Intensification of harmonic spontaneous radiation with a novel undulator
- Department of Applied Physics, Columbia University, New York City 10027 (United States)
- Physics Department 901 A, Brookhaven National Laboratory, Upton, New York 11973 (United States)
We have calculated the on-axis spectrum of spontaneous radiation emitted by an electron moving along a planar undulator that has a magnetic profile along the axis that approximates a square wave. (This could be obtained in practice by driving a ferromagnetic undulator into saturation by {open_quotes}excessive{close_quotes}current in the windings.) We find considerable enhancement of the harmonic radiation spectrum. We compare the harmonic power emitted by an electron moving through an undulator having a sine-wave field profile with the radiation emitted from an undulator having a {open_quotes}square-wave{close_quotes} profile; the latter is approximated by the first three Fourier components of the undulator magnetic field profile along the axial direction. Examples are computed for 40MeV electrons taking K{lt}1, for spontaneous radiation emitted along the axis of the system. The emission at harmonics f{gt}1 is greatly enhanced for the approximate square-wave magnetic profile: the ratio of the power emitted at f=5 by the {open_quotes}square-wave{close_quotes} undulator to that of the sine-wave undulator is about 15 (whereas the corresponding ratio at f{minus}1 is only 1.5). While this enhancement might be expected because of the appreciable n{minus}1 and n=5 Fourier components of the undulator field, higher odd harmonics are enhanced even more (e.g., x1000 at f=11). FEL gain at the harmonics should be enhanced by similar factors. {copyright} {ital 1999 American Institute of Physics.}
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 687954
- Report Number(s):
- CONF-980742--
- Journal Information:
- AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 472; ISSN 0094-243X; ISSN APCPCS
- Country of Publication:
- United States
- Language:
- English
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