Limiting Energy Spread at High Laser Intensities Using Phase Space Displacement.

摘要

Phase space displacement is investigated as a method of reducing energy spread in free electron lasers producing long-wavelength (approx. 1 mm) at high laser intensity (approx. 10 to the 7th power - 10 to the 8th power W/sq cm). The technique is described and compared with the more conventional tapered wiggler that traps electrons in decelerating phase space buckets. A band model is developed to describe the movement of electrons around the phase space buckets and estimate the resulting energy spread. The energy spread obtained from the band model is compared with that obtained from a multiparticle computer simulation. Laser gain obtained by bucket capture is found to be comparable to gain obtained by phase space displacement at high intensities but energy spread is a factor of a few lower.