Origin of visibility phase fluctuations causing correlated decoherence on redundant baselines

Determine the physical origin of the visibility phase fluctuations observed in the ALBA optical synchrotron radiation interferometry measurements—particularly the strongly correlated decoherence seen across redundantly sampled baselines in the 6-hole mask—and quantify the contributions of laboratory atmospheric turbulence versus mechanical vibrations or other optical instabilities.

Background

The 6-hole mask contains two redundant baselines that sample the same spatial frequency. In the presence of element-based phase fluctuations, these redundantly sampled visibilities exhibit decoherence at the ~5% level and notably larger temporal scatter than non-redundant baselines.

A striking observation is the close correlation over time between the decoherence behavior of the two redundant baselines, suggesting a common underlying process. The authors note possible causes such as laboratory atmospheric turbulence or vibrations of optical components but state that the true origin remains to be determined, necessitating further experimental investigation.