Conceptual design of a1013-W pulsed-power accelerator for megajoule-class dynamic-material-physics experiments

Abstract

We have developed a conceptual design of a next-generation pulsed-power accelerator that is optimized for megajoule-class dynamic-material-physics experiments. Sufficient electrical energy is delivered by the accelerator to a physics load to achieve-within centimeter-scale samples-material pressures as high as 1 TPa. The accelerator design is based on an architecture that is founded on three concepts: single-stage electrical-pulse compression, impedance matching, and transit-time-isolated drive circuits. The prime power source of the accelerator consists of 600 independent impedance-matched Marx generators. Each Marx comprises eight 5.8-GW bricks connected electrically in series, and generates a 100-ns 46-GWelectrical-power pulse. A 450-ns-long water-insulated coaxial-transmission-line impedance transformer transports the power generated by each Marx to a system of twelve 2.5-m-radius water-insulated conical transmission lines. The conical lines are connected electrically in parallel at a 66-cm radius by a water-insulated 45-post sextuple-posthole convolute. The convolute sums the electrical currents at the outputs of the conical lines, and delivers the combined current to a single solid-dielectric-insulated radial transmission line. The radial line in turn transmits the combined current to the load. Since much of the accelerator is water insulated, we refer to it as Neptune. Neptune is 40 m in diameter, stores 4.8 MJ of electrical energy in its Marx capacitors, and generates 28 TW of peak electrical power. Since the Marxes are transit-time isolated from each other for 900 ns, they can be triggered at different times to construct-over an interval as long as 1 μs-the specific load-current time history required for a given experiment. Neptune delivers 1 MJ and 20 MA in a 380-ns current pulse to an 18-mΩ load; hence Neptune is a megajoule-class 20-MA arbitrary waveform generator. Neptune will allow the international scientific community to conduct dynamic equation-of-state, phase-transition, mechanical-property, and other material-physics experiments with a wide variety of drive-pressure time histories.

Impedance-matched Marx generators

“…Such IMGs have already been developed, and serve as the prime-power source of the new Thor accelerator [18,20,[22][23][24][25]27]. Presently, each Thor brick drives four polyethyleneinsulated 11-Ω coaxial transmission lines connected electrically in parallel.…”

“…The impedance of the set of four parallel lines is approximately matched to that of a single brick. Sandia National Laboratories is presently building a prototype Thor machine that could eventually be driven by as many as 288 bricks [18,20,[22][23][24][25]27].…”

“…IMGs could also be developed to serve as prime power sources for a wide variety of other pulsed-power accelerators, such as the Neptune machine [18,20,23,26,27] and possibly Z 300 and Z 800 [18][19][20].…”

“…VIII, the simplest form of an IMG is a single brick that drives an impedance-matched load. Such IMGs have already been developed and serve as the prime-power source of the new Thor accelerator [18,20,[22][23][24][25]27]. (The first Thor machine has been designed and is being assembled at Sandia.)…”

“…Motivated by these observations, we have conceived a new class of prime-power sources that do not use ferromagnetic cores: impedance-matched Marx generators (IMGs) [18,20,[22][23][24][25][26][27]. An IMG comprises a single stage or several stages distributed axially and connected electrically in series.…”