Simulations of the 100kW TJNAF FEL using a step-tapered undulator

Abstract

The Thomas Jefferson National Accelerator Facility (TJNAF) free electron laser (FEL) can be upgraded to operate at 100 kW average power in the near future using a configuration that recirculates the electron beam to recover energy. It is important to extract the maximum energy from the electron beam in a pass through the undulator while inducing the minimum amount of exhaust energy spread. A larger energy extraction reduces the requirement for a large recirculating current, while a smaller exhaust energy spread allows the intense electron beam to be recirculated without damaging components. To improve FEL performance, we explore the use of the step-tapered undulator, which alters the resonance condition halfway through the undulator. Short pulses complicate the desired interaction. Comparisons are made to the conventional periodic and linearly-tapered undulators.

Small Signal Bi-Period Harmonic Undulator Free Electron Laser

“…The photons per second per mrad 2 per 0.1% BW is modified by cos 2 Λ, Λ = ξ 3a sin ϕ+ξ 3b sin 2ϕ−nϕ in Eq. (15). We call this as bi-period index parameter.…”

“…The synchrotron radiation source and free electron laser performance have been upgraded by the use of a step tapered undulator. The scheme of the step tapered undulator alters the resonance condition halfway through the undulator [14][15][16]. A step tapered undulator provides two independently tunable resonances, and a two-color operation is feasible similar to two-stream free electron laser or two-stream electron cyclotron resonance maser [17][18][19][20][21].…”