Study of Magnetically Driven Cylindrical Compression to Create Strongly Coupled Matter

Board Of Regents, Nshe, Obo University Of Nevada, Reno, Reno NV

Investigators

Abstract

This project develops a new experimental platform combining strong magnetic fields for compression of a metal rod, and a high power laser for high-energy x-ray generation as diagnostics. When a solid material is gradually compressed to high pressures above a million atmospheres, the solid state can be transformed to liquid, gas and eventually plasma. This high density, low temperature state of matter is called a strongly coupled plasma, as found in laser fusion cores and dense astrophysical objects. Modeling of material properties in this regime is challenging because it is too cold and dense to apply ideal plasma theory, but the thermal temperature is too high to be treated with condensed matter physics. Thus, experimental benchmarking of the physics models is important for understanding fundamental properties of high-pressured materials. So far, most compression experiments have been conducted on large laser or pulsed electrical current facilities at national laboratories with limited numbers of shots. Using a cost-effective, university-scale facility, this project will explore the feasibility of magnetically driven cylindrical compression to produce pressures comparable to or even higher than those with a planar compression technique used on large facilities. Laser-produced hard x-rays penetrate through a compressed cylinder, providing information on its density profile and material structure. If successful, the cylindrical compression with a compact pulsed power will allow researchers to study a wide range of materials in the strongly coupled regime for fundamental science and applications. This project will provide full-time support for a graduate student to be trained in relativistic laser-plasma interaction and pulsed power plasma physics. The goal of this project is twofold: characterization of short-pulse laser-produced hard x-rays and demonstration of x-ray probing of a magnetically compressed millimeter-diameter aluminum rod. Coupled experiments simultaneously using a Mega Ampere (MA) pulsed power and a high power laser in the same vacuum chamber are currently available only at the University of Nevada - Reno Nevada Terawatt Facility (NTF) and at the Z-Machine at Sandia National Laboratory. The experiments will fully utilize the NTF's coupled capability with the 1.0 MA Zebra pulsed power and 50 Terawatt Leopard short-pulse laser. Broadband and monochromatic hard x-rays (> 10 keV) produced in the laser-target interaction will be measured with calibrated x-ray spectrometers and filter stack spectrometers. Compression of a solid Al rod with a diameter ranging from several hundred microns to a few millimeters will be studied with x-ray radiography and x-ray diffraction.