Multicavity Magnetron With the “Rodded” Quasi-Metamaterial Cathode

Abstract

We report on the use of the “rodded” or the longitudinally oriented metal-thin-wire structure as the explosive-emission cathode in high-power multicavity magnetrons. The rodded structure is transparent to the time-varying induced electric field <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$E_{1}$</tex></formula> oscillating orthogonally to the individual rods or wires of the structure. The rods (wires) are longitudinally oriented, i.e., along the magnetron axis and parallel to the external dc axial magnetic field <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX"> $H_{0}$</tex></formula> . The mode pattern established within the magnetron resonant cavity corresponds to one of the TE-like cavity modes of the magnetron operation. This allows defining the rodded structure as the quasi-metamaterial (i.e., not-entirely-metamaterial) structure. Particle-in-cell simulations of the U.S. Air Force Research Laboratory's six-cavity (AFRL-A6) L-band magnetron demonstrate that the rodded quasi-metamaterial cathode allows the magnetron to much more faster select the desired <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$2 \pi/3$</tex></formula> magnetron operating mode within the broader range of the input operating parameters (from 130 to 200 kV at 0.15 T), as compared with the same magnetron working with the traditional smooth cylindrical cathode (from 140 to 160 kV at 0.15 T).