J. Kissel, K. Venkateswara

After gathering a "first light" performance measurement of the H1 EX Beam Rotation Sensor (see first attachment -- the system is at air, poorly thermal shielded, and auto collimator is not well-secured to structure), we've spent nost of the day characterizing the separation between suspension point and center of mass, or "d". The goal is to have this separation be as small as possible, to maximize the rejection of translation noise.

We're running one final 1 [mHz] data point over night to confirm, but we believe the C.o.M. is currently 20+/-4 [um] above the suspension point. We think we should be able to get this down to 2 [um], with an overall mass adjustment, which we'll do tomorrow. The second attachment shows the process -- drive the platform at X [mHz], measure the ASD, and since we do not change the amplitude of excitation, this is a direct map of the Beam Tilt / Ground Tilt transfer function. In reality, we make a fit to a sine wave to gather the amplitude with more precision and to have an uncertainty estimate. The first page shows a single measurement to demonstrate our signal is well above the noise floor, the second shows the collection of measurements in the form of an ASD, and the final page shows the modeled transfer function against our measurement points.