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ID Date Authorup Type Category Subject
  13956   Wed Jun 13 18:08:36 2018 keerthanaUpdate Finesse code for cavity scan

The unit mentioned in the x-axis was wrong. So I have remade the graphs. The point where frequency equals to zero is actually the frequency corresponding to the laser, which is in the range of 1014 Hz and it caliberated as zero.

Quote:

The cavity scan data obtained from the Finesse simulation is attached here. Fig1 indicates the cavity scan data in the absence of induced misalignment. In that case only the fundemental mode is resonating. But when a misalignment is induced, higher order modes are also present as seen in Fig2. This is in the absence of surface figure error in the mirrors. Now I am trying to provide perturbations to the mirror surface in the form of zernike polynomials and get the scan data fom the simulation. These cavity scan data can be used to develop fitting models. Once we have a model, we can use it to analyse the data from the experimental cavity scan.

finesse1.pdffinesse2.pdf

  13995   Thu Jun 21 13:24:00 2018 keerthanaUpdateelogThe cavity scan data of June 20

(Jon, Keerthana, Sandrine)

We tried to align the AUX and PSL laser yesterday. We collected the data from the spectrum analyser for the Y-ARM reflection and also for the Y-ARM transmission from the ETM mirror. I am attaching the plots here.

  14017   Tue Jun 26 10:06:39 2018 keerthanaUpdateAUXFirst Coherent AUX Scan of PRC Using AM Sidebands

(Jon, Keerthana, Sandrine)

I am attaching the plots of the Reflected and transmitted AUX beam. In the transmission graph, we are getting peak corresponding to the resonance frequencies, as at that frequency maximum power goes to the cavity. But in the Reflection graph, we are obtaining dips corresponding to the resonance frequency because maximum power goes to the cavity and the reflected beam intensity becomes very less at those points.

 

  14045   Sun Jul 8 22:27:25 2018 keerthanaUpdate AUX diagram

(Analisa, Keerthana, Sandrine)

So far we tried four different techniques to scan the AUX laser. They are,

1. Scanning the marconi frequency to sweep the central frequency of the AUX laser.

2. Sweeping the side band frequency of the AUX laser by providing RF frequency from the spectrum analyser.

3. Double demodulation technique.

4. Single demodulation technique.

Now we are taking all the scan data with the help of Single demodulation technique.

  Draft   Wed Jul 11 18:13:19 2018 keerthanaSummaryAUXGouy Phase Measurements from AUX-Laser Scans

From the Measurement Jon made, FSR is 3.967 MHz and the Gouy phase is 52 degrees. From this, the length of the Y-arm cavity seems to be 37.78 m and the radius of curvature of the mirror seems to be 60.85 m.

 

Guoy Phase = \cos^{-1} \sqrt{g1.g2}

\\ g = 1- \frac{L}{R}

L = \frac {c} {2*FSR}

FSR = Free spectral Range

L = Lenth of the arm

R = Radius of curvature of the mirror (R1 =\infty  , R2= unknown)

Quote:

This note reports analysis of cavity scans made by directly sweeping the AUX laser carrier frequency (no sidebands). The measurement is made by sweeping the RF offset of the AUX-PSL phase-locked loop and demodulating the cavity reflection/transmission signal at the offset frequency.

Y-Arm Scan

Due to the simplicity of its expected response, the Y-arm cavity was scanned first as a test of the AUX hardware and the sensitivity of the technique. Attachment 1 shows the measured cavity transmission with respect to RF drive signal.

The AUX laser launch setup is capable of injecting up to 9.3 mW into the AS port. This high-power measurement is shown by the black trace. The same measurement is repeated for a realistic SQZ injection power, 70 uW, indicated by the red curve. At low power, the technique still clearly resolves the FSR and six HOM resonances. From the identified mode resonance frequencies the following cavity parameters are directly extracted.

YARM Gautam V. Finesse Model Actual
FSR 3.966 MHz 3.967 MHz
Gouy phase 54.2 deg 52.0 deg

 

 

  14057   Thu Jul 12 14:06:39 2018 keerthanaUpdateelogFinesse and Analytical solution - Comparison

I tried to compare the cavity scan data we get from the Finesse simulation and that we expect from the Analytical solution. The diagram of the cavity I defined in Finesse is given below along with the values of different quantities I used. For the analytical solution I have used two different equations and they are listed below.

Analytical 1 - Blue Graph

\phi = \frac {2.L.\Omega_1}{c}

t_{cav} = \frac{t_e. t_f \exp^{-i\frac{\phi}{2}}}{1- r_f. r_e \exp^{-i\phi} }

T_{cav} = \left|{t_{cav}} \right|^2

 

Analytical 2 - Red Graph

F = \frac {4. r_f.r_e}{(1-r_f.r_e )^2}

\phi = \frac {2.L.\Omega_1}{c}

T_{cav} = \left|{t_{cav}} \right|^2 = \frac {(t_e.t_f)^2}{(1 - r_f . r_e)^2} \frac{1}{1+F(\sin\frac {\phi}{2})^2}

The graph obtained from both these solutions completely matches with each other.

Finesse Solution

The cavity which I defined in Finesse is shown below. The solution from Finesse and the Analytical solution also matches with each other. Another plot is made by taking the difference between Finesse solution and Analytical solution. The difference seems to be of the order of \approx 10^{-19}.

The Difference plot is also attached below.

  13938   Mon Jun 11 11:45:13 2018 keerthana UpdateelogComparison of the analytical and finesse values of TMS and FSR.
Quantity Analytical Value Finesse Value Percentage Error
Free Spectral range (FSR) 3.893408 MHz 3.8863685 MHz 0.180 %
Transverse Mode Spacing (TMS) 1.195503 MHz 1.1762885 MHz 1.607 %

The values obtained from both analytical and finesse solution is given in the above table along with the corresponding percentage errors.finesse1.pdf

The parameters used for this calculation are listed below.

Parameter Value
length of the cavity (L) 38.5 m
Wavelength of the laser beam (\lambda) 1064 nm
Radius of curvature of ITM (R1) \infty
Radius of curvature of ETM (R2) 58 m

The cavity scan data obtained from Finesse is also attached here.

  14039   Thu Jul 5 17:33:36 2018 keerthana, sandrineUpdateelogLights not working
  • N/S ARM FL.
  • N/S ARM INC.

These two lights inside the 40m-lab are not working.

  14040   Thu Jul 5 17:58:04 2018 keerthana, sandrineUpdateelog 

(Analisa, Sandrine, Keerthana)

Today Annalisa helped us to understand the new set up used to make the frequency scans of the AUX laser. While tracking the cables it seemed that there were quite a lot of cables near the mixer. So we have reconnected one of the splitter which was splitting the RF out put signal from the Agilent and have placed it just near the Agilent itself. A picture of the changed setup is provided below. The splitter divides the signal into two components. One goes to the LO port of the mixer and the other goes to the R port of the Agilent. We have tried locking the PLL after the change and it works fine. We are trying to make a diagram of the setup now, which we will upload shortly.

 

  6360   Mon Mar 5 23:47:15 2012 keikoConfigurationLSCND2 at REFL OSA

ND filter ND3 (which is at the REFL port to the REFL OSA) is removed. Don't forget to put it back when you restore PRM!!!

  6361   Tue Mar 6 00:13:20 2012 keikoUpdateLSCASI signal offset

Screenshot-Untitled_Window.png

AS55Q and AS55I signals. AS55Q is around zero while AS55I has a large offset which is about the signal amplitude. It is likely because of the RAM?

keiko, kiwamu

 

 

 

 

  6368   Tue Mar 6 23:37:31 2012 keikoUpdateSUSMICH noise budget - SUS check

Here are the OSEM spectrum of MICH suspensions (BS, IX, IY). Bounce and Roll modes are shown on 16 and 23 Hz. The filters for them has been checked.

Mar6sus1.pdf

Mar6sus2.pdf

Mar6sus3.pdf

keiko, kiwamu, Rana

  6375   Wed Mar 7 16:32:09 2012 keikoUpdateLSCOSA

 I swap an OSA at PSL and OSA at REFL. It was because the PSL-OSA had a better resolution, so we place this better one at REFL. The ND filter (ND3) which was on the way to REFL OSA was replaced by two BSs, because it was producing dirty multiple spots after transmitting.

  6376   Wed Mar 7 17:39:40 2012 keikoUpdateLSCMICH noise budget on 5 Mar

 This is the calibrated MICH noise budget on Mar 5. There was a sharp peak at 1Hz and a blob on 3 Hz. The demod phase was adjusted for AS55Q.

Mar5-MICHbudget.png

 

  6380   Wed Mar 7 20:53:13 2012 keikoUpdateLSCMICH noise budget on 5 Mar

 

 Mar6-MICHbudget.png

This is the MICH noise budget on 6th March. 1Hz peak got a bit better as the BS sus control gain was increased.

 

  6384   Wed Mar 7 23:29:28 2012 keikoUpdateLSCREFL OSA observation

 kiwamu, keiko

 

 

REFLOSA.png

We measure the REFL OSA spectrum when (1) direct reflection from the PRM (2) CR lock at PRC (3) SB lock at PRC. When CR lock, both SBs are reflected from the PRC and when SB lock (ref line), some SB is sucked by PRM and looked lower than the other two lines.

 

  6385   Thu Mar 8 00:57:48 2012 keikoUpdateLSCMICH noise budget on Mar 5, Mar 6, and old

Here is the recent two noise budgets of MICH, with the old measurement by Jenne. The most latest Mar 6 data is quite close to the old data, even better around 20-30 Hz. Probably some scattering source was improved?

Mar7MICHbudgettotal.png

  6393   Fri Mar 9 13:34:13 2012 keikoUpdateLSCupdate on the locking activity

We tried to measure the sensing matrix for MICH and PRCL last night. They look too much mixed as we expect... the matrix may be posted later. We suspect the IX and IY of the MICH excitation is not balanced very well, although Kiwamu adjusted that about two weeks ago, and it is mixing the dof. We'll try to balance it again, ans see the matrix. 

Keiko, Kiwamu

 

Quote:

[Keiko / Kiwamu]

 Some updates on the locking activity:

  • Started summarizing the data of the Michelson lock in a wiki page:
  • Gradually moving on to the PRMI lock
    • The lock stays for reasonably a long time (~20 min or more)
    • POP22/110 demod signals seemed just ADC noise.
    • A first noise budget is in process
      • The glitches make the noise level worse above 40 Hz or so in both the MICH and PRCL budgets.
    • Sensing matrix will be measured tomorrow
    • The data will be also summarized in a wiki page

 

  6398   Sat Mar 10 02:00:03 2012 keikoUpdateLSCupdate on the locking activity

ITMX and ITMY balance for the MICH excitation (lockin) is adjusted again. Now it's ITMx = -0.992, ITMy = 1 for MICH (lockin output matrix values).

RA: what were the old values? Does this change make any difference for the signal mixing noticed before?

  6400   Mon Mar 12 01:04:18 2012 keikoUpdateLSCRAM simulation update, RAM LSC matrix

 I calculated the DRMI RAM LSC matrix with RAM and the operation point offsets.

  • configuration: C1 DRMI
  • RAM is added by an Mach-Zehnder ifo placed before the PRM
  • demodulation phases are optimised for each DoF
  • the operation points offset from the PDH signals are calculated and added to the optical configuration as mirror position offsets
  • Then the matrix is calculated with the offsets and the RAM
  • The set of the scrips are found as RAMmatrix.m, normMAT.m, newGetMAT.m,  on CVS/ifomodeling/40m/fullIFO_Optickle. They are a bit messy scripts at this moment.

Results:

(1) No RAM LSC matrix

  PRCL MICH SRCL
REFL11I 1 -0.001806 -0.000147
AS 55Q 0.000818 1 0.000474
AS 55 I 1.064561 902.292816 1

(2) With 1% RAM mod index of PM (normalised by (1) )

  PRCL MICH SRCL
REFL11I 1.000618 -0.001837 -0.000163
AS 55Q 0.000919 1.000521 0.000495
AS 55 I 1.169741 924.675187 1.018479
 

(3) With 5% RAM mod index of PM (normalised by (1) )

  PRCL MICH SRCL
REFL11I 0.999986 -0.001812 -0.000150
AS 55Q 0.000838 1.000028 0.000479
AS 55 I 1.084598 906.83668 1.003759
 

  6401   Mon Mar 12 18:57:58 2012 keikoUpdateLSCRAM simulation update, RAM LSC matrix

Quote:

 I calculated the DRMI RAM LSC matrix with RAM and the operation point offsets.

  • configuration: C1 DRMI
  • RAM is added by an Mach-Zehnder ifo placed before the PRM
  • demodulation phases are optimised for each DoF
  • the operation points offset from the PDH signals are calculated and added to the optical configuration as mirror position offsets
  • Then the matrix is calculated with the offsets and the RAM
  • The set of the scrips are found as RAMmatrix.m, normMAT.m, newGetMAT.m,  on CVS/ifomodeling/40m/fullIFO_Optickle. They are a bit messy scripts at this moment.

Results:

(1) No RAM LSC matrix

  PRCL MICH SRCL
REFL11I 1 -0.001806 -0.000147
AS 55Q 0.000818 1 0.000474
AS 55 I 1.064561 902.292816 1

(2) With 1% RAM mod index of PM (normalised by (1) )

  PRCL MICH SRCL
REFL11I 1.000618 -0.001837 -0.000163
AS 55Q 0.000919 1.000521 0.000495
AS 55 I 1.169741 924.675187 1.018479
 

(3) With 5% RAM mod index of PM (normalised by (1) )

  PRCL MICH SRCL
REFL11I 0.999986 -0.001812 -0.000150
AS 55Q 0.000838 1.000028 0.000479
AS 55 I 1.084598 906.83668 1.003759
 

Adding some more results with more realistic RAM level assumption.

(4) With 0.1% RAM mod index of PM (normalized by (1) )

  PRCL MICH SRCL
REFL11I 0.99999 -0.001807 -0.000148
AS 55Q 0.000822 1.000002 0.000475
AS 55 I 1.068342 906.968167 1.00559
 

(5) With 0.5% RAM mod index of  PM (normalized by (1) )

  PRCL MICH SRCL
REFL11I  0.999978  -0.001810    -0.000149 
AS 55Q 0.000830  1.000010  0.000476 
AS 55 I 1.075926 904.321433  1.001677
 

  6417   Wed Mar 14 16:33:20 2012 keikoUpdateLSCRAM simulation / RAM pollution plot

In the last post, I showed that SRCL element in the MICH sensor (AS55I-mich) is chaned 1% due to RAM.

Here I calculated how is this 1% residual in MICH sensor (AS55 I-mich) shown in MICH sensitivity. The senario is:

(1) we assume we are canceling SRCL in MICH by feed forward first (original matrix (2,3) element).

(2) SRCL in MICH (matrix(2,3) is changed 1% due to RAM, but you keep the same feed forward with the same feedforward gain

(3) You get 1% SRCL residual motion in MICH sensor. This motion depends on how SRCL is quiet/loud. The assumed level is

Pollution level = SRCL shot noise level in SRCL sensor  x  SRCL closed loop TF  x  1% residual .... the following plot.

 

 

AS sensor = AS55I-mich  --- SN level 2.4e-11 W/rtHz ------- MICH SN level 6e-17 m/rtHz

SRCL sensor = AS55 I-SRCL --- SN level 2e-11 W/rtHz ---  SRCL SN level 5e-14 m/rtHz

 

 

RAMexampleplot.png

 

 

Quote:

Adding some more results with more realistic RAM level assumption.

(4) With 0.1% RAM mod index of PM (normalized by (1) )

  PRCL MICH SRCL
REFL11I 0.99999 -0.001807 -0.000148
AS 55 Im 0.000822 1.000002 0.000475
AS 55 Is 1.068342 906.968167 1.00559
 

 

 

 

 

  6419   Wed Mar 14 21:01:36 2012 keikoUpdateLSCevolution of the sensing matrix in PRMI as a function of time

This is the simulated signals to compare with the original post #6403

 

 

PRMI configuration, PRCL signal

[W/m] Simulation Measured
REFL11 575440

 

~10000

REFL33 4571 ~50
REFL55 288400 ~5000
REFL165 891 NA
AS55 71 70

 

PRMI configuration, MICH signal

[W/m] Simulation Measured
REFL11 2290

 

~600

REFL33 36 ~4
REFL55 5623 ~200
REFL165 17 NA
AS55 6456 ~200
 

Simulated DC REFL power is 9mW (before the attenuator). AS DC is 0.3mW.

They don't agree. I suspect the PR gain for the SBs are somehow different. It is about 40 (or a bit less) in the simulation for 11MHz.

 

 

 

 

  6449   Tue Mar 27 02:18:31 2012 keikoUpdateIOOBeam Profile measurement: IPPOS beam

Keiko, Rana, Suresh

Related to the beam profile of IPPOS today, we tried to measure the beam size at the ETMY point in order to estimate the input beam mode. We measured the beam size hitting at the suspension frame by a camera image, with two situations to see two "z" for beam profile.

(1) Input beam is slightly misaligned and the injected beam hits the end mirror frame. Assuming z=0 at the input mirror, this should be z=40m.

(2) Input beam hits the centre of the end mirror, and ITMY is slightly misaligned and the beam hits the end mirror frame after the one-round trip. Assuming z=0 at the ITM, this position should be z=120m.

text9149.png

The injected beam at the end point and the one round trip ligt at the end point should be the same size, if the input mode matches to the cavity mode. You can see if your injected light is good for the cavity or not. We compared and assumed the above two beam sizes by looking at the photo of the beam spot.

(1) first_cap.png (2) second_cap.png

 Assuming the zoom factor difference by the part below the beam (shown with allow in the photos. Arbitrary unit.), the beam in (2) is smaller than expected (roughly 40%?).

However this is a very rough estimation of the beam sizes! It is difficult to assume the beam size shown on the photos! It looks smaller only because the power of (2) is smaller than of (1). I don't think we can say anything from this rough estimation. One may be able to estimate better with CCD camera instead of this normal camera. 

 

  6452   Tue Mar 27 16:06:59 2012 keikoUpdateIOOBeam Profile measurement: IPPOS beam

I changed the ETMY CCD camera angle so that we can see the suspension frame in order to repeat the same thing as yesterday. The ETMY camera is not looking at the beam or mirror right now.

  6458   Tue Mar 27 21:37:51 2012 keikoConfigurationIOOBeam Profile measurement: IPPOS beam

 From the mode measurement I and Suresh have done yesterday, I calculated what beam size we expect at ETM ((1) upper Fig.1)  and at ETM after one bounce ((2) lower Fig.1).

expsche.png

Fig.1 (Yarm)

In case of (1), we expect approximately w=6300 um (radius), and w=4800 um for one-bounce spot (2) from the measured mode, see Fig.2.

drawing.png

Fig.2

This roughly agree with what we observed on CCD camera. See, pic1 for (1) and pic2 for (2). The spot at the ETMY (1) is larger than the one-bounced spot (2). From the monitor it is difficult to assume the radius ratio. The observed spot of (2) is a bit smaller than the prediction. It could happnen when (A) the ETMY (as a lens) is slightly back of the ideal position (= the distance between the ITM and ETM is longer than 40m) (B) the real waist is farer than ITM position toward MC (I assumed roughly 5 m from Jenne's plot, but could be longer than that).

P3270007-s.jpg  P3270008-s.jpg

pic1 (left): beam spot hitting on the suspension frame. pic 2 (right): the one-bounced beam spot hitting on the suspension frame.

 

  6464   Thu Mar 29 11:29:27 2012 keikoUpdateLSCPOP22/POP110 amplifires

Yesterday I and Kiwamu connected two amplifiers (mini-circuit, ZFL-1000LNB+) for POP22/110. Dataviewer can see some signals. I'll test the signal levels and freq components before the rack just in case. [Kiwamu, Keiko]

  6466   Thu Mar 29 18:42:11 2012 keikoUpdateLSCPOP22/POP110 amplifires

Adding two amplifiers on POP22/110, I checked the signals going to the dmod board of 22 and 110.

The signal flows: Photodetector of POP --> Amp1 --> Amp2 --> RF splotter --> bandpass filter for 22MHz / 110MHz --> 22MHz / 110MHz demod board.

 

 

 

 Here is the picture of RF spectrum just after the bandpass filter of 22MHz going to the 22MHz demod board. The signal peak at 22MHz is about -40dBm. There is a structure slightly lower than 22MHz.

P3290004.JPG

The below is the RF spectrum for 110MHz branch. The peak at 110MHz is about -15dBm. The peak on the left of 110MHz is 66MHz peak.

P3290005.JPG

 

Quote:

Yesterday I and Kiwamu connected two amplifiers (mini-circuit, ZFL-1000LNB+) for POP22/110. Dataviewer can see some signals. I'll test the signal levels and freq components before the rack just in case. [Kiwamu, Keiko]

 

  6475   Mon Apr 2 18:24:34 2012 keikoUpdateLSCRAM simulation for Full ifo

 I extended my RAM script from DRMI (3DoF) to the full IFO (5DoF).

Again, it calculates the operation point offsets for each DoF from the opt model with RAM. Then the position offsets are added to the model, and calculates the LSC matrix. RAM level is assumed as 0.1% of the PM modulation level, as usual, and lossless for a simple model.

 

 

Original matrix without RAM:

REFL f1 : 1.000000    0.000000    0.000008    -0.000005    0.000003 

  AS f2 : 0.000001    1.000000    0.000005    -0.003523    -0.000001 

 POP f1 : -3956.958708    -0.000183    1.000000    0.019064    0.000055 

 POP f2 : -32.766392    -0.154433    -0.072624    1.000000    0.024289 

 POP f2 : 922.415913    -0.006625    1.488912    0.042962    1.000000 

 

(MICH and SRCL uses the same sensor, with optimised demodulation phase for each DoF.) 

Operation position offsets are:

PRCL   -3.9125e-11 m

SRCL    9.1250e-12 m

CARM  5.0000e-15 m  

and no position offsets for DARM and MICH (because they are differential sensor and not affected by RAM offsets).

 

Resulting matrix with RAM + RAM offsets, normalised by the original matrix:  

REFL f1 : 0.001663    -0.000000    0.003519    0.000005    -0.000003 

  AS f2 : 0.000004    0.514424    0.000004    -0.001676    -0.000001 

 POP f1 : 7.140984    -0.001205    15.051807    0.019254    0.000417 

 POP f2 : 0.029112    -0.319792    0.042583    1.000460    0.024298 

 POP f2 : -0.310318    -0.014385    -1.761519    0.043005    0.999819 

 

As you can see in the second matrix, the CARM and DARM rows are completely destroyed by the RAM offsets! The signals are half reduced in the DARM case, so the mixture between DARM and MICH are about 50% degraded.

 I also would like to extend this script to use the DC readout, but don't know how to calculate the postion offset for AS_DC because the error signal is not zero-crossing for AS_DC anymore. Do you have any suggestions for me?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  6480   Tue Apr 3 14:11:33 2012 keikoUpdateLSCRAM simulation for Full ifo

Quote:

Quote:

 I also would like to extend this script to use the DC readout, but don't know how to calculate the postion offset for AS_DC because the error signal is not zero-crossing for AS_DC anymore. Do you have any suggestions for me?

 I don't think I understand the question. AS_DC should not have a zero crossing, correct?

 That's right. I calculate the offset of the operation point (when you have RAM) from the zero-crossing point of the PDH signals. I don't know how to do that for AS_DC, because it doesn't cross zero anymore anytime.

  6481   Tue Apr 3 14:17:18 2012 keikoUpdateLSCRAM simulation for Full ifo

I add a flow-chart drawing what the scripts do and how the scripts calculate the LSC matrix.

flowchart.png

 

(1) First, you calculate the LSC matrix WITHOUT RAM or anything, just for a reference. This is the first matrix shown in the quoted post.

(2) The script calculates the LSC matrix with RAM. Also, the heterodyne signals for all 5 DoF are calculated. The signals have offsets due to the RAM effect. The operating position offsets are saved for the next round.

(3) The script calculates the LSC matrix again, with RAM plus the offset of the operation points. The matrix is shown in the last part of the quoted post.

 

Now I am going to check (A) LSC matrices (matrix 2, the second matrix of above chart) with different RAM levels (B) Are pos-offsets degrade the CARM and DARM so much (See, the quated result below), is that true?

Quote:

Original matrix without RAM:

REFL f1 : 1.000000    0.000000    0.000008    -0.000005    0.000003 

  AS f2 : 0.000001    1.000000    0.000005    -0.003523    -0.000001 

 POP f1 : -3956.958708    -0.000183    1.000000    0.019064    0.000055 

 POP f2 : -32.766392    -0.154433    -0.072624    1.000000    0.024289 

 POP f2 : 922.415913    -0.006625    1.488912    0.042962    1.000000 

 

(MICH and SRCL uses the same sensor, with optimised demodulation phase for each DoF.) 

Operation position offsets are:

PRCL   -3.9125e-11 m

SRCL    9.1250e-12 m

CARM  5.0000e-15 m  

and no position offsets for DARM and MICH (because they are differential sensor and not affected by RAM offsets).

 

Resulting matrix with RAM + RAM offsets, normalised by the original matrix:  

REFL f1 : 0.001663    -0.000000    0.003519    0.000005    -0.000003 

  AS f2 : 0.000004    0.514424    0.000004    -0.001676    -0.000001 

 POP f1 : 7.140984    -0.001205    15.051807    0.019254    0.000417 

 POP f2 : 0.029112    -0.319792    0.042583    1.000460    0.024298 

 POP f2 : -0.310318    -0.014385    -1.761519    0.043005    0.999819 

 

 

 

  6482   Tue Apr 3 15:50:58 2012 keikoUpdateLSCRAM simulation for Full ifo

Oops, Yesterday's results for DARM was wrong!

I got more convincing results now. 

 

> (B) Are pos-offsets degrade the CARM and DARM so much (See, the quoted result below), is that true? 

 

Here is the new results. It does change CARM a lot, but not DARM:
 
Matrix1 (normalised so that the diagonals are 1):
REFL f1 : 1.000000    0.000000    0.000008    -0.000005    0.000003 
  AS f2  : 0.000001    1.000000    0.000005    -0.003523    -0.000001 
 POP f1 : -3956.958708    -0.000183    1.000000    0.019064    0.000055 
 POP f2 : -32.766392    -0.154433    -0.072624    1.000000    0.024289 
 POP f2 : 922.415913    -0.006625    1.488912    0.042962    1.000000 
(=Matrix 2)
 
Position offsets:
only CARM, 4.6e-16 (this number changed because I increased the resolution of the calculation)
 
Matrix3 (normalised by matrix 1):
REFL f1 : 0.039780    -0.000000    0.003656    0.000005    -0.000003 
  AS f2  : 0.000008    1.000017    0.000005    -0.003499    -0.000001 
 POP f1 : 159.146819    -0.000138    15.605155    0.019393    0.000055 
 POP f2 : 1.277223    -0.154415    0.047344    1.000008    0.024289 
 POP f2 : -35.422498    -0.006633    -1.886454    0.042963    1.000000 

 

  • CARM got a small position offset which degrades CARM signal 2 orders of mag (still the biggest signal in the sensor, though).
  • DARM was not so bad, and probably the change of the DoF mixture is mostly not changed.
  • Matrices don't change only with 1e-4 RAM. It changes with position offsets.
  • I'll see how the matrix changes without position offsets but only with RAM effects, changing RAM levels.
  • Again, above is C1 configuration, 1e-4 RAM level of PM level.

 

 

Quote:

I add a flow-chart drawing what the scripts do and how the scripts calculate the LSC matrix.

flowchart.png

 

(1) First, you calculate the LSC matrix WITHOUT RAM or anything, just for a reference. This is the first matrix shown in the quoted post.

(2) The script calculates the LSC matrix with RAM. Also, the PDH signals for all 5 DoF are calculated. The PDH signals have offsets due to the RAM effect. The operating position offsets are saved for the next round.

(3) The script calculates the LSC matrix again, with RAM plus the offset of the operation points. The matrix is shown in the last part of the quoted post.

 

Now I am going to check (A) LSC matrices (matrix 2, the second matrix of above chart) with different RAM levels (B) Are pos-offsets degrade the CARM and DARM so much (See, the quated result below), is that true? 

 

  6483   Tue Apr 3 22:50:37 2012 keikoUpdateLSCRAM simulation for Full ifo

Koji and Jamie suggested me to include the coupling between DoFs when I calculate the last matrix. So far, I just add all the pos-offsets of 5 DoFs and re-calculate the matrix again. However, once I add one DoF pos-offset, it could already change the LSC matrix therefore different pos-offset to the other four DoF, we must iterate this process until we get the equilibrium pos-offsets for 5 DoFs.

I also noticed an error in the optical configuration file. AM mod levels were smaller than that supposed to be because of the hald power going through the AM-EOMs in the MZI paths. Also I have put PM-Mods in the MZT path which gives the smaller mod indexes. So, smaller mod levels were applied both for PM and AM. As PM-AM ratio is still kept in this, so the matrices were not very wrong, I assume. I'll modify that and post the results again.

  6486   Wed Apr 4 23:57:35 2012 keikoUpdateLSCRAM simulation for Full ifo

 I'm still wondering whether iteration version or simple version is closer approximation to the real situation. Sorry for few explanations here. I will try to present those on Friday.

 

Anyway, here is the results for both:

%*.*.*. Original matrix w/o RAM .*.*.*

REFL f1 : 1.000000        0.000000    -0.000003    -0.000005    0.000007 

  AS f2 : 0.000002        1.000000    0.000009    -0.003522    -0.000002 

 POP f1 : -3954.521443    -0.000965    1.000000    0.019081    -0.000152 

 POP f2 : -32.770726    -0.154433    -0.072594    1.000000    0.024284 

 POP f2 : 922.393978    -0.006608    1.488319    0.042948    1.000000 

 

*** Iteration *** 

%*.*.*. Resulting matrix w/ RAM .*.*.*

REFL f1 : 0.039125    -0.000000    0.003665       0.000005    -0.000007 

  AS f2 : 0.000010    1.000431    0.000009       -0.003500    -0.000002 

 POP f1 : 156.420221    -0.000246    15.586838    0.019406    -0.000154 

 POP f2 : 1.255806    -0.154275    0.047313       1.000008    0.024285 

 POP f2 : -34.814720    -0.006600    -1.884850    0.042950    1.000000 

Offsets converged to:

PRCL =  2.1e-15, MICH = 1.1e-17, SRCL = -3.8e-15, CARM = 2.2e-16, DARM = 0 

(POP CARMs became so much smaller compared with the other matrix below, because the offsets are added al of 5 DoFsl at once here.)

 

*** no iteration, offsets added for each DoF separately ***

REFL f1 : 0.020611        -0.000000    0.003600    0.000005    -0.000007 

AS f2   : 0.000002        1.000000    0.000009    -0.003522    -0.000002 

POP f1  : 1842.776419    -0.000198    21.533358    0.019404    -0.000132 

POP f2  : -32.700639    -0.153095    -0.072481    0.999995    0.024360 

 POP f2 : 922.393862    -0.006435    1.488298    0.042949    0.999982 

Added offsets:

PRCL =  7.5e-15, MICH = 6.25e-16, SRCL = -1.4e-14, CARM = 4.5e-16, DARM = 0

* So far, I used to add all the offsets at once. This time I add CARM and get the CARM row, add PRCL and get the PRCL row... and so on.

Quote:

Koji and Jamie suggested me to include the coupling between DoFs when I calculate the last matrix. So far, I just add all the pos-offsets of 5 DoFs and re-calculate the matrix again. However, once I add one DoF pos-offset, it could already change the LSC matrix therefore different pos-offset to the other four DoF, we must iterate this process until we get the equilibrium pos-offsets for 5 DoFs.

I also noticed an error in the optical configuration file. AM mod levels were smaller than that supposed to be because of the hald power going through the AM-EOMs in the MZI paths. Also I have put PM-Mods in the MZT path which gives the smaller mod indexes. So, smaller mod levels were applied both for PM and AM. As PM-AM ratio is still kept in this, so the matrices were not very wrong, I assume. I'll modify that and post the results again.

 

  6504   Sat Apr 7 00:31:12 2012 keikoUpdateLSCRAM simulation for Full ifo

I didn't understand how CARM can be decreased 2 orderes of magnitude and PRCL can be INCREASED by such small offsets (see the matrix quoted).

Apparently it was because of an optical-spring ish effect from the "detuning" (which is actually RAM position offsets). I put two plots which are CARM and PRCL tranfer functions to REFL f1 or POP f1, when there is a slight PRCL offset (0, 1e-14m, and 1e-15m cases are plotted). Looking at these plots, it was not a good idea to calculate the LSC matrix in DC because they are affected by this detuning a lot. I'll try f = 150 Hz for the matrix.

plot4a.pngplot4b.png

Quote:

*** Iteration *** 

%*.*.*. Resulting matrix w/ RAM .*.*.*

REFL f1 : 0.039125    -0.000000    0.003665       0.000005    -0.000007 

  AS f2 : 0.000010    1.000431    0.000009       -0.003500    -0.000002 

 POP f1 : 156.420221    -0.000246    15.586838    0.019406    -0.000154 

 POP f2 : 1.255806    -0.154275    0.047313       1.000008    0.024285 

 POP f2 : -34.814720    -0.006600    -1.884850    0.042950    1.000000 

Offsets converged to:

PRCL =  2.1e-15, MICH = 1.1e-17, SRCL = -3.8e-15, CARM = 2.2e-16, DARM = 0  

  2064   Wed Oct 7 11:18:40 2009 kiwamuSummaryElectronicsracks of electronics

 

I took the pictures of all racks of electronics yesterday, and then uploaded these pictures on the wiki.

http://lhocds.ligo-wa.caltech.edu:8000/40m/Electronics

You can see them by clicking "pictures" in the wiki page.

 

  2111   Sun Oct 18 22:05:40 2009 kiwamuUpdateLSCLSC timing issue

Today I made a measurement to research the LSC timitng issue as mentioned on Oct.16th.

*method

I put the triangular-wave into the OMC side (OMC-LSC_DRIVER_EXT) by AWG,

then looked at the transferred same signal at the LSC side (LSC_DARM_IN1) by using tdsdata.

I have compared these two signals in time domain to check whether they are the same or not.

In the ideal case it is expected that they are exactly the same.

 

*preliminary result

The measured data are shown in attached fig.1 and 2.

In the fig.1 it looks like they are the same signal.

However in fig.2 which is just magnified plot of fig.1, it shows a time-delay apparently between them.

The delay time is roughly ~50 micro sec.

The surprising is that the LSC signal is going beyond the OMC signal, although the OMC signal drives the LSC !!

We can say it is "negative delay"...

Anyway we can guess that the time stamp or something is wrong.

 

*next plan

Tomorrow I'm going to measure the transfer-function between them to see the delay more clearly.

( And I would like to fix the delay. )

  2114   Mon Oct 19 10:00:52 2009 kiwamuUpdateLSCRE: LSC timing issue

Of course I know there is a downconversion in OMC signal from 32k to 16k.

But I was just wondering if the delay comes from only downconversion.

And I can not find any significant noise in both signals because I use the triangular, which cause the higer harmonics and can hide the timing noise in frequency domain.

So I'm going to make the same measurement by using sinusoidal instead of triangular, then can see the noise in frequency domain.

 

Quote:

You yourself told me that tdsdata uses some downconversion from 32k to 16k!

So, how does the downconversion appears in the measurement?
How does the difference of the sampling rate appears in the measurement?
If you like to understand the delay, you have to dig into the downconversion
issue until you get the EXACT mechanism including the filter coefficients.

AND, is the transfer function the matter now?

As far as the LSC and OMC have some firm relationship, whichever this is phase delay or advance or any kind of filering,
this will not introduce any noise. If so, this is just OK.

In my understanding, the additional noise caused by the clock jitter is the essential problem.
So, did you observe any noise from the data?

Quote:

*preliminary result

The measured data are shown in attached fig.1 and 2.

In the fig.1 it looks like they are the same signal.

However in fig.2 which is just magnified plot of fig.1, it shows a time-delay apparently between them.

The delay time is roughly ~50 micro sec.

The surprising is that the LSC signal is going beyond the OMC signal, although the OMC signal drives the LSC !!

We can say it is "negative delay"...

Anyway we can guess that the time stamp or something is wrong.

 

*next plan

Tomorrow I'm going to measure the transfer-function between them to see the delay more clearly.

( And I would like to fix the delay. )

 

 

  2122   Mon Oct 19 23:14:32 2009 kiwamuUpdateLSCLSC timing issue

I measured the noise spectrum of LSC_DARM_IN1 and OMC-LSC_DRIVE_EXC by using DTT,

while injecting the sin-wave into the OMC-LSC_DRIVE by AWG.

The attached are the results.

No significant differences appears between OMC and LSC in this measurement.

It means, in this measurement we can not figure out any timing noise which might be in LSC-clock.

In addition there are the noise floor, whose level does not change in each 3-figures. The level is about ~4*10^{-8} count/sqrt[Hz]

(The source of the noise floor is still under research.)

  2145   Mon Oct 26 18:49:18 2009 kiwamuUpdateLSCOMC-LSC timing issue

According to my measurements I conclude that LSC-signal is retarded from OMC-signal with the constant retarded time of 92usec.
It means there are no timing jitter between them. Only a constant time-delay exists.

(Timing jitter)
Let's begin with basics.
If you measure the same signal at OMC-side and LSC-side, they can have some time delay between them. It can be described as followers.

exp1.png
where tau_0 is the time delay. If the tau_0 is not constant, it causes a noise of the timing jitter.

(method)
I have injected the sine-wave with 200.03Hz into the OMC-LSC_DRIVE_EXC. Then by using get_data, I measured the signal at 'OMC-LSC_DRIVE_OUT' and 'LSC-DARM_ERR' where the exciting signal comes out.
In the ideal case the two signals are completely identical.
In order to find the delay, I calculated the difference in these signals based on the method described by Waldman. The method uses the following expression.
exp2.png
Here the tau_s is the artificial delay, which can be adjusted in the off line data.
By shifting tau_s we can easily find the minimal point of the RMS, and at this point we can get tau_0=tau_s.
This is the principle of the method to measure the delay.  In my measurement I put T=1sec. and make the calculation every 1sec. in 1 min.


(results)
Attachment is the obtained results. The above shows the minimum RMS sampled every 1sec. and the below shows the delay in terms of number of shifts.
1 shift corresponds to Ts (=1/32kHz).  All of the data are matched with 3 times shift, and all of the minimum RMS are completely zero.
Therefore I can conclude that LSC-signal is retarded from OMC-signal with constant retarded times of 3*Ts exactly, and no timing jitter has been found.
 

  2146   Mon Oct 26 19:12:50 2009 kiwamuUpdateLSCdiagnostic script for LSC timing

The diagnostic script I've written is available in the 'caltech/users/kiwamu/work/20091026_OMC-LSC-diag/src'.

To run the script, you can just execute 'run_OMC_LSC.sh' or just call the m-file ' OMC_LSC_timinig.m'  from matlab.

 

NOTES:

The script destructs the lock of DARM and OMC, be careful if you are working with IFO.

  2153   Tue Oct 27 19:37:03 2009 kiwamuUpdateLSCcron job to diagnose LSC-timing

I set a cron job on allegra.martian to run the diagnostic script every weekend.

I think this routine can be helpful to know how the trend of timing-shift goes

The cron runs the script on every Sunday 5:01AM and diagnostics will take about 5 min.

 

! Important:

During the running of the script, OMC and DARM can not be locked.

If you want to lock OMC and DARM in the early morning of weekend, just log in allegra and then comment out the command by using 'crontab -e'

 

 

  2167   Mon Nov 2 10:56:09 2009 kiwamuUpdateLSCcron job works succesfully & no timing jitter

As I wrote on Oct.27th, the cron job works every Sunday.

I found it worked well on the last Sunday (Nov.1st).

And I can not find any timing jitter in the data, its delay still stay 3*Ts.

  2169   Mon Nov 2 13:34:36 2009 kiwamuConfigurationPSLremoved multiply resonant EOM

I removed the multiply resonant EOM that has been set by a SURF student from PSL table.

I will use it for checking the resonant circuit.

  2179   Thu Nov 5 12:34:26 2009 kiwamuUpdateComputerselog rebooted

I found elog got crashed. I rebooted the elog daemon just 10minutes before.

  2244   Wed Nov 11 20:57:06 2009 kiwamuUpdateElectronicsMulti-resonant EOM --- LC tank circuit ---

I have been working about multi-resonant EOM since last week.

In order to characterize the behavior of the each components, I have made a simple LC tank circuit.

You can see the picture of the circuit below.

DSCN0160.JPG

Before constructing the circuit, I made an "ideal" calculation of the transfer function without any assumptions by my hand and pen.

Most difficult part in the calculation is the dealing with a transformer analytically. Eventually I found how to deal with it in the analytical calculation.

The comparison of the calculated and measured transfer function is attached.

 It shows the resonant frequency of ~50MHz as I expected. Those are nicely matched below 50MHz !!

For the next step, I will make the model of the circuit with stray capacitors, lead inductors, ... by changing the inductance or something. 

 

  2262   Fri Nov 13 03:38:47 2009 kiwamuUpdateElectronicsmulti-resonant EOM --- impedance of LC tank circuit ----

I have measured the impedance of the LC tank circuit which I referred on my last entry.

The configuration of the circuit is exactly the same as that time.

In order to observe the impedance, by using Koji's technique I injected a RF signal into the output of the resonant circuit.

In addition I left the input opened, therefore the measured impedance does not include the effect of the transformer.

 

- - - - - - - - - - - - results

The measured impedance is attached below; "LCtank_impedance.png"

The peak around 50MHz is the main resonance and it has impedance of ~1500 [Ohm], which should go to infinity in the ideal case (no losses).

In fact the impedance looked from the input of the circuit gets reduced by 1/n^2, where "n" is the turn ratio of the transformer.

By putting the n=4, the input impedance of the circuit should be 93 [Ohm]. This is a moderate value we can easily perform impedance-matching by some technique.

I also fitted the data with a standard model of equivalent circuit (see attachment 2).

In the figure.2 red component and red letter represents the design. All the other black stuff are parasites.

But right now I have no idea the fitted value is reasonable or not.

For the next I should check the input impedance again by the direct way; putting the signal into the input.

 

 

 

  2263   Fri Nov 13 05:03:09 2009 kiwamuUpdateElectronicsmulti-resonant EOM --- input impedance of LC tank ----

I measured the input impedance of the LC tank circuit with the transformer. The result is attached.

It looks interesting because the input impedance is almost dominated

by the primary coil of the transformer with inductance of 75nH (see attachment 1).

The impedance at the resonance is ~100 [Ohm], I think this number is quite reasonable because I expected that as 93 [Ohm]

 

Note that the input impedance can be derived as follower;

(input impedance) = L1 + Z/n^2.

Where L1 is the inductance of the primary coil, Z is the load in the secondary loop and n is the turn ratio.

 

I think now I am getting ready to enter the next phase \(^o^)/

  2277   Mon Nov 16 17:35:59 2009 kiwamuUpdateLSCOMC-LSC timing get synchronized !

An interesting thing was happened in the OMC-LSC timing clock.

Right now the clock of the OMC and the LSC are completely synchronized.

 The trend data is shown below. At the first two measurements (Oct.27 and Nov.1),  LSC had constant retarded time of 3Ts (~92usec.).

The last measurement, on Nov.15, number of shifts goes to zero, this means there are no retarded time.

Also the variance between the two signal gets zero, so I conclude the OMC and the LSC are now completely synchronized.

The measurement on Nov.8 is somehow meaningless, I guess the measurement did not run correctly by an influence from megatron(?)

 

OMC-LSC.png

 

  2292   Wed Nov 18 14:55:59 2009 kiwamuUpdateElectronicsmulti-resonant EOM --- circuit design ----

The circuit design of multi-resonant EOM have proceeded.

By using numerical method, I found the some best choice of the parameters (capacitors and inductors).

In fact there are 6 parameters (Lp, L1, L2, Cp, C1, C2) in the circuit to be determined.

whole_circuit.png

In general the less parameter gives the less calculation time with performing the numerical analysis. Of course it looks 6 parameters are little bit large number.

In order to reduce the arbitrary parameters, I put 4 boundary conditions.

Each boundary conditions fixed resonant peaks and valleys; first peak=11MHz, third peak=55MHz, first valley=19MHz, second valley=44MHz.

designed.png

So now the remaining arbitrary parameters successfully get reduced to 2. Only we have to do is optimize the second peak as it to be 29.5MHz.

Then I take C1 and C2 as free parameters seeing how the second peak agree with 29.5MHz by changing the value of the C1 and C2.

mont.png

the red color represents the good agreement with 29.5MHz, in contrast blue contour represents the bad.

 You can see some best choice along the yellow belt. Now what we should do is to examine some of that and to select one of those.

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