DESIGN OF RF CONDITIONER CAVITIES

Theoretical studies are made of radio frequency structures which can b e used to condition electron beams so as to greatly reduce the stringe nt emittance requirements for successful lasing in a free-electron las er. The basic strategy of conditioning calls for modulating an electro n beam in the transverse dimension, by a periodic focusing channel, wh ile it traverses a series of rf cavities, each operating in a TM210 mo de. In this paper, we analyze the cavities both analytically and numer ically (using MAFIA simulations). We find that when cylindrical symmet ry is broken the coupling impedance can be greatly enhanced. We presen t results showing various performance characteristics as a function of cavity parameters, as well as possible designs for conditioning cavit ies.