Tendency of spherically imploding plasma liners formed by merging plasma jets to evolve toward spherical symmetry

Abstract

Three dimensional hydrodynamic simulations have been performed using smoothed particle hydrodynamics (SPH) in order to study the effects of discrete jets on the processes of plasma liner formation, implosion on vacuum, and expansion. The pressure history of the inner portion of the liner was qualitatively and quantitatively similar from peak compression through the complete stagnation of the liner among simulation results from two one dimensional radiationhydrodynamic codes, 3D SPH with a uniform liner, and 3D SPH with 30 discrete plasma jets.Two dimensional slices of the pressure show that the discrete jet SPH case evolves towards a profile that is almost indistinguishable from the SPH case with a uniform liner, showing that non-uniformities due to discrete jets are smeared out by late stages of the implosion. Liner formation and implosion on vacuum was also shown to be robust to Rayleigh-Taylor instability growth. Interparticle mixing for a liner imploding on vacuum was investigated. The mixing rate was very small until after peak compression for the 30 jet simulation.

Experimental evidence for collisional shock formation via two obliquely merging supersonic plasma jets

“…For the most conservativeZ = 1.4 of the 30%/70% mixture case, n merged = 5.0-5.3×10 14 cm −3 , and n merged /n single = 2.1-2. 4. These values are summarized in Table I.…”

“…One study concluded that a series of shocks occurring during plasma liner convergence would degrade the implosion performance, 50 while the other showed that initial non-uniformities arising from jet merging were largely smeared out by the time of peak compression. 4 More detailed studies are needed to resolve the discrepancy. We envision a five-jet experiment on PLX followed by a 30-or 60-jet experiment to study this and other issues.…”

“…These physics issues have been considered recently via theory and numerical modeling. 4,49,50 In spherical plasma liner formation via an array of plasma jets, the initial merging would be among more than two jets, and the detailed merging geometry would depend on the port geometry of the vacuum chamber. In the case of PLX, a quasi-spherical arrangement of 60 plasma guns would result in twelve groups of five jets, with each group arranged in a pentagonal pattern.…”

“…These experiments were the second in a series of experiments intended to demonstrate the formation of imploding spherical plasma liners via an array of merging supersonic plasma jets. [3][4][5] The latter has been proposed 3,6,7 as a standoff compression driver for magneto-inertial fusion [8][9][10] (MIF) and, in the case of targetless implosions, for generating cm-, µs-, and Mbar-scale plasmas for high-energy-density physics 11 research. In our first set of experiments, the parameters and evolution of a single propagating plasma jet were characterized in detail.…”

Possible energy gain for a plasma-liner-driven magneto-inertial fusion concept

“…The efficiency of plasma guns creating and launching the jets can be optimized for a given velocity. Several recent studies have investigated various aspect of PJMIF: [11][12][13][14][15][16][17][18][19][20][21]. Methodical experimental efforts were initiated at Los Alamos National Lab (LANL) [22,-24] in collaboration with Hyper V Technologies [10,25], and the University of New Mexico [26].…”