Numerical Simulations of Annular Wire-array Z-pinches in (x, Y), (r, [theta], and (r, Z) Geometries PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages : 25
Book Description
The Total Immersion PIC (TIP) code has been used in several two-dimensional geometries to understand better the measured dynamics of annular, aluminum wire-array z-pinches. The areas investigated include the formation of the plasma sheath from current-induced individual wire explosions, the effects of wire number and symmetry on the implosion dynamics, and the dependence of the Rayleigh-Taylor instability growth on initial sheath thickness. A qualitative change in the dynamics with increasing wire number was observed, corresponding to a transition between a z-pinch composed of non-merging, self-pinching individual wires, and one characterized by the rapid formation and subsequent implosion of a continuous plasma sheath. A sharp increase in radiated power with increasing wire number has been observed experimentally near this calculated transition. Although two-dimensional codes have correctly simulated observed power pulse durations, there are indications that three dimensional effects are important in understanding the actual mechanism by which these pulse lengths are produced.
Author: Publisher: ISBN: Category : Languages : en Pages : 25
Book Description
The Total Immersion PIC (TIP) code has been used in several two-dimensional geometries to understand better the measured dynamics of annular, aluminum wire-array z-pinches. The areas investigated include the formation of the plasma sheath from current-induced individual wire explosions, the effects of wire number and symmetry on the implosion dynamics, and the dependence of the Rayleigh-Taylor instability growth on initial sheath thickness. A qualitative change in the dynamics with increasing wire number was observed, corresponding to a transition between a z-pinch composed of non-merging, self-pinching individual wires, and one characterized by the rapid formation and subsequent implosion of a continuous plasma sheath. A sharp increase in radiated power with increasing wire number has been observed experimentally near this calculated transition. Although two-dimensional codes have correctly simulated observed power pulse durations, there are indications that three dimensional effects are important in understanding the actual mechanism by which these pulse lengths are produced.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Trac-II is a two dimensional axisymmetric resistive MHD code. It simulates all three spatial components (r, z, & phi;) of the magnetic field and fluid velocity vectors, and the plasma is treated as a single fluid with two temperatures (Te, Ti). In addition, it can optionally include a self-consistent external circuit. Recent modifications to the code include the addition of the 3-T radiation model, a 4-phase (solid-liquid-vapor-plasma) equation of state model (QEOS), a 4-phase electrical/thermal conductivity model, and an implicit solution of poloidal Bz, Br) magnetic field diffusion. These changes permit a detailed study of fiber and wire array Z-pinches. Specifically, Trac-II is used to study the wire array Z-pinch at the PBFA-Z pulse power generator at Sandia National Laboratory. First, in 1-D we examine the behavior of a single wire in the Z-pinch. Then, using these results as initial radial conditions in 2-D, we investigate the dynamics of wire array configurations in the r-z and r- & theta; plane. In the r-z plane we examine the growth of the m=0 or sausage instability in single wires within the array. In the r- & theta; plane we examine the merging behavior between neighboring wires. Special emphasis is placed on trying to explain how instability growth affects the performance of the Z-pinch. Lastly, we introduce Trac-III, a 3-D MHD code, and illustrate the m=1 or "kink" instability. We also discuss how Trac-III can be modified to simulate the wire array Z-pinch.
Author: Publisher: ISBN: Category : Languages : en Pages : 18
Book Description
A systematic study of annular aluminum-wire z-pinches on the Saturn accelerator shows that the quality of the implosion, including the radiated power, increases with wire number. Radiation magnetohydrodynamic (RMEC) xy simulations suggest that the implosion transitions from that of individual wire plasmas to that of a continuous plasma shell when the interwire spacing is reduced below (approximately) 1.4 mm. In the plasma-shell regime, the experimental implosions exhibit 1D- and 2D-code characteristics as evidenced by the presence of a strong first and a weak second radiation pulse that correlates with a strong and weak radial convergence. In this regime, many of the radiation and plasma characteristics are in agreement with those simulated by 2D-RMHC rz simulations. Moreover, measured changes in the radiation pulse width with variations in array mass and radius are consistent with the simulations and are explained by the development of 2D fluid motion in the rz plane. Associated variations in the K-shell yield are qualitatively explained by simple K-shell radiation scaling models.
Author: Publisher: ISBN: Category : Languages : en Pages : 14
Book Description
A systematic study of annular aluminum-wire z-pinches on the Saturn accelerator shows that the quality of the implosion, (as measured by the radial convergence, the radiated energy, pulse width, and power), increases with wire number. Radiation magnetohydrodynamic (RMHC) xy simulations suggest that the implosion transitions from that of individual wire plasmas to that of a continuous plasma shell when the interwire spacing is reduced below (approximately) 1.4 mm. In this plasma-shell regime, many of the global radiation and plasma characteristics are in agreement with those simulated by 2D-RMHC rz simulations. In this regime, measured changes in the radiation pulse width with variations in load mass and array radius are consistent with the simulations and are explained by the development of 2D fluid motion in the rz plane. Associated variations in the K-shell yield are qualitatively explained by simple radiation-scaling models.
Author: Publisher: ISBN: Category : Languages : en Pages : 44
Book Description
Characteristics of annular wire-array z-pinches as a function of wire number and at high wire number are reviewed. The data, taken primarily using aluminum wires on Saturn are comprehensive. The experiments have provided important insights into the features of wire-array dynamics critical for high x-ray power generation, and have initiated a renaissance in z-pinches when high numbers of wires are used. In this regime, for example, radiation environments characteristic of those encountered during the early pulses required for indirect-drive ICF ignition on the NIF have been produced in hohlraums driven by x-rays from a z-pinch, and are commented on here.
Author: Publisher: ISBN: Category : Languages : en Pages : 34
Book Description
Recent improvements in z-pinch wire array load design at Sandia National Laboratories have led to a substantial increase in pinch performance as measured by radiated powers of up to 280 TW in 4 ns and 1.8 MJ of total radiated energy. Next generation, higher current machines will allow for larger mass arrays and comparable or higher velocity implosions to be reached, possibly extending these result.dis the current is pushed above 20 MA, conventional machine design based on a 100 ns implosion time results in higher voltages, hence higher cost and power flow risk. Another approach, which shifts the risk to the load configuration, is to increase the implosion time to minimize the voltage. This approach is being investigated in a series of experimental campaigns on the Saturn and Z machines. In this paper, both experimental and two dimensional computational modeling of the fist long implosion Z experiments will be presented. The experimental data shows broader pulses, lower powers, and larger pinch diameters compared to the corresponding short pulse data. By employing a nested array configuration, the pinch diameter was reduced by 50% with a corresponding increase in power of> 30%. Numerical simulations suggest load velocity is the dominating mechanism behind these results.
Author: Kenro Miyamoto Publisher: Taylor & Francis ISBN: 1584887109 Category : Science Languages : en Pages : 393
Book Description
Resulting from ongoing, international research into fusion processes, the International Tokamak Experimental Reactor (ITER) is a major step in the quest for a new energy source.The first graduate-level text to cover the details of ITER, Controlled Fusion and Plasma Physics introduces various aspects and issues of recent fusion research activ
Author: Fernando Ferroni Publisher: IOS Press ISBN: 1614991286 Category : Science Languages : en Pages : 286
Book Description
Impressive progress has been made in the field of laser-plasma acceleration in the last decade, with outstanding achievements from both experimental and theoretical viewpoints. Closely exploiting the development of ultra-intense, ultrashort pulse lasers, laser-plasma acceleration has developed rapidly, achieving accelerating gradients of the order of tens of GeV/m, and making the prospect of miniature accelerators a more realistic possibility.This book presents the lectures delivered at the Enrico Fermi International School of Physics and summer school: 'Laser-Plasma Acceleration', held in Varenna, Italy, in June 2011.
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