Miyakawa, Tanaka
## Abstract
This afternoon, we restored an IMC lock with a neoLASE laser. The UGF of IMC loop is ~96 kHz and the cross-over frequency between PZT and EOM loops is 10 kHz. This situation is the same as last Christmas (klog32138).
## What we did
After PMC lock as reported in klog34870, we tried to lock IMC by guardian. This trial is suceeded smoothly and then IMC was locked with ASC.
Then, we remembered the 330 Hz issue by 150 kHz oscillation when we used a neoLASE laser previously (the detail in klog32114, klog32138). I restored the IMC guardian script for using the high-power laser in DOWN and LOCK_PREP states and disengaged the script for using the fiber-amp laser to restore the setup in klog32138 (IMC-SERVO_IN1GAIN:16 dB, IMC-SERVO_FASTGAIN:30 dB).
After that, we locked IMC. IMC lock itself was succeeded but the stablillity was so bad. The lock duration at that time seems to be at most 1 min. First, previously we locked IMC with this setup when a mode of the PSL room is an OBSERVING mode but currently the mode of PSL room was the WORKING mode. We suspected that the WORKING mode of the room was too noisy to lock IMC so we switched the mode to the OBSERVING mode. Then the stability seems to be improved to 1 hour.
In this state, we measured the OLTF of the IMC LSC loop and the cross-over frequency between PZT and EOM loop. the UGF of the OLTF is ~95 kHz (fig.1) and the cross-over frequency is ~10 kHz (fig.2). Also, we measured the spectrum at the TEST A port. Fig. 3 shows the spectrum and 149 kHz peak such as the peak in fig.3 of klog32138 cannot be seen. Therefore, current situation is the same as last Christmas.
## Next to do for the recovery
- IMC common mode servo offset tuning
- PMC fine input alignment with pico-motors
- optimize the polarization of the input beam to PMC
- check current RFAMs in main modulation frequencies(17, 45, and 56 MHz)
- attach an interlock system on the high power laser
- PLL X/Y lock
- Arm lock with both GR and IR
