title: Self-amplification of coherent spontaneous emission in a cherenkov free-electron maser
abstract: Ultrashort pulses of microwave radiation have been produced in a dielectric-lined Cherenkov free-electron maser (FEM) amplifier. An intense initial seed pulse, due to coherent spontaneous emission (CSE), arises at the leading edge of the electron pulse. There is evidence to show that 3-4 cycle spikes are produced through the amplification of these seed pulses. A strong dependence of the start-up power on the rise time of the electron pulse has been found. The experimental results are verified by a theoretical analysis. Our study shows that amplification in a FEM amplifier is always initiated by CSE arising from the edge of the electron pulse when the rise time is comparable to the electromagnetic wave period.
authors.affiliation: Department of Physics and Applied Physics, University of Strathclyde, Glasgow G4 0NG, United Kingdom.
authors.initials: SM
authors.lastname: Wiggins
authors.initials: DA
authors.lastname: Jaroszynski
authors.initials: BW
authors.lastname: McNeil
authors.initials: GR
authors.lastname: Robb
authors.initials: P
authors.lastname: Aitken
authors.initials: AD
authors.lastname: Phelps
authors.initials: AW
authors.lastname: Cross
authors.initials: K
authors.lastname: Ronald
authors.initials: NS
authors.lastname: Ginzburg
authors.initials: VG
authors.lastname: Shpak
authors.initials: MI
authors.lastname: Yalandin
authors.initials: SA
authors.lastname: Shunailov
authors.initials: MR
authors.lastname: Ulmaskulov