Last week, we reduced the common mode displacement of the beam through MC1 to MC3.
Next work is to tilt the beam and center it.
What we did:
1. Changed the offset going into 1201 Low Noise Amplifier(1201 is for adding +5V offset so that the feedback signal will be in the range of 0-10V)
2. Using the last steering mirror(SM@PSL) and IM1, tilted the beam
3. As the beam height changed alot(~0.5cm higher at IM1), MC1 reflection could not reach MCREFL PD. So, we tilted the mirror just after MC1, too.
- continue to tilt IM1 in small increments in order to reduce PIT/YAW to length coupling
If large increments, it takes so much time re-aligning MC to get flashing!
By the way:
The signal we kept saying "MCL" was not the error signal itself. It was a feed back signal(output of the mode cleaner servo board). The cable labeled "MC REFL" is the error signal. Compare MEDM screen C1IOO_MC_SERVO.adl and the mode cleaner servo board at 1X2. You will be enlightened.
4. Disconnected the cable labeled "MC OUT1" at 1X2 (which is MCL signal to ADC) and put MC2_ULCOIL output directly using long BNC cable.