[Tomaru, Mitsuhashi, Futaba Kogyo Members, Rishabh]

We organized and cleaned up the ATC lab (outside the speed-meter cleanroom) to enhance floor space utilization. some photos.

If possible, we should avoid using the newly cleared area for storage purposes.

[Tomaru, Rishabh]

The regulator from KEK was delivered, so we recharged the compressor to 16.6 bar. I will monitor the pressure for a week and have a cool-down test around mid-April.

Date: 2024/03/19

[Tomaru, Rishabh]

While working to recharge the compressor, we noticed that the inside of the storage shed (and the compressor) was extremely dirty. This is because of the openings on three sides of the shed. I looked for aluminium sheets to cover these openings temporarily but couldn't find any. I will order some plastic or aluminium sheets to cover up the openings and clean up the inside of the shed.

[Tomaru, Rishabh]

Date: 2024/03/19

We tried to recharge the compressor with G1 Helium in the ATC lab. For this work, we used the flexible line brought from KEK. Since there was no adapter to evacuate the flexible line, we just purged it with helium before connecting it to the compressor's recharge port. After connecting the line, we tried to recharge the compressor but found the reading on the regulator fell to 0. We realized the regulator is only rated for 0-3kgf/cm^2, an order smaller than we need. So, we requested Node-san in KEK to send a 2-3MPa regulator to NAOJ. We will use it to recharge the compressor and purchase a new one in the next fiscal year.

Since there was no chain, the He tank was tied to a white rack using a crane belt for safety. Also, random items stored around the cryogenic optical table and DAQ rack were moved around for this work and left that way. They shouldn't be in anyones way. I want to clean up/move unused so they are not in the way.

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. 

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.

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

[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..

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.

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.

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

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...

[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

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. 

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

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

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.

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

[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).

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'