A novel laser technique for constructing a plasma micro-undulator and a compact X-ray source

A plasma micro-undulator has been previously proposed for a compact, short-wavelength free electron laser in which a relativistic electron beam is forced to oscillate transversely in the near-sinusoidal electric field of the rippled ion-space-charge. This paper proposes a new scheme to create a plasma density ripple for the plasma micro-undulator: the laser-interference, resonance-ionization-scheme, where the pitch and density of ripple can be controlled independently by adjustment of the wavelength, intersection angle and intensity of two laser beams. A preliminary design of an undulator with a pitch of 10–100 μm, a number of pitches of 100–1000 and an undulator constant of 0.1–1.0 is discussed and concluded to be attainable by present-day technology.