Demonstration of cascaded modulator-chicane micro-bunching of a relativistic electron beam

TL;DR

This paper demonstrates a novel cascaded micro-bunching technique using modulator-chicane pre-bunchers and a high-power IR laser to produce phase-locked microbunches in a relativistic electron beam, advancing laser-based phase space control.

Contribution

It introduces the first successful implementation of a cascaded micro-bunching scheme with significant improvements over traditional single-buncher methods.

Findings

96% electron trapping in tapered IFEL undulator

78% of electrons accelerated to final energy

Enhanced phase space manipulation capabilities

Abstract

We present results of an experiment showing the first successful demonstration of a cascaded micro-bunching scheme. Two modulator-chicane pre-bunchers arranged in series and a high power mid-IR laser seed are used to modulate a 52 MeV electron beam into a train of sharp microbunches phase-locked to the external drive laser. This configuration allows to increase the fraction of electrons trapped in a strongly tapered inverse free electron laser (IFEL) undulator to 96\%, with up to 78\% of the particles accelerated to the final design energy yielding a significant improvement compared to the classical single buncher scheme. These results represent a critical advance in laser-based longitudinal phase space manipulations and find application both in high gradient advanced acceleration as well as in high peak and average power coherent radiation sources.