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H1 SQZ
naoki.aritomi@LIGO.ORG - posted 11:14, Thursday 30 May 2024 (78125)
SQZ scatter noise investigation

Naoki, Andrei, Sheila

To investigate the scatter noise from SQZ at low frequency, we excited the ZM2 or ZM5 length at 1 Hz with same amplitude. The attached figure shows the scatter shelf in DARM with ZM2 or ZM5 excitation.

The scatter shelf by ZM5 excitation is much larger than ZM2, which means that the origin of the scatter light is different for these two scatter shelves. The scatter light with ZM2 excitation should come from FC, but the scatter light with ZM5 excitation should come from between ZM2 and ZM5.

We also changed the SFI2 temperature. The scatter shelf does not change much with SFI2 25.2 and 35.2, but got worse with SFI2 20.2 for ZM2 excitation.

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