Vacuum Arcs with Diffuse Cathode Attachment (Review)
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Vacuum Arcs with Diffuse Cathode Attachment (Review) V. P. Polishchuka, *, R. A. Usmanova, **, A. D. Melnikova, N. A. Voronaa, I. M. Yartseva, R. Kh. Amirova, A. V. Gavrikova, G. D. Liziakina, I. S. Samoylova, V. P. Smirnova, and N. N. Antonova aJoint
Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412 Russia *e-mail: [email protected] **e-mail: [email protected] Received March 4, 2020; revised March 4, 2020; accepted March 10, 2020
Abstract—The review covers the results of predominantly experimental studies of stationary vacuum arcs with diffuse cathode attachment that burns in vapor of the cathode material with a current density of less than 100 A/cm2. Such discharges are of great interest for a number of technologies that require the formation of high-intensity plasma flows without a droplet fraction. The discharges on cathodes made of graphite, pure metals, and oxides, as well as mixed cathodes, are considered. The specificity of the processes on vacuum arc cathodes is characterized by the ratio of the fluxes of thermally vaporized atoms and thermionic electrons. The review presents the results of studies of cathode materials with an atom-electron ratio of ~10–2 to ~108. Data on the working cathode temperature, the current–voltage characteristic of the discharge, the heat flux from the plasma to the cathode, the plasma parameters, its radiation spectrum, and the ion energy in the cathode jet are presented. Depending on the cathode material, the working temperature ranged from 1.2 to 2.5 kK. An analysis of the features of the charge-transfer processes on various cathodes is also presented. DOI: 10.1134/S0018151X20040124
CONTENTS Introduction 1. Influence of cathode emission properties on vacuum arc characteristics 2. Cathodes with a ratio of fluxes of thermally vaporized atoms and thermionic electrons of !1 2.1. Diffuse vacuum arc on a Gadolinium Cathode 2.2. Diffuse vacuum arc on a Graphite Cathode 3. Cathodes with a ratio of fluxes of thermally vaporized atoms and thermionic electrons of @1 3.1. Diffuse vacuum arc on Chromium and Lead Cathodes 3.2. Diffuse vacuum arc on Titanium with Cathode Heating by an Electron Beam 4. Diffuse vacuum arc on cerium dioxide cathode 5. Theoretical models describing the phenomena on the cathode of diffuse vacuum arc Conclusions References INTRODUCTION The principal feature of the vacuum arcs (VAs) is that the electrode erosion products are a plasmaforming medium. Thus, VAs are useful for practical applications that require a highly ionized plasma flow, not only of metal [1, 2] but of dielectric material as well [3, 4]. VA-based plasma sources are used to create functional coatings [5, 6], semiconductor doping [7],
and nanomaterials [8] and in the mass separation technologies of isotopes [9], in particular, spent nuclear fuel (SNF) [10, 11]. An arc with cathode spots (CSs) is the best-known type of VA. It is described in the literature in detail [12–15]. The cathode surface in it is speckled with domains of moving or stationary lum
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