[Haba, Ushiba, Komori]

The open-loop transfer function was measured in the CARM control loop.
The signal injection point is right before branch to fast and slow path in the CARM CMS.
The result is shown in the image.

• Unity gain frequency: 46 kHz
• Phase mergin: 40 deg.

These values are similar as those in O3.
The related conditions were as follows.

• The initial gain at the CARM CMS: +13dB
• The gain in the fast path block: +5 dB
• REFL power (LSC-REFL_PDA1_DC_OUTPUT): 0.50 ± 0.01 mW

In order to keep this gain with PRFPMI configuration, it might be better to get the CARM signal at POP