With T.Ushiba and K.Tanaka
Summary
- This was the first RF lock of the interferometer since closing the IFI chamber. We successfully achieved an RF lock with 10 W laser power.
- Initial alignment was completed, and the REFL HWP rotation was integrated into the
INITIAL_ALIGNMENTguardian to automate the procedure. - Adjusting the CARM OLTF to set the UGF at 50 kHz allowed us to achieve the lock at 10 W.
Key Activities and Progress
REFL HWP automation
The REFL HWP rotation process was integrated into the INITIAL_ALIGNMENT guardian for XARM, YARM, and PRMI. Proper angle targets (125° for X/YARM, 155° for PRMI) were configured. Code was updated by refering LSC_LOCK.py.
Initial alignment procedures
XARM and YARM alignment was completed; beam positions on the ITM and ETM were adjusted based on camera views. OMC and PRMI alignment followed. For the XARM alignment, we also needed to adjust the alignment of PR3.
CARM OLTF measurement and tuning
Using MokuLab, we measured the CARM open-loop transfer function. The gain was adjusted from -14 dB to -16 dB to shift the UGF from 60 kHz to 50 kHz. After this, we were able to achieve the RF lock with 10 W laser power. Attached figure is the CARM OLTF measured after the adjustment.
