Physical design of FEL injector based on performance-enhanced EC-ITC RF gun

TL;DR

This paper presents a compact, high-performance FEL injector design using an enhanced EC-ITC RF gun with thermionic cathode, achieving high charge, low emittance, and stable high-brightness electron bunches through detailed physical design and simulations.

Contribution

It introduces a novel FEL injector scheme employing an enhanced EC-ITC RF gun with thermionic cathode, improving charge and beam quality while simplifying structure.

Findings

Effective bunch charge ~200pC achieved.

Energy of ~14MeV with improved beam quality.

Stable high-brightness electron bunches obtained.

Abstract

To meet requirements of high performance THz-FEL (Free Electron Laser), a compact scheme of FEL injector was proposed. Thermionic cathode was chosen to emit electrons instead of photo-cathode with complex structure and high cost. The effective bunch charge was improved to ~200pC by adopting enhanced EC-ITC (External Cathode Independently Tunable Cells) RF gun to extract micro-bunches, and back bombardment effects were almost eliminated as well. Constant gradient accelerator structures were designed to improve energy to ~14MeV, while focusing system was applied for emittance suppressing and bunch state maintenance. Physical design and beam dynamics of key components for FEL injector were analyzed. Furthermore, start-to-end simulations with multi-pulses were performed by using homemade MATLAB and Parmela. The results show that continual high brightness electron bunches with low energy spread and emittance could be obtained stably.