The physics of electron beams, as well as their interactions and applications, are complex phenomena that require direct, microscopic measures of the beam properties. In combination with start-to-end simulations, beam diagnostics can give a detailed microscopic view of the beam's phase space distributions. Such a view has turned out, in the cases of free-electron laser, bunch compression, and plasma wakefield experiments, to be critical to our basic understanding of experimentally relevant processes. The enterprise of beam diagnosis is quite challenging, as relevant time scales are below the ps level; transverse phase space characteristics must be diagnosed in the context of enormous space-charge forces.
Electron beam diagnostics can be classified as direct and indirect, longitudinal and transverse, destructive and non-destructive, single-shot and multiple shots, etc. Here we briefly describe different e-beam diagnostics commonly used in PBPL and collaborating institutions, by the type of measurements: namely, beam position monitors (BPMs), transverse spot size diagnostics, transverse emittance measurement techniques, longitudinal bunch length measurements, tomographic methods, etc.