Nonlinear amplification in a second-harmonic waveguide free-electron laser
ZhongXiehe
KongMichael G.
2009
This paper describes the results of numerical simulation
of second-harmonic waveguide free-electron lasers (FELs)
from the small-signal regime to the large-signal regime. Aimed at
reducing the size and hence the cost of compact waveguide FELs
operated from the microwave to the far infrared, these unconventional
waveguide FELs can substantially decrease the minimum
electron energy required for strong FEL radiation at a given frequency
while increasing the small-signal gain. This contribution
focuses on their saturation behaviors, taking into consideration
variation in wiggler field and electron-energy spread. Depending
on the roundtrip power loss within the FEL cavity and the initial
electron-energy spread, the computed relationship between interaction
gain and in-cavity power can be used to maximize the output
power at a given electron current. Furthermore, it is found that
gain degradation due to electron-energy spread remains relatively
unchanged regardless of radiation power and wiggler field.