Interaction of imploding shock waves with expanding central plasma in spherical pinch experiments: Simulation analysis
ABSTRACT In the spherical pinch scheme, the hot D-T plasma produced in the center of the high pressure spherical vessel is confined by means of imploding shock waves launched from the periphery of the vessel for a time sufficiently long to achieve break-even conditions for plasma fusion. Theoretical studies on spherical pinch made so far have been limited up to the conditions of substantial expansion of the central plasma and the well-defined time delay between the creation of central plasma and the launching of the peripheral shock which led to the conclusion that, in realistic situations of SP experiments, negative time delays should be adopted, i.e., the launching of the imploding shock wave should precede the formation of the central plasma. However, the interaction of converging shock wave with the central plasma causing an additional heating and compression of the central plasma favoring plasma fusion conditions was not taken into account. Starting from the hydrodynamic equations of the system, the proposed simulation code deals with the propagation of converging shock waves and its interaction with the expanding central plasma. Considering the above-mentioned interaction in a self-consistent manner, the temporal evolution of temperature of central plasma is studied. Some results of the numerical simulation on the dynamics of shock wave propagation are also compared with the predictions of point strong explosing theory.
- SourceAvailable from: Francesco Giammanco[show abstract] [hide abstract]
ABSTRACT: The propagation of the implosive front and its evolution is studied with a shadowgraphic technique. Shadowgrams performed with glass balls are used to plot the propagation law of the shock front in the explosion, implosion, and the re-explosion stages. Based on a large number of shadowgrams, the shock front retains its quasi-spherical shape during the implosion and, after the collapse, the same shape appears in the new explosive stage. The location of the initial spark very close to the center of the ball is critical to obtain quasi-spherical and stable implosions. A lab-made Nd-glass laser provides the light source to produce gas breakdown.Optics Communications 06/1980; · 1.44 Impact Factor
- 01/1959; Academic Press.
Article: The spherical pinch[show abstract] [hide abstract]
ABSTRACT: This is essentially a review article covering several years of work on the spherical pinch (SP) concept of plasma formation and containment. Central to this concept is the creation of a hot plasma in the center of a sphere, plasma which is then compressed by strong imploding shock waves launched from the periphery of the vessel. The experimental program, which started with the classical cylindrical theta-pinch and continued with the inductive spherical pinch, has taken a turn, in recent times, with the discovery of the scaling laws governing spherical pinch experiments, which prescribe that high gas pressures are required for achieving fusion breakeven conditions. As a consequence, energy deposition in present spherical pinch devices is done through resistive, rather than inductive, discharges. In a pilot experimental program of modest initial condenser bank energy (∼ 1 KJ), we find that the instantaneous energy deposition in the central plasma can lead to temperatures of the order of 2 KeV, in agreement with the prediction of the Braginskii resistivity for such a plasma, and with the relation to the velocity of the diverging shock wave generated by the sudden deposition of energy into this plasma. Moreover, when the imploding shock waves contain the central plasma, we find the containment time to be as long as 5.4μ sec and the plasma to be stable. In discharges in deuterium, neutrons are emitted close to 107 per shot. From the experimental parameters of the plasma, one can derive a particle density for the shocked gas equal to 3.21×1019 cm−3, a plasma temperature equal to 730 eV and a productnτ=1.73 × 1014 cm−3· sec.Journal of Fusion Energy 09/1987; 6(3). · 1.00 Impact Factor