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ID Date Author Type Category Subject
13924   Thu Jun 7 10:26:36 2018 keerthanaUpdatePSLobserving the resonance signal corresponding to the injected frequency.

(Johannes, Koji, Keerthana)

The PLL loop ensures that the frequency difference between the PSL laser and the AUX laser is equal to the frequency we provide to the Local Oscillator (LO) with the help of a Marconi. Only a small pick off part of both the AUX and PSL lasers are going to the PLL loop. The other part of both the lasers are going to the interferometer. Before entering into the optical fibre, the AUX laser passes through an AOM which changes its frequency by an amount of 80MHz. When the PLL is locked, the frequency coming out of the PLL will be equal to the frequency set up in the Marconi (fm). When it passes through AOM, the frequency becomes fdiff = fm ±80 MHz. If this frequency beam and the PSL laser beam is aligned properly, and if this frequency is equal to the product of an integer and the free spectral range of the cavity, this will resonate in the cavity.  Then we expect to get a peak in the ETM transmission spectrum corresponding to the frequency we injected through the optical Fibre.

Through out the experiment we need to make sure that the PSL is locked. Thus, the signal detected by the photo detector when only PSL is resonating inside the cavity, act as a DC signal. Then we give a narrow scan to the Marconi. When fdiff = N*FSRy this condition is satisfied, we will observe a peak in the output. Here FSRy  is the free spectral range of the cavity which is approximately equal to 3.893 MHz.

Yesterday afternoon, Johannes, Koji and myself tried to observe this peak. We aligned the cavity by observing the output signal from the AS100 photo detector. We made the alignment in such a way that the intensity output getting from this photo detector is maximum. We used a Spectrum analyser to see the output. After that we connected a photo detector to collect the YEND transmission signal from the ETM mirror. We used a lens to focus this directly to the photodetector. Then we connected this photodetector to the spectrum analyser, which was located near the AS table. We took a large cable to meet this purpose. But still the cable was not lengthy enough, so we joined it with another cable and finally connected it with the spectrum analyser. Then we gave a scan to the Marconi from 51 MHZ to 55 MHz. We repeated this experiment with a scan of 55 MHz to 59 MHz also. We repeated this a few times, but we were not able to see the peak.

We assume that this can be because of some issue with the alignment or it can be because of some issue with the photo detector we used. We would like to repeat this experiment and get the signal properly.

I am attaching a flow chart of the setup and also a picture of the mirrors and photo detector we inserted in the Y-End table.

Attachment 1: photodetector_alignment.jpg
Attachment 2: design1.PNG
13926   Thu Jun 7 14:35:26 2018 keerthanaUpdateelogTable- useful for doing the scanning.

I think this table will help us to fix the scanning range of the Marconi frequency. This will also help in predicting the position of the resonance peak corresponding to the injected frequency.

fdiff = fm ±80 MHz ;                     fdiff = N*FSRy ;              FSRy = 3.893 MHz.

 N = Integer number fdiff =injected fm = Marconi frequency 1 3.893 76.107 2 7.786 72.214 3 11.679 68.321 4 15.572 64.428 5 19.465 60.535 6 23.34 56.66 7 27.251 52.749 8 31.144 48.856 9 35.037 44.963 10 38.93 41.07 11 42.79 37.21 12 46.716 33.284 13 50.609 29.391
13939   Mon Jun 11 13:55:33 2018 keerthanaUpdateGeneralProject Updates

As of now, I have made the codes needed to sweep the marconi frequency for taking the cavity scan data, the photo diode at the y-end is conected to the spectrum analyser already and I also have the finesse simulation of the Ideal Fabry-perot cavity. By seeing my last elog entry, Gautam suggested me that I need to take a different approach for estimating the FSR and TMS value from the Finesse graph. That is, by using least square fit models. Now I am trying to do that and get a better estimate of the error values. Based on my understanding I am dividing this project into various tasks.

1. Getting a better estimate of the error value by using least square fits. Also plotting a graph of frequency Vs mode number and finding the value of Free Spectral Range from its slop.

2. Inserting zernike polynomials to the Finesse simulation and with the help of least square fit, plotting the graph of frequency Vs mode number. Understanding the shifts from the Ideal graph we obtained from step 1. Using this data, plotting the phase map corresponding to this.

3. Repeating step 2 by taking different zernike polynomials and creating a data base which will be useful for the analysis of the real data. This will also prepare me to do the fitting models easily.

4. Collecting data from the IFO and applying these fitting models to it. Finding the set of zernike polynomials which are similar to the actual fugure error of the mirror. Plotting the Phase map corresponding to those zernike polynomials.

If you feel that there is some mistake in the steps, please correct me. It will be really helpful!

13943   Mon Jun 11 19:16:49 2018 keerthanaUpdateelogComparison of the analytical and finesse values of TMS and FSR.

The percentage error which I found out =[(analytical value - finesse value)/analytical value]*100

But inorder to find the finesse value, I just used curser to get the central frequency of each peak and by substracting one from the other I found TMS and FSR.

The resolution was 6500 Hz. Thus, it seems that this method is not actually reliable. I am trying to find the central frequency of each mode with the help of lorentzian fits. I am attaching a fit which I did today. I have plotted its residual graph also.

I am uploading 4 python scripts to the github.

1. Analytical Solution

2. Finesse model- cavity scan

3. Finesse model- fitting

4. Finesse model- residual

 Quote: Hmm? What is the definition of the percentage error? I don't obtain these numbers from the given values. And how was the finesse value obtained from the simulation result? Then what is the frequency resolution used in Finesse simulation?

fitting_1.pdf

Attachment 1: fitting_1.pdf
13945   Mon Jun 11 22:18:18 2018 keerthanaUpdateelogComparison of the analytical and finesse values of TMS and FSR.

Oopss !! I made a mistake while taking the values from my notes. Sorry.

 Quote: > The percentage error which I found out =[(analytical value - finesse value)/analytical value]*100 Yes, I this does not give us 0.70% (3.893408 - 3.8863685)/3.893408 *100 = 0.18% But any way, go for the fitting.

13954   Wed Jun 13 11:59:03 2018 keerthanaUpdateelogcommand line enabled code for frequency scanning

I have modified the code for frequency scanning and have made it completely command line enabled. The code is written in python. It is saved in the name "frequency_scanning_argparse.py". I have uploaded it to the Mode-Spectroscopy Github repository.

Inorder to use this code there are two ways.

1. We can mention the ' frequency' on which marconi need to work. Then it will change the marconi frequency to that perticular value.

eg: Type in the terminal as follows for changing the marconi frequency to 59 Mhz.

python frequency_scanning_argparse.py 59e6

2. Inorder to give a scan to the marconi frequency, provide the 'start frequency', 'end frequency' and the 'number of points' in between. This will be more conveniant when we want to run the scan in different ranges.

eg: Type in the terminal as follows for a start frequency of 59 Mhz, end frequency of 62MHz and number of points in between equal to 1000.

python frequency_scanning_argparse.py 59e6 62e6 1000

In both cases the code will show you the frequency of the marconi before we run this code and it will change the marconi frequency to the desired frequency.

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.
Attachment 1: finesse1.pdf
Attachment 2: finesse2.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.

Attachment 1: AS110_Beat.pdf
Attachment 2: YEND_Beat.pdf
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.

Attachment 1: TRANS.pdf
Attachment 2: REFL.pdf
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.

Attachment 1: PLL-single_demodulation.pdf
Attachment 2: PLL-double_demodulation.pdf
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.

Attachment 1: finesse_cavity.png
Attachment 2: Analytical1.pdf
Attachment 3: Finesse_Analytical.pdf
Attachment 4: Difference.pdf
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.

Attachment 1: finesse1.pdf
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.

Attachment 1: setup1.jpg
Attachment 2: setup2.jpg
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

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.

keiko, kiwamu, Rana

Attachment 1: Mar6sus1
Attachment 2: Mar6sus2
Attachment 3: Mar6sus3
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.

Attachment 1: Mar5-MICHbudget.png
6380   Wed Mar 7 20:53:13 2012 keikoUpdateLSCMICH noise budget on 5 Mar

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

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?

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: https://wiki-40m.ligo.caltech.edu/Interferometer_Characterization/Michelson_Noise_Budget Some careful analysis of the OSA signals are missing Besides the analysis we need to work on the mode matching to get a better resolution as Mirko achieved. 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

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

Attachment 1: Mar14pollution.png
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.

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)  (2)

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.

Attachment 1: text9149.png
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).

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.

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).

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

Attachment 1: expsche.png
Attachment 3: mmtdrawing.png
Attachment 4: drawing.png
Attachment 5: drawing.png
Attachment 8: drawing.png
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.

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.

 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.

(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.   (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

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.

 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. )

Attachment 1: rough.png
Attachment 2: detail.png
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.)

Attachment 1: SPE20Hz.png
Attachment 2: SPE200Hz.png
Attachment 3: SPE2kHz.png
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.

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.

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.

Attachment 3: OMC_LSC60sec.png
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.

### 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.

ELOG V3.1.3-