Free electron micro-lasers

Fabrication of metallic double-gate field emitter arrays and their electron beam collimation characteristics

“…23 To reduce the beam divergence and the transverse electron velocity spread, double-gate FEAs equipped with a beam collimation gate electrode G col in addition to the electron extraction gate electrode G ext have been intensely studied. 5,[7][8][9][24][25][26][27][28][29][30][31] This is due to the fact that the emittance of a FEA can be small only when the individual beamlets are maximally collimated, 1 even though the emittance of individual beamlets is small. 33 In double-gate FEAs, a divergent field emission beam is collimated by applying a negative collimation potential V col to G col .…”

“…7,18 FEAs are expected to help simplify the gun design and extend the operation range of such TWTs. 1,15 A recent report on a 5 GHz TWT using a single-gate Spindt FEA with 100 W output 17 demonstrates the practical feasibility of FEA-based TWTs. The possibility to generate high currents with densities above 10-100 A cm À2 (Ref.…”

“…Research on field emitter arrays (FEAs) has been actively pursued [1][2][3][4][5][6][7][8][9][10][11][12][13] with the aim of realizing high current and high current density cathodes, e.g., for compact microwave vacuum electronic amplifiers, such as traveling wave tubes (TWTs) [14][15][16][17] and compact free electron lasers. 7,18 FEAs are expected to help simplify the gun design and extend the operation range of such TWTs.…”

Highly collimated electron beams from double-gate field emitter arrays with large collimation gate apertures

“…Among these, stacked double-gate devices providing a G col aperture for individual emitters exhibit the smallest electron beam emission angle. Toma et al 17 reported a factor of 15 beam size reduction, but it was accompanied by the decrease of the emission current by a factor of ϳ10 3 . With volcano-structured double-gated FEAs, electrostatic shielding of the emitter tip from G col in a nonplanar configuration largely prevented current reduction.…”

“…͓doi:10.1063/1.3551541͔ Double-gate field emitter arrays ͑FEAs͒ have been studied for high-brightness cathode applications. [1][2][3][4] Microwave vacuum electronic devices using single-gate FEAs, which allow for a compact and simplified gun design, have been successfully demonstrated. [5][6][7][8] However, a high current density field-emission electron beam with reduced transverse electron velocity spread is a crucial factor in extending the FEA-based vacuum electronic device technology to higher power densities and frequencies in the terahertz gap.…”