Eigenmode analysis of a high-gain free-electron laser based on a transverse gradient undulator

Journal Article · Tue Jan 27 00:00:00 EST 2015 · Physical Review Special Topics - Accelerators and Beams

DOI:https://doi.org/10.1103/PhysRevSTAB.18.010701· OSTI ID:1181185

Baxevanis, Panagiotis; Huang, Zhirong; Ruth, Ronald; Schroeder, Carl B.

Here, the use of a transverse gradient undulator (TGU) is viewed as an attractive option for free-electron lasers (FELs) driven by beams with a large energy spread. By suitably dispersing the electron beam and tilting the undulator poles, the energy spread effect can be substantially mitigated. However, adding the dispersion typically leads to electron beams with large aspect ratios. As a result, the presence of higher-order modes in the FEL radiation can become significant. To investigate this effect, we study the eigenmode properties of a TGU-based, high-gain FEL, using both an analytically-solvable model and a variational technique. Our analysis, which includes the fundamental and the higher-order FEL eigenmodes, can provide an estimate of the mode content for the output radiation. This formalism also enables us to study the trade-off between FEL gain and transverse coherence. Numerical results are presented for a representative soft X-ray, TGU FEL example.

• Research Organization: SLAC National Accelerator Lab., Menlo Park, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-76SF00515; AC02-05CH11231
• OSTI ID: 1181185
• Alternate ID(s): OSTI ID: 1307563
• Journal Information: Physical Review Special Topics - Accelerators and Beams, Journal Name: Physical Review Special Topics - Accelerators and Beams Vol. 18 Journal Issue: 1; ISSN 1098-4402
• Publisher: American Physical Society
• Country of Publication: United States
• Language: English

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