THz-driven Surface Plasmon Undulator as a Compact Highly Directional Narrow Band Incoherent X-Ray Source

We propose a short period undulator which is based on the alternating electromagnetic field pattern of THz-driven surface plasmons in a thin conductive layer on a dielectric grating. An approximate analytical model allows to assess the key performance parameters of the undulator and to estimate the emitted radiation spectrum. The specific example of a graphene based undulator is simulated in detail. For a moderate electron beam energy of 100 MeV and a bunch charge of 0.5 pC the 40 mm long undulator is shown to emit narrow band 1 keV x-ray pulses with a peak brightness of approximately 1016 photons/(s mrad2 mm2 0.1% BW). It therefore has potential for a compact and low cost x-ray source