This is continued from klog27045.
In order to get the full range of the PZT, the amplification of the power supply of Dsub-BNC converter should have been doubled.
However this Dsub-BNC converter(S2214287)that it was used for POP DC centering loop was not modified.
So another Dsub-BNC converter( S2214289) was modified and replace with this.
And for placing dark offset of POP WFS QPDs, we measured this with the shutters closed. (FIg1)
In this case, we did it with the PRM in the state "MISALIGNED_BF". (FIg2,3) ("MISALIGNED_BF" is state for reflected light from misaligned PRMs to hit the beam dump in the IMMT2 chamber. )
After this, the offsets was placed.(FIg4)
We put the 75 V offset in the DC centring loop of the POPWFS to see if the movement is doubled. The movement has doubled compared to before.