Self-amplification of coherent spontaneous emission in a cherenkov free-electron maser
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.
Wiggins
SM
Department of Physics and Applied Physics, University of Strathclyde, Glasgow G4 0NG, United Kingdom.
Jaroszynski
DA
McNeil
BW
Robb
GR
Aitken
P
Phelps
AD
Cross
AW
Ronald
K
Ginzburg
NS
Shpak
VG
Yalandin
MI
Shunailov
SA
Ulmaskulov
MR