Transmission-Line-Circuit Model of an 85-TW, 25-MA Pulsed-Power Accelerator
Journal Article - Open Access
NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
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We have developed a physics-based transmission-line-circuit model of the Z pulsed-power accelerator. The 33-m-diameter Z machine generates a peak electrical power as high as 85 TW, and delivers as much as 25 MA to a physics load. The circuit model is used to design and analyze experiments conducted on Z. The model consists of 36 networks of transmission-line-circuit elements and resistors that represent each of Zs 36 modules. The model of each module includes a Marx generator, intermediate-energy-storage capacitor, laser-triggered gas switch, pulse-forming line, self-break water switches, and tri-plate transmission lines. The circuit model also includes elements that represent Zs water convolute, vacuum insulator stack, four parallel outer magnetically insulated vacuum transmission lines MITLs, double-post-hole vacuum convolute, inner vacuum MITL, and physics load. Within the vacuum-transmission-line system the model conducts analytic calculations of current loss. To calculate the loss, the model simulates the following processes i electron emission from MITL cathode surfaces wherever an electric-field threshold has been exceeded ii electron loss in the MITLs before magnetic insulation has been established iii flow of electrons emitted by the outer-MITL cathodes after insulation has been established iv closure of MITL anode-cathode AK gaps due to expansion of cathode plasma v energy loss to MITL conductors operated at high lineal current densities vi heating of MITL-anode surfaces due to conduction current and deposition of electron kinetic energy vii negative-space-charge-enhanced ion emission from MITL anode surfaces wherever an anode-surface-temperature threshold has been exceeded and viii closure of MITL AK gaps due to expansion of anode plasma. The circuit model is expected to be most accurate when the fractional current loss is small.
- Electricity and Magnetism