Simulation of a cascaded longitudinal space charge amplifier for broadband radiation production using a superconducting linac

TL;DR

This paper models and optimizes a cascaded longitudinal space charge amplifier in a superconducting linac to generate broadband radiation, challenging the view of space charge effects as purely detrimental.

Contribution

It introduces a high-fidelity, grid-less space charge simulation integrated with Elegant, and applies it to optimize a novel broadband radiation source.

Findings

Validated the high-fidelity space charge model against conventional models.

Demonstrated potential for broadband radiation generation using the cascaded LSC amplifier.

Optimized beam parameters for implementation at Fermilab FAST facility.

Abstract

Longitudinal space charge (LSC) effects are generally considered harmful in free-electron lasers as they can seed unfavorable energy modulations that can result in density modulations with associated emittance dilution. It was pointed out, however, that such "micro-bunching instabilities" could be potentially useful to support the generation of broadband coherent radiation. Therefore there has been an increasing interest in devising accelerator beam lines capable of controlling LSC induced density modulations. In the present paper we augment these previous investigations by combining a grid-less space charge algorithm with the popular particle-tracking program Elegant. This high-fidelity model of the space charge is used to benchmark conventional LSC models. We finally employ the developed model to optimize the performance of a cascaded longitudinal space charge amplifier using beam parameters comparable to the ones achievable at Fermilab Accelerator Science & Technology (FAST) facility currently under commissioning at Fermilab.