Eigenmode analysis of a high-gain free-electron laser based on a transverse gradient undulator
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, a...
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Published in | Physical review special topics. PRST-AB. Accelerators and beams Vol. 18; no. 1; p. 010701 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
College Park
American Physical Society
27.01.2015
American Physical Society (APS) |
Subjects | |
Online Access | Get full text |
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Summary: | 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. |
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Bibliography: | USDOE AC02-76SF00515; AC02-05CH11231 |
ISSN: | 1098-4402 1098-4402 2469-9888 |
DOI: | 10.1103/PhysRevSTAB.18.010701 |