LO
6 - HI
connected to J2-3113A  53/54 (CH26)

------------------------------------------------------------------------------

PMC_TRANSPD:
block TB4
3 - LO
4 - HI
connected to J3-3113A   (CH34) (?)

 

 

  242   Wed Jul 28 22:12:41 2010 FrankNotesDAQold connections - J4 / J5

- personal notes -

VMIC3123 (16bit)

J-4:

12/25 : FSS_RMTEMP

6/19 : FSS_MINCOMEAS

 

J-5:

2/14 : FSS_RCTEMP

  243   Wed Jul 28 22:17:15 2010 FrankNotesDAQsome connections to P4-3113A (J2 and J3)

- personal notes -

 

J2  63/64  CH31  PSL-ISS_AOMRF

J2  45/46  CH22  PSL-FSS_LODET

J2  49/50  CH24  PSL-FSS_FAST

J2  51/52  CH25  PSL-FSS_PCDRIVE

J2  43/44  CH21  PSL-FSS_RFPDDC

J2  53/54  CH26  PSL-FSS_RCTRANSPD

J2  47/48  CH23  PSL-FSS_PCDET

 

J3  ?   CH34  PSL-PMC_TRANSPD

  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>
  248   Fri Jul 30 13:23:29 2010 FrankNotesDAQVMIC 3123 connections (J4 and J5) (16bit adc)

- personal notes -

list of current connections to the VMIC 3123 card in the PSL rack:

J-4:

LO/HI

2/14 : FSS_RCTRANSPD

16/3 : ACAV_RCTRANSPD

5/17 : PMC_PMCTRANSPD

19/6 :

8/20 :

22/9 :

11/23 :

25/12 :

J-5: no connections

 25/12 : "TEST" , test input, shorted

 

list of old connections to the VMIC 3123 card in the PSL rack according to document D980535-C-C:

J-4:

2/14 : FSS_MIXERM

3/16 : FSS_SLOWM

5/17 : PMC_PMCTRANSPD

6/19 : FSS_MINCOMEAS

8/20 : ISS_ISERR

9/22 : PMC_PMCERR

12/25 : FSS_RMTEMP

 

J-5:

2/14 : FSS_RCTEMP

3/16 : FSS_RCTRANSPD

  250   Mon Aug 2 16:23:59 2010 FrankNotesDAQconnectins for PMC, RCAv and ACAV to VME-based system

- personal notes -

current cross-connect connections

 

------------  PMC --------------

C3:PSL-PMC_RFPDDC:
block TB4
1 - LO
2 - HI
connected to J3-3113A, 1/2 (CH32)

-------------

C3:PSL-PMC_PMCERR:
block TB4
3 - LO
4 - HI
connected to J3-3113A,  5/6 (CH34)

-------------

C3:PSL-PMC_PMCTRANSPD:
connected to J4-3123  5/17 (CH2)
5 - LO  /  17 - HI

 

------------  RCAV --------------

C3:PSL-FSS_RFPDDC:
block TB2
1 - LO
2 - HI
connected to J2-3113A  43/44 (CH21)

-------------

C3:PSL-FSS_RCTRANSPD:
connected to J4-3123  2/14 (CH0)
2 - LO  /  14 - HI

-------------

C3:PSL-FSS_MIXERM
block TB2
5 - LO
6 - HI
connected to J2-3113A  53/54 (CH26)

 

------------  ACAV --------------

C3:PSL-ACAV_RFPDDC:
block TB2
3 - LO
4 - HI
connected to J2-3113A  47/48 (CH23)

-------------

C3:PSL-ACAV_RCTRANSPD:
connected to J4-3123  16/3 (CH1)
16 - LO  /  3 - HI

 

------------  TEST --------------

C3:PSL-TEST_SHORT:
connected to J4-3123  25/12 (CH7)
25 - LO  /  12 - HI

 

  252   Tue Aug 3 14:41:59 2010 FrankNotesPurchaseslenses to replace in kit

KPX088  75.6mm

KPX100  150mm

KPX103  175mm

KPX106  200mm

KPX109  250mm

  254   Wed Aug 4 16:21:01 2010 FrankNotesRefCavslow actuator values for both cavities

 - personal notes -

slow actuator values

RCAV : 0.1915ACAV : 0.2050

(.1915 V - .2050 V) * 1180 MHz/V = -15.93 MHz difference

  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

  260   Fri Aug 6 22:24:46 2010 FrankNotesComputersmissing file for medm screens

- personal notes -

medm error message: loadGIF: Cannot open file:  /cvs/cds/caltech/scripts/utilities/nova_logo.gif

  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

  264   Mon Aug 9 12:55:40 2010 FrankNotesRefCavslow actuator values for both cavities

both cavities @35 degrees +/- 5mK

 

slow actuator values

RCAV : 0.1890
ACAV : 0.1993

(.1890 V - .1993V) * 1180 MHz/V =  12 MHz difference

  • temperature of one cavity has to be tuned about ~12MHz with 6mK/MHz, so ~70mK
  • loosing lock @~+3V input to the VCO which should go up to at least 5V

anyway, the tuning range is only 10MHz in that direction, so can't lock both at the same time right now

frequency see here: VCO tuning

  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

  270   Tue Aug 10 22:57:25 2010 FrankDailyProgressRefCavstrange channel behavior

we have probably some minor network problems which causes some channels not beeing available at all times even on the same computer.

example:
if you open the Striptool and Probe at the same time and access the same channel, one of the tools can see the channel, the other doesn't.
Or one tools sees a different value, e.g. if i change the setpoint of the temp loop, probe still sees the old value, but the Striptool already the new one.
Sometimes it helps if you close the application and after restarting it everything is fine. Same for the framebuilder. Sometimes some of the channels get lost.
I don't know where it comes from. It happens randomly to any of the channels. It's not the traffic on the network, but could be some routing problem.

  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.

  277   Fri Aug 13 01:14:53 2010 FrankNotesNoiseBudgetDC simulation

graph?

Quote:

I used COMSOL to simulate temperature change caused by 10^-4 fluctuation from the main DC power.

That is the temperature change in the substrate due to power change from Pin to Pin + Pin*10^-4.  Pin is 10mW.

This should give us the upper limit of the expected frequency noise.

The area under the plot of Temperature vs Depth is 1.9 * 10^-8 [meter*Kelvin].

 

thermal coefficient for substrate is 0.51 *10^-6

thus dL is (0.51*10^-6) * (1.9*10^-8) ~ 10^-14.

Use dL/L  = df/f ;  where L is the cavity length = 0.2035m,  f = c/ lambda.

df = 15 Hz. (effect from thermal expansion 1 mirror in the cavity only)

 

  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

  286   Tue Aug 17 14:52:57 2010 FrankPhotos beat setup panorama picture incl beams

beat_panorama_small_with_beams3.jpg

  287   Tue Aug 17 15:57:11 2010 FrankNotesBEATpower on beat PD

- personal notes -

New Focus PD:

power from ACAV: 0.958mW
power from RCAV: 0.967mW

DC-OUT: 1.94V
AC-OUT: 1.27Vpp @160MHz in 50R

  288   Tue Aug 17 18:54:19 2010 FrankNotes list of current problems and things to do

 - personal notes -

  • tiny, periodic spikes in acav RF PD
  • ~36MHz oscillation (without light too) at RCAV RF pd dc output
  • PMC transPD signal into DAQ broken, changes periodic from real value to some random number. However real signal at input of cross-connect panel is constant (on scope & multimeter)
  • kicking the table introduces 5mK jumps in temp signals (random channels)

to-do-list (other stuff)

  • switch temp readout to VME based system (3123, channel 9-16, J5 and remaining channels from J4)
  • improve PID parameters (so I and D so far)
  • exchange linux workstation (freezes from time to time)
  • update boot values for all channels
  • change channel name for VCO input signal
  • change channel names for all PID controllers
  • measure TF for all loops
  • ...
  289   Wed Aug 18 00:07:37 2010 FrankDailyProgress noise level of beat signal

i tried a couple of things today to figure out what determines the low frequency noise level of the beat measurement.
I did the following steps, nevertheless the noise level didn't change:

  • re-aligned everything starting with the PMC
  • coupling into the cavities is >90%
  • matched power levels in both paths to match power at RF photodetector
  • re-positioned the RF photodiodes for locking the caviries
  • added beam dumps for beams reflected from RF photodiodes
  • optimized overlap of both beams on RF photodiode (beat)
  • changed mixer from 7dbm model to 13dbm model
  • removed cable going to DAQ from DC output of RCAV RF photodiode as it is causing ~36MHz oscillation of RF PD (even with no light)
  • changed gains for both loops, ACAV and RCAV
  • added first QPD at pick-off right in front of periscope into chamber for RCAV to check pointing

things to be checked tomorrow:

  • power fluctuations of beams into both cavities
  • power fluctuations of transmitted beam
  • pointing of both beams (should also show up in power noise spectrum in transmission)
  • measure TF of all loops with current setting for noise estimation

other things to change:

  • move temp readout to VME based stuff
  • rename VCO input monitor signal channel name
  • remove PSL RT stuff from fb0 to see if networking problems are caused by that
  • replace current cables for temp readout due to loose connection somewhere on table
  • check ACAV RF photodiode
  • change PID controller variable names in order to add other software loops like feedback from VCO input signal to RCAV temp setpoint. Right now we have already 4 software loops:
  1. feedback to laser for RCAV using FAST actuator signal
  2. temp ctrl for RCAV
  3. temp ctrl for ACAV
  4. feedback to laser temp for ACAV using VCO input signal (used to track ACAV temp tuning to match RCAV resonance)

 

  291   Wed Aug 18 12:19:17 2010 FrankPhotos beat setup panorama picture incl beams

i know the the asymmetry is not nice but we made the first beat setup symmetric and suffered a lot from the (former) little space behind the cavities.
Also one of the cavities is tilted and so the beam height is about .5in different.
Now as me moved both cavities a bit further away from the end of the table we should re-think about changing it to a symmetric setup. I think it's a good idea.
Anyway, shouldn't we just see all the resonances of the mounts in the spectrum, not a broadband noise hump? or do you expect lots of scatter from all the unnecessary optics?

you are right with the power, i reduced it by a factor of 10 and 100 but no change in noise spectrum (almost absolutely the same). But if i reduce the power some pickup of the 35.5MHz shows up in the signal (which is tiny), which i didn't see before. But it's ground loop related as you can change it by connecting/disconnecting some more channels to the scope e.g.. About the gain: i didn't measure the TIA gain of the PD, but the manual says 24e3 in the text, and 40e3 in the table at the end. Which one is right?

Another problem is that the bandwidth is only 125MHz, but we are looking at 160MHz. That shouldn't be much of a problem, only the noise of the PD increases and we are more sensitive to changes in the TF of the PD due to almost anything like power fluctuations, power supply fluctuations, temperature etc... So that probably the best argument right now to add the second AOM to reduce the beat frequency to something we can handle much better

Quote:

The panorama is a good idea. We should make it a mandatory step whenever we make any change to the setup.

The asymmetry in the paths of the transmitted beams is dis-satisfying though. I would have tried to just take the transmitted beam and interfere them via short path lengths and no lenses. The cavity eigenmodes of each cavity should already be matched to ~1%. If the path length from the cavities to the BS can be made equal, the overlap should also be good. In general, it is hard to make a low phase noise setup with a long path length.

To ensure low backscatter from the transmission RFPDs back into the cavity, the beat signal PD should be placed slightly ahead of the focus of the final lens.

And since the Z=40 kOhms for the 1811, the light power from each cavity should be made ~200 mV / 40000 ~ 5 uW. I know its tiny, but otherwise the 1811 is not going to be very linear. And the RF signal going into a level 13 mixer ought to be less than 300 mVrms.

The better option is to use a RFPD with only ~1 kOhm of RF transimpedance...

 

  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)

  295   Wed Aug 18 20:16:24 2010 FrankNotesDAQtemp sensor 2 of RCAV is too noisy

temp sensor number 2 of the reference cavity shows much more (horrible) noise compared to the other ones (2K pkpk).

broken, oscillating?

Will check this tomorrow.

 

- personal notes -

things to do: change limit of both heaters to match new situation. much less power required and messing up things causes both cavities to heat up too much (50 C)...

  296   Wed Aug 18 20:27:00 2010 FrankNotesDAQVMIC3123 address jumper settings for 1st card in PSL crate

jumper.jpg

  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.

ELOG V3.1.3-