High power microwave generation from coaxial virtual cathode oscillator using graphite and velvet cathodes

Menon, R.; Roy, Amitava; Singh, Sandeep; Mitra, S.; Sharma, Vishnu; Kumar, Satendra; Sharma, Archana; Nagesh, K. V.; Mittal, K. C.; Chakravarthy, D. P.

doi:10.1063/1.3399650

Cited by 42 publications

(11 citation statements)

References 19 publications

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“…Considerable experimental and theoretical studies have been recently performed to understand the emission properties and mechanisms of these cathodes. [2][3][4][5][6][7][8][9][10][11][12][13][14] Among the materials for explosive emission cathodes, polymer velvets have been applied in single-shot HPM tubes, 15 owing to their outstanding performance such as large emission current density and high beam uniform at relatively low field levels. 2,5 However, during the process of electron emission to form cathode plasmas with large expansion velocity, polymer velvet cathode could discharge a large amount of matters including surface contaminants and eroded velvet fibers.…”

Section: Introductionmentioning

confidence: 99%

Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances

et al. 2013

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The effect of surface Mo coating on the high-current electron emission performances for polymer velvet cathode has been investigated in a diode with A-K gap of 11.5 cm by the combination of time-resolved electrical diagnostic and temporal pressure variation. Compared with uncoated polymer velvet cathode under the single-pulsed emission mode, the Mo-coated one shows lower outgassing levels ($0.40 Pa L), slower cathode plasma expansion velocity ($2.30 cm/ls), and higher emission stability as evidences by the change in cathode current, temporal pressure variation, and diode perveance. Moreover, after Mo coating, the emission consistency of the polymer velvet cathode between two adjacent pulses is significantly improved in double-pulsed emission mode with $500 ns interval between two pulses, which further confirms the effectiveness of Mo coating for enhancement of electron emission performance of polymer velvet cathodes. These results should be of interest to the high-repetitive high-power microwave systems with cold cathodes. V C 2013 AIP Publishing LLC. [http://dx.

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Section: Introductionmentioning

confidence: 99%

Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances

et al. 2013

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“…The IREB is used to generate high-power microwave when fed to a coaxial virtual cathode (VC) oscillator (vircator) [2]. HV nanosecond discharge in gases initiated by runaway electrons (RAEs) preionizes the gas in the anode-cathode (AK) gap.…”

Section: Introductionmentioning

confidence: 99%

Effect of Spacer Surface and Geometry on Surface Discharge in Gas Using PIC Simulation

Tewari

Roy

Sharma

et al. 2015

IEEE Trans. Plasma Sci.

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The presence of spacer in a spark-gap system leads to a reduction in breakdown voltage. This paper studies the effect of spacer surface profile and surface protrusions on the breakdown voltage in compressed gases. Different spacer profiles comprising of conical angled insulators, bush-bar insulators, and double ended frustum insulators are used to study the effect of spacer profile on spacer efficiency under nanosecond pulsed voltage using particle-in-cell simulation. The effect of protrusions on the surface of the insulators is modeled to study the effect of teeth height on spacer efficiency. An increase in spacer efficiency from 86% in case of cylindrical spacer to 97% with negative angled and bush bar spacer is observed for a 20-mm spacer length placed between the spark gap electrodes with nitrogen as background gas.

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“…These calculations, however, are entirely different for very high-voltage diodes, that is, relativistic cases (>500 keV) [18]. This paper presents the experimental study of timedependent diode voltage and current waveform for various cathode materials namely graphite, stainless steel (SS), and red polymer velvet cathode [19]. Initial cathode emission area and plasma expansion velocity have been deduced for these cathode materials from perveance data comparing with 1-D Child Langmuir law.…”

Section: Introductionmentioning

confidence: 99%

Explosive Emission Properties of Cathode Materials in Relativistic Electron Beam Generation

Chandra¹,

Roy²,

Kalyanasundaram³

et al. 2014

IEEE Trans. Plasma Sci.

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Relativistic electron beam generation studies have been carried out in LIA-400 system through explosive electron emission for various cathode materials. This paper presents the emission properties of different cathode materials at peak diode voltages varying from 10 to 220 kV and at peak current levels from 0.5 to 2.2 kA in a single pulse duration of 160-180 ns. The cathode materials used are graphite, stainless steel, and red polymer velvet. The perveance data calculated from experimental waveforms are compared with 1-D Child Langmuir formula to obtain the cathode plasma expansion velocity for various cathode materials. Various diode parameters are subject to shot to shot variation analysis. Velvet cathode proves to be the best electron emitter because of its lower plasma expansion velocity and least shot to shot variability.Index Terms-Electron beam applications, electron beams, electron emission, electron sources, plasma devices, pulse power systems.

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High power microwave generation from coaxial virtual cathode oscillator using graphite and velvet cathodes

Cited by 42 publications

References 19 publications

Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances

Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances

Effect of Spacer Surface and Geometry on Surface Discharge in Gas Using PIC Simulation

Explosive Emission Properties of Cathode Materials in Relativistic Electron Beam Generation

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