Linear Transformer Drivers (LTDs) represent a new pulsed power architecture that could dramatically reduce the size and cost of large pulsed-power drivers. Large LTD systems, however, will require hundreds, to tens-of-thousands, of lowinductance gas switches that can be DC-charged to -200kV and then be triggered with low jitter and low prefire probability. We are studying several competing gas switch geometries in an attempt to design an optimum switch for these applications as well as to increase our knowledge of the physics of the switching process. In addition to standard electrical diagnostics (V, I), we are studying the switches with a variety of optical diagnostics including fast photodiodes, a framing camera and a time-resolved spectroscopy system. In our test system, 20-nF capacitors on top and bottom of the switch are charged to voltages up to +100 kV, then the switch is triggered and current flows through the switch and a load resistor in a geometry that resembles the LTD architecture.Initial results have been obtained with a 6-stage, air-insulated switch based on a design by B. Koval'chukl. When the trigger arrives at the switch, two of the 6 gaps break down promptly but there is a delay of up to 50 ns before the other 4 gaps break down. Despite this delay, the 1-sigma jitter is + 10 ns. The 10%-to-90% risetime of the current pulse is 45 ns. Results from several competing switches will be presented.
A compact, short pulse, repetitive accelerator has many useful military and commercial applications in biological counter-proliferation , materials processing, radiography, and sterilization (medical instruments, waste, and food). The goal of this project was to develop and demonstrate a small, 700 kV accelerator, which can produce 7 kA particle beams with pulse lengths of 10-30 ns at rates up to 50 Hz. At reduced power levels, longer pulses or higher repetition rates (up to 10 kHz) could be achieved. Two switching technologies were tested: (1) spark gaps, which have been used to build low repetition rate accelerators for many years; and (2) high gain photoconductive semiconductor switches (PCSS), a new solid state switching technology. This plan was economical, because it used existing hardware for the accelerator, and the PCSS material and fabrication for one module was relatively inexpensive. It was research oriented, because it provided a test bed to examine the utility of other emerging switching technologies, such as magnetic switches. At full power, the accelerator will produce 700 kV and 7 l~4 with either the spark gap or PCSS pulser.Mature spark gap technology was used to demonstrate operation of the accelerator. Later multiple PCSS were tested with a PFL, which could drive 1/8" of the accelerator. The spark gap based system is pulse charged with a low impedance pulse forming line (PFL) which is switched by a single high current spark gap. The PFL drives four small linear induction accelerator (LIA) cavities. In FY95 and 96, the spark gap system was assembled and tested. A field-enhanced diode was tested, and the LIA was analyzed for modifications to operate continuously at 50 Hz. Prolonged testing at 500 kV and 5.5 kA produced several cable breakdown problems, which were repaired, but eventually, the cables will have to be replaced with higher breakdown strength cables for continuous operation. The longest burst tested was 3000 pulses at 30 Hz.The main advantages of PCSS versus spark gaps for the LIA are lower inductance and greater design flexibility due to the distributed switching that is possible with precisely triggered PCSS. For the LIA and the diode, this translates to faster rise-times, more rectangular pulses, the capability of shorter pulses, and potentially higher diode efficiency. The PCSS-based pulser is composed of 8 identical modules. Each module is switched with six 2-inch diameter PCSS. In FY97, 30 simultaneous current filaments were initiated on a 3-cm wide section of a single switch to limit the current per filament to less than 50 A (500 Ncm) and improve switch lifetime. The first module was assembled and tested to 210 kV and 8 kA. Further optimization of the optical trigger delivery system is necessary to reach 250 kV and 10 kA (full power for 1 module) with reasonable PCSS lifetimes (>10,000 pulses). Improved PCSS contacts were developed which demonstrated switch lifetime greater than lo7 pulses.. However, further resources are necessary to incorporate the new switches, ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.