Abstract and subjects
Although planar beams appears to be the ultimate solution for realizing high frequency vacuum electron devices, it is very challenging to form a sheet beam that exhibits high transport characteristics and low beam loss. Typically, a circular/elliptical beam from thermionic cathode is compressed to a high compression ratio using high magnetic focusing. The compression often causes rapid increase of transverse momentum, increasing emittance. The emittance growth in turn leads to beam interceptions at the narrow aperture of SWS/cavities. To mitigate this, we propose to use planar array of field emitters that will eventually provide a uniform planar electron beam. Field emitters are electron emitters capable of emitting electrons after the application of high voltage. The idea is to form a sheet beam from a planar array Field Emitter Arrays (FEAs), obviating the need for high magnetic compression of the beam, with the hypothesis that there will be no anomalous emittance growth. The emittance behavior of the Diamond FEAs has been analyzed and demonstrated at LANL before. This presentation will focus on beam coalescing effect of multiple beamlets emitted from field emitters and how they form sheet beam from a planar array of these beamlets.