Formation and Acceleration of Uniformly-Filled Ellipsoidal Electron Bunches Obtained via Space-Charge-Driven Expansion from a Cesium-Telluride Photocathode

TL;DR

This paper demonstrates the experimental creation and characterization of high-charge, uniformly-filled ellipsoidal electron bunches generated via space-charge-driven expansion from a Cs-Te photocathode, advancing beam quality control.

Contribution

It introduces a novel method for producing high-charge ellipsoidal electron bunches using a Cs-Te photocathode in an RF photoinjector, with detailed experimental validation.

Findings

Produced ellipsoidal bunches with up to 0.5 nC charge

Observed signatures confirming ellipsoidal shape

Achieved 20-fold increase in charge compared to previous methods

Abstract

We report the experimental generation, acceleration and characterization of a uniformly-filled electron bunch obtained via space-charge-driven expansion (often referred to as "blow-out regime") in an L-band (1.3-GHz) radiofrequency photoinjector. The beam is photoemitted from a Cesium-Telluride semiconductor photocathode using a short ($<200$ fs) ultraviolet laser pulse. The produced electron bunches are characterized with conventional diagnostics and the signatures of their ellipsoidal character is observed. We especially demonstrate the production of ellipsoidal bunches with charges up to $\sim0.5$ nC corresponding to a $\sim20$-fold increase compared to previous experiments with metallic photocathodes.