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MIF (ITF Control)
yutaro.enomoto - 23:36 Wednesday 07 August 2019 (9860) Print this report
First results of ALS sensing noise with fiber noise cancellation

[Sugimoto, Enomoto]

We evaluated the sensing noise of the ALS system with and without the fiber noise cancellation.
We found that the cancellation successfully reduced the sensing noise of the ALS!!!
See the following spectra.

= Method =
Same as 7546.
We locked the main laser frequency to the X arm, and evaluated the ALS CARM signal in this condition.
This tells us the sensing noise of the ALS system as a whole.
We used SUMMING node and universal whitening filters as whitening filers.

= Note =
- 60 Hz hum noise is larger than that observed in the X arm commissioning (7561, for example). Currently these lines are limiting the RMS.
One reason we soon came up with is that we left an oscilloscope connected to servos today.
In any case, we will investigate about this from tomorrow.
 

Images attached to this report
Comments to this report:
kiwamu.izumi - 5:14 Thursday 08 August 2019 (9863) Print this report

This is a cool result.

How much does it reduce the rms in Hz?

yutaro.enomoto - 10:24 Thursday 08 August 2019 (9867) Print this report

Current RMS (incl. cavity pole effect) is 34 Hz, which is limited by the 60Hz line.
It was not like that during the X arm commissioning. We will investigate on that.

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