On the brightness, transverse emittance, and transverse coherence of field emission beam

The highly brilliant electron beam produced by field emitters is one of the enabling factors high resolution microscope with atomic resolution. In addition to brightness, are also current, current density, and coherent cathodes. These characteristics motivated use for high-frequency vacuum electric tubes accelerator applications in experiments including diffraction, holography, diffraction imaging, name a few. Here, we present an overview key applications: transverse emittance, coherence. We further discuss their implications on propagation emission beam.