| Autor: |
Zhen Zhang, Ryan Lindberg, William M. Fawley, Zhirong Huang, Jacek Krzywinski, Alberto Lutman, Gabriel Marcus, Agostino Marinelli |
| Jazyk: |
angličtina |
| Rok vydání: |
2016 |
| Předmět: |
|
| Zdroj: |
Physical Review Accelerators and Beams, Vol 19, Iss 5, p 050701 (2016) |
| Druh dokumentu: |
article |
| ISSN: |
2469-9888 |
| DOI: |
10.1103/PhysRevAccelBeams.19.050701 |
| Popis: |
Measurements of the multishot-averaged, soft x-ray, self-seeding spectrum at the LCLS free-electron laser often have a pedestal-like distribution around the seeded wavelength, which limits the spectral purity and can negatively affect some user applications not employing a post-undulator monochromator. In this paper, we study the origins of such pedestals, focusing on longitudinal phase space modulations produced by the microbunching instability upstream of the free-electron laser (FEL) undulator. We show from theory and numerical simulation that both energy and density modulations can induce sidebands in a high-gain, seeded FEL whose fractional strength typically grows as the square of the undulator length. The results place a tight constraint on the longitudinal phase space uniformity of the electron beam for a seeded FEL, possibly requiring the amplitude of long-wavelength modulations to be much smaller than the typical incoherent energy spread if the output sideband power is to remain only a couple percent or less of the amplified seed power. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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