Gas switch development for application in Z refurbishment (ZR) has continued since PPPS Conference 2001. Several iterations have been tested both in oil and water dielectrics. The first switch tested was an evolved version of the Sandia designed HERMES III switch [G. J. Denison et al., 1985]. The 6 MV ZR baseline switch consists of a self-breakdown (cascade) section in which the discharge current flows in several parallel channels, and a trigger section where the current flows through a single spark channel. The second switch tested is a cantilevered switch. The entire cascade section is cantilevered on a plastic support rod allowing for a single continuous insulator housing but having the same characteristics as the baseline. The third switch tested is a Sandia hybrid switch. The laser triggered section of the hybrid switch includes 5 cascade like electrodes connected in parallel to a triggered gap via a /spl sim/2 /spl mu/H series isolation inductor. The discharge current in the hybrid switch trigger section flows in several parallel channels eliminating the single channel flow as in the baseline switch trigger section. The design iterations of these switches and results of these tests are presented.

Development/tests of 6-MV triggered gas switches at SNL

Many accelerators at Sandia National Laboratories utilize the Rimfire gas switch for high-voltage, high-power switching. Future accelerators will have increased performance requirements for switching elements. When designing improved versions of the Rimfire switch, there is a need for quick and accurate simulation of the electrical effects of geometry changes. This paper presents an advanced circuit model of the Rimfire switch that can be used for these simulations. The development of the model is shown along with comparisons to past models and experimental results.

Modeling and analysis of the rimfire gas switch

Many pulsed power applications require multichannel switching because of stringent low erosion and low impedance requirements. Rimfire, which is a multigap multichanneling switch, has been implemented extensively for this purpose at Sandia National Laboratories for several decades, but with incomplete understanding. This paper presents a thorough experimental analysis of impedance and multichanneling characteristics for a multigap switch under the influence of a laser trigger and in an SF6 environment. The implications of these results on the future design of multichanneling multigap gas switches are also presented

Multichannel and Impedance Analysis of the Laser-Triggered Rimfire Gas Switch

The "rimfire", or "cascade" gas switch Bloomquist, DD. et. al.,(1985), developed at Sandia National Laboratories, presently operates both in Hermes III (in oil with peak voltage of 2.5 MV) and in Z (in water at 4.8 MV). In the proposed ZR accelerator Struve, KW. et. al., (2001), pulse-compression section the switch needs to reliably function (less than 0.2 % probability of pre-fire, and /spl sim/2.5 ns jitter) at up to 5.5 MV, above any previous operation. We are studying appropriate design enhancements theoretically and in the laboratory Corley, JP. et. al., on Sandia's Advanced Pulsed Power Research Module (APPRM, 1 MA, 800-ns pulse).

http://ieeexplore.ieee.org/iel5/9002/28564/01277683.pdf

Modeling 6 MV gas switches for the ZR accelerator

In a wide variety of high-power pulsed devices, the megavolt switch plays a key role in the system performance. A capacitance-resistance coupling structure was designed to produce UV light which triggered the switch to decrease the breakdown jitter. High-speed electrical measurements with a circuit integrating probe in the nanosecond range were employed to measure the voltage before the switch. From the experimental results, the breakdown characteristic of a 3-MV UV-illumination switch was obtained in the range of 1.6-2.5 MV: The jitter of the breakdown voltage is lower than 25 kV, and the jitter of the breakdown time is shorter than 5 ns.

A 3-MV Low-Jitter UV-Illumination Switch

Summary form only given. The Advanced Pulsed Power Research Module (APPRM) was created at Sandia National Laboratory (SNL) to serve as a test bed for the development of pulsed power technologies and components that could be used in future generation high power facilities. In the present configuration the test bed is comprised of a 56 stage, 850-kJ Marx generator that charges a 5.5-Ohm water insulated Intermediate Storage Capacitor (ISC) to more than 7 MV in /spl sim/1.5 us. The switches tested were located at the output end of the ISC where they connected the output to a 5.5-Ohm CuSO/sub 4/ resistive load. Several switches have been tested on APPRM. The first switch tested was an evolved version of the Sandia designed HERMES III switch. It consists of self-breakdown (cascade) section where the discharge current flows in several parallel channels, and a trigger section where the current flows through a single spark channel. The second switch tested was a Russian/Sandia Hybrid switch. The trigger section of the Hybrid switch, designed at High Current Electronics Institute (HCEI) in Tomsk, Russia, includes six HCEI composite electrodes connected in parallel to a triggered gap via a 4-uH series isolation inductor. The discharge current in the Hybrid switch trigger section flows in several parallel channels eliminating the single channel flow as in the Sandia switch trigger section. The last switch tested is a HCEI switch design where the trigger and cascade sections are comprised of HCEI composite electrodes. The design of the switches and results of these tests will be presented as well as the analysis and comparison of results.

J.M. Navarro

Papers

Development/tests of 6-MV triggered gas switches at SNL

Tests of 6-MV triggered switches on APPRM at SNL