70% Efficient Relativistic Magnetron With Axial Extraction of Radiation Through a Horn Antenna

Abstract

At the Nagaoka University of Technology (Japan), Daimon and Jiang used particle-in-cell (PIC) code simulations to demonstrate that the electronic efficiency of the A6 magnetron with axial extraction can be increased from 3% up to 37% applying different diffraction outputs, from tapered cavities in a conical horn antenna to modified expanded ones that improve magnetron matching with the antenna. This paper presents PIC code simulation results for the modified magnetron design using a transparent cathode, in contrast with Daimon and Jiang's simulations that used a solid explosive emission cathode. Furthermore, by further optimizing the magnetron parameters, we demonstrate an efficiency approaching 70% with gigawatt radiation power for an applied voltage of 400 kV. By maintaining a synchronous interaction of electrons with the operating wave, we found that the radiation power increases as the square of the diode voltage up to a diode voltage of 800 kV with short rise time that does not exceed 20 ns. In addition, we show that using a transparent cathode promotes avoiding the regime of hard excitation of magnetrons.

Hysteresis dependence of mode separation on time-varying applied voltage in a magnetron with diffraction output

“…For the A6 MOO [2] with fixed voltage Uo = 400 kV it is found that a critical value magnetic Hoo of the applied axial magnetic field Hoz that separates regions of synchronous interaction of electrons with neighboring :rr and 2:rr: /3 modes (Fig. 2) is Hoo = 4.527 kOe.…”

“…2 raises the question, why apply an input RF signal for mode switching if there is a simpler way -by changing the axial magnetic field Haz near its critical value Haa? As a practical matter, to change the magnetic field Haz during nanosecond pulses in order to change the azimuthal drift velocity of electrons (2) is impossible because of the large inductance of the solenoid that produce the magnetic field. Therefore, it is easy to rapidly change (2) by varying the applied voltage U and, thus, change the applied electric field E O on the emitters and electron hub drifting around the cathode (Fig.…”

Experimental demonstration of a compact high efficient relativistic magnetron with directly axial radiation

“…[1][2][3][4] The relativistic magnetron with diffraction output (MDO), [5][6][7][8][9][10][11] known as magnetron with axial radiation, is a promising device to be the most compact narrow band high power microwave (HPM) source. Compared with the traditional relativistic magnetron with radial extraction, the MDO not only succeeds the advantages such as simple structure and high efficiency but also has other special attractive features such as good azimuthal symmetry, compact magnetic coils, and directly radiating microwave in the axial direction.…”

Frequency agile characteristics of a dielectric filled relativistic magnetron with diffraction output

“…Relativistic magnetron with diffraction output (MDO) 1-11 is a small size, light weight, high power efficiency, and direct radiating TE 11 mode high power microwave (HPM) source. Recently, the investigations of the MDO are focused on optimizing the fundamental outputs such as enhancing the power conversion efficiency, 5,6,8 increasing the pulse duration, [11][12][13] and improving the radiation patterns. 4,6 However, as a promising portable HPM tube, the MDO should not only have the basic abilities to produce high power microwaves but also have the upgrade capabilities for different military and industrial applications.…”