ID |
Date |
Author |
Type |
Category |
Subject |
14529
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Wed Apr 10 00:33:09 2019 |
Anjali | Update | Frequency noise measurement | Frequency noise measurement of 1 micron source |
- Attachement #1 shows the input (ch4-green) modulation frequency and the photodiode output (ch1-yellow) when the modulation frequency is about 100 Hz
- Attachement #2 shows the input (ch4-green) modulation frequency and the photodiode output (ch1-yellow) when the modulation frequency is about 30 Hz
- The output frequency is varying in accordance with variation in modulation frequency. It is observed that, for a given modulation frequency also, the output frequency is fluctuating. There could be multiple reasons for this behaviour. One of the main reasons is the frequency noise of the laser itself. Also, there could be acoustic noise coupled to the system (eg, by change in length of the fiber).
- The experimental setup is then modified as shown in attachment #3. The thick beam spliiter is replaced with a thinner one. The mount is also changed such that the transmitted beam can be now coupled to an other photodiode (earlier the transmitted light was blocked by the mount). One more photodiode (PDA55) is introduced .So now the two photodiodes in the setup are PDA520 and PDA 55.
- We then applied frequency modulation on the input laser and observed the output of the two photodiodes. But we didn't get the results as we expected and observed earlier (shown in attachment #1 &2). Looks like, the problem is poor mode matching between the two beams.
Quote: |
- The alignment of the output beam from the delayed path of MZI to the photodetector was disturbed when we did the polarisation characterisation yesterday. So, today we tried to align the output beam from the delayed path of MZI to the detector .
- We then observed the beat output from the detector on oscilloscope.We initialy observed a dc shift . We then applied a frequency modulation on the input laser and observed the output on oscilloscope. We expected to see variation in output frequency in accordance with variation of input frequency modulation. But we didnt observe this and we were not really getting the interference pattern.
- We tried to make the alignment better. With a better alignment, we could see the interference pattern. We also observed that the output frequency was varying in accordance with variation in the input frequency modulation. We would expect a better result with proper mode matching of the two beams on the photodetector.
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Attachment 1: Modulation_frequency_100Hz.jpg
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Attachment 2: Modulation_frequency_30Hz.jpg
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Attachment 3: Modified_setup.JPG
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14540
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Fri Apr 12 01:22:27 2019 |
Anjali | Update | Frequency noise measurement | Frequency noise measurement of 1 micron source |
The alignement was disturbed after the replcement of the beam splitter. We tried to get the alignment back . But we are not succeeded yet in getting good interfernce pattern. This is mainly because of poor mode matching of two beams. We will also try with the spooled fiber.
Quote: |
- The experimental setup is then modified as shown in attachment #3. The thick beam spliiter is replaced with a thinner one. The mount is also changed such that the transmitted beam can be now coupled to an other photodiode (earlier the transmitted light was blocked by the mount). One more photodiode (PDA55) is introduced .So now the two photodiodes in the setup are PDA520 and PDA 55.
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14544
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Mon Apr 15 22:39:10 2019 |
gautam | Update | Frequency noise measurement | Alternate setup with PSL pickoff |
[anjali, gautam]
just main points, anajli is going to fill out the details.
To rule out mode-matching as the reason for non-ideal output from the MZ, I suggested using the setup I have on the NW side of the PSL enclosure for the measurement. This uses two identical fiber collimators, and the distance between collimator and recombination BS is approximately the same, so the spatial modes should be pretty well matched.
The spooled fiber we found was not suitable for use as it had a wide key connector and I couldn't find any wide-key FC/PC to narrow-key FC/APC adaptors. So we decided to give the fiber going to the Y end and back (~90m estimated length) a shot. We connected the two fibers at the EY table using a fiber mating sleeve (so the fiber usually bringing the IR pickoff from EY to the PSL table was disconnected from its collimator).
In summary, we cannot explain why the contrast of the MZ is <5%. Spatial mode-overlap is definitely not to blame. Power asymmetry in the two arms of the MZ is one possible explanation, could also be unstable polarization, even though we think the entire fiber chain is PM. Anjali is investigating.
We saw today that the Thorlabs PM beam splitters (borrowed from Andrew until our AFW components arrive) do not treat the two special axes (fast and slow) of the fiber on equal footing. When we coupled light into the fast axis, we saw huge asymmetry between the two split arms of the beamsplitter (3:1 ratio in power instead of the expected 1:1 for a 50/50 BS). Looking at the patch cord with an IR viewer, we also saw light leaking through the core along it. Turns out this part is meant to be used with light coupled to the slow axis only. |
14547
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Wed Apr 17 00:43:38 2019 |
gautam | Update | Frequency noise measurement | MZ interferometer ---> DAQ |
- Delay fiber was replaced with 5m (~30 nsec delay)
- The fringing of the MZ was way too large even with the free running NPRO (~3 fringes / sec)
- Since the V/Hz is proportional to the delay, I borrowed a 5m patch cable from Andrew/ATF lab, wrapped it around a spool, and hooked it up to the setup
- Much more satisfactory fringing rate (~1 wrap every 20 sec) was observed with no control to the NPRO
- MZ readout PDs hooked up to ALS channels
- To facilitate further quantitative study, I hooked up the two PDs monitoring the two ports of the MZ to the channels normally used for ALS X.
- ZHL3-A amps inputs were disconnected and were turned off. Then cables to their outputs were highjacked to pipe the DC PD signals to the 1Y3 rack
- Unfortunately there isn't a DQ-ed fast version of this data (would require a model restart of c1lsc which can be tricky), but we can already infer the low freq fringing rate from overnight EPICS data and also use short segments of 16k data downloaded "live" for the frequency noise measurement.
- Channels are C1:ALS-BEATX_FINE_I_IN1 and C1:ALS-BEATX_FINE_Q_IN1 for 16k data, and C1:ALS-BEATX_FINE_I_INMON and C1:ALS-BEATX_FINE_I_INMON for 16 Hz.
At some point I'd like to reclaim this setup for ALS, but meantime, Anjali can work on characterization/noise budgeting. Since we have some CDS signals, we can even think of temperature control of the NPRO using pythonPID to keep the fringe in the linear regime for an extended period of time. |
14571
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Thu Apr 25 03:32:25 2019 |
Anjali | Update | Frequency noise measurement | MZ interferometer ---> DAQ |
- Attachment #1 shows the time domain output from this measurement. The contrast between the maximum and minimum is better in this case compared to the previous trials.
- We also tried to extract the frequency noise of the laser from this measurement. Attachment #2 shows the frequency noise spectrum. The experimental result is compared with the theoretical value of frequency noise. Above 10 Hz, the trend is comparable to the expected 1/f characteristics, but there are other peak also appearing. Similarly, below 10 Hz, the experimentally observed value is higher compared to the theory.
- One of the uncertainties in this result is because of the length fluctuation of the fiber. The phase fluctuation in the system could be either because of the frequency noise of the laser or because of the length fluctuation of the fiber. So,one of the reasons for the discrepancy between the experimental result and theory could be because of fiber length fluctuation. Also, there were no locking method been applied to operate the MZI in the linear range.
- The next step would be to do a heterodyne measurement. Attachment #3 shows the schematic for the heterodyne measurement. A free space AOM can be inserted in one of the arms to do the frequency shift. At the output of photodiode, a RF heterodyne method as shown in attachment #3 can be applied to separate the inphase and quadrature component. These components need to be saved with a deep memory system. Then the phase and thus the frequency noise can be extracted.
- Attachment #4 shows the noise budget prepared for the heterodyne setup. The length of the fiber considered is 60 m and the photodiode is PDA255. I also have to add the frequency noise of the RF driver and the intensity noise of the laser in the noise budget.
Quote: |
- Delay fiber was replaced with 5m (~30 nsec delay)
- The fringing of the MZ was way too large even with the free running NPRO (~3 fringes / sec)
- Since the V/Hz is proportional to the delay, I borrowed a 5m patch cable from Andrew/ATF lab, wrapped it around a spool, and hooked it up to the setup
- Much more satisfactory fringing rate (~1 wrap every 20 sec) was observed with no control to the NPRO
- MZ readout PDs hooked up to ALS channels
- To facilitate further quantitative study, I hooked up the two PDs monitoring the two ports of the MZ to the channels normally used for ALS X.
- ZHL3-A amps inputs were disconnected and were turned off. Then cables to their outputs were highjacked to pipe the DC PD signals to the 1Y3 rack
- Unfortunately there isn't a DQ-ed fast version of this data (would require a model restart of c1lsc which can be tricky), but we can already infer the low freq fringing rate from overnight EPICS data and also use short segments of 16k data downloaded "live" for the frequency noise measurement.
- Channels are C1:ALS-BEATX_FINE_I_IN1 and C1:ALS-BEATX_FINE_Q_IN1 for 16k data, and C1:ALS-BEATX_FINE_I_INMON and C1:ALS-BEATX_FINE_I_INMON for 16 Hz.
At some point I'd like to reclaim this setup for ALS, but meantime, Anjali can work on characterization/noise budgeting. Since we have some CDS signals, we can even think of temperature control of the NPRO using pythonPID to keep the fringe in the linear regime for an extended period of time.
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Attachment 1: Time_domain_output.pdf
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Attachment 2: Frequency_noise.pdf
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Attachment 3: schematic_heterodyne_setup.png
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Attachment 4: Noise_budget_1_micron_in_Hz_per_rtHz.pdf
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14573
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Thu Apr 25 10:25:19 2019 |
gautam | Update | Frequency noise measurement | Homodyne v Heterodyne |
If I understand correctly, the Mach-Zehnder readout port power is only a function of the differential phase accumulated between the two interfering light beams. In the homodyne setup, this phase difference can come about because of either fiber length change OR laser frequency change. We cannot directly separate the two effects. Can you help me understand what advantage, if any, the heterodyne setup offers in this regard? Or is the point of going to heterodyne mainly for the feedback control, as there is presumably some easy way to combine the I and Q outputs of the heterodyne measurement to always produce an error signal that is a linear function of the differential phase, as opposed to the sin^2 in the free-running homodyne setup? What is the scheme for doing this operation in a high bandwidth way (i.e. what is supposed to happen to the demodulated outputs in Attachment #3 of your elog)? What is the advantage of the heterodyne scheme over applying temperature feedback to the NPRO with 0.5 Hz tracking bandwidth so that we always stay in the linear regime of the homodyne readout?
Also, what is the functional form of the curve labelled "Theory" in Attachment #2? How did you convert from voltage units in Attachment #1 to frequency units in Attachment #2? Does it make sense that you're apparently measuring laser frequency noise above 10 Hz? i.e. where do the "Dark Current Noise" and "Shot Noise" traces for the experiment lie relative to the blue curve in Attachment #2? Can you point to where the data is stored, and also add a photo of the setup? |
14576
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Thu Apr 25 15:47:54 2019 |
Anjali | Update | Frequency noise measurement | Homodyne v Heterodyne |
My understanding is that the main advantage in going to the heterodyne scheme is that we can extract the frequecy noise information without worrying about locking to the linear region of MZI. Arctan of the ratio of the inphase and quadrature component will give us phase as a function of time, with a frequency offset. We need to to correct for this frequency offset. Then the frequency noise can be deduced. But still the frequency noise value extracted would have the contribution from both the frequency noise of the laser as well as from fiber length fluctuation. I have not understood the method of giving temperature feedback to the NPRO.I would like to discuss the same.
The functional form used for the curve labeled as theory is 5x104/f. The power spectral density (V2/Hz) of the the data in attachment #1 is found using the pwelch function in Matlab and square root of the same gives y axis in V/rtHz. From the experimental data, we get the value of Vmax and Vmin. To ride from Vmax to Vmin , the corrsponding phase change is pi. From this information, V/rad can be calculated. This value is then multiplied with 2*pi*time dealy to get the quantity in V/Hz. Dividing V/rtHz value with V/Hz value gives y axis in Hz/rtHz. The calculated value of shot noise and dark current noise are way below (of the order of 10-4 Hz/rtHz) in this frequency range.
I forgor to take the picture of the setup at that time. Now Andrew has taken the fiber beam splitter back for his experiment. Attachment #1 shows the current view of the setup. The data from the previous trial is saved in /users/anjali/MZ/MZdata_20190417.hdf5
Quote: |
If I understand correctly, the Mach-Zehnder readout port power is only a function of the differential phase accumulated between the two interfering light beams. In the homodyne setup, this phase difference can come about because of either fiber length change OR laser frequency change. We cannot directly separate the two effects. Can you help me understand what advantage, if any, the heterodyne setup offers in this regard? Or is the point of going to heterodyne mainly for the feedback control, as there is presumably some easy way to combine the I and Q outputs of the heterodyne measurement to always produce an error signal that is a linear function of the differential phase, as opposed to the sin^2 in the free-running homodyne setup? What is the scheme for doing this operation in a high bandwidth way (i.e. what is supposed to happen to the demodulated outputs in Attachment #3 of your elog)? What is the advantage of the heterodyne scheme over applying temperature feedback to the NPRO with 0.5 Hz tracking bandwidth so that we always stay in the linear regime of the homodyne readout?
Also, what is the functional form of the curve labelled "Theory" in Attachment #2? How did you convert from voltage units in Attachment #1 to frequency units in Attachment #2? Does it make sense that you're apparently measuring laser frequency noise above 10 Hz? i.e. where do the "Dark Current Noise" and "Shot Noise" traces for the experiment lie relative to the blue curve in Attachment #2? Can you point to where the data is stored, and also add a photo of the setup?
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Attachment 1: Experimental_setup.JPG
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14579
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Fri Apr 26 12:10:08 2019 |
Anjali | Update | Frequency noise measurement | Frequency noise measurement of 1 micron source |
From the earlier results with homodyne measurement,the Vmax and Vmin values observed were comparable with the expected results . So in the time interval between these two points, the MZI is assumed to be in the linear region and I tried to find the frequency noise based on data available in this region.This results is not significantly different from that we got before when we took the complete time series to calculate the frequency noise. Attachment #1 shows the time domain data considered and attachment #2 shows the frequecy noise extracted from that.
As discussed, we will be trying the heterodyne method next. Initialy, we will be trying to save the data with two channel ADC with 16 kHz sampling rate. With this setup, we can get the information only upto 8 kHz. |
Attachment 1: Time_domain_data.pdf
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Attachment 2: Frequency_noise_from_data_in_linear_region.pdf
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14586
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Tue Apr 30 17:27:35 2019 |
Anjali | Update | Frequency noise measurement | Frequency noise measurement of 1 micron source |
We repeated the homodyne measurement to check whether we are measuring the actual frequency noise of the laser. The idea was to repeat the experiment when the laser is not locked and when the laser is locked to IMC.The frequency noise of the laser is expected to be reduced at higher frequency (the expected value is about 0.1 Hz/rtHz at 100 Hz ) when it is locked to IMC . In this measurement, the fiber beam splitter used is Non PM. Following are the observations
1. Time domain output_laser unlocked.pdf : Time domain output when the laser is not locked. The frequency noise is estimated from data corresponds to the linear regime. Following time intervals are considered to calculate the frequency noise (a) 104-116 s (b) 164-167 s (c) 285-289 s
2. Frequency_noise_laser_unlocked.pdf: Frequency noise when the laser is not locked. The model used has the functional form of 5x104/f as we did before. Compared to our previous results, the closeness of the experimental results to the model is less from this measurement. In both the cases, we have the uncertainty because of the fiber length fluctuation. Moreover, this measurement could have effect of polarisation fluctuation as well.
3.Time domain output_laser locked.pdf :Time domain output when the laser is locked. Following time intervals are considered to calculate the frequency noise (a) 70-73 s (b) 142-145 s (c) 266-269 s.
4. Frequency_noise_laser_locked.pdf : Frequency noise when the laser is locked
5. Frequency noise_comparison.pdf : Comparison of frequency noise in two cases. The two values are not significantly different above 10 Hz. We would expect reduction in frequency noise at higher frequency once the laser is locked to IMC. But this result may indicate that we are not really measuring the actual frequency noise of the laser. |
Attachment 1: Homodyne_repeated_measurement.zip
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1
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Wed Oct 17 18:46:33 2007 |
rana | Configuration | General | eLog Change |
This is the first entry in the new 40m eLog.
Its GWs or bust now! 
[Hnull][/Hnull] |
3
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Thu Oct 18 15:03:14 2007 |
ajw | Routine | General | this is only a test |

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7
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Mon Oct 22 12:02:59 2007 |
ajw | Routine | General | STACIS as microseismic shaker |
In case we ever want to use our Stacis systems as shakers, check this:
link |
10
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Tue Oct 23 11:08:20 2007 |
steve | Other | General | brush fires |
There are big brush fires around LA
40 days plot show no effect in the 40m lab |
Attachment 1: brushfires.jpg
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11
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Wed Oct 24 01:43:32 2007 |
Andrey Rodionov | Other | General | PDF-file -> Will report about first results for XARM during Wednesday meeting |
Here is the pdf-file with some graphs showing first results for XARM optimization.
We will discuss alltogether during our Wednesday meeting which starts at 2.40PM. Probably it would be necessary to project this pdf-file to the big screen,
so someone should bring laptop and probably connect it to the projector. I do not have a laptop.
See you on that meeting. |
Attachment 1: Andrey_October_24.pdf
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41
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Wed Oct 31 19:26:08 2007 |
Andrey Rodionov | Routine | General | Photographs of "Mode-Cleaner Entrance" |
Here are the pictures of "inside the chamber". |
Attachment 1: MC-Pictures-1.pdf
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Attachment 2: MC-Pictures-2.pdf
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Attachment 3: MC-Pictures-3.pdf
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Attachment 4: MC-Pictures-4.pdf
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Attachment 5: MC-Pictures-5.pdf
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Attachment 6: MC-Pictures-6.pdf
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Attachment 7: MC-Pictures-7.pdf
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Attachment 8: MC-Pictures-8.pdf
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Attachment 9: MC-Pictures-9.pdf
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48
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Thu Nov 1 16:51:33 2007 |
d40 | AoG | General | D40 |
If you vant see D40 againn, you leave one plate goulash by N2 tank in morning.
Vit the good paprikash this time!!! |
Attachment 1: PB010001.JPG
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94
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Mon Nov 12 14:09:19 2007 |
rob | DAQ | General | tpman dead on fb40m |
The testpoint manager was dead on fb40m. I know I re-started it sometime after the power outage, so something must have killed it. If you get an error from DTT like
"diagnostic kernel does not support: testpoints", then log into fb40m as root, check for the tpman with a ps -ef | grep tpman. If it's not there, then run /usr/controls/tpman & and close the terminal window. |
150
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Fri Nov 30 20:13:57 2007 |
dmass | Summary | General | HeNe UniPhase Laser |
Data for the Uniphase 1.9 mW HeNe laser (labeled: "051507 From ISCT-BS") SN: 1284131 Model: 1103P
I used the Photon Beamscanner to obtain all data, then fit w(z) as shown on the plot with parameters w_0, z_R, and hidden parameter delta,
where z = delta + x, z is waist distance, x is distance from the laser.
Copies of the matlab code used to fit (/plot) are attached in .zip below. |
Attachment 1: Matlabcode.zip
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Attachment 2: UniPhaseWaist.jpg
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218
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Sun Dec 30 02:36:35 2007 |
pkp | Update | General | Another update |
So I followed suggestions 1 and 3 so far and have started writing up what all needs to be done in order to compile and use the camera. I wrote a program to ping the camera and get its properties and am working on a program to get an image. The reason why I want to write my own programs to do this, is that it will be easier to reuse and also to compile/use in the first place. The programs currently rest in /cvs/cds/caltech/target/Prosilica/ . Unfortunately I will be away for the next couple of days and will have another update on the 2nd. |
238
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Mon Jan 14 23:11:26 2008 |
tobin | Configuration | General | fiber |
John and I removed the fiber that ran from the SP table to the cleanroom. We plan to build a MZ interferometer with this fiber inserted into one of the arms, for the purpose of measuring its phase noise. |
247
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Thu Jan 17 20:50:55 2008 |
tobin | Update | General | fiber coupling |
Sam, John, and I matched the beam from an NPRO into a fiber on the SP table today. In doing so we used our GigE camera for a physics application for perhaps the first time, viewing the transmitted mode from the fiber during initial alignment. (I used my laptop running Windows and a 100 megabit switch.) |
250
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Fri Jan 18 20:53:56 2008 |
tobin | Configuration | General | ETMY oplev |
I monkeyed around with the ETMY oplev, adding a folding mirror and moving the HeNe so that John, Sam, and I have more room for our auxiliary laser setup. (The ISCT-EY has more room than ISCT-EX; the latter has an extra photodiode for IP ANG.) I believe I successfully recommissioned the oplev, though it might not be up to the SV standard. I verified that wiggling the ETMY alignment sliders showed corresponding wiggles in the oplev signals. However, it seems poorly diagonalized.
Our current plan is to have an NPRO, EOM, and fiber coupler on the SP table. This fiber will take light to ISCT-EY where we'll have a mode-matching telescope and inject light to the Y arm via a polarized beamsplitter. This auxiliary beam will have polarization orthogonal to the beam from the PSL. |
262
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Thu Jan 24 22:52:18 2008 |
Andrey | Bureaucracy | General | Ants around a dirty glass (David - please read!) |
Dear coleagues,
there are rains outside these days, so ants tend to go inside our premises.
David was drinking some beverage from a glass earlier today (at 2PM) and left a dirty glass near the computer.
There are dozens, if not hundreds, of ants inside of that glass now.
Of course, I am washing this glass.
A. |
263
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Fri Jan 25 08:55:26 2008 |
rob | Configuration | General | Changes to Dataviewer channels (XARM) |
As a general rule,
Quote: | clicking random blue buttons chaotically |
is not a good problem solving technique. It is thus now explicitly discouraged as an option in the LIGO 40m Lab. |
269
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Fri Jan 25 17:11:07 2008 |
Max , Andrey | Configuration | General | NEW_FETCH_SHOUROV and GET_DATA do not work |
The problem which started yesterday after Andrey's framebuilder restart still persists.
It is still impossible to read data in the past from the channels using "get_data" which in turn uses "new_fetch_shourov".
Max was trying to read data from the channel
"C1:LSC-DARM_CTRL",
and he got the same error messages as Andrey.
Andrey tried earlier today to read data from "C1:SUS-ITMS_SUS" or "C1:SUS-ETMX_SUS" with the error meassge
Error in ==> new_fetch_shourov at 22
at (start_time+duration) > stops(end)
So, it seems that Robert Ward fixed just one problem out of two problems.
Robert revived the realtime signals in Dataviewer,
but did not revive the memory of channels for new_fetch_shourov.
To be more precise, channels have memory (it is possible to see the "Playback" curves in Dataviewer"),
but "get_data" and "new_fetch_shourov" do not see the data from those channels. The problem appeared immediately after Andrey's clicking on blue buttons to restart the framebuilder.
Andrey again apologizes. |
271
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Sat Jan 26 02:02:43 2008 |
John | Summary | General | New Channels |
I added the following channels.
# C1ASC_QPDs
[C1:SUS-ETMY_QPDSUM_MON]
[C1:SUS-ETMY_QPDYAW_MON]
[C1:SUS-ETMY_QPDPIT_MON]
[C1:SUS-ETMX_QPDSUM_MON]
[C1:SUS-ETMX_QPDYAW_MON]
[C1:SUS-ETMX_QPDPIT_MON]
The old .ini file is /cvs/cds/caltech/chans/daq/C0EDCU_26_1_2008.ini |
276
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Sat Jan 26 22:00:03 2008 |
John | Update | General | LSC-TRY_OUT and ETMY-QPD |
In the path from the ETM to the trans PD and QPD at the Y end I have replaced a BS1-1064-10-2037-45P with a polariser. The power falling on these diodes has been reduced. When the arm is locked in its nominal state the transmitted power is now less than 1.
This polariser should serve as an injection point for the auxiliary arm locking. I am attempting to use crossed polarisations to separate this loop from the main arm light. |
277
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Sun Jan 27 13:13:21 2008 |
tobin | Metaphysics | General | departure |
It's been grand. Thanks for having me!
GWAVES IN '08!
Sugar napoleons may be forwarded to T. F., c/o LLO, P.O. Box 940, Livingston, LA 70754-0940. |
288
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Thu Jan 31 12:39:14 2008 |
John | Configuration | General | Y arm test mass cameras |
I've adjusted the test mass cameras on the y arm to make the beam injected through ETMY more visible. |
328
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Thu Feb 21 18:29:28 2008 |
John | Summary | General | HP Network Analyser Analyzer |
The HP 4195A network analyser may be broken, measurements below 150MHz are not reliable. Above 150MHz everything looks normal. This may be caused by a problem with its output (the one you'd use as an excitation) which is varying in amplitude in a strange way.
Analyzer |
377
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Thu Mar 13 18:20:29 2008 |
John | Update | General | New Focus 4003 EOM 29.489MHz |
I measured the modulation index as a function of drive power using an OSA. Agrees well with spec of 0.2 rad/V.
 |
395
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Sun Mar 23 00:43:08 2008 |
mevans | HowTo | General | Online Adaptive Filtering |
I wrote a short document about the OAF running on the ASS. Since there is no BURT setup, I put a script in /cvs/cds/caltech/scripts to help with setting initial parameters: upass. |
Attachment 1: OnlineAdaptiveFilter.pdf
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409
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Wed Apr 2 15:03:51 2008 |
steve | Update | General | reflectivity of black glass |
The reflectivity of black glass, shade 12 was supplied by Donald O'Shea
of Emerald Glass Inc., Westlake, OH 44145
The reflectivity of this glass was measured as shown
Old 1064 nm Crysta Laser with poor beam quality was the source. |
Attachment 1: bg12refl.pdf
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Attachment 2: bg12refsetup.pdf
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417
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Mon Apr 7 18:58:49 2008 |
steve | Update | General | reflectivity of SS304 |
The reflectivity of stainless steel 304 super polished # 8 was measured the same way as elog entry 409
The reflectivity: 74 +- 1 % from incident angle 10 to 80 degrees |
Attachment 1: ss304s8refl.pdf
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446
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Thu Apr 24 23:50:10 2008 |
rana | Update | General | Syringes in George the Freezer |
There are some packets of syringes in the freezer which are labeled as belonging to an S. Waldman.
Thu Apr 24 23:48:55 2008
Be careful of them, don't give them out to the undergrads, and just generally leave them alone. I
will consult with the proper authorities about it. |
478
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Thu May 15 10:40:21 2008 |
steve | HowTo | General | Lisa Goggin, PhD |
Lisa Goggin successfully defended her thesis on May, 13 2008
"A Search For Gravitational Waves from Perturbed Black Hole Ringdowns in Ligo Data"
She started out as a surf student in the 40m.
Congratulation! |
Attachment 1: lisa.JPG
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483
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Fri May 16 17:27:55 2008 |
Andrey | Omnistructure | General | Toilets are broken, do not use them !!! |
Both toilets in 40-meter were constantly flushing, the leaking water was on the floor inside of the restrooms, so
BOTH RESTROOMS ARE CLOSED TILL MONDAY
I have heard the constant loud sound of flushing water, opened the door, and was unpleasantly surprised because all the floor was under the layer of water and the toilets were constantly flushing. I called security at X5000, a plumber came in and told that a team of plumbers needs to repair the flushing system after the weekend. The plumber today just shut off the flushing water, wiped off the floor and told not to use the restrooms in the weekend. We should expect a team of plumbers on Monday.
Sinks are working, so you can wash your hands. |
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Fri May 23 21:21:52 2008 |
Caryn | Summary | General | filtering mode cleaner with wiener filter |
I tried filtering some saved MC_L data (from Mon May19 4:30pm) with multiple MISO filters of different orders, with various sampling rates, at different times. Plotted the max rms error (where error is signal minus signal-estimate). 2min of data (around Mon May19 4:30pm) were used to calculate each filter. And each filter was applied to data at later times to see how well it performed as time progressed. Plots are attached. There appears to have been a disturbance during the 3rd hour. Rana pointed out perhaps it would be better to use data from the evening rather than during the day. |
Attachment 1: error_vs_N_for_different_times_64Hz.pdf
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Attachment 2: error_vs_N_for_different_times_128Hz.pdf
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Attachment 3: error_vs_N_for_different_times_256Hz.pdf
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Attachment 4: error_vs_N_for_different_times_512Hz.pdf
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Attachment 5: error_vs_srate_for_different_times_256.pdf
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Attachment 6: error_vs_srate_for_different_times_512.pdf
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Attachment 7: error_vs_srate_for_different_times_1024.pdf
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Attachment 8: error_vs_time_for_different_srates_256.pdf
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Attachment 9: error_vs_time_for_different_srates_512.pdf
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Attachment 10: error_vs_time_for_different_srates_1024.pdf
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546
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Thu Jun 19 20:22:03 2008 |
rana | Update | General | FE Computer Status |
I called Rolf (@LLO) who called Alex (@MIT) who suggested that we power cycle every crate
with an RFM connection as we did before (twice in the past year).
Rob and I followed Yoichi around the lab as he turned off and on everything. There
was no special order; he started at the Y-end and worked his way into the corner and
finishing at the X-End. Along the way we also reset the 2 RFM switches around fb0.
This cured the EPICS problem; the FEs could now boot and received the EPICS data.
However, there are still some residual channel hopping-ish issues which Rob and Yoichi are
now working on. |
551
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Sun Jun 22 21:38:49 2008 |
rob | HowTo | General | IFO CONFIGURE |
Now that we're getting back into locking, it's nice to have a stable alignment of the interferometer.
Thus, after you're done with your experiment using subsets of the interferometer (such as a single arm),
please use the IFO_CONFIGURE screen, and click "Restore last Auto-Alignment" in the yellow "Full IFO" section.
If you don't know what this means/how to do this, you shouldn't be using the interferometer on your own. |
555
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Mon Jun 23 21:51:19 2008 |
Alberto | Update | General | Arm Cavity Length Measurement |
We measured the arm cavity lengths sweeping the ETM mirror position and looking at the reflected demodulated output. We excited the mirror by a sine wave of 0.2 Hz and amplitude of 30000 counts. From the time series of the occurrences of the resonances of the sidebands and of the carrier we evaluated the free spectral range of the cavities and thus the lengths. The details of the procedure are explained in the attached document. As discussed in it, for each cavity we obtain two possible values of the length depending on which of the sideband resonances is that corresponding to the upper sideband and which corresponds to the lower one instead. The numbers are:
Lx=(38.30 +/- 0.08)m / (38.45 +/- 0.08)m
Ly=(38.16 +/- 0.08)m / (38.70 +/- 0.08)m
Since the difference between the two possibilities is quite large, we should be able to decide which one is correct by somehow measuring directly the cavity length. We want to try it tomorrow by a tape meter.
Alberto and Koji |
Attachment 1: 40mLengthMeasure.pdf
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Tue Jun 24 10:24:43 2008 |
Koji | Update | General | Abs. Len. Meas. ~ Cavity Swing Measurement (2) |
At the entry 555, Alberto reported the results of the cavity length measurement using cavity sweeping.
As expected, each result inevitably has an ambiguity depending on which resonance do we take as an upper sideband.
In order to exclude this ambiguity Steve and Koji performed a primitive non-optical measurement using a tape and photos:
This morning Steve and Koji did tape measurements to know the lengths between the ITM/ETM chambers.
Yesterday, Koji took photos of the optical tables in vacuum to know the actual positions of the suspensions.
The results are shown in the figures attached. From those non-optical measurements the lengths of the X/Y arm are known to be 38.48+-0.03 / 38.67+-/0.03 [m].
Then, we could exclude the shorter lengths of the values in the entry 555. i.e. The Y arm is longer than the X arm about 0.2 m.
These approximate lengths will be used in the further precise measurements which use precise scans of the FSR frequencies. |
Attachment 1: armlength.png
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Attachment 2: armlength2.png
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Wed Jun 25 00:35:40 2008 |
Koji | Summary | General | Optical Layout on the AP table |
I have visited the AP table in order to investigate where we are going to put the optical setup for the abs. length meas.
I have attached the PNG and PDF files to share the optical layout. It is not complete. Any comments or corrections are welcome. |
Attachment 1: optical_layout_ap_table.png
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Attachment 2: optical_layout_ap_table.pdf
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567
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Wed Jun 25 13:38:22 2008 |
Koji | Update | General | Abs. Len. Meas. ~ Placement of the 700mW NPRO on the AP table |
This morning I have put the 700mW NPRO on the AP table for the abs length measurement.
The RF amplifier was moved (the cables were not changed). I cleaned up some cable arrangements. I was keen not to disturb any of the other optical path. Even so, please let me know if any suspicious behaviour is found on the AP table. |
Attachment 1: NPRO700mW_placement.jpg
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570
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Thu Jun 26 01:08:22 2008 |
rana | Configuration | General | Alarm Handler Revived |
I have revived the Alarm Handler by turning it on on op540m and adjusting the levels of
several of the alarming channels to not alarm (like laser power). The alarm levels are now
set to something reasonable and people should start actually paying attention to them.
I also removed the EO Shutter and Stacis alarm stuff since we don't use them.
To really get in and edit it, you have to close the Alarm Handler and edit the file
in /cvs/cds/caltech/alh/. It allows you to add/subtract useful channels and put in
guidance information.
If the alarm handler beeps about something, don't just close it or silence it, Steve. Just
fix it somehow (either set the threshold better or find the real cause). |
Attachment 1: b.gif
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574
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Thu Jun 26 14:06:00 2008 |
Masha | Update | General | 500mW INNOLIGHT NPRO info |
Below is the placement of 500mW INNOLIGHT NPRO mephisto laser. It is set up on the Symmetric Port table.  |
590
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Sun Jun 29 02:33:28 2008 |
Koji | Update | General | Abs. Len. Meas. ~ Optical setup (I) |
I have constructed the beam injection optics for the abs length measurement.
The injection beam was coarsely aligned to the interferometer. The reflected beam from SRM was already seen at AS CCD.
I have attached the optical configration for this measurement and the optics layout at the AP table.
I am going to go to LHO for three weeks. During the absence Alberto tunes the mode matching and the alignment of the interferometer.
In the process of making this report, I noticed that one of the iris apertures is about disturbing the beam for OMCR CCD. I will check this before I go to Hanford. Also an RF spectrum analyzer is at the AP table. I try to return this near the PSL on Monday morning.
Attachment 1: Optical configuration for the abs length measurement.
1) One of the arms is locked to the PSL beam by the main control system (red).
2) A laser beam is injected from the AS port (blue). This laser essentially has different frequency from that of PSL.
3) The injected beam and the outgoing PSL beam appear at the output of the faraday in the injection system.
4) They beat each other at the frequency difference of those two lasers.
5) A PLL is used to lock the frequency difference to a local oscillator (LO).
6) The LO frequency is swept at around 3.87MHz, that is the approximate FSR frequency of the arm cavity.
7) If the LO frequency hits the FSR within the resonant width, the beating also appears at the transmitted light as the injected beam also becomes resonant to the arm cavity.
8) Amplitude of the beating at the transmitted light is measured by a RF spectrum analyzer as a function of the LO frequency. We get the FSR frequency (= the arm cavity length) from the top of the resonance.
Attachment 2: Optics at the AP table for the laser injection
700mW NPRO, laser source. vertically polarized.
Periscope, to raise the beam 1 inch to make the beam at the 4 inch elevation.
INJ_SM1/INJ_SM2, steering mirrors to align the injection beam to the IFO beam.
HWP1, half wave plate to make the beam to the farady horiz-polarized. nominal 42deg on the readout.
FI, Faraday isolator for protection of the NPRO from the returning light, for obtaining the returning light.
HWP2, to make the beam from the Faraday horiz-polarized. nominal 357deg on the readout.
MM_Lens, f=125mm to match the laser mode to the IFO beam.
SM1/SM2, steering mirrors to align the IFO beam to the Farady Isolator.
IRIS1/IRIS2, for the coarse alignment of the injection beam.
FLIP, flipper mount to turn on/off the injection optics.
Alignment procedure of the injection system
0) Ignite NPRO several hours before the experiment so that the laser frequency can be stable.
1) Turn up FLIP. Close the shutter of NPRO.
2) Adjust SM1/SM2 so that the ifo beam can appear at the output of FI.
3) Adjust height and position of IRIS1/IRIS2 with regard to the ifo beam so that the ifo beam goes through IRIS1/IRIS2 even when they are closed.
4) Turn down FLIP. Open the shutter of NPRO.
5) Adjust INJ_SM1/INJ_SM2 so that the injection beam can go through IRIS1/IRIS2 even when they are closed.
6) At this time, it is expected that the reflection of the injection beam from SRM appears at AS CCD, if SRM is aligned.
7) Adjust INJ_SM1/INJ_SM2 so that the injection beam at AS CCD can overlap to the IFO beam.
8) Confirm the beam at the output of the FI also overlaps.
---- We are here ----
9) Change the ifo configuration to the X or Y arm only.
10) Scan the crystal temperature of the 700mW NPRO in order to try to have the beating of the two beams at the PD. AS OSA may be useful to obtain the beating.
11) Once the beating is obtained, adjust INJ_SM1/INJ_SM2 such that the beating amplitude is maximized. |
Attachment 1: optical_configuration.png
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Attachment 2: optical_layout_ap_table2.png
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Attachment 3: optical_layout_ap_table2.pdf
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Mon Jun 30 05:33:38 2008 |
Koji | Update | General | Abs. Len. Meas. ~ Optical setup (II) |
o The position of the iris was adjusted so as not to disturub the beam for OMCR CCD.
o The RF spectrum analyzer was returned to the place of the network analyzer.
Quote: |
In the process of making this report, I noticed that one of the iris apertures is about disturbing the beam for OMCR CCD. I will check this before I go to Hanford. Also an RF spectrum analyzer is at the AP table. I try to return this near the PSL on Monday morning.
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613
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Tue Jul 1 12:51:34 2008 |
John | Summary | General | IFO alignment |
Rana, Rob, Yoichi, John
The recent computer problems and MZ work had disturbed the alignment of the interferometer.
We adjusted the MC alignment back to nominal positions using old OSEM values. We then walked
the input beam to match the MC. Coupling into the interferometer has increased noticeably.
The rest of the IFO was then aligned to the new input beam.
Proceeding to full IFO locking we were able to engage the AO path and hand off CARM to SPOBDC.
Arm powers got up to 4.
If the new alignment proves successful we will centre all QPDs etc so we can easily return to
this state. |
Attachment 1: align080701.png
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619
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Tue Jul 1 21:54:05 2008 |
Koji | Update | General | Re: Abs. Length Meas. setup |
I tried to look for the beating in the signal from the PD but I couldn't find. I had the temperature of the laser initially set to 40deg and then slowly increased by one degree. The manual of the laser says the frequency should change by several GHz. The problem is then that our PD is limited to no more than 30Mhz.
Although the two beams seem to overlap quite well, we might still need a better matching of the injected beam.
Alberto
Quote: | o The position of the iris was adjusted so as not to disturub the beam for OMCR CCD.
o The RF spectrum analyzer was returned to the place of the network analyzer.
Quote: |
In the process of making this report, I noticed that one of the iris apertures is about disturbing the beam for OMCR CCD. I will check this before I go to Hanford. Also an RF spectrum analyzer is at the AP table. I try to return this near the PSL on Monday morning.
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