[kTanaka, Hirose] PRXARM lock trial Day 3. Continued from klog30092

We also adjusted the CARM_CMS gain and the number of BOOST filter stages for XARMIR lock. In this state, we tried to manually try IR lock without ALS. It is difficult to close the control loop of the Xarm lock at the timing of the flash with TEM00, probably because of the ETMX swing and the small line width of the Xarm. Next time we will try it with ALS.

Detail

1. For the initial alignment, we performed Xarm lock, Xarm ADS. After the Xarm alignment, the TRANS normalisation power of Xarm is now 1.3.
2. For the initial alignment, The angle of the PRM was manually adjusted to improve the fringe of the POP's RF90.
3. Turned HWP +30deg before locking PRX. -->>
4. For the initial alignment, PRX lock and ADS of PRX. For initial alignment of the PRX, we lock the PRX by 3 f every time, but felt that it might be better to lock the PRX by 1 f because the POP90 fluctuates less.
   The OPLEV values of the mirrors moved by ADS were recorded in the PRFPMI box and FPMI box.(FIG1) 
5. After locking down the PRX to the PRM reflection, we added an offset so that the CARMCMS error signal is near zero. However, the offset adjustment may be better when PRX+ETMX.
6. Did PRX lock and ETMX align. We adjusted the CARMCMS gain for Xarm IR lock. This is -10 dB when Xarm single lock at 3 W input power. But this time, the REFL power is multiplied by 100 in PRX. Also, the input power is 1W. We also turned the HWP to 1/3 the power of RFPD. Therefore, we set it to -16 dB.
7. We tried IR lock with this, set to one stage of boost on the CARM_CMS. The control loop closes, but the light intensity is very low. (FIG2)
   To get Xarm lock, the control loop must be closed at the flash timing with TEM00. The flash timing is very few. We also tried to close the control manually by sweeping the ETMX and sweeping the laser frequency, but it is difficult to do this manually due to the ETMX swing and the small line width of the Xarm. We will try ALS next time.