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MIF (ITF Control)
ryousuke.sugimoto - 1:04 Monday 13 April 2020 (14128) Print this report
Green fiber alignment procedure

The attached figure shows the corner of the PSL table (Especially Y side, The original file is in JGW-T1808565-v7).

Actually, alignment work itself is easy, but ALS optics are dense, so please be careful to do not interfere with other stuffs while working.

 

1. The value of fiber output should be 0.8 or more.

If not, adjust the PZT mirror just before the fiber (the blue circle in the figurewhile monitoring the K1:ALS-Y_ARM_INPUT_OUTPUT to maximize the fiber trans beam.

 

2. After that, check the fringe value of the FIB cancellation interferometer by ALS-Y_FIB_SERVO_IN1_DQ .

Its should be over than -1000~1000 (like 13349).

If smaller than that, adjust the end mirror of FIB cancellation interferometer (the orange circle in the figure).

 

3. Finally, adjust the input gain of FIB servo and check that the loop closes.

 

Images attached to this report
Comments to this report:
shinji.miyoki - 8:44 Monday 13 April 2020 (14131) Print this report

>1. The value of fiber output should be 0.8 or more. If not, adjust the PZT mirror just before the fiber (the blue circle in the figurewhile monitoring the K1:ALS-Y_ARM_INPUT_OUTPUT to maximize the fiber trans beam.

At present, 0.61, so me need a little bit adjustment. 

 

>2. After that, check the fringe value of the FIB cancellation interferometer by ALS-Y_FIB_SERVO_IN1_DQ . Its should be over than -1000~1000 (like 13349). If smaller than that, adjust the end mirror of FIB cancellation interferometer (the orange circle in the figure).

At present, 0 ~ -220 is obtained. So small. The attached file is the decrease of fringe  from 20 days ago. However, maybe, this adjustment is easy.

 

>3. Finally, adjust the input gain of FIB servo and check that the loop closes.

This is easy.

thank you.

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shinji.miyoki - 10:04 Tuesday 14 April 2020 (14141) Print this report

I adjusted only the end mirror for larger fringe.

The fringe recovered for Y at the level of about -1000 ~ 1000.

Actually, the nobs for end mirror is so soft. It shoulbe more tight and can be fixed.

 

At present,  FIB phase lock servo gains for Y were set from -9dB to -18dB for both inputs. The common offset was set from -16 to 2 to obtain zero level signal after phase lock engaging.

Yamamoto-kun, please set this value for default. 

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