Nanometer emittance ultralow charge beams from rf photoinjectors
- R. K. Li
- K. G. Roberts
- C. M. Scoby
- H. To
- P. Musumeci
DOIAbstract
In this paper we discuss the generation of a new class of high brightness relativistic electron beams, characterized by ultralow charge (0.1–1 pC) and ultralow normalized emittance (<50 nm). These beams are created in rf photoinjectors when the laser is focused on the cathode to very small transverse sizes (<30 μm rms). In this regime, the charge density at the cathode approaches the limit set by the extraction electric field. By shaping the laser pulse to have a cigarlike aspect ratio (the longitudinal dimension much larger than the transverse dimension) and a parabolic temporal profile, the resulting space charge dominated dynamics creates a uniformly filled ellipsoidal distribution and the emittance can be nearly preserved to its therm...
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