Fluctuation Optical Microscopy of mesoscale materials.
Fluctuation microscopy, although developed on the TEM, is a technique applicable to all forms of scattered radiation that can be focused. (In principle, neutrons can also be used, but as a practical matter it is hard to focus neutrons or constrict beams by pinholes.)
Dushyant Kumar is building an optical bench to carry out Fluctuation Optical Microscopy experiments. Primarily, this apparatus is a test bed for the FXM experiments at the 2-ID-B beamline at the Argonne National Laboratory. Beam time at 2-ID-B is valuable an dlimited. This apparatus allows us to pursue ideas and develop software for analyzing data.
One important experiment we are planning is to see if we can acquire variable resolution data within one experiment. The key idea is that an elliptical aperture will generate an (approximately) elliptical focused probe. The width of the probe varies as a function of azimuthal angle (see image on right). The normalized variance plots of an isotropic sample will therefore have an azimuthal dependence. To first order, the azimuth angle will correspond to the nominal resolution dictated by the diameter of the elliptical mask at that azimuthal angle. Thus, the variable resolution information, as a function of scattering angle, is contained in one dataset. This will increase the data collection efficiency considerably.
In addition to being a testbed for the x-ray experiments, the FOM will be used to study colloids.