Volumetric creation of ultra-high-energy-density plasma by irradiation of ordered nanowire arrays

Bargsten, Clayton, author
Rocca, Jorge J., advisor
Marconi, Mario C., committee member
Roberts, Jacob L., committee member
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Creating appreciable volumes of Ultra-High-Energy Density (UHED) matter in the laboratory is a challenge. Recent developments in the fabrication of vertically aligned nanowire array targets, in coordination with ultra-high-contrast femtosecond laser pulses focused to relativistic intensity, have opened the door to creating UHED matter using compact laser facilities with laser pulses of ~ 0.6 J. These high aspect ratio, vertically aligned nanostructure targets allow the laser energy to penetrate deep into the near-solid density material and heat plasmas to keV temperatures, generating Gbar pressures that are only surpassed in the laboratory by the central hot-spot of highly compressed thermonuclear fusion plasmas. The depth of the heated volume is key in governing the properties of these new UHED plasmas, and is reported here for the first time in vertically aligned nanowire arrays using a buried-tracer technique. In this study, arrays of 55 nm diameter nanowires, manufactured with a variable length segment of nickel on top of a buried cobalt segment, were irradiated with relativistic femtosecond laser pulses of (4±1) x 1019 W cm-2 intensity. Buried Co atoms are observed to ionize to the He-like state for depths greater than 4 μm, in good agreement with particle-in-cell simulations. The measured heat penetration demonstrates that the UHED plasma regime can be accessed with small high repetition rate lasers.
2016 Spring.
Includes bibliographical references.
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high energy density
plasma physics
volumetric heating
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