What do you need for diffraction?

Synopsis

Diffraction limits the resolution of optical systems as well as those of other types of radiation. Scattered light or electrons from the edges of apertures generate self interference fringes that depend on the wavelength of the radiation source.  If the radiation is coherent, with a uniform wavelength and phase, then multiple events overlap to result in constructive interference called diffraction. One of the projects in my group is to measure the degree of coherence of a focussed He ion beam by testing whether we can produce a diffraction pattern. This talk will consider what we need for this experiment and the likelihood of its success.