We will use the numbers to refer to each spot in the rest of this report. We are currently centered on beamspot 1

          2. We modify the HWS magnification H1:TCS-ITMY_HWS_MAGNIFICATION from 17.5 to 7.5 according to T1400686

         3. This morning, we moved SR3 alignment to the PITCH and YAW values corresponding to the four spots. At each spot:

                         - Stream the HWS images to make sure the spot was centered

                         -Create a new folder that does not contain reference *.mat file so the HWSY take new reference each time a new spot was centered.

                         -Start HWS and steam data

                         -Initiate 50 mHz, 2urad amplitude excitation on ITMY YAW (H1:SUS-ITMY_M0_OPTICALIGN_Y_EXC)

                         -Observe the changes in the three signals:

                                    1. H1:SUS-ITMY_L3_OPLEV_YAW_OUTPUT (OPLEV Yaw)

                                    2. H1:SUS-ITMY_M0_OPTICALIGN_Y_OUTPUT

                                    3. H1:TCS-ITMY_HWS_PROBE_PRISM_X (Prism X)

                         - Let the excitation run for 5-10 mins, turn off the excitation, let the OPLEV Yaw and Prism X signals to stabilize and epeat the procedure for all the spots.

        4. We then plot the signals H1:TCS-ITMY_HWS_PROBE_PRISM_X and H1:SUS-ITMY_L3_OPLEV_YAW_OUTPUT and compared the magnitude of oscillation in Prism X measured (if any). The one that has the largest 50 MHz signal is the one reflected off the HR surface of ITMY.

shows the four plots of time series of H1:TCS-ITMY_HWS_PROBE_PRISM_X signal compared to H1:SUS-ITMY_L3_OPLEV_YAW_OUTPUT.  From these plots:

                    Beam spots 3 and 4: definitely do not reflected from any surface of ITMY since there is no evidence of 50 mHz oscilliation. They may come from the CP, which fit with the fact that CP is horizontally wedged.  It is also interesting to note that the Prism X values for these two beams decrease contiously during measurement.

                    Beam spots 1 and 2: these two beams come from the 2 surfaces of ITMY.

                                                         The oscillation in X prism measured for beamspot 1 has an amplitude of approximately 0.6±0.2 urad

                                                         The oscillation in X prism measured for beamspot 2 has an amplitude of approximately 1.5±0.2 urad

                                                         Therefore, the magnitude of oscillation in x prism for beamspot 2 is greater. This can be clearly seen if the two time series are plotted together:

Spectrum_POS0102.png

CONCLUSION:

We are currently centered on the wrong beam. We will need to realign such that beamspot 2 is centered on the HWSY. This will involved moving the periscope mirrors . Our previous attempt to walk this beam onto the the HWSY while returning SR3 to nominal values have resulted in some clipping of the beam. So it will be important to identify where the clipping of the beam occurs.