Abstract
Foilless diode are widely used in high-power microwave devices, but the traditional foilless diodes have large volume, heavy weight, and high power consumption, which are not conducive to the application of high-power microwave system on mobile platform. In order to reduce the size of the foilless diode, improve the transmission efficiency of electron beams, and reduce the weight and power consumption of the guiding magnetic field system, an axial foilless diode with a composite guiding magnetic field system is developed in this paper. By adjusting the structure size and magnetic field parameters of solenoid coil, permanent magnet, and soft magnet, the configuration of the composite magnetic field is optimized. The diameter of the anode tube is about 40% smaller than that of the original structure, and the weight and power consumption of the guiding magnetic system are about 40% lower than that of the original system when the same axial magnetic field intensity in the uniform region is generated. When the magnetic field strength of the permanent magnet is set as 1.4 T and that of the solenoid coil is in the range of 0.5 T∼1 T, the electron beam transmission efficiency is 100%, and the diode impedance is adjustable in the range of 100 Ω∼240 Ω. The experimental results verify the correctness of the simulation analysis. The experimental results show that when the magnetic field strength of the solenoid coil is 0.98 T (0.5 T) and that of the permanent magnet is 1.4 T, the transmission efficiency of the high-current annular electron beam with a peak voltage of 636 kV (590 kV) and a peak current of 3.3 kA (2.6 kA) is 100%, and the diode impedance is about 194 Ω (220 Ω).
Highlights
Foilless diode is widely used in high-power microwave generation [1,2,3], free-electron lasers [4], and magnetically confined plasma heating [5]
In order to reduce the size of the foilless diode, improve the transmission efficiency of electron beam, and reduce the weight and power consumption of the guiding magnetic field system, a new type of axial foilless diode with a composite guiding magnetic field system is developed in this paper. e simulated and experimental results are believed to lay the foundation for the miniaturization, lightweight, and low power consumption of high-power microwave system
Structure Design of the Foilless Diode. e structure of miniaturized foilless diode guided by a composite magnetic field system is shown in Figure 2. e composite magnetic field system is mainly composed of solenoid coil, permanent magnet, and soft magnet. e inner radius, outer radius, and axial length of the solenoid coil are 47.5 mm, 168.5 mm, and 400 mm, respectively, and the ampere-turns of the solenoid coil is 315,000. e soft magnet material is steel Q235. e permanent magnet is made of sintered Nd-Fe-B with magnet brand N48, and its outer surface is coated with stainless steel 304, which has the functions of fixing and protecting permanent magnet, blocking electron bombardment, and preventing corrosion of permanent magnet material
Summary
Foilless diode is widely used in high-power microwave generation [1,2,3], free-electron lasers [4], and magnetically confined plasma heating [5]. E advantage of the structure is that the diode cathode is completely immersed in the uniform strong magnetic field of solenoid coil, which is conducive to the generation of high-quality annular electron beams. Laser and Particle Beams coil much larger than that of microwave device and drift tube, resulting in waste of excitation space; (b) if the diode is to be further miniaturized, it is necessary to reduce the distance between diode cathode and drift tube wall, and this change will lead to the enhancement of the electric field intensity on the cathode emitter, which is very easy to cause the radial emission of electrons on the cathode, causing the loss of electron energy. In order to reduce the size of the foilless diode, improve the transmission efficiency of electron beam, and reduce the weight and power consumption of the guiding magnetic field system, a new type of axial foilless diode with a composite guiding magnetic field system is developed in this paper. e simulated and experimental results are believed to lay the foundation for the miniaturization, lightweight, and low power consumption of high-power microwave system
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