Tapering studies for Terawatt level X-ray FELs with a superconducting undulator

TL;DR

This paper investigates tapering optimization in superconducting undulators to achieve terawatt-level X-ray pulses, analyzing effects of module length, technology, and limiting factors for high-power FELs.

Contribution

It introduces an optimized tapering scheme for short superconducting undulators and compares NbTi and Nb3Sn technologies for high-power X-ray FELs.

Findings

Achieves over 1 TW peak power at 4 keV with optimized tapering.

Identifies optimal section length of 1.5 m for the undulator.

Discusses limiting factors like particle detrapping and sideband modes.

Abstract

We study the tapering optimization scheme for a short period, less than two cm, superconducting undulator, and show that it can generate 4 keV X-ray pulses with peak power in excess of 1 terawatt, using LCLS electron beam parameters. We study the effect of undulator module length relative to the FEL gain length for continous and step-wise taper profiles. For the optimal section length of 1.5m we study the evolution of the FEL process for two different superconducting technologies NbTi and Nb3Sn. We discuss the major factors limiting the maximum output power, particle detrapping around the saturation location and time dependent detrapping due to generation and amplification of sideband modes.