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  26   Thu Dec 17 16:57:10 2009 FrankComputingDAQnew analyzer cavity DAQ system

we set up a second, independent DAQ system for the analyzer cavity. It has one 16bit D/A card, 16bit A/D card and 12bit A/D card. The system is called "acav1" and has the ip-address, which we can access from the ATF as well via fb1 (fb1 is in peters network too). Here is a boot screen dump of the new system with a list of the new channels at the end. The new channels are now in C3, the new numbering scheme for the PSL subsystem, not in C anymore! (but all the old channels are still C as i would take to long to change all the existing medm screens...


                            VxWorks System Boot

Copyright 1984-1996  Wind River Systems, Inc.

CPU: Heurikon Baja4700
Version: 5.3.1
BSP version: 1.1/1
Creation date: Dec 11 1998, 10:29:37

Press any key to stop auto-boot...

boot device          : ei
processor number     : 0
host name            : bdl1
file name            : /usr1/epics/baja/vxWorks
inet on ethernet (e) :
host inet (h)        :
user (u)             : root
flags (f)            : 0x0
target name (tn)     : acav1
startup script (s)   : /usr1/epics/acav/startup.cmd

Mapping RAM base to A32 space at 0x40000000... done.
No longer waiting for sysFail to clear. D.Barker 14th Sept 1998
Attaching network interface ei0... done.
Attaching network interface lo0... done.
Loading... 795028
Starting at 0x80010000...

Mapping RAM base to A32 space at 0x40000000... done.
No longer waiting for sysFail to clear. D.Barker 14th Sept 1998
Attaching network interface ei0... done.
Attaching network interface lo0... done.
Mounting NFS file systems from host bdl1 for target acav1:
Loading symbol table from bdl1:/usr1/epics/baja/vxWorks.sym ...done

      ]]]]]]]]]]]  ]]]]     ]]]]]]]]]]       ]]              ]]]]         (R)
 ]     ]]]]]]]]]  ]]]]]]     ]]]]]]]]       ]]               ]]]]
 ]]     ]]]]]]]  ]]]]]]]]     ]]]]]] ]     ]]                ]]]]
 ]]]     ]]]]] ]    ]]]  ]     ]]]] ]]]   ]]]]]]]]]  ]]]] ]] ]]]]  ]]   ]]]]]
 ]]]]     ]]]  ]]    ]  ]]]     ]] ]]]]] ]]]]]]   ]] ]]]]]]] ]]]] ]]   ]]]]
 ]]]]]     ]  ]]]]     ]]]]]      ]]]]]]]] ]]]]   ]] ]]]]    ]]]]]]]    ]]]]
 ]]]]]]      ]]]]]     ]]]]]]    ]  ]]]]]  ]]]]   ]] ]]]]    ]]]]]]]]    ]]]]
 ]]]]]]]    ]]]]]  ]    ]]]]]]  ]    ]]]   ]]]]   ]] ]]]]    ]]]] ]]]]    ]]]]
 ]]]]]]]]  ]]]]]  ]]]    ]]]]]]]      ]     ]]]]]]]  ]]]]    ]]]]  ]]]] ]]]]]
 ]]]]]]]]]]]]]]]]]]]]]]]]]]]]]       Development System
 ]]]]]]]]]]]]]]]]]]]]]]]]]]]       VxWorks version 5.3.1
 ]]]]]]]]]]]]]]]]]]]]]]]]]]       KERNEL: WIND version 2.5
 ]]]]]]]]]]]]]]]]]]]]]]]]]       Copyright Wind River Systems, Inc., 1984-1997

                               CPU: Heurikon Baja4700.  Processor #0.
                              Memory Size: 0x1000000.  BSP version 1.1/1.
                             WDB: Ready.

Executing startup script /usr1/epics/acav/startup.cmd ...
shellPromptSet "acav> "
value = -2146677404 = 0x800c4d64 = shellHistSize + 0x4
cd "/usr1/epics/baja"
value = 0 = 0x0
ld < iocCore
value = -2130992736 = 0x80fba1a0 = prsrv_cast_client + 0x770
ld < drvSup
value = -2131103904 = 0x80f9ef60
ld < devSup
value = -2132426208 = 0x80e5c220 = pwf_xy566 + 0x70
ld < recSup
value = -2132416016 = 0x80e5e9f0
ld < seq
value = -2130995152 = 0x80fb9830
dbLoad "default.dctsdr"
value = 0 = 0x0
cd "/usr1/epics/acav/db"
value = 0 = 0x0
dbLoadRecords "n3113.db"
value = 0 = 0x0
dbLoadRecords "n3123a.db"
value = 0 = 0x0
dbLoadRecords "n4116.db"
value = 0 = 0x0
cd "usr1/epics/baja"
value = 0 = 0x0
value = 1 = 0x1
iocInit "resource.def"
###  @(#)Version R3.12.2patch1 Date: 1996/04/02
bdl1:sh: /usr1/epics/acav/db/usr1/epics/baja/resource.def: cannot open
task: 0X80fbf430 tShell
iocLogClient: unable to connect to port 7004 because "errno = 0x33"

Unable to start log server connection watch dog
No such Resource file - resource.def
vmi4116_addr 1f045c00
entry 0 address 0x0
entry 1 address 0x0
entry 2 address 0x0
entry 3 address 0x6000
entry 4 address 0x7000
entry 5 address 0xe000
entry 6 address 0xc014
entry 7 address 0x0
entry 8 address 0x0
entry 9 address 0xff00
entry 10 address 0x0
entry 11 address 0x0
entry 12 address 0x0
entry 13 address 0x0
entry 14 address 0x2000
entry 15 address 0x2c00
Failed to set time from Unix server
0x80fbf430 (tShell): iocInit: Database Failed during Initialization
0x80fbf430 (tShell): iocInit: All initialization complete
value = 0 = 0x0
###  @(#)Version R3.12.2patch1 Date: 1996/04/02
value = 226 = 0xe2
0x80f435f0 (CA UDP): CAS: couldnt start up online notify task

Done executing startup script /usr1/epics/acav/startup.cmd
acav> dbl
value = 0 = 0x0

  848   Mon Feb 27 21:45:55 2012 FrankNotesRefCavnew beam height for cavities

The beam height changed by 1/8". Current beam height is 5-7/8". The top stack plate is slightly off-centered towards the ACAV side but we don't want to re-open the chamber now to fix this (it's not much, but one can see it). We can do this the next time we open it anyway or if we see weird coupling between different stack modes. When we open it next time we will add some markings at the end faces of the top stack plate to better see if it's centered or not.

We will align the beams along the hole pattern as designed first and move the cavities to the right position. Once we add the air springs (hopefully soon) we have to change the beam height again.

  485   Wed Feb 9 19:57:43 2011 FrankNotesBEATnew cable length - calibration data

shorter cable: cable length 62 inches

amplified (DC-coupled) signal from mixer using SR560, LP@30Hz, gain20 in channel C3:PSL-GEN_DAQ15

185.0MHz :  -2.405V
154.2MHz :   0.005V
123.2MHz :   2.263V

max range of double-passed VCO signal: 142MHz-170MHz

142MHz :  1.38V
170MHz : -1.685V

As the FET preamp need some more time to set up i added the AC-coupled signal using a SR560, gain 10k, LP30Hz into C3:PSL-GEN_DAQ16

FET pre-amplified signal will be connected to C3:PSL-GEN_DAQ14   preamp broken

  663   Fri Sep 2 00:37:11 2011 FrankDailyProgressRefCavnew cavity setup - status update

yesterday i got the new top stack plate from the machine shop. They couldn't finish the entire job on time so i had to tap the holes and do the surface cleaning (sand blasting, grinding and polishing to clean the surface and reduce surface area) myself.
Getting a machined surface would have taken until mid next week (minimum, no guarantee) which would have delayed things too much to get a measurements done before the LVC meeting. Looks pretty nice, has kind of a mirror finish.

I started cleaning it this afternoon, the final sonic cleaning is underway right now and i will start air baking tonight (talked to Bob and he said that this is enough). Also boiled the viton in isoprop and it's getting baked in vacuum at the moment (for 24h). The teflon parts and screws i already baked.

We already removed the insulation from acav and vented it. So we are ready to install the new stack once the plate and the teflon is ready. As i don't know how bad the new parts are (outgassing)  thought about assembling the new stack and putting it in the acav chamber to pump on it over the weekend. Then we transfer the (cleaner) stack to the final chamber next week. We can then align both beams into the cavities and set up the beat parts while pumping on it with the turbo before we switch over to the ion pump. Or should we put everything together and start pumping Friday? Any suggestions? I tend to do it in two steps as i don't want to ruin the cavities and and if you ask Bob we should have gone through the whole class A cleaning process (which would take a month or more at the moment because they are somewhat of behind)

  96   Fri Apr 2 00:35:00 2010 FrankMiscRefCavnew chamber almost ready

the new chamber is almost ready. I've attached three of four heaters, the fourth one has a fabrication error and has to be replaced. The chamber is currently pumped using the old varian ion pump. Current is already down to 100uA and one can watch it further decreasing. So my guess is that it will be clean beginning next week. I turned on two of the heaters to "bake" it a little bit. I baked the ion pump this afternoon while pumping with the turbo at 250C. The new insulated feet are ready and fit now to the chamber. Next task will be cutting the remaining holes into the foam and putting the temp sensors on the chamber.

Here a picture of the current status:



  460   Mon Jan 31 21:40:50 2011 Frank, TaraSummaryDAQnew channel for frequency counter added

We added a new channel C3:PSL-FSS_FREQCOUNT which contains the analog output of the SR620 frequency counter connected to the beat photodiode.


  • C3:PSL-FSS_FREQCOUNT is connected to CH6 of the first 3123 card, connector P3 (first D-SUB). This is also J4 of the PSL x-connect.
  • Added channel entry in fss.db database. Sampling rate is 10Hz.  Scaled from -10 to 10V in unit  "volts" as we don't know which settings we will use later.
  • Also added channel to daqd. restarted daqd. Manual restart of daqd as controls using script requires password for controls.
    That shouldn't be so but i was to lazy to search for the bur


Counter output is 0 to 8V, right now used in relative mode which means zero frequency deviation equals 4V. Current gain for first test is 100kHz/V.

  56   Sun Feb 7 18:29:06 2010 FrankLaserLasernew channels + changes

added the following channels:

C3:PSL-RCAV_DIFFPWR : diffracted power (single pass) measured behind curved mirror
C3:PSL-126MOPA_PWRMON : laser output power monitor measured after PC



C3:PSL-RCAV_QPDSUM changed back to QPD sum signal


all signals available in both framebuilders

  749   Wed Dec 7 23:13:37 2011 FrankNotesDAQnew channels for EOM temp stab

Have added 8 new 16bit channels. Terminal block is tied to the frame of the table enclosure right next to the BNC breakout panel near the ACAV aom (pictures follows). Card is plugged into the second crate whic is currently not used. D-sub cable is run across the floor using a extruded aluminum cable bridge to keep it short. Made some BNC breakout cables to connect the EOM temp stab stuff.

Have to come up with some channel names and edit database file. Will be ready to use tomorrow afternoon

  843   Sun Feb 26 02:18:38 2012 FrankNotesDAQnew channels for in-vac sensors

the new AD590 sensors are physically connected to

  • VME3123, C0 S3 (RCAV)
  • VME3123, C0 S4 (ACAV #2)
  • VME3123, C0 S5 (ACAV #1)

measured across 30kOhm (+/-1%, 100ppm) to gnd, so voltage is ~9V at 30C. Had no precision resistors but doesn't matter as the channels are used for monitoring purposes only

Software channels are not assigned yet.

  166   Wed Jun 16 00:10:36 2010 FrankComputingDAQnew channels for temp ctrl of both cavities

some new channels for the temp ctrl of the two cavities, most of them for debugging purposes only

# ACav
# Sensor1
# Sensor2
# Sensor3
# Sensor4
# Ambient Sensor1
# Ambient Sensor2
# SUM signal
# Stack Sensor1
# Servo channels

# RefCav
# Sensor1
# Sensor2
# Sensor3
# Sensor4
# Ambient Sensor1
# Ambient Sensor2
# SUM signal
# Stack Sensor1
# Servo channels

  761   Fri Dec 9 11:55:21 2011 FrankNotesDAQnew channels from second VME crate

Added the following channels. Data is valid from now on.

# RF-AM monitor channels (not used at the moment, no calibration)
[C3:PSL-FSS_RFAM_RCAV]   # monitor for RCAV
[C3:PSL-FSS_RFAM_ACAV]   # monitor for ACAV

# EOM temp stabilization channels
[C3:PSL-FSS_EOM_TSET]  # EOM temp setpoint value (no calibration,units=Volt)
[C3:PSL-FSS_EOM_TACT]  # actual (in-loop) temperature (no calibration, units=Volt)
[C3:PSL-FSS_EOM_IMON]  # EOM heater current monitor - does not exist yet
[C3:PSL-FSS_EOM_SETTEMP]  # Analog output to set EOM temperature - not used at the moment

# aux channels (no calibration, input range -10V to 10V

  2604   Wed Dec 9 18:13:12 2020 PacoMiscEquipment loannew focus 1811

Borrowed two broadband PDs (new focus 1811) and one power supply unit (new focus 0901) from CTN into Crackle.

  61   Mon Feb 8 22:03:32 2010 FrankLaserRC noisenew results

everything is back, pointing is much much less, power modulation too, ugf of the other loop is much higher - but nevertheless the performance is not much better, only one order of magnitude. it turns out that the noise is limited by the existing FSS stuff. tuning the gains (common, fast) can produce almost any shape and level (see graph), except much lower levels are not possible, at least not for more than a couple of seconds before everything starts to oscillate. so i will to debug the old FSS stuff first to see whats going on there. will try to investigate the noise of the FSS loop and maybe replace the VCO by a function generator and probably the RF photodiode to see if that changes something. Those can be exchanged easily without changing to much...


  37   Sun Jan 24 18:35:47 2010 FrankLaserRefCavnew slow actuator values

- more insulation to the refcav chamber added

actual slow actuator values for both cavities:
refcav : 0.4385
acav : 0.2539

-> ~215MHz difference

with ~6mK/Mhz  -> refcav temp reduced by 1.3K

01/25/10  8am:

refcav temp now 67.7, slow actuator 0.304 -> reduced temp further to 67.5

01/26/10  1pm: 

refcav : 0.243
acav : 0.251

01/27/10  11am

refcav: 0.2456    temp:67.4
acav: 0.2582      temp: 40.0

01/27/10  9 pm

refcav: 0.2423    temp:67.55
acav: 0.2578      temp: 40.0

01/28/10  1am

refcav: 0.2525   temp:67.65
acav: 0.2578      temp: 40.0

01/29/10  4 pm

refcav: 0.2485   temp:67.65
acav: 0.2335      temp: 40.0

  665   Fri Sep 2 20:19:31 2011 Frank, TaraDailyProgressRefCavnew stack parts

checked if the cavities fit on the new support, they do . We've put the assembled new stack top plate in vacuum over the weekend to clean it a bit more. Also turned on the heaters which won't do much but won't hurt. Will move everything into the other, final chamber and start aligning the cavities on Tuesday.

  1360   Mon Oct 7 19:53:53 2013 taraDailyProgressSeismicnew table legs installed

New legs were installed.  The table is floated. The cables for signals/ power supplies will be reconnected later

 Evan and I replaced the old legs. I made sure that the leak was not in the connections and the tube. After the legs replacement, the air pump can reach 25 psi within ~25 minutes and the table can be floated.

The regulating valves are adjusted and the table is leveled.



  1370   Tue Oct 22 04:34:12 2013 taraDailyProgressSeismicnew table legs installed

After installing the table legs, I have been trying to measure the beat. However, there is an unknown scattered light noise up to 400 Hz. I'm still trying to fix that.

  Here are some bullets about what happened, I'll add the details later.

  • Extra noise that looks like scattered light goes up to 400Hz ( was around 100 Hz before, not from floating the table)
  • One of the air spring supporting the vac tank has a leak. But it is unlikely to be the source of the extra noise mentioned above.
  • The finesse of the cavities may be less than the designed value (10 000) because of the not so clean isoprop I used on the mirrors.

Note: check if the beams in the tank is blocked by wires or not.

  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

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

  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....

  704   Thu Oct 13 00:24:35 2011 FrankDailyProgressRefCavnext iteration of refcav stack

we got the stainless compression springs and i cleaned them together with the all the other parts for the radiation shield/heater assembly (except the heater wire). The only thing i'm not sure about is how to attach the temp sensors (ad590, metal/ceramic package) to the copper shields. I would like to solder them on it, probably using indium. I don't like to glue them as i don't want to bake the stuff (we don't have a large enough oven so i would have to wait for a spot at the 40m). I could just put it into our spare chamber and pump on it for a while. The other parts are small enough to fit into the baking chamber.

Something i'm not sure about is: What happens to the springs (stainless steel) if baking them at let's say 120C for a few days? Do they change their hardness? Does anyone know?

I also wanna try to cut holes into the RTV springs to make them softer by removing material. We checked the cork drill's at the 40m. Most of them are broken. Looks like someone used them to open bottles or for cutting metal
So i probably buy a set (~$12 for a set of 6), but could also make one for the diameter i want to try (it's only a thin-walled tube with sharp end, so very easy do make if the machine shop has the right tube).

Before i bake the stuff i will try different versions with the spare stack on the hepa bench (which has not the right size of top plate, but we can add some load)

  2354   Tue Jun 4 20:44:21 2019 ranaSummaryOthernext steps
  1. Fix the temperature control so that the fluctuation over hours time scale is low as Tara/Evan had it. This will allow for using the Marconi with a low FM range (or potentially none; we could just demod with a fixed frequency and directly digitize the IF signal in the CYMAC).
  2. Debug and fix the FSS misbehavior. Circuit creep in the last few years has degraded its performance relative to the in-loop performance achieved back in 2015.
  3. Recalculate the Brownian noise.
  701   Mon Oct 10 11:17:46 2011 FrankNotesPurchasesnitrogen bottle replaced

we got the new nitrogen bottle this morning. We could check the price for nitrogen and compressed air bottles to see if it's worth getting a regulator for compressed air bottles in the future. But i think we should stick to the nitrogen. Once we fixed the leaking leg we shouldn't need much air anymore...

  815   Wed Feb 8 22:10:56 2012 frank, taraDailyProgressBEATnoise budget and beat

The noise budget is updated and plotted with today's beat measurement.

(*The electronic noise plotted in the graph is not correctly calibrated, see psl:816 for the complete calculation)

     After we replaced the table's broken leg, we floated the table and measured the beat signal as a reference before modifying the seismic stack. The calculation agree with the measured data quite well.

   We also measured the electronic noise from PLL. This was the signal which was fed back to the LO (with SR560 gain = 20). Apparently, we are sitting on it at 1kHz and above. We definitely need to work on PLL readout system to measure at lower sensitivity.


New traces in the noise budget:

  1. Beat noise (floated table)
  2. PLL electronic noise

I removed noises from room temperature fluctuation/ heater noise and spacer thermal noise because they are way smaller than coating noise and crowd the plot.

==Details about some traces in the noise budget==

Seismic noise:

     The vertical seismic noise coupling is calculated by applying the seismic measurement times stack transfer function times cavity bending coupling

     [ Frequency noise from seismic ] = [measured data] x [stacks TF] x [bending factor].

  • For seismic noise, The data was taken by a seismometer on a floated table.
  • Stack TF is computed based on springs and the weight of the blocks, see PSL: .. 
  • The cavity bending coupling is obtained from COMSOL simulation. However, the value used in the noise budget is about 1 order of magnitude larger than the value COMSOL provides. This is probably due to the fact that the cavity's support positions do not match exactly at the optimum point.

The peak around 6 Hz might be coupled from horizontal direction. This will be added soon.

RIN induced length noise is still an estimated. We have not been able to measured the real coupling yet, as the SNR is so low.

LO phase noise:  This is from measurement. I'm not quite sure if I miss some calibration factors. The phase noise does not show up in the beat yet even though it is very close together right now.

  816   Thu Feb 9 22:31:03 2012 frank, taraDailyProgressBEATnoise budget and beat

Noise calculation from PD in PLL: ( I actually asked Koji once and did this already, see psl:730 . The results are similar)

1) determining which setup gives the best performance:

  • Gain on SR560 = 200. This gives UGF of 33kHz with 60 degree phase margin. Gain 500 has phase margin of 18 degree, which is too low, see fig 1.
  • Tuning range on Marconi = 1kHz. Currently, we cannot go with lower range. Usually, this noise couple directly to the readout and cannot be suppressed, so the lower noise (smaller range) the better.


fig1: OLG TF of PLL with different gain setup.



2) Measure electronic noise from readout system with the chosen setup. This noise will show up (after some correction) in the beat and determine what is the limitation of PLL readout technique.

     The PD was blocked, the feedback signal (Vfb) to the actuator (LO) was removed and measured.

3) Block diagram

[add block diagram and calculation]

4) After Koji explained on how to calculated noise budget from electronic noise in PLL to us, here the nb with PLL noise. (note: the LO phase noise has updated to 1kHz input range)


With the electronic noise from PLL, the sensitivity of this technique will prevent us from observing coating noise above 1kHz.

I'll calculate the noise from cable delay technique later and compare which one will give us better sensitivity.


Attachment 2: nb_2012_02_09.png
  411   Mon Nov 29 14:34:35 2010 taraNotesNoiseBudgetnoise budget update

I updated the noise budget, see the plot below. LO phase noise and RIN are updated in this version

 The code is also attached below.

1) LO noise

I used Megan's LO phase noise measurement, converted it to freq noise and added it to the nb.

Note that the plot is from 160MHz carrier and 100Hz range.

She has data for 160 MHz, 100Hz range and 160MHz, 10Hz range. There is no measurement at 100kHz range which I used for my measurement.

At larger range the LO noise is higher, and the shape of LO noise between two ranges are different at high frequency (1k and above).

 My beat measurement was taken at 160MHz, 100kHz range. So the actual LO noise in the measurement will be higher,

but should not be more than an order of magnitude. 

I decide to keep it as it is,and that should give us the lower limit of the current LO phase noise.



Second, I injected intensity modulation at 100Hz and measure the beat to get the conversion from RIN -> fbeat.

This is not accurate, since the output adjustment that I used for intensity modulation also changes the frequency as well, but

it should give us some limit how intensity couples to fbeat.

Right now we cannot purely modulate the intensity, and AOM will be added to modulate/stabilize the intensity soon.

Attachment 1: nb_2010_11_29.png
Attachment 2: beat_and_RIN_2010_11_29.mat
Attachment 3: psl_nb_2010_11_29.m.zip
Attachment 4: Phase_Noise_160MHz_100HzRange_1.txt.zip
  1286   Wed Aug 7 18:53:20 2013 EricaDailyProgressfiber opticnoise budget, Matlab notes.

pink is deltaV = 2.1 V for the 400 Hz. blue is deltaV = 2.24 V for each of the frequencies.
deltaV is the Vmax - Vmin of the signal, as seen below in my calculations. As stated in yesterday's post, the deltaV's aren't the same because the maximum drifted a little bit, probably due to alignment or slight changes in intensity. The different delta V's affect the calibration from voltage to length.
More details such as Vmax and Vmin values are in 1284. Laser was not locked to cavity.

I combined plots from yesterday taken at different frequencies. I used the concatenate command that Tara gave me.

Started thinking about presentation.

Reading up on the AD590 and potential circuits for measuring temperature. Evan mentioned doing one based off of Fig 13. from the AD 590 spec sheet.
We would use the AD 587 and put in a capacitor for a low pass filter, to get rid of noise.

Chloe pointed out an error in my calculations from yesterday for the calibration between voltage and length. Instead of calculating at pi/4, I was actually doing it at pi/8. so here is dV/dx at pi/4.

Matlab Notes:
can't load excel files into Matlab.

first number indicates direction of combination the matrices, 1 is vertical concatenation, 2 is horizontal.
the numbers in the parentheses indicate the elements wanted from each file.

Also, I attended the Wednesday lecture at lunch. It was about modeling polar ice caps. They seem to be using techniques that are similar to some people in the data analysis group, using hypothetical data, plugging those parameters in, and seeing the result, though they seem to know even less about the constraints that are going into the simulation.
  1423   Wed May 7 12:27:25 2014 taraNotesNoiseBudgetnoise comparison

I plotted our measurement together with other experiments. The source file and fig files are attached below.

Details about each experiment (cavity length, wavelength), are included in the source file.





Attachment 3: df_compare.fig
Attachment 4: dx_compare.fig
Attachment 5: Exp_compare.zip
  1424   Fri May 9 17:10:25 2014 taraNotesNoiseBudgetnoise comparison

Add the measurement from AlGaAs coating, and Silicon refcav (see CRYO:1045). The source file, figs, and eps files are attached in the zip file.



Attachment 3: EXP_compare2.zip
  947   Mon Apr 30 01:41:18 2012 taraDailyProgressBEATnoise due to air leaking from legs

I suspected that the air leaking from the legs might cause  noise in acoustic bandwidth, so I measured the beat signal with unfloated /floated table. The beat signals from the two look similar. Air leaking from legs does not cause any extra acoustic coupling from 100Hz - 3kHz in the beat signal. 



fig1: Beat signal between floated and unfloated table. There is no significant difference between the two.

       On Friday evening, I turned off the air compressor. When I came back on Sunday night, the table was not floated. I measured the beat signal, then turned on the compressor, realigned the beam, then measured the beat again. The results were similar in 100Hz- 6 kHz band. Floating the table with these leaking legs will not add any extra acoustic noise to our signal (at least, at this level).

      Since the result looked nice with fewer mechanical peaks at night, I took a chance to check if it was limited by frequency noise of marconi in PLL loop or not. I changed the input range from 1kHz to 200Hz (their frequency noise level should be different and observable at 100-1kHz bandwidth, see here), but there was not different between the two input range, see fig2 below.


fig2: beat with different input range. There is no significant change in the results.

    It is likely that the flat level we are sitting on are detection noise + shot noise. This will be carefully checked next.

  1266   Tue Jul 30 15:48:47 2013 EricaDailyProgressfiber opticnoise for GYRO


Talked to Evan to better understand GYRO. The goal of GYRO is to be able to differentiate between tilt and actual noise. There is a laser that is split and goes in opposite directions around a cavity which has mirrors on opposite corners and beam splitters on the other 2 corners; the laser is locked to the cavity. This setup uses the Sagnac effect. We are sending the CTN laser over because it has a lower noise, due to the shorter cavity, and will serve as reference for the noise level for the GYRO setup. I emailed Zach to ask about more specifics on the GYRO noise because he has a better idea but he has not yet replied.

Here is Zach's reply:

Because of common-mode rejection from the way the gyro works, the cavity length fluctuations only contribute to the gyro noise at the level of ~10^-7 or 10^-6. The gyro noise requirement for the beat frequency from the two counter-propagating beams is ~1 mHz/rtHz down to ~10 mHz or so, so this means the required stability of the light from the fiber is more like 1-10 kHz/rtHz at those frequencies.
  555   Mon Mar 28 22:47:48 2011 taraNotesBEATnoise hunting

I noticed that when the power to both cavities increases (6 mW to 12 mW), the beat noise get smaller at high frequency, broadband (200Hz and above.)

The problem is when I increase the power, I change several things:

1) + 2) error signals from both cavities

3) shot noise on RFPD

4) SNR on the beat

,so I haven't show the improved beat signal before I can pinpoint what actually limits the signal.


I checked the noise from both RFPDs, from 1MHz to 50MHz, ACAV's RPFD looks very different from RCAV's RFPD.

ACAV's RFPD noise also changes between morning and evening measurements, I'm not sure what is happening here.

The first set of data (in solid lines) is taken with the amplifier to increase the noise level, then divided by 30 which is

the increasing factor of the amplifier, see below. The second set in dotted lines are taken without the amplifier.

The signal without the amplifier is quite low ~ 5 - 10 nV which is close to the noise floor of the analyzer already. 

This might cause the factor of 3 in the signal of RCAV's RFPD noise.

About the changing noise shape of ACVA's RFPD, I stil don't have a clue. I'll check again tomorrow.




so I tried to switch the RFPDs to see if the beat signal can be improved.

Since the error signal on RCAV's loop is better, I thought that in can compensate with the effect from

bad RFPD. However, I could not get it locked, I increased the signal with the low noise amplifier before the mixer.

Still could not lock it. I returned the setup back to original and still could not lock it. No error signal coming out during the scan.

I worked around and then it's back on lock. So I guess there might be loosen connectors in ACAV's RFPD.



Note about the low noise amplifier I used:

The amplifier increases the signal by a factor of 30 (29.5 dB) flat from 1MHz to 100MHz, I used this to amplify the RFPD noise so that it's higher than the noise floor of the analyzer.


  1290   Fri Aug 9 16:00:14 2013 taraNotesNoiseBudgetnoise hunting

I measured the slope of the error signal for ACAV path to be 200 kHz/V. This will be used for calibration the error point noise to frequency noise.

 See some details about the error signal's slope and calibration in psl:562.

THe setup for ACAV path is

  • Input power to the cavity 1 mW.
  • RF power on marconi for the driver = 13dB, to 4-way splitter then 14.75 MHz resonant EOM.
  • The error point noise was measured at COMMON channel out1 on RCAV TTFSS.

Next: Measure the slope at RCAV path, measure error noise from both loops, compare to beat signal.


Plan for opening the chamber:

I'm certain that the beam reflected from the window that overlaps with the reflected beam from the cavity going to the RFPD causes a lot of noise. This should show up in the error noise. So to avoid the reflection from the window, I have open the chamber to turn the cavity axis a bit. I need to:

  • calculate how much the cavity has to be turned if we will dump the beam at the lens for the RFPD.
  • see if the beam path is still ok for the rotated cavities.
  • Replace the cavity mount wall. The current one is too short due to the mistake in the design. I needed to use  nuts to raise the height, see pic.  Without the gap on the side, temperature control between the two cavities will be better due to smaller coupling. The walls will be ready on Monday, I might need a day or two to clean and bake them before the installation.
  • use screws to hold the cavities down firmly, instead of resting on four point supports.
  • I don't plan to replace the AD590s on the thermal shield. This will take too much work to remove the feed through, fix the cable. Otherwise, we can just slide the stack half way out of the chamber for replacing the wall and rotating the cavities. Plus, we can use beat signal as an error signal for Temp control.


  1305   Fri Aug 16 22:05:27 2013 taraDailyProgressBEATnoise hunting

 Noise hunting is in progress, I checked the error noise from ACAV and RCAV loops and compared them to the beat. The beat is about an order of magnitude higher than the sum of error noise.

 NOte: slope of error signal RCAV = 1.57 MHz/V (13 dBm from Marconi, throug 4-way splitter, to BB EOM, 1mW input power).


ABOVE: beat signal in comparison with noise at error points from ACAV and RCAV loops. The beat signal is about an order of magnitude higher than the error noise.


I'm working on optimization and noise characterization of the setup. Before measuring the beat I have to make sure that:

  • The beams to the cavities are aligned
  • The power input is 1mW for both cavities
  • I aligned the polarization of the beams into EOM for side band ( minimizing RFAM)
  • The gains for TTFSS are adjusted and recorded
  • Beams in the beat setup are aligned, and dumped properly.
  • The PD is not saturated.
  • PLL is setup properly.

I think the gain in the TTFSS is the problem. For ACAV, the scattered light from the window interferes with the main beam and causes the loop to oscillate when the gain is up. For RCAV, the EOM is a broadband one and does not have enough gain. The bump in the frquency lower than 100Hz is probably the contribution from scattered light. I have not properly dumped all beams yet.


Also I noticed that the beat signal has weird sidebands at +/- 100kHz, 200kHz, and 300kHz, see the figure below. I'm not sure why, I have not seen it before. I might saturate the PD making it distorted from a perfect sine wave. I'll investigate this.


Attachment 2: nb_short_cav.fig
  1307   Tue Aug 20 20:10:01 2013 taraDailyProgressBEATnoise hunting

Noise hunting is in progress. Today I identified that scattered light from the window is one of the problem.

I spent sometime making sure that all the beams in the input optic and the beat areas were dumped properly. I also tightened all the screws on the optics and the mounts on the table.

I mentioned in the previous entry that for RCAV, the reflected beams from the cavity and the vacuum window overlapped a little bit. The window beam was much smaller and actually closer to the edge of the main beam, so I used an iris to remove the outer path, and let only the beam in the center area go through to the RFPD. With that I could increase the gain in RCAV loop to Common/Fast = 624/750, where they used to be ~ 600/600 before. The iris might introduce some extra scattered lights, since it clips a part of the beam.

The scattered noise around DC to 100 Hz is reduced a bit, see the below figure. However, not much improvement in the flat region (100Hz and above). Plus, some mechanical peaks around 1kHz appear with higher level than before.


I expected the scattered noise will be even lower if the cavities are tilted a bit to avoid the beams overlapping. At higher frequency, it might be the gain limit from RCAV loop where the modulation depth is very small.

Next thing to do is to increase more power in the modulation depth for RCAV.


I found out that the sidebands in the beat signal mentioned in the previous entry changed with the gain of the TTFSS (both ACAV and RCAV). With higher gain, the sidebands are suppressed more. It might have to do with the PZT resonant of the NPRO. 

  496   Mon Feb 14 21:38:10 2011 taraNotesElectronics Equipmentnoise level from cable delay setup, SR560,

 The noise floor for cable delay method, and SR560 noise level are measured. The result is plotted below. We are not sure about the

Volt to Hz conversion yet. Once we know the calibration factor, we can decide if we have to replace SR560 with something less noisy or not. 


The Red and Blue plots are taken through daq (16 Hz)and FFT, then divided by the gain setup (1e4) and corrected for AC couple.

Green and Purple plots are taken via SR785 for fast measurement.

From the plot, we learn that,

1) SR560 turns out to be the dominating noise source for the current cable delay technique, from dc to 0.2 Hz, since the noise level from SR560 alone

and the whole setup are comparable.

2) The flat part from 200mHz to 2 Hz is probably the noise from analog to digital converter (ADC)


3) SR560 has corner frequency around 100 Hz.

Peaks from 60 Hz and its harmonic become smaller if we disconnect the power cord, and run SR560 with its battery, see fig2.

Attachment 1: cable_delay_noise.png
Attachment 2: cable_delay_noise.fig
Attachment 3: sr560corner.pdf
Attachment 4: data_2011_02_14.mat
Attachment 5: code_2011_02_14.m
%[y,f]   = myasd('C3:PSL-GEN_DAQ14',981430365,3600*10,1024,16);
%[y16,f] = myasd('C3:PSL-GEN_DAQ16',981430365,3600*3,1024,16);

load data_2011_02_14.mat   
%[y,f]   = myasd('C3:PSL-GEN_DAQ14',981430365,3600*10,1024,16);
%[y16,f] = myasd('C3:PSL-GEN_DAQ16',981498948,3600*3,1024,16);

%correct for 30mHz AC couple on SR560
ycorrect = y .*...
... 19 more lines ...
  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)


  500   Wed Feb 16 00:02:51 2011 FrankDailyProgressElectronics Equipmentnoise of SR560

to have real data for comparison i measured the noise of the SR560 for different (high) gain settings.
Will add lower gain settings and line powered measurements later.

test setup: SR560, AC-coupled, low-noise setting, battery powered measured with SR785


datafiles contain raw output noise values, so for input referred noise plz divide by gain given in filename. first col = frequency, second col = noise spectral density







  1193   Tue Jun 11 00:45:48 2013 taraNotesNoiseBudgetnoisebudget for 8" SiO2/Ta2O5 cavity



  1. Somiya paper also include Brownian noise in Coatings with finite size substrate/coatings (see fig2) which is not done in Harry etal 2002. Finite size effect increases the noise level by a lot, I think this might explain why the beat result we measured from 8" cavities is a bit higher than the estimated noise using the result from Harry etal. I'll check that later.

 Here I applied Somiya&Kazuhiro (SK)2009 coating brownian noise calculation to the previous 8" cavity setup. The estimated noise matches up with the measured result well.



The result for coating Brownian noise presented in SK is for finite size mirror. They emphasize that the estimated noise diverges from Harry2002 result (half infinite mirror) in the case of a thin mirror (thickness is less than mirror radius) which is our case (radius = 0.5inch, thickness = 0.25 inch). 

I'll attached the calculation and explain some differences between the two calculations later. Here are some notes about the parameters:

  • Loss angle of the coatings used in the calculation is phi perpendicular (1.326 e-4), from GWINC, (phi parallel - 1.4e-4);
  • Young's modulus of the coatings is 93 GPa
  • Poisson's ratio  = 0.2
  • m = 45; (# of zeroes for besselj(1,x))
  • stepsize for radial integral = wspot/1000


Attachment 2: sk2009nb.fig
  1194   Tue Jun 11 16:46:52 2013 taraNotesNoiseBudgetnoisebudget for 8" SiO2/Ta2O5 cavity

note about the calculation for coating Brownian noise in a finite size mirror .

==Coatings Parameters==

Young's modulus, Poisson's ratio, and loss angle are taken from the volume averaged value of the coatings (Yavg = d/ ( d1/Y1 + d2/Y2) , sigma avg = 1/2 (sigma1+sigma2 ). These are used for "perpendicular" direction in Harry2002 formula.

Loss angles

  • SiO2 loss angle  = 1e-4
  • Ta2O5 loss angle = 2.3e-4
  • coatings loss = 1.32e-4

Young's moduli

  • SiO2 Young's modulus = 72e9  Pa
  • Ta2O5                         =140e9  Pa
  • Coatings Young's modulus = 93e9 Pa

Coatings structure

  • 1/2 lambda cap of SiO2
  • 26 layers
  • 300 ppm transmission

 ==calculation codes==

  • I got the file for finding zeroes of the bessel function from Matlab exchange.
  • The code for calculating Br noise is attached below.
  • For the finite size bdy condition, the solutions include all the besselj function of all orders (m=1 to inf). I used m from 1 to 55 in the calculation since it converged quite fast after that.
  • For the integration to calculate all the elastic energy, I used Riemann sum, with stepsize of ~0.15 um. The result does not change much (less than 3%) if I go from 0.8*a to a where a is the radius of the mirror. This is important to note because our coatings do not cover the whole surface of the mirror. There is an annulus edge with ~3mm width for optical contact area. The result means that the elastic energy is still localized in the spot area.

 ==Implication to AdvLIGO coatings==

As noted in SK2009, the estimated values for half infinite and finite size analyses are about the same (~2.5% difference) (I have not verified this). Then, the result from GWINC using Harry2002 formula is still accurate.


  • The calculation in SK2009 uses an overall loss angle of the coatings, while calculation in Harry2002 separates the elastic energy in two directions,parallel and perpendicular to the surface, and also loss angles in the associated directions.  I use the perpendicular average under the assumption that most energy/deformation occurs in that direction.
  • The result matches the measurement quite well. This reassures us that other noises introduced by the setup (i.e. noise in optical bonding/ noise from supporting structure/ thermoelastic/ brownian noise in the spacer) are not higher than coating thermal noise.


Attachment 1: getCoatBrownian2.m.zip
  1195   Wed Jun 12 01:34:27 2013 KojiNotesNoiseBudgetnoisebudget for 8" SiO2/Ta2O5 cavity

Wait. Do you mean that you found the last push to match the experiment and the calcualtion?
Do you also mean there is no fitting to make it happen. Correct?

  1196   Wed Jun 12 14:32:22 2013 not KojiNotesNoiseBudgetnoisebudget for 8" SiO2/Ta2O5 cavity


Wait. Do you mean that you found the last push to match the experiment and the calcualtion?
Do you also mean there is no fitting to make it happen. Correct?

 That is correct, all the numbers used in the calculations are nominal values (under some assumptions though, about how I average the coatings material properties), and the result just matches the measurement. It's magic!

  1197   Wed Jun 12 14:49:47 2013 KojiNotesNoiseBudgetnoisebudget for 8" SiO2/Ta2O5 cavity

Careful check is necessary as usual, but for now let me say congraturation! It's beautiful!

  1198   Fri Jun 14 02:36:22 2013 taraNotesNoiseBudgetnoisebudget for 8" SiO2/Ta2O5 cavity

I'm checking the result for the calculation.  I think it is too early to celebrate.

Nic suggested that I should use comsol to estimate the coating Brownian noise. There are a few problems:

  • For 3D model, I cannot mesh the geometry properly yet. The layer is too small for the rest of the mirror.
  • For 2D model, I cannot integrate the elastic energy from the coating layer. There is no choice to select the domain I want to integrate. I'll find out what happen.

I double checked the calculation code. I changed m to 65, and stepsize to w0/4000, the elastic energy (U) calculated is still ~ 1.5e-10 J. It did not change much from my last calculation. However, what I do not understand is the analytical result for half-infinite mirror (as given in SK2009 but different from GWINC), the number does not change that much.

I found a missing 2pi factor that causes the estimated noise to be higher and to match the measurement.  I'll check the calculation carefully again, but it might be that it's still not coating noise.


  1199   Tue Jun 18 11:53:17 2013 taraNotesNoiseBudgetnoisebudget for 8" SiO2/Ta2O5 cavity

After careful checks, the estimated result is still below the measurement. For our geometry, the result from SK2009 is similar to that from Harry2002.


 So here are the results

  • The calculation for coating Brownian noise from SK2009 (finite size mirror) is similar to Harry2002 result (half infinite mirror).
  • I double checked my code by changing my parameters to those used in SK2009 paper and got the same result. Apparently, their spotsize is very big compare to ours (1/3 of the mirror radius vs 1/40 of the mirror radius).
  • I revisited my comsol model again to check Brownian noise from substrate and spacer when the mirror is curve (more realistic model). The difference is small. (add fig).spacer_br_8_edge.png

The optical bonding area in this model is similar to the real cavity, compared to what is done before where the bonding area is everywhere on the mirror beside the bore hole. So it is quite certain that it is the noise from the substrate/spacer.

Since the measurement has 1/f slope, it is very likely to be Brownian thermal noise (Thermoelastic/ TO will have different slopes). It might be that the 1998 mirrors have high loss. We will see that with shorter cavity measurement.

  1007   Thu Jun 28 16:52:42 2012 FrankDailyProgressPDnot laser power drift

the funny shape i see for that particular diode is NOT caused by power fluctuations - it's real. The diode shows that huge change in responsivity across the surface after being damaged. it might have to do with the position of the bond wires and the fact that the diode exhibits a large amount of dark current in addition to the photocurrent which probably cancel depending on the position od the beam relative to the defect and the bond wires. But that's just a guess.

panel5.jpg C30655_15um_PS.png

  799   Wed Jan 25 23:41:38 2012 frank, taraDailyProgressopticnot much improvement on mode matching

We tried to redo the mode matching to RCAV by adjusting the lense position using translational stages. However the result does not improve that much. The visibility is still roughly the same at 96.5%. 



We will do the mode match for ACAV. Right now the visibility for ACAV is ~90%.

We also monitored the beam reflected from ACAV. TEM02 shows up (see below figure), but we could not get rid of it by beam alignment. It is probably the distortion from the AOM.


  315   Mon Aug 30 20:11:51 2010 taraNotesComputersnote for resetting psl crate

  C3:PSL-ACAV_TEMPAVG that tells the average temperature from ACAV is dead. Frank told me to reboot the PSL crate.

                                       RCAV      ACAV

C3:PSL-XXXX_SETPT      35.0       36.75

C3:PSL-XXX_HEATER    1.47521   4.9


I rebooted the crate, reload the cavity.stp file, the channel is still inactive. (only this channel)

  316   Mon Aug 30 22:16:51 2010 FrankNotesComputersnote for resetting psl crate

set temp for the ACAV should be 37.3, that was the value since about a week. see here :


  C3:PSL-ACAV_TEMPAVG that tells the average temperature from ACAV is dead. Frank told me to reboot the PSL crate.

                                       RCAV      ACAV

C3:PSL-XXXX_SETPT      35.0       36.75

C3:PSL-XXX_HEATER    1.47521   4.9


I rebooted the crate, reload the cavity.stp file, the channel is still inactive. (only this channel)


  1517   Mon Sep 15 04:32:21 2014 taraNotesBEATnote for tonight beat

 RCAV transPD_DC :0.54 V

ACAV transPD_DC: 0.16 V (loop might oscillate when DC level was measured, need to double check)

  1518   Mon Sep 15 07:18:38 2014 EvanNotesBEATnote for tonight beat


 RCAV transPD_DC :0.54 V

ACAV transPD_DC: 0.16 V (loop might oscillate when DC level was measured, need to double check)

 In this noise budget I corrected the PDH shot noise level (incident power is 1 mW, visibility is 0.5).

Attachment 1: noiseBudget.pdf
ELOG V3.1.3-