Small-size controlled vacuum spark-gap in an external magnetic field
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Small-Size Controlled Vacuum Spark-Gap in an External Magnetic Field V. I. Asyunin, S. G. Davydov, A. N. Dolgov, A. A. Pshenichnyi, and R. Kh. Yakubov All-Russia Research Institute of Automatics, Sushchevskaya ul. 22, Moscow, 127055 Russia e-mail: [email protected], [email protected] Received March 31, 2014; in final form, June 26, 2014
Abstract—It is demonstrated that the operation of a small-size controlled spark-gap can be controlled by applying a uniform external magnetic field. It is shown that the magnetic field of such a simple configuration efficiently suppresses the effect of localization of the discharge current after multiple actuations of the sparkgap. DOI: 10.1134/S1063780X15020014
1. INTRODUCTION In order to provide long lifetime and high stability of a vacuum spark-gap, it is necessary to resolve the problem of localization of the discharge region in it. Due to this effect, in the course of multiple switchings, the discharge occurs in a limited region of the sparkgap. As a result, the discharge affects only definite regions of the electrode system, thereby enhancing their surface erosion and decreasing the lifetime and stability of the spark-gap as a whole. One of the means to prevent discharge localization is to place the discharge unit in an external magnetic field. It is well-known that the presence of a magnetic field tangential to the cathode surface results in the shift of the cathode spot. In a spark discharge, this leads to the appearance of new electron emission centers, due to which the cathode spot moves in the direction of the Ampère force, whereas in an arc discharge, the cathode spot moves in the “anomalous” direction, i.e., in the direction opposite to the Ampère force [1].
well logging [3]. The vacuum spark-gap used in our experiments is a three-electrode coaxial system (the cathode, anode, and igniter electrode) placed in a dielectric vacuum case (Fig. 1). The ignition system consists of a cathode, an igniter electrode, and a 100-μm-thick dielectric (mica) washer tightly pressed between them. The length of the cathode−anode gap is 1 mm. The diameter of the aluminum cathode is
2. SCHEME OF THE EXPERIMENT AND ITS RESULTS A.A. Brish [2] proposed to create a small-size highvoltage spark-gap on the basis of an auxiliary breakdown of a vacuum gap along a dielectric surface. He also devised the first version of such a spark-gap capable of operating in a broad voltage range, from 100 V to 10 kV [3]. The use of breakdown along the dielectric surface allows one to decrease the breakdown voltage of the igniter and, accordingly, the amplitude of the start pulse. At present, small-size vacuum spark-gaps of this type are widely used in devices for photorecording of fast processes, in generators of probing electromagnetic pulses of different wavelengths, and in oil 198
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Fig. 1. Scheme of the controlled spark-gap: (1) anode, (2) cathode, (3) sealing metal spacer, (4) dielectric washer, (5) igniter electrode, (6) vacuum case, and (7) permanent magnets.
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