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KAGRA MIR (Absorption)
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NaokiAritomi - 08:10, Sunday 11 April 2021 (2444)Get code to link to this report
IR beam height adjustment

[Aritomi, Abe, Marc]

Since IR beam height was higher than red beam by ~3 mm as shown in elog2446, we adjusted the height of two lenses for IR beam. We made the first lens lower by 3 turn of screw to make the beam lower after the first lens. By doing this, the IR beam height just after the second lens changed from 55 mm to 52 mm. Then we made the second lens lower by 6 turn of screw to make the beam flat.

We did knife edge measurement in X direction at Z = 25 mm and 70 mm to check if the IR beam is flat. Attached figures show knife edge measurement at Z = 25 mm and 70 mm. The beam height are X = 316.96 mm and 316.85 mm, respectively.

Now IR beam is flat and the IR beam height is almost the same as the red beam height.

We did knife edge measurement in X direction at Z = 25 cm and 70 cm to check if the IR beam is flat.
Attached figures show knife edge measurement at Z = 25 cm and 70 cm. The beam height are 316.96 mm and 316.85 mm, respectively. 
Since IR beam height was higher than red beam by ~3 mm, we adjusted the height of two lenses for IR beam.
We made the first lens lower by 3 turn of screw to make the beam lower after the first lens. By doing this, the IR beam height just after the second lens changed from 55 mm to 52 mm. Then we made the second lens lower by 6 turn of screw to make the beam flat.
Since IR beam height was higher than red beam by ~3 mm, we adjusted the height of two lenses for IR beam.
We made the first lens lower by 3 turn of screw to make the beam lower after the first lens. By doing this, the IR beam height just after the second lens changed from 55 mm to 52 mm. Then we made the second lens lower by 6 turn of screw to make the beam flat.
Images attached to this report
2444_20210411011037_ir20210409z25.png 2444_20210411011043_ir20210409z70.png