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Message ID: 1593     Entry time: Sun Oct 18 20:15:55 2015
Author: Antonio 
Type: DailyProgress 
Category: ISS 
Subject: ISS on the North path and new optical setup 

Summary

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The work done yesterday and today gave us a working ISS in the North path with a different optical setup.

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Yesterday I have made several attempts to make the ISS working again in the North path. I have failed until I have noticed

the following setup for the AEOM:

 

lambda/2 ———p————> AEOM —-—> lambda/4 ——> PBS —> lambda/4 ———s—>EOM…..

 

Because I was not in agreement and I have asked Evan and I have figured out that this setup was not what it was meant to be.

Today I have replaced the second lambda/4 with a lambda/2 which made the ISS North working. Now the setup is:

 

lambda/2 ———p————> AEOM —-—> lambda/4 ——> PBS —>lambda/2———s—>EOM

 

The spectrum shows the intensity noise measured at the photodiode in transmission of the North cavity. Not clear what is happening

with the dark noise.

 

Loop setup: PD North ---> SR560 --->AEOM

SR560 setup: Gain at 5e4, HP=30Hz; LP=1kHz;

 

From  Yesterday I have also measured:

 

1. TF from AEOM to PD North;

2. TF from PD North to PLL control signal (injecting noise on AEOM);

 

SOME of the THINGS that I think need TO BE DONE in a short term:

 

1. We should implement the second AEOM in the South path. My plan is to replace the EOM that currently is in the path with the

AEOM because the beam shape requirement are the same, so it will be faster, given that we will not use the PMC. 

 

2. We need to check the shape of the beams at the modulators (ALL) in order to figure out if the (A)EOM requirements are respected.

This could be important for beam deformations which affect the mode matching at the cavities.

 

3. Need of a working dataviewer/IRcamera and a beam profiler;

 

4. It is very important that we spend some time in organizing the lab. The amount of time spent for looking for things is becoming an

obstacle for a proper lab work.

 

5. We also need to consider about the height of the table. Aside note: After two days in the lab my back is very painful.

 

6. Implement two Faraday Isolators in order to use only one polarization; for the moment I am even tempted to use a 50/50 BS, j

ust for the moment.

 

Curiosity:

So far we have been locking the cavities on the resonance given by the S-polarized light.

 

Data

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controlfb2/data/2015101718_PLL_ISS/

 

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