Experimental studies of short-period wigglers and relativistic sheet electron-beam propagation in a free-electron laser.

摘要

Short-period {dollar}(lsb{lcub}w{rcub}leq{dollar} 1cm) wiggler electromagnets and sheet electron beam propagation and focusing in an FEL configuration has been studied. A novel short-period wiggler electromagnet was designed using a copper conductor wound around regions of ferromagnetic material. Saturation can be a significant limiting factor in such electromagnets, but may be minimized by the optimization of the wiggler dimensions. Experimental verification of an optimized wiggler is reported. Studies of the peak magnetic flux density and period-to-period uniformity of the wiggler as a function of alternative lamination and winding design are reported. Two critical issues for a high power FEL are beam stability and beam interception by the waveguide walls. Wiggler focusing of sheet electron beams and theoretical limits on beam parameters for negligible interception are presented. Results and analysis from a series of experiments conducted to study relativistic sheet beam generation and propagation through a short-period planar wiggler are reported. A 500 keV, 7A sheet electron beam was propagated through a 3.2mm waveguide with negligible losses due to intercepted current. In addition, the first observation of wiggler induced radiation was obtained from the sheet beam FEL in a short-period wiggler oscillator configuration.