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New entries since:Wed Dec 31 16:00:00 1969
ID Date Authorup Type Category Subject
  6654   Mon May 21 21:27:39 2012 yutaUpdateCDSMEDM suspension screens using macro

Background:
 We need more organized MEDM screens. Let's use macro.

What I did:
1. Edited /opt/rtcds/userapps/trunk/sus/c1/medm/templates/SUS_SINGLE.adl using replacements below;

sed -i s/#IFO#SUS_#PART_NAME#/'$(IFO)$(SYS)_$(OPTIC)'/g SUS_SINGLE.adl
sed -i s/#IFO#SUS#_#PART_NAME#/'$(IFO)$(SYS)_$(OPTIC)'/g SUS_SINGLE.adl
sed -i s/#IFO#:FEC-#DCU_ID#/'$(IFO):FEC-$(DCU_ID)'/g SUS_SINGLE.adl
sed -i s/#CHANNEL#/'$(IFO):$(SYS)-$(OPTIC)'/g SUS_SINGLE.adl
sed -i s/#PART_NAME#/'$(OPTIC)'/g SUS_SINGLE.adl

2. Edited sitemap.adl so that they open SUS_SINGLE.adl with arguments like
    IFO=C1,SYS=SUS,OPTIC=MC1,DCU_ID=36
instead of opening ./c1mcs/C1SUS_MC1.adl.

3. I also fixed white blocks in the LOCKIN part.

Result:
  Now you don't have to generate every suspension screens. Just edit SUS_SIGNLE.adl.

Things to do:
 - fix every other MEDM screens which open suspension screens, so that they open SUS_SINGLE.adl
 - make SUS_SINGLE.adl more cool

  6663   Tue May 22 20:46:38 2012 yutaUpdateCDSMEDM suspension screens using macro

I fixed the problem Jamie pointed out in elog #6657 and #6659.

What I did:
1. Created the following template files in /opt/rtcds/userapps/trunk/sus/c1/medm/templates/ directry.

SUS_SINGLE_LOCKIN1.adl
SUS_SINGLE_LOCKIN2.adl
SUS_SINGLE_LOCKIN_INMTRX.adl
SUS_SINGLE_OPTLEV_SERVO.adl
SUS_SINGLE_PITCH.adl
SUS_SINGLE_POSITION.adl
SUS_SINGLE_SUSSIDE.adl
SUS_SINGLE_TO_COIL_MASTER.adl
SUS_SINGLE_COIL.adl
SUS_SINGLE_YAW.adl
SUS_SINGLE_INMATRIX_MASTER.adl
SUS_SINGLE_INPUT.adl
SUS_SINGLE_TO_COIL_X_X.adl
SUS_SINGLE_OPTLEV_IN.adl
SUS_SINGLE_OLMATRIX_MASTER.adl

To open these files, you have to define $(OPTIC) and $(DCU_ID).
For SUS_SINGLE_TO_COIL_X_X.adl, you also have to define $(FILTER_NUMBER), too. See SUS_SINGLE_TO_COIL_MASTER.adl.

2. Fixed the following screens so that they open SUS_SINGLE.adl.

C1SUS_WATCHDOGS.adl
C1IOO_MC_ALIGN.adl
C1IOO_WFS_MASTER.adl
C1IFO_ALIGN.adl

  6677   Thu May 24 16:13:05 2012 yutaUpdateComputersASS scripts on new ubuntu machines

[Den, Yuta]

Background:
 ASS and many other scripts don't work on new ubuntu machines.

What we did:
1. Installed C-shell on rossa and rosalba(Ubuntu machine).
  sudo apt-get insall csh

2. Find out that
  /opt/rtcds/caltech/c1/scripts/AutoDither/alignY

runs, but
  /opt/rtcds/caltech/c1/scripts/medmrun /opt/rtcds/caltech/c1/scripts/AutoDither/alignY

doesn't run. It gives us the following error messages.

ezcawrite: error while loading shared libraries: libca.so: cannot open shared object file: No such file or directory
ezcaswitch: error while loading shared libraries: libca.so: cannot open shared object file: No such file or directory

Result:
 ASS scripts run on rossa and rosalba, but not with medmrun.
 At least ASS scripts run on pianosa(ubuntu machine) with medmrun. So we decided to wait for JAMIE to fix it.

  6709   Tue May 29 21:05:30 2012 yutaUpdateIOOPMC, MC alignment are shit

Quote:

  [Keiko, Jenne]

PMC aligned.  Suresh is fixing the measure MC spot positions script, then we'll remeasure MC spot positions.

 [Suresh, Jenne, Yuta]

We measured the MC spot positions twice tonight. Procedure for measuring them is in elog #6688.
The results were;

spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
    3.3359    3.9595    2.3171   -7.7424   -0.8406    6.4884

spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
    3.2681    4.0052    2.2808   -7.3965   -0.7624    7.1302

The spot moved by about 0.5 mm since May 25, but we concluded that this displacement is negligible and difficult to be fixed by aligning PSL beam.

We'll align Y arm and X arm next.

  6713   Wed May 30 01:35:15 2012 yutaUpdateGreen Lockingaligned Y arm green beam

[Jenne, Yuta]

We aligned the Y arm for IR (C1:LSC-TRY_OUT is now ~ 0.9), and aligned the green beam from the ETMY table. The Y arm green is now resonating in TEM00 mode, but we need some monitors (green trans or green refl) to maximize the coupling.

We noticed that the MC beam spot are oscillating at ~ 1 Hz, mostly in YAW.  This wasn't observable before the PMC realignment (elog #6708). We should find out why and fix it.

  6715   Wed May 30 15:51:22 2012 yutaUpdateIOOMC beam spot oscillation

[Koji, Suresh, Jenne, Yuta]

Background:
  We noticed that the beam spots on MC mirrors are oscillating in ~ 1 Hz yesterday. It means MC mirrors are actually oscillating. This was observable even if the WFS servo is off.

What we did:
  1. By measuring the spectra of OSEM sensor outputs, we found that MC3 is the one that is oscillating.

  2.  Oscillation at ~ 1 Hz only happened when the local damping using OSEMs are on (see Attachment 1; REF is when the damping is on).

  3.  We found that this oscillation came from insufficiency in phase margin in SUSPOS loop. So, we increased the gain, C1:SUS-MC3_SUSPOS_GAIN, from 95 to 200. It helped a little, but oscillation is still there.

  4.  We measured openloop transferfunctions of SUSPOS, SUSPIT, SUSYAW, SUSSIDE loop, and concluded that diagonalization some how went wrong. The amplitude of the oscillation (peak height in the OSEM spectra) changed by pushing the MC SUS connectors.

Plan:
  - Fix the connectors so that we don't have to push them any more.
  - Redo the diagonalization of the MC suspensions.

Attachment 1: specMC3_onoff_localdamping.pdf
specMC3_onoff_localdamping.pdf
  6718   Wed May 30 19:27:38 2012 yutaUpdateIOOMC beam spot oscillation

[Koji, Yuta]

We found that C1:SUS-MC{1,2,3}_TO_COIL_3_4_GAIN was somehow changed to -1, and feedback signal for SIDE was fedback to LLCOIL, which is apparently not correct.
We checked the snapshots on May 25 and confirmed that it was used to be 0, so we fixed it.
We suspect that it happened during the beam spot measurement, because the measurement changes the TO_COIL matrix gains.

Now, we don't see any MC beam spot oscillation.

Quote:

[Koji, Suresh, Jenne, Yuta]

Background:
  We noticed that the beam spots on MC mirrors are oscillating in ~ 1 Hz yesterday. It means MC mirrors are actually oscillating. This was observable even if the WFS servo is off.

 

  6724   Thu May 31 01:27:16 2012 yutaUpdateGreen LockingPSL and Y arm green beams aligned

[Jenne, Yuta]

We aligned the PSL green optics so that the PSL green beam and Y arm green beam interfere. 2 beams are now hitting the Y arm beat PD. The DC level from the beat PD is about 13 mV.

We didn't try to see the beat signal for today, because the temperature of the doubling crystal seemed funny. We need to look into it tommorow.

Currently, the temperature control is enabled and the set point is 36.9 deg C, but the temperature is stuck at 33.0 deg C.

  6725   Thu May 31 01:36:17 2012 yutaUpdateGreen LockingGREEN_TRX/GREEN_TRY PDs

I did the cabling for monitoring DC transmission of the green beam from the end table.
The two PDs are called GREEN TRX and GREEN TRY, and the channel names are C1:GCV-GREEN_TRX and C1:GCV-GREEN_TRY.
The two signal from the PDs go to the ADC_0 card of the c1ioo computer.

Now, C1:GCV-GREEN_TRX/Y are actually connected to the respective PDs, but green beams are not hitting on the PD. We need two pickoff mirrors.

  6726   Thu May 31 02:27:24 2012 yutaUpdateIOOscript for reliefing MC WFS

I wrote a simple script for reliefing MC WFS servo. The script is located at /opt/rtcds/caltech/c1/scripts/MC/reliefMCWFS.
It simply uses ezcaservo to minimize the offset of the WFS feedback signal using MC alignment sliders.

    ezcaservo -r C1:SUS-MC${optic}_ASC${dof}_OUT16 -s 0 -g 0.0001 -t 10 C1:SUS-MC${optic}_${dof}_COMM


I put "MC WFS relief" button on the WFS medm screen (/opt/rtcds/caltech/c1/medm/c1ioo/master/C1IOO_WFS_MASTER.adl).

  6727   Thu May 31 04:03:17 2012 yutaUpdateIOOscript for MC beam spot measurement

I wrote a wrapping script for measuring MC beam spot. We had to run several scripts for the measurement (see elog #6688), but now, you only need to run /opt/rtcds/caltech/c1/scripts/ASS/MC/mcassMCdecenter.

The measured data file will be stored in /opt/rtcds/caltech/c1/scripts/ASS/MC/dataMCdecenter/ directory, with a timestamp.
The calculated beam spot position data will be logged in /opt/rtcds/caltech/c1/scripts/ASS/MC/dataMCdecenter/logMCdecenter.txt file.
I had to edit sensemcass.m file, in order to write the result into the log file. In this way, we can keep track of the beam displacement.

Currently, the calculation script is written in the MATLAB file(sensemcass.m), which isn't very nice.
To run a MATLAB file from the command line
, you have to write something like this;

matlab -nodesktop -nosplash -r "sensemcass('./dataMCdecenter/MCdecenter201205210258.dat')"

 

  6731   Thu May 31 16:19:07 2012 yutaUpdateGreen Lockingtemperature setting for PSL doubling crystal

I fixed the temperature control of the oven for the PSL doubling crystal.
The PID settings were not good, and also, TC200 was beging DETUNED. So, I activated TUNE function and adjusted PID settings.
I'm not sure what the DETUNE function is for. The manual can be found here;
   http://www.thorlabs.com/thorproduct.cfm?partnumber=TC200

Current settings for Thorlabs TC200 are (Red ones are what I changed from the previous setting);

parameters Xend Yend PSL
TEMP SET (deg C) 37.5 35.7 36.9
P 250 250 250
I 60 60 200 (was 117)
D 25 25 40 (was 19)
(DE)TUNE on? TUNE TUNE TUNE (was DETUNE)
TMAX (deg C) 200 200 170
PMAX (Watts) 18 18 18
temperature sensor PTC100 PTC100 PTC100
  6746   Sat Jun 2 03:19:37 2012 yutaUpdateGreen LockingY green beat note found? - too small

Summary:
  I tried to find Y arm green beat in order to do the mode scan.
  I found a beat peak(see attached picture), but the amplitude seems too small.
  It is may be because the alignment/mode matching of the green beams at the PSL table is so bad. Or, the peak I found might be a beat from junk light.

What I did:
  1. Aligned Y arm to the IR beam from MC.

  2. Re-aligned Y end green beam to the Y arm using steering mirrors on the Y end table.

  3. Re-aligned PSL green optics.

  # C1:GCV-GREEN_TRY is temporary connected to the DC output of the Y green beat PD.

  4. Temperature of the PSL laser was 31.48 deg C, so I set "T+" of the Y end laser to 34.47 deg C, according to Bryan's formula (elog #4439);

  Y_arm_Temp_set = 0.87326*T_PSL + 6.9825

  5. Scanned Y end laser temperature by C1:GCY-SLOW_SERVO2_OFFSET. Starting value was 29725 and I scanned from 27515 to 31805, by 10 or 100. Laser frequency changes ~ 6 MHz / 10 counts, so it means that I scanned ~ 2.5 GHz. During the scan, I toggled C1:AUX-GREEN_Y_Shutter to make sure the green beam resonates in TEM00 mode.

  # I made a revolutionary python script for toggling channels(/opt/rtcds/caltech/c1/scripts/general/toggler.py). I made it executable.

  6. Found a tiny beat note when C1:GCY-SLOW_SERVO2_OFFSET = 29815. I confirmed it is a beat signal by blocking each PSL and Y arm green beam into the beat PD. I left  C1:GCY-SLOW_SERVO2_OFFSET = 29815.

  7. I found that Bryan's formula;

Y_arm_Temp_meas = 0.95152*T_PSL + 3.8672
Y_arm_Temp_set = 0.87326*T_PSL + 6.9825

  was actually

Y_arm_Temp_set = 0.95152*T_PSL + 3.8672
Y_arm_Temp_meas = 0.87326*T_PSL + 6.9825

  according to his graph(elog #4439). So, I set  "T+" of the Y end laser to 33.82 deg C.

  8. This time, I scanned PSL laser temperature by C1:PSL-FSS_SLOWDC. I found a tiny beat note when C1:PSL-FSS_SLOWDC = 1.0995. C1:PSL-FSS_SLOWDC has 10 V range, so I scanned ~ 10 GHz, assuming the laser frequency changes 1 GHz/K and the temperature changes 1 K/V.

  9. Re-aligned PSL green optics so that the beam hits optics at their center, and checked that the poralization of the two green beams are the same.

  10. Checked that amplifier ZFL-100LN+ on the beat PD is working correctly. The power was supplied correctly (+15 V) and measured gain was ~ 25 dBm.

  11. Exchanged BNC cable which connects the beat PD to the spectrum analyzer. Previous one we used was too long and it had -15 dB loss(measured). I exchanged to shorter one which has -2 dB loss.

Beat note amplitude estimation:
  The amplitude of the beat note observed in the spectrum analyzer was ~ -54 dBm. According to the estimation below, it seems too small.

  The measured power of the two green beams are

  P_Y = 4 uW
  P_PSL = 90 uW

  So, the power of the beat signal should be

  P_beat ~ 2 sqrt(P_Y * P_PSL) = 37 uW

  Responsivity and transimpedance of the beat PD (Broadband PD, LIGO-T0900582) are 0.3 A/W and 2 kOhm. So, the power of the electrical signal is

  W = (P_beat * 0.3 A/W * 2 kOhm / sqrt(2))^2 / 50 Ohm = 5 uW

  5 uW is -23 dBm. We have +25 dB amplifier after the PD and the loss of the BNC cable is -2 dB. So, if the two beams interfere perfectly, the peak height of the beat signal should be ~ 0 dBm. The measured value -54 dBm seems too small. According to elog #5860, measured value by Kiwamu and Katrin was -36 dBm.

Current values:
  PSL laser temperature: 31.48 deg C (PSL HEPA 100%)
  Y end laser "T+": 33.821 deg C
  Y end laser "ADJ": 0
  C1:GCY-SLOW_SERVO2_OFFSET = 29815 (was 29725)

Attachment 1: CIMG1437.JPG
CIMG1437.JPG
  6757   Tue Jun 5 21:09:40 2012 yutaUpdateComputer Scripts / Programshacked ezca tools

Currently, ezca tools are flakey and fails too much.
So, I hacked ezca tools just like Yoichi did in 2009 (see elog #1368).

For now,

/ligo/apps/linux-x86_64/gds-2.15.1/bin/ezcaread
/ligo/apps/linux-x86_64/gds-2.15.1/bin/ezcastep
/ligo/apps/linux-x86_64/gds-2.15.1/bin/ezcaswitch
/ligo/apps/linux-x86_64/gds-2.15.1/bin/ezcawrite

are wrapper scripts that repeats ezca stuff until it succeeds (or fails more than 5 times).

Of course, this is just a temporary solution to do tonight's work.
To stop this hack, run /users/yuta/scripts/ezhack/stophacking.cmd. To hack, run /users/yuta/scripts/ezhack/starthacking.cmd.

Original binary files are located in /ligo/apps/linux-x86_64/gds-2.15.1/bin/ezcabackup/ directory.
Wrapper scripts live in /users/yuta/scripts/ezhack directory.

I wish I could alias ezca tools to my wrapper scripts so that I don't have to touch the original files. However, alias settings doesn't work in our scripts.
Do you have any idea?

  6763   Wed Jun 6 02:28:02 2012 yutaUpdateGreen Lockingtried to see Yarm length change with weak beat note

[Jenne, Yuta]

Summary:
  We tried to see the Yarm length change using Yarm green beat note. The beat note is still puny, so we put an extra amplifier. We saw something, but still can't control the arm length with ALS.

What we did:
  1. Aligned Y arm and PSL green optics as usual.

  2. By changing the temperature of the PSL laser with C1:PSL-FSS_SLOWDC, we find small beat note when

  PSL laser temperature on display: 30.59 deg C (PSL HEPA 100%)
  C1:PSL-FSS_SLOWDC = 5.2100
  Y end laser "T+": 34.049 deg C
  Y end laser "ADJ": 0
  Y end laser measured temperature: 34.68 deg C (*)
  C1:GCY-SLOW_SERVO2_OFFSET = 29425

 (*) Measured using diagnostic output on the back of the laser controller(Lightwave 125/6-OPN-PS) - between pins 2(GND) and 4. Calbration factor is 10 degC/V.

  3. The peak height right after the amplifier on the Y green beat PD was ~ -48dBm, so we put another amplifier (and attenuator) because the beat note which goes into the frequency divier should be -30 dBm to +7 dBm. After we put the amplifier, the peak height was ~ -23 dBm.

  4. We could see the C1:ALS-BEATY_COARSE_I_ERR ringing down, when opening and closing the control room door, which may introduce Y arm length change(screenshot of dataviewer below). But we are still not sure if we are actually getting the Y arm length signal because closing and opening Y end green shutter doesn't make difference on C1:ALS-BEATY_COARSE_I_ERR. The ring down was seen when we turned on the unWhiten filters in C1:ALS-BEATY_COARSE filter modules.

beatycoarseringdown20120605.png

  5. Tried to hold Y arm length with ALS, but couldn't.

Current setup:
  Red ones are the ones we added or changed.

beatysetup20120605.png

Note:
  Dataviewer is so slow and flakey now.

  6767   Wed Jun 6 15:16:00 2012 yutaUpdateIOOMC WFS offsets adjusted

MC reflection (C1:IOO-MC_RFPD_INMON) got worse when WFS servos were on. After aligning MC optics, it will be ~0.5 but if I turned on WFS, it became ~0.8.
I measured the beam spot positions on MC optics. They seemed like the same from the measurement yesterday.

# filename      MC1pit  MC2pit  MC3pit  MC1yaw  MC2yaw  MC3yaw  (spot positions in mm)
./dataMCdecenter/MCdecenter201206052111.dat     3.234388        4.234564        2.654212        -6.656221       -0.677541       4.506170       
./dataMCdecenter/MCdecenter201206061420.dat     3.300867        4.567555        2.692971        -6.484464       -1.705443       4.423250

So, I ran /opt/rtcds/caltech/c1/scripts/MC/WFS/WFS_FilterBank_offsets to adjust the WFS offsets.

C1:IOO-MC_RFPD_INMON is now ~ 0.5 and  C1:IOO-MC_TRANS_SUM is now ~ 2.7e3 with WFS on.

  6771   Wed Jun 6 21:11:45 2012 yutaUpdateGreen Lockingimproved Y arm green alignment

Summary:
  Y arm green transmission to the PSL table improved from ~ 20 uW to 61 uW. Improvement was done by adjusting steering mirrors before and after the faraday on the Y end table.
  But 61 uW is not enough!

What I did:
  1. The incident power to the faraday for the green beam on the Y end table was 1.4 mW, but the transmission was 1.2 mW. So, I adjusted the steering mirrors and the transmission increased to 1.4 mW.

  2. I found that adjusting the steering mirrors to the faraday also increased alignment of the green beam to the Y arm. We always adjusted only the steering mirrors after the faraday for the alignment. I adjusted the alignment using both steering mirrors this time. Reflection of the green beam on the ETMYT camera seems more reasonable now and more frequently lock to TEM00 when closing and opening the Y end green servo loop.

  3. For the adjustment, I tried to utilize PD at the reflection port, or the transmission port. However, I couldn't do that because they fluctuates too much. I don't know why.

  4. Measured the green transmission to the PSL table, The transmitted power was ~20 uW, but after the aligning, it improved to 61 uW.

Current green power:
  I measured the green beam power at various places using Newport power meter (Model 840) with its filter on.

beatygreenpower20120606.png

  Incident green power to the Y arm is ~ 1 mW (more than 1 mW because the aparture of the power meter was smaller than the beam size) and Y arm transmission is designed to be 55%. So, if the alignment and mode matching are perfect, the transmission to the PSL table should be ~ 600 uW. The measured value 61 uW seems too small. Kiwamu says it was 140 uW when he did Y arm.

Next:
  I will find the beat note again tonight and check if the beat PD is working correctly and if the mode matching of the two beams at the PSL table is good.

  6775   Thu Jun 7 01:46:05 2012 yutaSummaryGreen LockingY green beat - found it!!

I found the big big Y green beat. Details will be posted later.

CIMG1504.JPG

  6776   Thu Jun 7 02:25:27 2012 yutaUpdateGreen Lockingimproved Y arm green alignment - even more

[Koji, Yuta]

Summary:
  We improved the Y arm green transmission to the PSL table. It is now 197 uW.
  The improvement was done mainly by adjusting the Y arm green servo gain.

What we did:
  1. Fine-adjusted steering mirrors after the faraday on Y end table by monitoring Y arm green transmission (used Thorlabs PDA36A as a PD, C1:GCV-GREEN_TRY as a channel). We decided which way to adjust the mirrors by just pushing/pulling its mount.

  2. The output of the reflection PD on the oscilloscope seemed like the Y end frequency servo was oscillating. So, we reduced the amplitude of the frequency modulation from 2.83 V to 0.13 V.

  3. We noticed there were two TEM00, one is brighter and the other is dim. We thought this came from a mode-hopping or something. So, we changed the Y end laser temperature from 34.68 deg C to 34.13 deg C (measured). This reduced dim TEM00 and the main one got brighter. C1:GCY-SLOW_SERVO2_OFFSET was changed from 29425 to 29845.

  4. Fine-adjusted the position of the mode-matching lens by reduing LG modes.

Current green power:
  Current measured green power values are as follows.

beatygreenpower20120607.png

  Calculated value for the Y arm green transmission is ~ 600 uW, but we think we are almost at the maximum we can get. So, we have about 70% loss from the Y end table to the PSL table. There may be large loss in windows. The beam shape of the transmitted beam seems OK, but there may be some clipping.

To do:
  - Fine tune the Y end frequency servo loop. Reducing the amplitude of the frequency modulation for reducing the gain is not a very good idea.

  6777   Thu Jun 7 02:59:31 2012 yutaUpdateGreen LockingY green beat - found it!!

Summary:
  I found the big green beat note for the Y arm. The alignment of the green optics on the PSL table was crappy.

What I did:
  1. By adjusting PSL laser temperature, I found tiny beat note when

  PSL laser temperature on display: 31.35 deg C (PSL HEPA 100%)
  C1:PSL-FSS_SLOWDC = 1.75

and

  PSL laser temperature on display: 33.21 deg C (PSL HEPA 100%)
  C1:PSL-FSS_SLOWDC = -6.82

Y end laser temperature settings are fixed as follows during the measurement.

  Y end laser "T+": 34.049 deg C
  Y end laser "ADJ": 0
  Y end laser measured temperature: 34.13 deg C (*)
  C1:GCY-SLOW_SERVO2_OFFSET = 29845

Bryan's formula (swapped one; see elog #6746),  suggests the paring

  (Yend laser temp, PSL laser temp) = (34.13 deg C, 31.09 deg C).

  2. Checked that beat PD is working by swapping the beat PDs for Y arm and X arm.

  3. Checked that the mode-matching of the two beams, one from Y arm and the other from PSL, is OK by moving mode-matching lens and measuring the beam spot size at near/far field are the same.

  4. When checking the beam spot size at far field(~ 1 m from the BS), I noticed the relative beam tilt by ~ 1 mrad. We aligned them few days ago, but I think the green beam from the Y arm has shifted. Of course we align IR to the Y arm first, but we difinitely need dither servo or A2L for the arm, too.

  5. As soon as aligning the PSL green optics near the BS, I found a large beat note. The measured amplitude was ~ -26 dBm, without any amplifiers after the PD.

  Currently the measured green beam power onto the beat PD from Y end is 75 uW and from PSL is 92 uW. So the calculated beat amplitude will be ~ -10 dBm (see calculation in elog #6746). So there is about 84% loss. Anyway, I will go on to the mode scan.

  6778   Thu Jun 7 03:37:26 2012 yutaUpdateCDSmx_stream restarted on c1lsc, c1ioo

c1lsc and c1ioo computers had FB net statuses all red. So, I restarted mx_stream on each computer.

ssh controls@c1lsc
sudo /etc/init.d/mx_stream restart

  6779   Thu Jun 7 05:39:41 2012 yutaUpdateGreen Lockingcoarsely stabilized Y arm length with ALS

I coarsely stabilized Y arm length to off resonance point for IR using ALS.
Currently, ASL servo loop is unstable and oscillates so much that I can't hold the length to the resonance point.
We need more investigation on the servo loop before doing the mode scan.

Below is a snapshot of ALS medm screens and time series data of the error signal for ALS coarse loop (C1:ALS-BEATY_COARSE_I_ERR) and IR transmission for the Y arm (C1:LSC-TRY_OUT) when I turned the servo on.

MyFirstALS20120607.png

 

Note:
  I took off amplifiers right after the beat PD on PSL table.
  Also, I reverted the gain change Jenne made last night (elog #6750), because they no longer show overload lights.

  6788   Thu Jun 7 18:46:13 2012 yutaUpdateSUSPRM oplev centered

PRM oplev beam was not hitting on the QPD since Jun 1, so I centered it. I reverted the oplev servo gains and now oplev servo looks fine.

C1:SUS-PRM_OLPIT_GAIN = 1.0
C1:SUS-PRM_OLYAW_GAIN = -0.7

There's SIDE to UL/UR/LL/LR coil element in PRM TO_COIL matrix. They were 0 until Mar 31, 2012, but someone changed them to -0.160. I couldn't find elog about it.
Same thing happened to BS on Mar 13, 2012 (see elog #6409), so I think somebody did the same thing to PRM.

  6789   Fri Jun 8 15:08:27 2012 yutaUpdateGreen Lockingaligned/mode-matched Y green beat setup

Laser temperature settings for Y arm green work today are;

  PSL laser temperature on display: 31.38 deg C (PSL HEPA 100%)
  C1:PSL-FSS_SLOWDC = 1.68
  Y end laser "T+": 34.049 deg C
  Y end laser "ADJ": 0
  Y end laser measured temperature: 34.13 deg C (*)
  C1:GCY-SLOW_SERVO2_OFFSET = 29845

Green transmission from Y end and PSL green power on the beat PD are;

  P_Y = 28 uW
  P_PSL = 96 uW

P_Y decrease from its maximum we got (75 uW, see elog #6777) is because the alignment for Y arm green is decreased. I can see the decrease from the green reflection on ETMT camera, but I will leave it because we already have enough beat.

I aligned PSL optics, including the mode-matching lens to maximize the beat note. The beat note I got is about 26dBm.
The calculated value is -14 dBm, so we have about 75 % loss.
I measured the reflection from the PD window and its reflectivity was about 30%. We still have unknown 45% loss.

  6794   Mon Jun 11 21:50:08 2012 yutaUpdateGreen Lockingbeatbox looks OK

Summary:
  We need I-Q frequency deiscriminator to control the arm length fine and continuously.
  I checked the beatbox (LIGO-D1102241-v4; see elog #6302) and it was working.

What I did:
  1. Measured some transferfunctions with a network analyzer (Aligent 4395A) and checked the cabling is correct.

  2. Put 30 m/1.5 m delay line and checked I-Q outputs are actually orthogonal. I did this by sweeping the frequency of RF input to the beatbox. See attached picture. You can see nice circle on the oscilloscope.

Some measurement results:

  - Gains of the transferfunctions(@ 10-100MHz) between;

   RF in -> RF mon: -25 to -20 dB
   RF in -> fine delay out: -50 to -40 dB
   RF in -> coarse delay out: -50 to -40 dB
   RF in -> LO of mixer RMS-1: ~ +4 dB  (RMS-1 needs +7 dB LO)
 
  - 30m delay line(RG-142B/U) had -2 dB loss.

Note:
  - RF input must be larger than about -3 dBm to get enough LO to the mixer. Otherwise, you won't get I-Q outputs.
  - The comparator, whitening filter and differential DAQ outputs are not installed in the current beatbox.
  - Current beatbox only has electronics for the one arm.
  - The print on the board D1102241 says +15V and -15V, but they are actually opposite. Cabling is swapped in order to supply correct power to the ICs.

Attachment 1: CIMG1522.JPG
CIMG1522.JPG
  6798   Tue Jun 12 01:58:33 2012 yutaUpdateGreen Lockingaligned Y arm to Y end green

[Jenne, Yuta]

We aligned Y arm to the Y end green incident beam.
We noticed two TEM00, bright and dim, so we decreased Y end laser temperature to 34.13 deg C.
It doubled the transmission of the green, and now the transmission to the PSL table is 178 uW, which is close to the maximum(197 uW) we got so far.

Current settings for Y end laser is;

  Y end laser "T+": 34.049 deg C
  Y end laser "ADJ": 0
  Y end laser measured temperature: 34.13 deg C
  C1:GCY-SLOW_SERVO2_OFFSET = 31025
  Y end slow servo: on (was off)

We aligned IR beam to the Y arm by mostly adjusting PZTs and got the transmission, C1:LSC-TRY_OUT ~ 0.9.

We tried to calculate the mode-matching ratio for IR by taking TRY data while ITMY and ETMY are swinging (without ALS), but it was difficult because we see too many higher order modes.

Tomorrow, we will (1) connect the beatbox to ADC, (2) edit c1gcv model, (3) scan the arm using I-Q signals.

  6808   Tue Jun 12 20:35:46 2012 yutaUpdateGreen Lockingc1gcv recompiled

[Jamie, Yuta]

We recompiled c1gcv because the order of the channels were confusing. We found some change in the phase rotation module when we did this.

I did some cabling and checked each signals are actually going to the right channel. I labeled all the cables I know, which go into the AA chasis for ADC1 of c1ioo machine.

Below is the list of the channels. If you know anything about "unknown" channels, please let me know.

Current channel assignments for ADC1 of c1ioo machine:
  Red ones were added today. Green ones existed in the past, but channel assignment were changed.

cable

# on AA chassis name in Simulink channel name

connected
but unknown

J1A    
   
not connected J1B    
   
not connected J2 adc_1_2 C1:ALS-XARM_BEAT_DC
not connected adc_1_3 C1:ALS-YARM_BEAT_DC
connected
but unknown
J3    
   
connected
but unknown
J4    
   
connected
but unknown
J5    
   
connected
but unknown
J6    
   
connected
but unknown
J7    
   
beat Y arm fine I J8A adc_1_14 C1:ALS-BEATY_FINE_I
beat Y arm fine Q adc_1_15 C1:ALS-BEATY_FINE_Q
not connected J8B    
   
connected
but unknown
J9A    
   
not connected J9B    
   
connected
but unknown
J10    
   
connected
but unknown
J11    
   
not connected J12 adc_1_22 C1:ALS-BEATX_COARSE_I
not connected adc_1_23 C1:ALS-BEATX_COARSE_Q
not connected J13 adc_1_24 C1:ALS-BEATX_FINE_I
not connected adc_1_25 C1:ALS-BEATX_FINE_Q
beat Y arm coarse I
J14 adc_1_26 C1:ALS-BEATY_COARSE_I
beat Y arm coarse Q adc_1_27 C1:ALS-BEATY_COARSE_Q
not connected J15 adc_1_28 Broken! Don't use this!!
adc_1_29 (not broken)
not connected J16A adc_1_30 (not broken)
adc_1_31 Broken? Funny signal.
not connected J16B    
   

Memorandum for me:
  Recompiling procedure;

ssh c1ioo

rtcds make c1gcv
rtcds install c1gcv
rtcds start c1gcv

Attachment 1: c1gcv20120612-2.png
c1gcv20120612-2.png
  6809   Tue Jun 12 23:18:18 2012 yutaUpdateGreen LockingI-Q signals for the beat

[Mengyao, Yuta]

Yes!! We have I-Q signals for the beat!!

What we did:
  1. Aligned Y arm to the Y end green incident beam. The transmission to the PSL was about 195 uW.

  2. Aligned IR beam to the Y arm by adjusting PZTs and got the transmission, C1:LSC-TRY_OUT ~ 0.86.

  3. Aligned green optics on the PSL table to get the beat signal. The beat was found when;

  PSL laser temperature on display: 31.41 deg C
  C1:PSL-FSS_SLOWDC = 1.43
  Y end laser "T+": 34.049 deg C
  Y end laser "ADJ": 0
  Y end laser measured temperature: 34.14 deg C
  C1:GCY-SLOW_SERVO2_OFFSET = 29950
  Y end slow servo: off (was on)

  4. Connected the beat PD output to the beatbox.

  5. Kicked ETMY position to change the cavity length and while the ringdown, we run pynds to get data. We plotted C1:ALS-BEATY_FINE_I_ERR vs C1:ALS-BEATY_FINE_Q_ERR, and C1:ALS-BEATY_COARSE_I_ERR vs C1:ALS-BEATY_COARSE_Q_ERR (below). We got nice circle as expected.

FINEIQplot20120612.pngCOARSEIQplot20120612.png

Current setup:
  Only AA filers are put between the output of the beatbox and the ADC.

beatysetup20120612.png

  6810   Wed Jun 13 02:11:59 2012 yutaUpdateGreen Lockingmy first modescan (sort of)

I stabilized Y arm length by using only I phase coarse signal from the beat(C1:ALS-BEATY_COARSE_I_ERR).
I sweeped the arm length by injecting 0.05Hz sine wave from C1:ALS_OFFSETTER2_EXC.
Below is the plot of TRY and the error signal(ideally, Y arm length) while the sweep.

modescan20120612_1.png

I couldn't hold the arm length tight, so you can see multiple peaks close to each other.
We need to
  - adjust offsets
  - adjust rotation phase of I-Q mixing
  - adjust servo filters

to hold the length tighter.

Also, I couldn't sweep the Y arm length very much. I need to calibrate, but to do the modescan for many FSRs, we need to
  - introduce automatic phase optimizing system
There were sin/cos function in the CDS_PARTS, so I think we can feedback I_ERR to control rotation phase of I-Q mixing.

  6812   Wed Jun 13 03:03:38 2012 yutaUpdateGreen Lockingmy first modescan (sort of)

Linear range df of the delay line technique is about df ~ c/(2D). So, the linear range for the fine signal(delay line length D=30m) is about 5 MHz.
Arm cavity FSR = c/(2L) = 3.7 MHz.
So, I think we need phase shifting to do mode scan for more than 2 FSRs by holding the arm length finely with fine servo.
For the coarse (D=1.5m), the linear range is about 100 MHz, so if we can do mode scan using coarse servo, it is OK.

In any case, I think it is nice to have linear signal with fixed slope even if we don't adjust the phase every time.

Quote:

 That sounds goofy.

With the delay line technique, you can get a linear signal over 50 MHz with no phase shifting. What is with all this I/Q stuff?

 

  6815   Wed Jun 13 17:39:13 2012 yutaUpdateGreen Lockingcalibrating the beatbox

[Jenne, Yuta]

We put 0 dBm sine wave to the RF input of the beatbox and linear-sweeped frequency of the sine wave from 0 to 200 MHz using network analyzer (Aligent 4395A).
(We first tried to use 11 MHz EOM marconi)

Whlile the sweep, we recorded the output of the beatbox, C1:ALS-BEATY_(FINE|COARSE)_(I|Q)_IN1_DQ. We made them DQ channels today. Also, we put gain 10 after the beatbox before ADC for temporal whitening filter using SR560s.

We fitted the signals with sine wave using least squares fit(scipy.optimize.leastsq).
Transision time of the frequency from 200 MHz to 0 Hz can be seen from the discontinuity in the time series. We can convert time to frequency using this and supposing linear sweep of the network analyzer is perfect.

Plots below are time series data of each signal(top) and expansion of the fitted region with x axis calibrated in frequency (bottom).

ALS-BEATY_COARSE_I_IN1_DQ.pngALS-BEATY_COARSE_Q_IN1_DQ.png
ALS-BEATY_FINE_I_IN1_DQ.pngALS-BEATY_FINE_Q_IN1_DQ.png


We got

C1:ALS-BEATY_COARSE_I_IN1_DQ = -1400 sin(0.048 freq + 1.17pi) - 410
C1:ALS-BEATY_COARSE_Q_IN1_DQ = 1900 sin(0.045 freq + 0.80pi) - 95

C1:ALS-BEATY_FINE_I_IN1_DQ = 1400 sin(0.89 freq + 0.74pi) + 15
C1:ALS-BEATY_FINE_Q_IN1_DQ = 1400 sin(0.89 freq + 1.24pi) - 3.4

(freq in MHz)

The delay line length calculated from this fitted value (supposing speed of signal in cable is 0.7c) is;

  D_coarse = 0.7c * 0.048/(2*pi*1MHz) =  1.6 m
  D_fine = 0.7c * 0.89/(2*pi*1MHz) = 30 m

So, the measurement look quite reasonable.

FINE signals looks nice because we have similar response with 0.5pi phase difference.
For COARSE, maybe we need to do the measurement again because the frequency discontinuity may affected the shape of the signal.

  6816   Thu Jun 14 01:36:34 2012 yutaUpdateGreen Lockingcan't scan Y arm for 1FSR

[Jenne, Koji, Yuta]

We tried to scan of the Y arm but we couldn't scan for more than 1FSR.
In principle, we can do that because the error signal we are using, C1:ALS-BEATY_COARSE_I_IN1, has the range of ~ 40 MHz, which is about 10FSR (see elog http://nodus.ligo.caltech.edu:8080/40m/6815).

ALS stays for more than 10 min when we don't do the scan. If we put some offset gradually from C1ALS-OFFSETTER2, the lock breaks.
We monitored PZT output of the Y end laser, C1:GCY-SLOW_SERVO1_IN1, but it stayed in the range when scanning. So, there must be something wrong in the ALS loop.

Current in-loop arm length fluctuation is about 0.1 nm RMS (0.5 counts RMS).
Below is the spectrum of the error signal when the ALS is off(green) and on (pink,red). Below ~ 50 Hz, the measurement of the Y arm length is limited by ADC noise (~ 2uV/rtHz).
BEATY_COARSE_LoopOnOff.png

  6817   Thu Jun 14 04:53:39 2012 yutaSummaryGreen Lockingdesigning ALS loop for mode scan

[[Requirement]]
 Arm cavity FWHM for IR is

  FWHM = FSR / F = c/(2LF) = 8 kHz.

 In cavity length, this is

  L/f * FWHM = 40m/(c/1064nm) = 1.2 nm

 So, to do mode scan nicely, arm length fluctuation during resonant peak crossing should be much less than 1.2 nm.


[[Diagram]]
 Let's consider only ADC noise and seismic noise.
ALSloop.png

* S: conversion from Y arm length to the beat frequency

  dL/L = df/f

 So,

  S = df/dL = f/L = c/532nm/40m = 1.4e7 MHz/m


* W: whitening filter

 We set it to flat gain 50. So,

  W = 50


* D: AD conversion of voltage to counts

 D = 2^16counts/20V = 3300 counts/V


* B: frequency to voltage conversion of the beatbox.

 We measured BWD(elog #6815). When we measured this, W was 10. So, the calibration factor at 0 crossing point(~ 50 MHz) is

  B = 1400*0.048/10/D = 0.0021 V/MHz


* A: actuator transferfunction

 I didn't measure this, but this should look like a simple pendulum with ~ 1 Hz resonant frequency.


* n_ADC: ADC noise

 ADC noise is about

  n_ADC = sqrt(2*LSB^2*Ts) = sqrt(2*(20V/2^14)**2*1/64KHz) = 1.6 uV/rtHz


* n_seis: seismic noise

 We measured this by measuring C1:ALS-BEATY_COARSE_I_IN1. This is actually measuring

  D(WBSn_seis + n_ADC)

 Calibrated plot is the red spectrum below.


* F: servo filter (basically C1:ALS-YARM)

 We need to design this. Stabilized arm length fluctuation is

  x_stab = 1/(1+G)*n_seis + G/(1+G)*n_ADC/(WBS)

 where openloop transferfunction G = SBWDFA.
 Below ~ 50 Hz, n_seis is bigger than n_ADC/(WBS). We don't want to introduce ADC noise to the arm. So, UGF should be around 50 Hz. So, we need phase margin around 50 Hz.
 We also need about 10^3 DC gain to get the first term comparable to the second term.

 Considering these things, openloop transferfunction should look like the below left. Expected error signal when ALS on is the below right. I put some resonant gain to get rid of the peaks which contribute to the RMS (stack at 3.2Hz, bounce at 16.5 Hz).
 Inloop RMS we get is about 0.3 nm, which is only 4 times smaller than FWHM.
ALSopenloop.pngyarmlength.png



[[Discussion]]
 We need to reduce RMS more by factor of ~ 30 to get resolusion 1% of FWHM.
 Most contributing factor to the RMS is power line noise. We might want comb filters, but it's difficult because UGF is at around this region.

 So, I think we need more fancy whitening filters. Currently, we can't increase the gain of the whitening filter because SR560 is almost over loading. Whitening filter with zero at 1 Hz might help.

  6818   Thu Jun 14 21:37:37 2012 yutaUpdateGreen Lockingsucceeded in 1FSR mode scan

[Jenne, Yuta]

We couldn't scan the Y arm for 1FSR last night because the ALS servo breaks while sweeping.
We thought this might be from the amplitude fluctuation of the beat signal. The amplitude of the beat signal goes into the beatbox was about -5 dBm, which is not so enough for the beatbox to get good LO. So, we put an amplifier (and attenuators) and the amplitude became +1 dBm. The range beatbox can handle is about -3 dBm to +3 dBm, according to our calculation.

This increased stability of the lock, and we could scan the arm for 1FSR. Below is the plot of scanned ALS error signal (blue), Y arm IR PDH signal (green) and TRY (red).

YarmScan20120614.png

For each slope, we can see two TEM00 peaks, some higer order modes(may be 01, 02, 02) and sidebands (large 11MHz, small 55MHz?).

We couldn't scan for more. This is still a mystery.

Also, we need to reduce residual Y arm length fluctuation more because we get funny TRY peak shape.

Scan speed:
  For C1:ALS-BEATY_COARSE_I_IN1, 1 count stands for 0.21 nm(see elog #6817). We sweeped 4000 peak to peak in 50 sec. So, the scan speed is about 17 nm/sec.
  This means it takes about 0.06 sec to cross resonant peak.
  Cavity build up time is about 2LF/(pi*c) ~ 40 usec. So, the scan is quasi-static enough.
  Characteristic time scale for the Y end temperature control is about 10 sec, so Y end frequency is following the Y arm length change with temperature control.

  Currently, sampling frequency of DQ channels are 2048 Hz. This means we have 100 points in a TRY peak. I think this is enough to get a peak height.

Next step:
  - Reduce RMS. We are trying to use a whitening filter.
  - Find why we can't scan more. Why??
  - ETMY coil gains may have some unbalance. We need to check
  - Characterize Y end green frequency control. Koji and I changed them last week (see elog #6776).
  - Calculate positions of RF SBs and HOMs and compare with this result.

  6819   Fri Jun 15 00:50:54 2012 yutaUpdateGreen Lockingscanned Y arm for 5FSR

I scanned Y arm for 5FSR (below).
I could done this after I put a whitening filter.
Currently, whitening filter between the beatbox and AA filter is made of

  Ponoma blue box(passive filter with zero at 1 Hz, pole at 10 Hz) + SR560(flat gain 100)

I couldn't do more than 5FSR because SR560 overloads. I checked it by staring at the indicator during the scan.
Reason why we kept loosing lock last night was the overload of  SR560. Mystery solved!

Anyway, 5FSR is enough.
Our next step is to reduce residual arm length fluctuation.

YarmScan20120614_2.png


Also, I increased the alingnment of IR. So, the higher order modes are less than the last scan.

  6821   Fri Jun 15 13:33:39 2012 yutaUpdateGreen LockingADC noise contribution to ALS

ADC noise is not a limiting noise source in a current ALS setup.

Below is the calibrated spectrum of C1:ALS-COARSE_I_ERR when
  Y arm swinging with just damping (red; taken last night)
  terminated before AA (green)
  blocked PSL green beam (blue)

Blue and green curve tells us that noise from the beat PD to ADC is not contributing to the Y arm length sensing noise.

YarmALSnoise20120615.png

  6822   Sat Jun 16 01:03:21 2012 yutaUpdateGreen Lockingused longer delay line for mode scan

[Mengyao, Yuta]

Last night, I used 1.5 m delay line COARSE and got 5FSR mode scan. The range 5FSR was limited by the range of SR560.
So, this time, we used 6.4 m(21 feet) cable as a delay line for FINE servo. This should increase the sensitivity by factor of 4. But the range will be 4 tmes smaller, ~ 1.3FSR.

Below is the plot of the mode scan.
You can see the peak height difference between TEM00s, but it's just from the resolution of pixels.

You still can see noisiness goes up when blue plot goes down. But this time, 2000 stands for 27 MHz and -2000 stands for 15 MHz in the beat frequency because we flipped the filter gain this time.
Last night, the top of the triangle was about 40 MHz and bottom was about 60 MHz.


YarmScan20120615.png

We are going to derive mode-matching and some cavity parameters using this plot.

  6824   Sat Jun 16 13:01:17 2012 yutaUpdateGreen Lockingscanned Y arm for 5FSR

Quote:

Is that time stamp really correct?

 Yes. I used pyNDS to get data, but here's a screenshot of dataviewer playing back 300 seconds from GPS time 1023780144.


YarmScanDV.png

  6825   Sat Jun 16 18:17:00 2012 yutaUpdateGreen LockingY arm length using 5FSR scan

Calibrating error signal to beat frequency;
  I injected 0 dBm RF sine wave into the beatbox and sweeped the frequency(just like we did in elog #6815).
  This time, we have different whitening filters. I sweeped the frequency from 0 to 100 MHz in 200 sec.
  The length of the delay line is ~1.5 m for COARSE.
ALS-BEATY_COARSE_I_IN1_DQ.png

Y arm length;
  Here, I think we need some assumption. Let's assume wavelength of IR lamb_IR = 1064 nm and Y end green frequency is nu_g = 2*nu_IR.
  There is a relation
    dnu_g / nu_g = dL / L
  So,
    dnu_g / (dL/lamb_IR) = 2*nu_IR * lamb_IR / L = 2c/L
  We know that dL/lamb_IR = 1/2 for difference in beat frequency between TEM00s. Therefore, slope of the dnu_g vs dL/lamb_IR plot gives us the arm length L(figure below, middle plot).

CalibYarmScan20120614_2.png

  Error estimation is not done yet, but I think the COARSE_I_IN1 error signal to the beat frequency calibration has the largest error because it seems like the amplitude of sine wave changes ~10% day by day.

Calibrating beat frequency to Y arm length change;
  I used L = 32.36 m (figure above, bottom plot).
    dnu_g / dL = c / lamb_g / L = 1.74 MHz/m

  6827   Sat Jun 16 19:32:11 2012 yutaUpdateGreen LockingY arm length using 5FSR scan

I know!
But I think there's some error (~ 10% ?) in calibrating the beatbox. In elog #6815, slope near zero crossing point is about 68 counts/MHz, but now, its 60 counts/MHz. Also, zero crossing point in elog #6815 was 47 MHz, but now, its 45 MHz. 5FSR scan was done between these two calibration measurement.

Quote:

Quote:

Calibrating beat frequency to Y arm length change;
  I used L = 32.36 m (figure above, bottom plot).
    dnu_g / dL = c / lamb_g / L = 1.74 MHz/m

Wow. This is way too short.

You don't need to use Albertoo's arm length as his measurement was done before the upgrade.

 

  6828   Mon Jun 18 02:31:43 2012 yutaSummaryGreen Lockinganalysis of mode scan data

I analyzed mode scan data from last week.
Mode matching ratio for Y arm is 86.7 +/- 0.3 %. Assuming we can get rid of TEM01/10 by alignment, this can be improved up to ~ 90%.

Peak search, peak fitting and finnesse calculation:
  I made a python script for doing this. It currently lives in /users/yuta/scripts/modescanresults/analyzemodescan.py.
  What it does is as follows

  1. Read mode scan data(coarse5FSRscan.csv, fine1FSRscan.csv). Each column in the data file should be

[time] [some thing like C1:ALS-BEAT(Y|X)_(COARSE|FINE)_(I|Q)_IN1] [C1:LSC-POY11_I_ERR] [C1:LSC-TRY_OUT]

Each separated by comma. Currently, this script uses only TRY, but it reads all anyway

  2. Find peak in TRY data. For the peak search, it splits data in 1 sec and find local maximum. If the local maximum is higher than given threshold, it recognize it as a peak. If two peaks are very close, it uses higher one. This sometimes fails, because mode scan data we have is not so nice.

  3. Fit each peak with Lorentzian function,

TRY = a*b/(4*(t-c)^2+b^2) + d  (a>0, b>0)

  where a/b is a peak height, b is a linewidth (FWHM), c is a peak position in time, and d is a offset.
  I don't like this, but currently, a/b+c is fixed to the maximum value of TRY data used for fitting. This is because sometimes TRY data is so bad and I couldn't get the peak height correctly. Each points of TRY data doesn't have same error because cavity length is fluctuating and relation between cavity length and TRY is not linear. I think I should use some weighting for the fit, but currently, I just use least squares.

  4. Find TEM00 and calculate FSR in "seconds". I just used "seconds" assuming we did a linear sweep. This script recognize TEM00 from the given threshold.

  5. Calculate finesse using FSR and linewidth of the closest TEM00.

  Below are the result plots from this analysis. Calculated finesse looks quite high (~1000). I think this is from non-linearity in the sweep and error in "measured" line width.
coarse5FSRscan.pngfine1FSRscan.png


Higher order modes and RF sidebands:

  Assuming the curvature of ITMY/ETMY are flat/57.5 m, Y arm length is 38.6 m(FSR 3.9 MHz), positions of HOMs and RF sidebands(11/55 MHz) in frequency domain should look like the plot below.
  The script for calculating this currently lives in /users/yuta/scripts/modescanresults/HOMRFSB.py, inspired by Yoichi's script for KAGRA
HOMRFSB.png

Mode-matching ratio:
  By comparing mode scan data and HOM/RF SB positions in a sophisticated way, you can tell which peak is which.
coarse5FSRscanHOMRFSB.png


  From COARSE 5FSR measurement, peak heights are

TEM00 0.884, 0.896, 0.917, 0.905, 0.911
TEM01 0.040, 0.037, 0.051, 0.054, 0.062
TEM02 0.083, 0.078, 0.079, 0.071, 0.078
TEM03 0.018, 0.015, 0.013, 0.015, 0.014

  So the mode-matching ratio is

MMR = 86.2 %, 87.3 %, 86.5 %, 86.6 %, 85.5 %

  From FINE 1FSR measurement, peak heights and mode matching ratio is

TEM00 0.921
TEM01 0.031
TEM02 0.078
TEM03 0.014

MMR = 88.2 %

  Assuming each measurement had same error, mode-matching ratio from these 6 values is

MMR = 86.7 +/- 0.3 %  (error in 1 sigma)

  This can be improved by ~5% by alignment because we still see ~5% of TEM01/10. Study in systematic errors on going.

  6830   Mon Jun 18 17:28:03 2012 yutaSummaryComputersbugs in CDS_PARTS/simLinkParts/Fcn

Fcn module in CDS_PARTS is used to include a user defined function in a model.
We should be able to use this by entering desired function, but I found some bugs.

BUG1: Fcn doen't work without ";"

If you put ";" after the function, we can compile.

 sin(u[1]);

But if you put without ";", like

 sin(u[1])

you get the following error message when compiling.

controls@c1ioo
~ 0$ rtcds make c1gcv
### building c1gcv...
Cleaning c1gcv...
Done
Parsing the model c1gcv...
Done
Building EPICS sequencers...
Done
Building front-end Linux kernel module c1gcv...
echo >> target/c1gcvepics/README.making_changes
echo 'Built on date' `date` >> target/c1gcvepics/README.making_changes
make[1]: Leaving directory `/opt/rtcds/caltech/c1/rtbuild'

make[1]: Entering directory `/opt/rtcds/caltech/c1/rtbuild/src/fe/c1gcv'
make -C /lib/modules/2.6.34.1/build SUBDIRS=/opt/rtcds/caltech/c1/rtbuild/src/fe/c1gcv modules
make[2]: Entering directory `/usr/src/linux-2.6.34.1-cs'
  CC [M]  /opt/rtcds/caltech/c1/rtbuild/src/fe/c1gcv/c1gcv.o
make[2]: Leaving directory `/usr/src/linux-2.6.34.1-cs'
make[1]: Leaving directory `/opt/rtcds/caltech/c1/rtbuild/src/fe/c1gcv'
/opt/rtcds/caltech/c1/rtbuild/src/fe/c1gcv/c1gcv.c: In function 'feCode':
/opt/rtcds/caltech/c1/rtbuild/src/fe/c1gcv/c1gcv.c:615: error: expected expression before ';' token
make[3]: *** [/opt/rtcds/caltech/c1/rtbuild/src/fe/c1gcv/c1gcv.o] Error 1
make[2]: *** [_module_/opt/rtcds/caltech/c1/rtbuild/src/fe/c1gcv] Error 2
make[1]: *** [default] Error 2
make: *** [c1gcv] Error 1


BUG2: sindeg doesn't work properly

sindeg should work as cosine with input in degrees.
I made a simple model to test this(below).
model_sindegbug.png


Output of the filter module C1:ALS-BEATY_FINE_PHASE goes to "PHASE_in"
sindeg of this goes to C1:ALS-BEATY_FINE_I_ERR
cosdeg of this goes to C1:ALS-BEATY_FINE_Q_ERR

If you sweep the phase input, you should get sin and cos, but you get the following.
cosdeg (C1:ALS-BEATY_FINE_Q_ERR) looks OK, but sindeg (C1:ALS-BEATY_FINE_I_ERR) looks funny. It looks like ~20000 is its period.

dv_sindegbug.png

  6832   Mon Jun 18 23:54:31 2012 yutaUpdateGreen Lockingphase tracker for ALS

[Koji, Jenne, Yuta]

Summary:
  We put phase tracker in FINE loop for ALS. We checked it works, and we scanned Y arm by sweeping the phase of the I-Q rotator.
  From the 8 FSR scan using FINE (30 m delay line), we derived that Y arm finesse is 421 +/- 6.

What we did:
  1. We made new phase rotator because current cdsWfsPhase in CDS_PARTS doesn't have phase input. We want to control phase. New phase rotator currently lives in /opt/rtcds/userapps/trunk/isc/c1/models/PHASEROT.mdl. I checked that this works by sweeping the phase input and monitoring the IQ outputs.

  2. We made a phase tracker (/opt/rtcds/userapps/trunk/isc/c1/models/IQLOCK.mdl) and included in c1gcv model. Unit delay is for making a feed back inside the digital system. Currently it is used only for BEATY_FINE (Simulink diagram below). We edited MEDM screens a little accordingly.
newIQLOCK.png


  3. Phase tracking loop has UGF ~ 1.2 kHz, phase margin ~50 deg. They are enough becuase ALS loop has UGF ~ 100 Hz. To control phase tracking loop, use filter module C1:ALS-BEATY_FINE_PHASE (with gain 100). Sometimes, phase tracking loop has large offset because of the integrator and freedom of 360*n in the loop. To relief this, use "CLEAR HISTORY."

  4. Locked Y arm using C1:ALS-BEATY_FINE_PHASE_OUT as an error signal. It worked perfectly and UGF was ~ 90 Hz with gain -8 in C1:ALS-YARM filter module.

  5. Swept phase input to the new phase rotator using excitation point in filter module C1:ALS-BEATY_FINE_OFFSET. Below is the result from this scan. As you can see, we are able to scan for more than the linear range of FINE_I_IN1 signal. We need this extra OFFSET module for scanning because BEATY_FINE_I_ERR stays 0 in the phase tracking loop, and also,  error signal for ALS, output of PHASE module, stays 0 in ALS loop.
YarmScan20120618.png

  6. We analyzed the data from 8FSR scan by FINE with phase tracker using analyzemodescan.py (below). We got Y arm finesse to be 421 +/- 6 (error in 1 sigma). I think the error for the finesse measurement improved because we could done more linear sweep using phase tracker.
fine8FSRscan.png


Next things to do:
  - Phase tracker works amazingly. Maybe we don't need COARSE any more.
  - Install it to X arm and do ALS for both arms.
  - From the series of mode scan we did, mode matching to the arm is OK. There must be something wrong in the PRC, not the input beam. Look into PRC mode matching using video capture and measuring beam size.

  6834   Tue Jun 19 23:36:19 2012 yutaUpdateLSCcalibrated POY error signal

[Jenne, Yuta]

We calibrated POY error signal(C1:LSC-POY11_I_ERR). It was 1.4e12 counts/m.

Modeling of Y arm lock:
  Let's say H is transfer function from Y arm length displacement to POY error signal. This is what we want to measure.
  F is the servo filter (filter module C1:LSC-YARM).
  A is the actuator TF using ITMY. According to Kiwamu's calibration using MICH (see elog #5583),

  A_ITMY  = 4.832e-09 Hz^2*counts/m / freq^2

  We used ITMY to lock Y arm because ITMY is already calibrated.

What we did:
  1. Measured openloop transfer function of Y arm lock using POY error signal using ITMY (G=HFA). We noticed some discrepancy in phase with our model. If we include 1800 usec delay, phase fits well with the measurement. I think this is too big.
LSCyarmTF_usingITMY.png


  2. Measured a transfer function between actuator to POY error signal during lock. This should give us HA/(1+G).
LSCyarm_HAover1plusG.png

  4. Calculated H using measurements above. Assuming there's no frequency dependance in H, we got

  H = 1.4e12 counts/m

POYerrorcalibration.png

 For sanity check; Peak to peak of the POY error signal when crossing the IR resonance is about 800 counts. FWHM is about 1 nm, so our measurement is not so crazy.

  6836   Wed Jun 20 00:02:16 2012 yutaUpdateGreen Lockingslower scan using phase tracking ALS

For those of you who want to see plots from slower scan.

YarmScan20120619.png

  6838   Wed Jun 20 16:37:11 2012 yutaUpdateLockingETMX 1064 trans camera

[Jenne, Yuta]

We made ETMXT camera working.
We connected the camera to video mux, placed 10% pick off mirror in front of TRX PD, lead the beam go to ETMXT camera.
Transmission to the TRY PD was 23.8 uW, but now, it's 21.3 uW (2.3 uW goes to the camera).
So, we changed C1:LSC-TRX_GAIN from -0.00181818 to -0.00203158 (=-0.00181818*23.8/21.3).

There is a channel for power normalization, C1:LSC-TRX_POW_NORM, but is 1 and it looks like we are using this gain for the normalization. Situation of TRY is the same as TRX.

  6840   Wed Jun 20 18:09:23 2012 yutaUpdateLockingboth arms aligned, ITMX oplev centered

[Jenne, Yuta]

We aligned FPMI. I also centered ITMX oplev because the light was not hitting on QPD.
Alignment procedure we took was;

1. Align Y arm to the Y end green(Y green trans to PSL is now 195 uW with Y end laser measured temperature 34.14 degC).
2. Aligned IR using PZT2 to Yarm(Now, TRY ~ 0.90).
3. Aligned ITMX monitoring AS spots.
4. Aligned X arm so that TRX maximize.
5. Fine adjusted both BS and X arm(Now, TRX ~ 0.82).

Beam spot position on ETMX looks a little too high & left (from ETMXF camera), but we will leave it until ASS scripts is fixed.

FPMIalignment2010620.png

  6841   Wed Jun 20 18:43:57 2012 yutaUpdateLSCcalibrated POX error signal

[Jenne, Yuta]

We did the same calibration for POX. It was 3.8e12 counts/m. See elog #6834 for the details of calibration we did.

According to Kiwamu's calibration, actuator response of ITMX is;

A_ITMX  = 4.913e-09 Hz^2*counts/m / freq^2

Plots below are results from our calibration measurement.

LSCxarmTF_usingITMX.pngLSCxarm_HAover1plusG.pngPOXerrorcalibration.png

  6847   Thu Jun 21 12:56:49 2012 yutaUpdateLockingETMX 1064 trans camera

Quote:

[Jenne, Yuta]

We made ETMXT camera working.

 Xarm_EndTableLayout_NewTransCamera.png

Here's the new end table layout, for the transmitted IR stuff.

  6849   Thu Jun 21 15:36:51 2012 yutaUpdateLockingX arm alignment

I aligned X arm so that the beam spot comes roughly on the center.

1. Use ITMX and ETMX (mainly ITMX) to make beam spot come on center of the optic using eyeball.

2. Use ETMX and BS to maximize TRX power (reached ~ 0.85)

3. Aligned green optics on X end. Transmission of X green measured at PSL table is now 255 uW and TEM00 has the most power.

It was not easy to increase X green transmission more because beam spot on green transmission PD is wiggly when X end table is opened. When closed, wiggliness is about the same for Y green and X green.
Turning off HEPA on the X end didin't helped, but there must be something bad in the X end table. If we couldn't figure out why, let's wait for PZTs to come for end tables.

Considering the laser power is different(X end 1 W, Y end 700 mW), X green transmission should reach ~400 uW. But I think we should go on to X beat search.

I placed green shutter for X end back for convenience. I put some spacers to adjust its height and avoid beam clipping.


[Steve, Yuta]

What causing wiggly X green transmission was the air flow from the air conditioner. When we turned it off, beam spot motion became quiet. Air flow from HEPA was not effecting much.

ELOG V3.1.3-