[Aidan, Jeff G, Thomas, Elli]

We've been running the HWS without the Hartmann plate in place to simply measure the position of the return beam from the ETM on the sensor. We have been yawing L1 on the ETM quad suspension with a 0.35Hz sine wave excitation of 5000 counts into H2:SUS-ETMY_L1_TEST_Y.

We measured the ratio of the 0.35Hz signals on the HWS to the excitation (in magnitude and phase). The intent is to move the HWS along the optical axis (or adjust F1) such that the ETM HR surface is imaged on the HWS CCD (if this is the case, then a yawing of the ETM HR surface should produce no motion on the HWS CCD).

With a ruler bolted next to the HWS the following measurements were taken. Smaller values of position are closer to the lens F2. The 18 degree phase delay corresponds to about 140ms time delay (most likely associated with recording images, analyzing them and writing HWS data to EPICS - which occurs at roughy 7Hz).

This implies that we need to move the HWS to the position 189mm to be imaging the ETM HR surface. Alternatively, we could move the lens F1 by apprxoimately 3.5mm (increasing the distance between it and F0).