Generation and Characterization of Electron Bunches with Ramped Current Profiles in a Dual-Frequency Superconducting Linear Accelerator

TL;DR

This paper demonstrates a novel method to generate electron bunches with ramped current profiles in a dual-frequency superconducting linear accelerator, enabling high peak currents and tailored current distributions for advanced accelerator applications.

Contribution

It introduces a new technique using dual-frequency RF acceleration and dispersive sections to produce customizable ramped electron bunch profiles with high peak currents.

Findings

Successfully generated ~700 MeV electron bunches with kilo-Ampere peak currents.

Produced quasi-linear ramped current profiles with versatile shaping capabilities.

Simulations indicate potential for high-gradient acceleration and high transformer ratios.

Abstract

We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a superconducing radiofrequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced $\sim 700$-MeV bunches have peak currents of the order of a kilo-Amp\`ere. Data taken for various accelerator settings demonstrate the versatility of the method and in particular its ability to produce current profiles that have a quasi-linear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak accelerating electric fields with transformer ratios larger than 2 in dielectric-lined waveguides.