Abstract Details
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| iched.pdf | 2009-04-21 12:43:58 | Riccardo Betti |
Magnetic fields in inertial confinement fusion implosions
Author: Riccardo Betti
Requested Type: Oral Only
Submitted: 2009-04-21 12:42:56
Co-authors: O. Gotchev, O. Polomarov, PY Chang, J. P. Knauer, J. A. Frenjie, C. K. Li, M. Manuel, R. D. Petrasso, F. H. Seguin
Contact Info:
University of Rochester
253 East River Road
Rochester, NY 14623
USA
Abstract Text:
Magnetic fields in high energy density plasmas can be self-generated by the so-called grad_nXgrad_T effect and resistive electric fields (as in Fast Ignition), or they can be externally applied through a pair of Helmholtz coils energized by a capacitor discharge. The grad_nXgrad_T fields can be induced by the fluid vorticity originating at the ablation front and amplified by the Rayleigh-Taylor (RT) instability. They can also be driven by the diamagnetic heat flux that leads to the thermo-magnetic (TM) instability, and by the electro-thermal instability. Strong magnetic fields (~10MG) are induced by the electric field driving the return current in high-intensity laser-matter interaction. Such fields collimate the fast electron beam onto the dense core and reduce the ignitor beam energy required for fast ignition. We present the results of two-dimensional simulations of the resistive magnetic fields, and the grad_nXgrad_T magnetic fields driven by the RT and TM instabilities. We also present experimental evidence of the resistive fields in intense laser-solid interactions. One and two-dimensional MHD simulations have also been carried out to investigate the effect of an externally applied magnetic field on the performance of cylindrical and spherical target implosions. Starting from a ~0.05 MG seed field, imploding plastic shells are predicted to compress the B-field up to 70 MG. Evidence for successful flux compression of the ~5T seed field is provided in recent cylindrical target implosion experiments on the OMEGA laser. The measurements were performed through the deflectrometry of 14.7 MeV protons created from a D 3He-filled glass shell backlighter. These data show the presence of a strong magnetic field localized in the hot-spot. Near term plans for the use of magnetic fields in conventional and fast ignition implosions are presented.
This work was supported by the U.S. Department of Energy Office of Fusion Energy Sciences under Grant No. DE-FG0204ER54768.
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