Shot to shot variation in perveance of the explosive emission electron beam diode

Journal Article · Sun Mar 15 04:00:00 EDT 2009 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3097903· OSTI ID:21274203

Roy, Amitava; Menon, R; Singh, S K; Kulkarni, M R; Saroj, P C; Nagesh, K V; Mittal, K C; Chakravarthy, D P ^[1]

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1. Accelerator and Pulse Power Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

The shot to shot variation in perveance of a planar diode with explosive emission graphite cathode in a range of accelerating gaps 3-12 mm is investigated experimentally. The typical electron beam parameters were 200 kV, 12 kA, 100 ns, with a few hundreds of A/cm{sup 2} current density. The diode perveance remains less than the Child-Langmuir value, indicating that only a fraction of the cathode take part in the emission process. A simple statistical analysis of the diode perveance shows that the shot to shot variation is more pronounced for the later part of the accelerating pulse. The cathode plasma expansion velocity and the effective initial emission area have been calculated from the perveance data. It was found that the plasma expansion velocity varies from 3 to 6.5 cm/{mu}s. The mean expansion velocity and the standard deviation increase with the increase in the accelerating gap. The initial emission areas also varies randomly on a shot to shot basis and at the beginning of the accelerating pulse only 4%-35% of the cathode area take part in the emission process. The mean initial emission area and the standard deviation also increase with the increase in the accelerating gap. Experimental result indicates that the larger gaps and lower electric fields suggest a path to more uniform emission.

• OSTI ID: 21274203
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 3 Vol. 16; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CATHODES
ELECTRON BEAMS
GRAPHITE
PLASMA EXPANSION
THERMIONIC DIODES
VELOCITY