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Title: Influence of emission threshold of explosive emission cathodes on current waveform in foilless diodes

The emission threshold of explosive emission cathodes (EECs) is an important factor for beam quality. It can affect the explosive emission delay time, the plasma expansion process on the cathode surface, and even the current amplitude when the current is not fully space-charge-limited. This paper researches the influence of the emission threshold of an annular EEC on the current waveform in a foilless diode when the current is measured by a Rogowski coil. The particle-in-cell simulation which is performed under some tolerable and necessary simplifications shows that the long explosive emission delay time of high-threshold cathodes may leave an apparent peak of displacement current on the rise edge of the current waveform, and this will occur only when the electron emission starts after this peak. The experimental researches, which are performed under a diode voltage of 1 MV and a repetitive frequency of 20 Hz, demonstrate that the graphite cathode has a lower emission threshold and a longer lifetime than the stainless steel cathode according to the variation of the peak of displacement current on the rise edge of the current waveform.
Authors:
;  [1] ;  [2] ; ; ;  [3]
  1. Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)
  2. (China)
  3. Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an 710024 (China)
Publication Date:
OSTI Identifier:
22490077
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 8; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AMPLITUDES; BEAM PRODUCTION; CATHODES; CURRENTS; ELECTRIC POTENTIAL; ELECTRON EMISSION; GRAPHITE; PLASMA EXPANSION; PLASMA SIMULATION; ROGOWSKI COIL; SPACE CHARGE; STAINLESS STEELS; TIME DELAY; WAVE FORMS