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KAGRA MIR (General)
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MarcEisenmann - 23:40, Thursday 04 March 2021 (2386)Get code to link to this report
Preparation of KAGRA spare measurement

Aritomi, Marc, Matteo

Today we cleaned a bit the computer room and brought the KAGRA spare to the clean room. We putted first contact on the surface facing outside the protection box.

Then, we followed the realignment procedure described on the wiki and installed the surface reference sample to realign the setup with the goal of reproducing the calibration done in elog 1619 : R_surf = AC_surfref/(DC_surfref*P_in*abs_surfref) = 16.9 [1/W]

First, we putted the surface with the sample name facing the laser (PS : mirror center in z is 38 mm). Results are presented in figure 1 and gives (with abs_surfref = 0.22) : AC_surfref = 0.17V, DC_surfref = 3.91V, P_in= 16mW -> R_surf = 12.4 [1/W]

Then, we flipped the reference sample (PS : new center at 33.25 mm) to check if it could explain the discrepancy wrt to elog 1619.

During a scan, there were some troubles with some connections and we got several error messages from LabView... We had to restart the computer to use LabView again but there is still some troubles with the power-meter ( detected but not able to connect to the computer)

The result of this configuration is presented in figure 2 and gives : AC_surfref = 0.31V,  DC_surfref = 4.01V, P_in= 15mW -> R_surf = 23.4 [1/W]

This time the AC measurement is not as symmetrical as expected so we'll further tune the alignment tomorrow.

Images attached to this report
2386_20210304153851_29.png 2386_20210304153857_20.png
Comments related to this report
MatteoLeonardi - 10:46, Friday 05 March 2021 (2387)

I confirmed the coating of the surface reference sample is on the side with the written part. Therefore the correct orientation is with that side first (i.e. facing the periscope).

The discrepancy between the current and old measurement as well as the slight asymmetry can be caused by not optimal alignment of pump beam.