EXPERIMENTAL STUDY OF THE MULTICHANNELING, 3 MV RIMFIRE GAS SWITCH IN THE SELF BREAKDOWN MODE * M.A. Kemp, R.D. Curry, S.D. Kovaleski University of Missouri-Columbia, 349 EBW Columbia, MO 65201 USA K.W. Struve Sandia National Laboratories Albuquerque, NM 87185 USA * Work supported by Sandia National Laboratories. Abstract Many accelerators at Sandia National Laboratories utilize the Rimfire gas switch for high voltage, high power switching. In addition, there are many multichannel closing switches used in pulsed power applications. This paper presents a brief overview of a study of the multichanneling section of the Rimfire switch. The effects of multichanneling and a method to force multichanneling are presented. I. THE RIMFIRE SWITCH Cascade switches have been used in the pulsed power industry for over 25 years. In particular, the Rimfire switch has been used extensively in accelerators at Sandia National Laboratories (Sandia) since 1985, beginning with PBFA II [1]. Other versions of the switch have been implemented into PBFA II-Z, Hermes III, Proto II, PBFA I, Saturn, and most recently, the MU Terawatt Test Stand (MUTTS) [2]. In addition, the switch will be utilized on the upcoming ZR accelerator [3]. Although the Rimfire switch has had many different versions used in its various implementations in accelerators, the basic concept and operating characteristics have not changed. A drawing of the MUTTS version of the Rimfire switch is shown in Fig. 1. Label 1 corresponds to the cascade section of the switch. This section contains nine floating toroidal electrodes separated by dielectric cylinders to form ten gaps. Label 2 is the trigger section. It consists of two hemispherical electrodes that switch one endplate, label 6, to the cascade section. Both the trigger and cascade section are contained in a dielectric housing, label 7, filled with a gas dielectric, label 8. The entire switch is immersed in oil, label 4. A photograph of the MUTTS version of the Rimfire switch is shown in Fig. 2 [4]. In this paper, all shots were taken with the switch untriggered. The switch closure process initiates when the self-break voltage of the switch is exceeded. A feature of the Rimfire switch is the multichannel breakdown in the cascade section. Instead of a single arc as in the hemispherical electrode trigger section, the toroidal electrodes promote multiple, parallel arcs for a single gap. This is beneficial because of lower switch inductance, lower energy losses, and reduced electrode erosion. Figure 1. Drawing of the MUTTS Rimfire switch. Approximate dimensions in parenthesis. Figure 2. Photograph of the MUTTS Rimfire switch. II. TEST SETUP A. MUTTS The University of Missouri Terawatt Test Stand was constructed in 2003 to supply Sandia with information 0-7803-9189-6/05/$20.00 ©2005 IEEE. 746