Brett S Arnaud P

This afternoon we measured the resonnance frequencies of the ETMY in two locking configurations in order for Brett to improve the parameters of the quad model. We used PUM/UIM osem signals as well as the "temporary" optical lever to measure them. We plugged the pd electronics to the three first channels of h1pemey ADC0 in order to read the op lev signal from dtt.

For the first measurement, the top mass was locked and PUM, UIM, test mass were free. At first we didn't have a really clear signal from the PD in Pitch and Yaw, and since the PUM flags seemed to be really low and touching the osems Brett had to adjust the earthquake stops of the reaction chain in order to get the lower masses freely suspended. After the few adjustements, measurement showed all the needed frequencies in the osems as well as in the op lev.

For the second measurement, the top mass and UIM were locked. This time, the reflected beam was moving too much due to excess pitch/yaw motion, and after waiting a long time for the suspension to settle down, we changed the plan, and pointed the beam to the right edge of the test mass (bottom edge of the ear) to measure only the bounce modes. The dtt spectra of the op lev sum looked somehow funny. Fortunately the PUM osem signals were sufficient and showed all the frequencies, even the ones of the bounce modes.

Brett will post the results when they will be processed