Output power and degree of transverse coherence of X-ray free electron lasers

• Published in: Optics communications Vol. 281; no. 18; pp. 4727 - 4734
• Main Authors: Saldin, E.L., Schneidmiller, E.A., Yurkov, M.V.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-09-2008; Elsevier Science
• Subjects: Electromagnetism; electron and ion optics; Exact sciences and technology; Free-electron lasers; Fundamental areas of phenomenology (including applications); Physics; Radiation by moving charges; Electron beams; Output power; Free electron lasers; X radiation; Initial value problems; Synchrotron radiation; Amplified spontaneous emission
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2008.05.033

The explicit solution of the initial value problem is obtained for a SASE FEL (self-amplified spontaneous emission free electron laser) operating with a large ratio of electron beam emittance to the reduced wavelength,
ϵ
ˆ
=
2
π
ϵ
/
λ
≫
1
. The output power and the degree of transverse coherence are explicitly calculated for a high-gain linear regime. The degree of coherence is shown to be dependent on the ratio of the number of FEL gain lengths to the parameter
ϵ
ˆ
. In particular, in the multi-mode limit the radiation from a SASE FEL has by the squared number of gain lengths higher degree of transverse coherence than a synchrotron radiation generated by a beam with the same emittance. An estimate for the degree of coherence of the radiation from X-ray SASE FEL at saturation is presented.