Jennie W, Josh F, Jeff K

Today we centred the beam on both QPDA and QPDB (see Josh's alog # 90659). In the process we calibrated the picomotors we use to steer onto QPD A in HAM3 and QPDB in HAM2.

We calibrated the beam steering to M_C1 (QPDA) using the picomotor M_M1 on the ISIK breadboard in HAM3.

The beam moves across the mirror (~2 inches) which corresponds to 3000 steps on the picomotor.

For future reference to move in -y global coordinates direction on QPD you move the M_M1 pciomotor down. This moves it in positive yaw or left on the photodiode, as we did small steps of 100 across the surface in yaw letting the QPD readout settle in between each step.

In the other degree of freedom, the beam moves across the mirror 2 inches with 2000 counts right on the picomotor. This move is in +z in global coordinates, and therefore down in pitch on the QPD.

I took another short calibration series of steps to calibrate the QPD with the picomotor and moving up or right with the picomotor moves up in pitch on QPD A.

Then we moved to HAM3 and did the same calibration for pitch and yaw on M_B4 and QPDB.

The calibration in M_B4 is 1500 counts of picomotor drive for the 1 inch optic. When driving up on picomotor, you drive in -z direction on M_B4, which should be up in pitch on QPD

We got another calibration in the x direction, with 1700 counts of picomotor to go across the optic, when driving picomotor right you move in +x on M_B4. which should be down in yaw on QPD.