Spatial Control of Photoemitted Electron Beams using a Micro-Lens-Array Transverse-Shaping Technique

TL;DR

This paper investigates using microlens arrays to improve laser beam uniformity on photocathodes, enhancing electron beam quality and enabling new beam diagnostics in accelerators.

Contribution

It demonstrates the application of microlens arrays for transverse laser shaping and beam modulation in photoemission electron sources.

Findings

Microlens arrays significantly improve laser uniformity on photocathodes.

Transversely-modulated electron beams can be generated using microlens arrays.

Potential for beam diagnostics using shaped electron beams.

Abstract

A common issue encountered in photoemission electron sources used in electron accelerators is the transverse inhomogeneity of the laser distribution resulting from the laser-amplification process and often use of frequency up conversion in nonlinear crystals. A inhomogeneous laser distribution on the photocathode produces charged beams with lower beam quality. In this paper, we explore the possible use of microlens arrays (fly-eye light condensers) to dramatically improve the transverse uniformity of the drive laser pulse on UV photocathodes. We also demonstrate the use of such microlens arrays to generate transversely-modulated electron beams and present a possible application to diagnose the properties of a magnetized beam.