Research on the Emission Uniformity of Explosive Emission Cathodes in Foilless Diodes

Sun, Jun; Wu, Ping; Huo, Shaofei; Tan, Weibing; Shao, Hongxia; Chen, Changhua; Liu, Guozhi

doi:10.1109/tps.2014.2338301

Cited by 29 publications

(6 citation statements)

References 26 publications

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“…Therefore, to enhance the cathode emission, it is crucial to improve β. Herein, the electric field enhancement on the cathode surface is usually described by the macroscopic field enhancement factor β 1 [28] and the microscopic field enhancement factor β 2 [29], which are determined by the macroscopic diode structure and the surface microscopic structure, respectively. And then, the field enhancement factor is [15]:…”

Section: B Improvement Of Emission Uniformitymentioning

confidence: 99%

“…Here, the delay time of the grooved cathode was decreased by 2.2 ns compared with that of graphite cathode. Therefore, with introduction of the additional microscopic field enhancement factors, the electron emission process of the grooved cathode is apparently expedited and the delay time for explosive emission is reduced, which may improve the emission uniformity [15].…”

Section: B Improvement Of Emission Uniformitymentioning

confidence: 99%

“…However, the distribution of the initial emission micro-points is random and non-uniform, consequently, the emission points might be discrete and of relatively large size due to cathode plasma expansion [18], [21], [22], which would result in the azimuthal uniformity of the electron beam. Graphite as a cathode material is widely used in HPM generation and many reports have demonstrated excellent emission characteristics such a very short explosive emission delay time, long lifetime and good emission uniformity [14], [15], [23]- [25]. However, for operation of the graphite cathode with a focusing electrode, the emission threshold of graphite is quite high and this is not conducive to achieving good emission uniformity.…”

Section: Introductionmentioning

confidence: 99%

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Emission Uniformity of an Annular Graphite Cathode With a Focusing Electrode in a High Power Vacuum Diode

Chen

et al. 2020

IEEE Access

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The emission uniformity of an annular knife-edged cathode in a coaxial diode with a focusing electrode and operating in a low macro electric field has been investigated. It was found that the emission uniformity deteriorated as the cathode width increased from 0.5 mm to 2.0 mm. To improve the emission uniformity, a grooved graphite cathode was prepared by a laser micro-etching treatment. Experimental results demonstrated that the emission threshold for the grooved cathode may be reduced and thus the delay in explosive emission can be decreased. Visual inspection of photographs of the cathode plasmas operating under different guiding magnetic fields (GMFs) was used to confirm improvements in emission uniformity. Even under a low GMF of 0.21 T, good emission uniformity was realized. INDEX TERMS Emission uniformity, graphite cathode, grooved cathode, low guiding magnetic field, high power microwave generation.

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Section: B Improvement Of Emission Uniformitymentioning

confidence: 99%

Section: B Improvement Of Emission Uniformitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Emission Uniformity of an Annular Graphite Cathode With a Focusing Electrode in a High Power Vacuum Diode

Chen

et al. 2020

IEEE Access

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“…Since Friedman and Ury developed an electron beam injection gun guided by external magnetic field in 1970 [6,7], extensive work has been done in the past 50 years in producing high-power relativistic annular electron beams [8][9][10][11][12]. e electron beam produced by foilless diode is usually highly annular, and its space-charge limited current is much higher than that of solid beam, which means that higher current can be transported in vacuum [13,14]. erefore, foilless diodes are well capable of high-power density, long pulsed, and repetitive operated applications, such as high-power microwave devices and microsecond pulse electron accelerators [9].…”

Section: Introductionmentioning

confidence: 99%

An Axial Foilless Diode Guided by Composite Magnetic Field for the Production of Relativistic Electron Beams

Xiao

Wang

et al. 2021

Laser Part. Beams

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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).

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“…In order to improve the output power of the RBWO to reach or exceed the gigawatt level, magnetically insulated coaxial diodes (MICDs) are widely adopted to generate an intensive relativistic electron beam (REB), where explosive emission cathodes (EECs) are used to provide an annular electron beam of multi-kiloampere. In the explosive electron emission (EEE) process of the EECs, 3,4 the EEE nonuniformity is unavoidable due to the cathode surface morphology, which may result in the excitation of asymmetric modes or mode competition. 5 The nonuniformity of the EEE lies in the explosions of the micropoints in the cathode surface and the subsequent formation of the cathode plasma.…”

Section: Introductionmentioning

confidence: 99%

Research on effect of emission uniformity on X-band relativistic backward oscillator using conformal PIC code

Chen

2016

Physics of Plasmas

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Research on effect of emission uniformity on X-band relativistic backward oscillator using conformal PIC code Explosive emission cathodes (EECs) are adopted in relativistic backward wave oscillators (RBWOs) to generate intense relativistic electron beam. The emission uniformity of the EEC can render saturation of the power generation unstable and the output mode impure. However, the direct measurement of the plasma parameters on the cathode surface is quite difficult and there are very few related numerical study reports about this issue. In this paper, a self-developed three-dimensional conformal fully electromagnetic particle in cell code is used to study the effect of emission uniformity on the X-band RBWO; the electron explosive emission model and the field emission model are both implemented in the same cathode surface, and the local field enhancement factor is also considered in the field emission model. The RBWO with a random nonuniform EEC is thoroughly studied using this code; the simulation results reveal that when the area ratio of cathode surface for electron explosive emission is 80%, the output power is unstable and the output mode is impure. When the annular EEC does not emit electron in the angle range of 30 , the RBWO can also operate normally.

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Research on the Emission Uniformity of Explosive Emission Cathodes in Foilless Diodes

Cited by 29 publications

References 26 publications

Emission Uniformity of an Annular Graphite Cathode With a Focusing Electrode in a High Power Vacuum Diode

Emission Uniformity of an Annular Graphite Cathode With a Focusing Electrode in a High Power Vacuum Diode

An Axial Foilless Diode Guided by Composite Magnetic Field for the Production of Relativistic Electron Beams

Research on effect of emission uniformity on X-band relativistic backward oscillator using conformal PIC code

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