Study of the contributions of the electrode materials to the plasma of a high-current vacuum spark
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MA DYNAMICS
Study of the Contributions of the Electrode Materials to the Plasma of a HighCurrent Vacuum Spark O. A. Bashutin, E. D. Vovchenko, E. I. Dodulad, A. S. Savjolov, and S. A. Sarantsev National Nuclear Research University Moscow Engineering Physics Institute, Kashirskoe sh. 31, Moscow, 115409 Russia Received September 21, 2011
Abstract—The contribution of the electrode material to the formation of the plasma of a lowinductive high current vacuum spark and its influence on the process of discharge micropinching were studied using Xray spectroscopy and laser diagnostics. Electrode system configurations are determined in which the contribu tions of the materials of both electrodes to the plasma emitting Xrays are comparable and in which the con tribution of one electrode is dominating. It is found that discharge pinching occurs primarily in the vapor of the pointed electrode independently of its polarity. The experimental results indicate the formation of a suprathermal electron beam in the micropinch region. DOI: 10.1134/S1063780X12030026
1. INTRODUCTION Spark discharges in vacuum have been studied for several decades. Interest in these discharges stems from their high radiative characteristics at a relatively simple design of the discharge system. At present, there are two main lines of research in this field: stud ies of vacuum spark discharges as Xray sources (for microscopy, microlithography, etc.) [1, 2] and as charged particle sources [3–5]. For each of these lines, the design of the electrode system and the parameters of the discharge circuit have their own specific features and it is assumed that the elemental composition of the radiating plasma is known. According to modern concepts, intense generation of charged particle beams is observed in the initial stage of a spark discharge, before the discharge gap is bridged by the plasma. In this case, in addition to the generation of electron beams propagating along the electric field toward the anode, ion beams propagating against the electric field from the cathode region are also observed [6, 7]. The charge of these ions can be rather high [3]. In highcurrent lowinductive vacuum spark (HLVS) discharges with a current on the order of 100 kA and higher, ions in high charged states (up to hydrogenlike ions) can form in the socalled “hot spots” arising due to plasma pinching [8]. The hot spot region is an intense source of the characteristic Xray radiation. It is commonly adopted that the most intensely radiating hot spots form in the evaporated material of the conical anode, which, as a rule, is the inner electrode [8, 9]. Nevertheless, observational data indicate that the pinching of the HLVS plasma can also occur near the inner electrode of negative polarity [10, 11]. Comparison of these data allows one
to assume that micropinch formation in a highcur rent vacuum spark always occurs in the plasma of the material of the inner electrode, regardless of its polar ity. This assumption seems to be important for better understanding of the p
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