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Birefringence mitigation (cavity)
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ShalikaSingh - 14:36, Monday 18 March 2024 (3484)Get code to link to this report
Polarimetry POl states

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Polarization states\20240314\

'Thu, Mar 14, 2024 1-34-25 PM.txt' for voltage from 0 to5V for both LC

'Thu, Mar 14, 2024 2-45-11 PM.txt' for voltage from 0 to 10V for LC1 and 0 to 5V for LC2

sweep done with 1V resolution for both LC to have unique azimuth and ellipticity and also avoiding the multiple of angles. 

R&D (Cryogenic)
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RishabhBajpai - 12:14, Thursday 14 March 2024 (3483)Get code to link to this report
Moving Swagelok Adapters

I moved three boxes of Swagelok adapters from TAMA circuit room to ATC lab. (image)

The boxes are now next to the DAQ rack near the cryostat. (image)

I will use them while recharing helium gas and should return them in a week or two.

Birefringence mitigation (LC)
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Shalika, Marc - 11:48, Tuesday 12 March 2024 (3479)Get code to link to this report
birefringence measurement of BB1EO3

BB1EO3 was installed after the BS. The reflected beam divergence is np.arctan(1/200)=0.29 deg. The LC are scanning roughly from 0-5V with 1V resolution. This is intended to directly estimate the birefringence of the mirror. 

measurement:

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Coating measurement\BB1-E03\20240311

Mon, Mar 11, 2024 5-25-22 PM

Birefringence mitigation (LC)
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MarcEisenmann - 11:03, Tuesday 12 March 2024 (3482)Get code to link to this report
ethernet failure

[Marc (remote), Mitsuhashi]

There seems to be some issue with TAMA ethernet switch as no PC are accessible from remote but WIFI is available.

Mitsuhashi-san went to check ethernet connection on LC PC, on new DGS switch and ethernet switch and everything seems plugged and properly on.

We also turned on/off the ethernet switch without success.

In the end the LC PC is connected to NAOJ open and we could recover the remote connection.

We need further check as FC and PCI pcs are still not accessible..

R&D (Speed meter)
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LuiseKranzhoff, YoheiNishino - 13:07, Monday 11 March 2024 (3481)Get code to link to this report
Lock stability of main laser

This is a report on the measurement we did on 03/07.

We measured the open-loop transfer function of the cavity by injecting a swept-sine disturbance signal between plant H and actuator A and taking the ratio of measurement data from directly before and directly after signal injection. Goal of this measurement was to assess lock stability by means of the phase margin. The lock of the main laser is achieved by a fast actuation with a piezo with servo transfer function F_pzt*A_pzt combined with slow thermal actuation with servo F_th*A_th, both actuations performed on the laser itself. While F_pzt, A_pzt and A_th are basically fixed , we can influence the stability of the lock by adjusting the servo F_th with the MokuLab. Based on trial and error, we designed the thermal servo to have the following parameters:

Integrator gain (saturation limit) and UGF: g_i = 43.6 dB, f_i = 160 Hz

Differentiator gain (saturation limit) and UGF: g_d = -45.5 dB, f_d = 315.6 kHz

With the above information and the knowledge of F_pzt, A_pzt and A_th, the optical gain can be inferred and found to be constant. UGF lies around 100 Hz and the phase margin amounts to around 85 deg. The lock seems reasonably stable, at least, enough for our purposes, so we will continue. A plot of the described analysis can be found here.

R&D (FilterCavity)
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MarcEisenmann - 21:16, Friday 08 March 2024 (3480)Get code to link to this report
Comment to Preparation of box for mixers (Click here to view original report: 3477)

7 mixers and their low pass filters, 2 DC blocks and 1 splitter has been fixed to the aluminium frame.

I also found a board with LEMO 'i-style' feedthrough so I'll take them from this board for the front panels.

Next step is to prepare front panel and several short length sma cables.

Birefringence mitigation (General)
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ShalikaSingh - 18:38, Friday 08 March 2024 (3478)Get code to link to this report
Finer resolution polarization states

For interpolation verification, did a small finer scan.

V1- 1-1.01V, 1mV

V2- 5-5.005V, 1mV

data is here:

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Polarization states\20240308\

Fri, Mar 8, 2024 6-36-13 PM.txt

R&D (FilterCavity)
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MarcEisenmann - 21:25, Thursday 07 March 2024 (3477)Get code to link to this report
Preparation of box for mixers

Since the failure of DDS boards last year we have too messy cabling around NIM rack.

I started to prepare a box to enclose all mixers and PLL monitor boxes.

I picked a 2U box and fitted a small aluminium plate to host these components.

The BNC mixers are now properly fixed.

For the SMA mixers I would like to use custom length SMA cables.

I would like to use LEMO feedthrough on the front panel but up to now I can't find the proper washers...

Comments related to this report
MarcEisenmann - 21:16, Friday 08 March 2024 (3480)

7 mixers and their low pass filters, 2 DC blocks and 1 splitter has been fixed to the aluminium frame.

I also found a board with LEMO 'i-style' feedthrough so I'll take them from this board for the front panels.

Next step is to prepare front panel and several short length sma cables.

Birefringence mitigation (cell birefringence)
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MarcEisenmann - 21:21, Thursday 07 March 2024 (3476)Get code to link to this report
hydrogel measurement with glass and plastic cell container

[Marc, Katsuki]

Thanks to Kanzawa-san we got the new pusher for the glass cell container.

We measured again birefringence versus pusher position. This time we saw small increase in ellipticity while it was strongly decreaseing with the plastic cell container.

One possibility is that the pusher pressure was inducing stress birefringence on the plastic walls.

We then measured mass versus pusher discplecements for both plastic and cell container with the 3d printed holder.

We still had some issue of hydrogel escaping from the space between the pusher and cell container walls so we then put the pusher into one finger of a plastic glove that mostly solved this issue.

We repeated measurement of hydrogel birefringence versus pusher position but this time the restoring force of hydrogel was stronger and pushing up the translation stage despite zip tie.

We should prepare a better enclosure for the translation stage.

I tried to apply large displacement while holding the translation stage but the glass cell container broke..

In any case it seems that hydrogel is sensitive enough to cell induced birefringence.

All measurements were done with 10% hydrogel mix.

All data and analysis are in 'hydrogel_birefringence.py' file

Birefringence mitigation (cavity)
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ShalikaSingh - 20:05, Thursday 07 March 2024 (3475)Get code to link to this report
Comment to Polarization states (Click here to view original report: 3474)

The measurement finished and when I plotted the data I realised, there was no data from LC1 at 0-5V and LC2 from 5-25V and LC1 at 5-25V and LC2 at 0-5V. 

started the measurement for both the above setting with 50mV resolution. 

Birefringence mitigation (General)
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ShalikaSingh - 20:47, Tuesday 05 March 2024 (3474)Get code to link to this report
Polarization states

Owing to the issue in saving data, polarization states are generated again. We have put a BS infront of the two LC. Now, the polarization states are being generated after the "LC1, LC2, BS". This configuration will be treated as one optical element from now on.

1. Both LC 0-5 V with 15mV resolution

2. Both LC 5-25V with 50mV resolution

All, done with LC @ 30degC. Data is being saved with average order of 10.

foldername: 'C:\Users\ShalikaSingh\Atamapc\OneDrive\LC-Experiment\Measurement Data\Polarization states\20240305'

filename: Tue, Mar 5, 2024 8-25-32 PM.txt

Comments related to this report
ShalikaSingh - 20:05, Thursday 07 March 2024 (3475)

The measurement finished and when I plotted the data I realised, there was no data from LC1 at 0-5V and LC2 from 5-25V and LC1 at 5-25V and LC2 at 0-5V. 

started the measurement for both the above setting with 50mV resolution. 

Birefringence mitigation (LC)
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ShalikaSingh - 20:24, Tuesday 05 March 2024 (3473)Get code to link to this report
Comment to BS birefringence (Click here to view original report: 3460)

There was issue with how data was saved. Even though there was averaging implented, there was no resetting of averging buffer after voltage change. Now, the data are being saved after the corrections.

New folder: C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Beam Splitter Calibration\20240305

Only LC, No BS:

Tue, Mar 5, 2024 7-45-18 PM.txt

Back face

transmission:

Tue, Mar 5, 2024 8-19-02 PM.txt

reflection:

Tue, Mar 5, 2024 8-03-47 PM.txt

Tue, Mar 5, 2024 8-13-04 PM.txt

Tue, Mar 5, 2024 8-16-36 PM.txt

Birefringence mitigation (General)
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ShalikaSingh - 17:12, Tuesday 05 March 2024 (3472)Get code to link to this report
Comment to Polarization Generation with BS (Click here to view original report: 3468)

According to the calculation it seems that for the last scan from 5-25V it will take time

1. with 0.1V resolution--> 5hrs

2. with 50mV resolution--> 24hrs

The scan finished and hence. I will begin another scan with 50mV resolution from 5.02V-25V.

Birefringence mitigation (cavity)
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ShalikaSingh - 11:48, Tuesday 05 March 2024 (3471)Get code to link to this report
Comment to Polarization Generation with BS (Click here to view original report: 3468)

10mV step with averaging of 10th order will take around 30hrs. So, I changed. Now the configuration is as below in format: LC1,LC2,Resolution

1. 0-5V, 0-0.52V, 10mV

2. 0-5V, 0.52-5V, 20mV

3. 5-25,5-25V, 0.1V

foldername:

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Polarization states\20240301

Birefringence mitigation (cell birefringence)
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MarcEisenmann - 19:52, Monday 04 March 2024 (3470)Get code to link to this report
hydrogel birefringence measurement

[Marc, Katsuki]

We tuned input polarization to 0deg azimuth and ellipticity with QWP and HWP.

Katrsuki-san made a 15% hydrogel and we started acquiring birefringence data.

However, the translation stage acting on the pusher was not too well fixed so it was moving a bit after every motion and also applying force on diagonal.

We used sand paper to increase the translation stage holder hole diameter and used zip tie to stabilitze it.

Then, we measured 10% hydrogel mixture at the bottom and the top of the cell container.

After small motions were nothing happen, we can see a clear linear relationship between birefringence and pusher position.

When the laser is hitting the bottom of the cell container, there is an intermediate phase where the effect is linear but smaller.

The pusher motion to force was calibrated using a kitchen scale.

data are saved in the cell birefringence folder :

#first 2 measurements below were done with pusher not too well fixed..
foldername = r'C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\cell birefringence'
#15%
filename = 'Mon, Mar 4, 2024 2-14-41 PM.txt'
#10%
filename = 'Mon, Mar 4, 2024 3-30-28 PM.txt'
#10% and better way to apply force
filename = 'Mon, Mar 4, 2024 3-56-22 PM.txt'
#same as before but laser beam close to top of box
# filename = 'Mon, Mar 4, 2024 4-30-33 PM.txt'

All measurements were made with the plastic cell container.

For the glass cell container we should use a .8 or .9 mm diameter pusher (vs 1 mm for the plastic one).

Birefringence mitigation (General)
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ShalikaSingh - 15:13, Monday 04 March 2024 (3468)Get code to link to this report
Polarization Generation with BS

We have put a BS infront of the two LC. Now, the polarization states are being generated after the "LC1, LC2, BS". This configuration will be treated as one optical element from now on.

1. Both LC 0-5 V with 10mV resolution

2. Both LC 5.001-25V with 20mV resolution

All, done with LC @ 30degC. Data is being saved with average order of 10.

foldername: 'C:\Users\ShalikaSingh\Atamapc\OneDrive\LC-Experiment\Measurement Data\Polarization states\20240301'

filename: 'Mon, Mar 4, 2024 2-13-11 PM.txt'

Comments related to this report
ShalikaSingh - 11:48, Tuesday 05 March 2024 (3471)

10mV step with averaging of 10th order will take around 30hrs. So, I changed. Now the configuration is as below in format: LC1,LC2,Resolution

1. 0-5V, 0-0.52V, 10mV

2. 0-5V, 0.52-5V, 20mV

3. 5-25,5-25V, 0.1V

foldername:

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Polarization states\20240301

ShalikaSingh - 17:12, Tuesday 05 March 2024 (3472)

According to the calculation it seems that for the last scan from 5-25V it will take time

1. with 0.1V resolution--> 5hrs

2. with 50mV resolution--> 24hrs

The scan finished and hence. I will begin another scan with 50mV resolution from 5.02V-25V.

Birefringence mitigation (General)
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ShalikaSingh - 15:05, Monday 04 March 2024 (3469)Get code to link to this report
VI modifications

The VI was modfied to access two Polarization camera from 2 different VI and save data in two VIs at the same time. 

But, there is issue now that the graphs are not displayed in 2 different VI at the same time. 

Birefringence mitigation (LC)
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ShalikaSingh - 19:24, Saturday 02 March 2024 (3460)Get code to link to this report
BS birefringence

I have set the laser to emit atleast 100mW. As such the power reaching the LC was 8-9mW. The mirror infront of the LC path was replaced with a 50:50 BS 10Q20HBS.33S. Now, the power is around 4mW. The input polarization before LC was tuned to be around 0+/-0.004deg in azimuth, and 0+/-0.003deg ellipticity.

An input polarizer was kept infront of the setup. In the past, sometimes the polarization changes overtime. So, for historical reasons, I kept the input polarizer back. After pol, azi 0+/-0.002 and ell 0+/-0.004 deg.

To estimate BS birefringence, LC is bein used as in polarimetry setup.

The BS Jones matrix has 4 parameters. Hence, 8 unknowns, taking real and imaginary parts into account for each element.

The BS was kept on removable magnetic mount after the pair of LC. The LC1 was scanned in voltage range 0 to 25V and LC2 from 0-5V, each with 1V step. This leaves us with atleast 8 to 10 measurements to create 8 equations. The measurements were taken with averaging of 10 order.

Calibration of BS back face

Measurement foldername : C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Beam Splitter Calibration\20242902

1. Modulation from LC, without BS.

C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Beam Splitter Calibration\20242902\

Fri, Mar 1, 2024 3-53-37 PM.txt

2. The camera is placed in the transmission of the BS.

filename: Fri, Mar 1, 2024 5-55-12 PM.txt

3. Camera in reflection of BS. The measurements were taken by removing BS 3 times. 

filename:

Fri, Mar 1, 2024 6-23-25 PM.txt

Fri, Mar 1, 2024 6-26-41 PM.txt

Fri, Mar 1, 2024 6-29-09 PM.txt

Comments related to this report
ShalikaSingh - 20:24, Tuesday 05 March 2024 (3473)

There was issue with how data was saved. Even though there was averaging implented, there was no resetting of averging buffer after voltage change. Now, the data are being saved after the corrections.

New folder: C:\Users\atama\OneDrive\LC-Experiment\Measurement Data\Beam Splitter Calibration\20240305

Only LC, No BS:

Tue, Mar 5, 2024 7-45-18 PM.txt

Back face

transmission:

Tue, Mar 5, 2024 8-19-02 PM.txt

reflection:

Tue, Mar 5, 2024 8-03-47 PM.txt

Tue, Mar 5, 2024 8-13-04 PM.txt

Tue, Mar 5, 2024 8-16-36 PM.txt

R&D (FilterCavity)
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MichaelPage - 03:57, Saturday 02 March 2024 (3467)Get code to link to this report
CC and green issues continued

I checked the polarization of the CC beam by looking at its transmission and reflection through the first polarized beam splitter on the injection path. It is almost completely reflected with very low transmission, so basically is s-pol. I guess the polarization wouldn't suddenly change for no reason but might as well check anyway.

I replaced the battery for the fiber PD and it turns out that fixed the issue with the disappearing CC PLL. I thought this fiber PD was outputting an electronic signal based on what I saw connecting it to the oscilloscope, but it seems that in fact the battery had run out. I used a Panasonic 12V A23 size battery from Yodobashi Camera, though Thorlabs only recommends Energizer ones from their website. Also the optimal laser temperature is about 37.96 C, somewhat less than what is listed on the wiki. If this remains consistent I will update the wiki. 

A scanning amplitude is sent to the CC1 error signal via the knob on the control servo to make it a sinusoidal shape, and from there we see the peak to peak level that is representative of the total squeezing (once the scan amplitude knob on the servo is turned past a certain number, the Vpk of the error signal is independent of the scan amplitude). I measured 560 mVpk at 25 mW green injection, which is about twice as much as what it was last time, the difference being that I optimized green alignment to the OPO using nonlinear gain of BAB last week.

I attempted to measure squeezing at 195 (39*5) MHz ppol but the glitch noise is extremely bad. The shot noise level while blocking squeezing is stable (-132 dBm, maybe slightly unbalanced homodyne but not important right now), so the noise has nothing to do with the homodyne path (we thought it might be an issue with homodyne power supply). I could barely make out that I was in a squeezed quadrature before the noise level glitched upwards by about 15 dBm.

After some time, the CC loops were behaving strangely, so I unlocked and relocked and noticed the green phase shifter HVD was sending 0.0 V and that the "LOCK" and "RAZ" lights on the GRMC/MZ servo boards were flashing. I saw that the green mode cleaner was *again* misaligned, which has become a repeating issue whenever large changes in PZT voltage get sent to the green phase shifter. I quickly recovered MZ/GRMC alignment to 92% mode matching but now the CC1 error signal was making some weird non sinusoidal shape. It was getting late so I didn't confirm, but I suspect that once again the green has misaligned to the OPO.

This CC glitch noise and green path hysterisis is very annoying and is severely impeding the ability to do priority tasks (ML data taking and OPO replacement). There are 4 points of suspect performance in my opinion - the CC PLL, green phase shifter, CC loop stability and CC loop signal to noise ratio. I personally do not believe the CC PLL is the issue since we measured the phase noise recently and it didn't have any of the glitch behaviour. We also tried to swap the boards ADF4001/ADF4002 used for CC and ppol, although now that I think about it I didn't do it correctly, but now I know the correct procedure - when the PLL software is loaded and the board is selected, I thought the initial screen was the correct settings, but in fact it is wrong and you have to load the correct settings for CC/ppol. Also, the signal frequency is set in the DDS software, but we have to input f*3 for CC frequency and f/5 for ppol frequency (i.e. above I input 39 MHz for a 195 MHz ppol lock). Last time we tried, I applied "division by 5" when switching the CC to the PLL board, but in fact the correct loaded settings also do the multiplication/division of the number coming from DDS, so I should have put 21 MHz (multiplication by 3). But even so, like I said, I want to check the CC control loop properties since I am more inclined to believe that these are the problem.

KAGRA MIR (General)
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MarcEisenmann - 23:05, Friday 01 March 2024 (3466)Get code to link to this report
30mm diameter holder

I designed a holder for 30mm diameter optics that can be installed inside the 2 inch holder of PCI.

The CAD file is in the workstation folder 'PCI holder'. There are 2 versions of this component :

'30mm_holder' was thought to be 3D printed but it might be too dangerous to use during absorption measurement

'30mm_holder_v2' is compatible with aluminium machining. 

The main difference between the 2 is that a slit to install a o-ring to stabilize small length component was replaced by a through hole in the v2.

The part will be manufactured at ATC.

A long cylinder will be 3D printed to be inserted into the through hole.

This holder should be useable for all the 30mm diameter sapphire we currently have (30mm to 120mm length).