[Stefan, Jeff K., Kiwamu]
We have aligned the BS this afternoon to maximize the amount of H1:ALS-C_TRY_A_DC.
This took some time since there was some confusion in the BS oplev and BS HEPI.
Current alignment biases :
H1:SUS-BS_M1_OPTICALIGN_P_OFFSET = -23
H1:SUS-BS_M1_OPTICALIGN_Y_OFFSET = 9
Current oplev nominal readout :
H1:SUS-BS_M3_OPLEV_PIT_OUTPUT ~ 5
H1:SUS-BS_M3_OPLEV_YAW_OUTPUT ~ 52
After aligning BS, H1:ALS-C_TRY_A_DC_VOLTS went to 0.3 which is higher than the value these days by a factor of 3. Also I see the red transmitted light becoming brighter as I aligned BS. This indicates that we are going back to the previous good alignment.
Before maximizing it we accidentally screwed up the BS alignment. It seems before Thomas centered the BS oplev the BS HEPI tripped for some reason. Therefore unfortunately the oplev centering was done with the wrong alignment. This complicated our alignment. Jeff untripped the BS HEPI with the intentional offsets enabled in V1 and V4 actuators which is the nominal configuration these days. Then we recovered the BS alignment by adjusting the top mass alignment biases. At the beginning we brought BS to roughly a good alignment by looking at the oplev trend and subtracting the offset introduced by the centering business. A fine alignment was done by maximizing H1:ALS-C_TRY_A_DC.