Rapid Start of Oscillations in a Magnetron with a "Transparent" Cathode

We report on the improvement of conditions for the rapid start of oscillations in magnetrons by increasing the amplitude of the operating wave that is responsible for the capture of electrons into spokes. This amplitude increase is achieved by using a hollow cathode with longitudinal strips removed, thereby making the cathode transparent to the wave electric field with azimuthal polarization. In addition, an optimal choice of the number and position of cathode strips provide favorable prebunching of the electron flow over the cathode for fast excitation of the operating mode. Particle-in-cell simulations of the A6 magnetron demonstrate these advantages of this novel cathode.

Figure 1

Dependencies of the azimuthal electric field of the synchronous wave on radius for a transparent cathode (1) and solid cathode (2).

Figure 2

Examples of an A6 magnetron with a transparent cathode (top) and solid cathode (bottom) in 3D magic simulations.

Figure 3

3D magic simulations illustrating the formation of electron spokes in the A6 magnetron using a solid cathode (left), cathode priming with 6 emitting regions (center), and a transparent cathode with 6 strips (right) at the same times in the simulation with the same voltage rise.

Figure 4

Dependence of radiated power on the azimuthal position of the cathode strip (for one period of the resonant system) with respect to the cavities (red lines) for a magnetron using a transparent cathode with 6 strips. The electron flow is right-to-left for this case. This was obtained from 3D magic simulations.

Figure 5

3D magic simulations calculating the anode current in the A6 magnetron using (a) solid cathode, (b) cathode priming, and (c) transparent cathode.

Figure 6

3D magic simulations calculating the radiated power of the A6 magnetron using (a) solid cathode, (b) cathode priming, and (c) transparent cathode.