Abstract
The frequency offset of the sideband instability in a free-electron laser (FEL) should depend on (1-/, where is the average longitudinal velocity of the electrons and is the group velocity of the electromagnetic waves. We have tested the / dependence of the sideband shift in a 2-mm, Raman-regime FEL oscillator. A change of / from 0.93 to 0.98, accomplished by an increase in the undulator period, resulted in the measured sideband shift increasing from 6% to 40%, in approximate agreement with theory.
- Received 30 June 1986
DOI:https://doi.org/10.1103/PhysRevLett.58.763
©1987 American Physical Society