Naoki, Vicky

To fix the FC injection axis, we plan to implement the beam spot control with green QPD or IR camera at FC transmission. First we measured the beam position on FC1/2 with dither method (alog66132) and tried to center them by ZM2/3. The last time when we centered the FC1/2 is reported in alog66662.

We dithered FC1/2 P/Y and tried to minimize the dither lines in FC IR error signal which is much more sensitive than the green error signal. The template is saved in userapps/sqz/h1/Templates/dtt/filter_cavity/FC_dither_IR.xml.

The FC2 dither lines are sensitive to ZM3 and can be removed by moving ZM3. The FC1 dither lines are not very sensitive to ZM2/3. Ideally we should center FC1/2 by moving ZM2/3 as reported in alog66662, but we think that centering the FC2 by ZM3 would be enough to fix the injection beam axis. So we decided to use ZM3 only for beam spot control to center FC2. 

We will check the error signal of green QPD and IR camera at FC transmission and will implement the beam spot control.