Experimental Demonstration of Energy Chirp Compensation by a Tunable Dielectric Based Structure

TL;DR

This paper demonstrates a tunable dielectric structure that effectively compensates for energy chirp in electron beams, potentially simplifying linac design and enhancing free-electron laser performance.

Contribution

It introduces a novel tunable dielectric de-chirper device and experimentally validates its effectiveness in reducing energy chirp in a high-energy electron beam.

Findings

Energy chirp reduced from 330 keV/mm to zero

Device performance agrees with simulations

Scalable design for FEL linacs

Abstract

A 60 MeV beam at the BNL Accelerator Test Facility (ATF) was manipulated by a planar tunable de-chirper made out of two 10 cm long dielectric slabs with copper plated backs. While the gap was changed from 5.8 mm to 1 mm, the correlated energy chirp of the low charge electron bunch was reduced from approximately 330 keV/mm to zero. This result is in agreement with simulations. Calculations show that similar devices, properly scaled to account for the expected electron bunch charge and length, can be used to remove residual correlated energy spread at the end of the linacs used for free-electron lasers (FEL). Potentially, this technique could significantly simplify linac design and improve FEL performance.