Jason, PeterK, Kiwamu (WP 6522)

We powered up the diagnostic bread board (DBB) this afternoon during the maintenance period and compared the pointing jitter signals against those from the bullseye sensor.

They show good agreement in their spectral magnitudes and showed high coherence. So pointing jitter noises seen by the bullseye are consistent with what the DBB sees.

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The attached are the plots showing the calibrated jitter noises and their coherence. As we know from the past measurements (e.g. 31631), the QPD2 spectra of the DBB show lower magnitudes than that of QPD1 by a factor of 5 or so across the entire frequency band. The calibrated bullseye jitters are found to be roughly at the identical magnitude to those seen by QPD1 of the DBB. Also, looking at the coherence, we found that the bullseye sensor seems to be almost at the same Gouy phase as QPD1.

After the measurement, we powered off the DBB by following the standard procedure (31717).

I also changed the input matrix for the pitch jitter mode of the bullseye in order to obtain zero offset when the beam is well centered. Now the input matrix is set such that (lower segment, upper right segment, upper left segment) = (-2, +1, +1) which had been (-1, +1, +1) since the week before the last week (34460). The calibration coefficient for it was then changed to reflect this change by a factor of 0.67. I updated the SDFs.