Demonstration of eigen-to-projected emittance mapping for an ellipsoidal electron bunch

Abstract

Phase-space partitioning offers an attractive path for the precise tailoring of complex dynamical systems. In beam physics, the proposed approach involves (i) producing beams with cross-plane correlations to control kinematic-moment invariants known as eigenemittances and (ii) mapping them to invariants of motion associated with given degrees of freedom via a decoupling transformation. Here we report on the direct experimental demonstration of the mapping of eigenemittances to transverse emittances for an electron beam. Measured phase space density confirms the generation of beams with asymmetric transverse emittance ratio $>200$ consistent with the initiated eigenemittance values. In addition, the bunches were produced via photoemission in the space-charge-driven expansion regime ultimately resulting in the generation of uniformly charged three-dimensional ellipsoidal bunches. The ellipsoidal character of the distributions is experimentally confirmed.