Spatial distribution of the plasma temperature under ion-beam fast ignition
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IAGNOSTICS
Spatial Distribution of the Plasma Temperature under IonBeam Fast Ignition S. Yu. Gus’kova, D. V. Il’inb, and V. E. Shermanb a
b
Lebedev Physical Institute, Russian Academy of Sciences, Leninskii pr. 53, Moscow, 119991 Russia St. Petersburg State Polytechnical University, Politekhnicheskaya ul. 29, St. Petersburg, 195251 Russia email: [email protected]; [email protected] Received December 12, 2013; in final form, January 23, 2014
Abstract—Results are presented from theoretical studies of the formation of the spatial temperature distri bution in plasma heated by a highenergy ion beam under the conditions in which the free path lengths of ions of different parts of the beam in plasma varies in the course of its heating. Special attention is paid to ion beam heating of deuterium–tritium (DT) plasma under the conditions of fast ignition of inertial confinement fusion (ICF) targets. The influence of the initial energy spectrum of the heating beam ions on the spatial tem perature distribution is investigated. For beams with different ion charges, masses, and initial energy spectra, criteria are determined for the formation of different types of spatial temperature distributions, namely, a dis tribution with a negative temperature gradient and a quasiuniform distribution, which correspond to the edge ignition of a precompressed ICF target, as well as a distribution with a temperature peak, which corre sponds to the ignition in the inner region of the target. DOI: 10.1134/S1063780X14070034
1. INTRODUCTION Interest in the physics of plasma heating by a high energy ion beam is motivated by studies in the field of fast ignition [1, 2] of inertial confinement fusion (ICF) targets. Fast ignition of a precompressed ICF target consists in that a relatively small fraction of the thermonuclear fuel is heated in such a way that the selfsustained burning wave propagates from the igni tion region into the rest of the cold compressed ther monuclear fuel surrounding the ignition region. The temperature of the ignition region must exceed 7 keV, while its density ρ and radius R in the case of a spher ical igniter should correspond to an areal density of no less than (ρR)ig = 0.4–0.6 g/cm2. The ignition of a pre compressed ICF target by a highenergy ion beam is currently regarded as one of the most promising meth ods of fast ignition. The advantage of this method as compared to the heating by an electron beam is rela tively small scattering of highenergy ions in both the residual plasma of the evaporated part of the target and the compressed fusion material. Therefore, in contrast to electronbeam heating, ionbeam heating can be implemented without using a special transport chan nel and can result in the formation of a compact spatial distribution of the energy deposited in the compressed fusion material. Clearly, the burning dynamics and the final fusion yield depend substantially on the position of the igni tion region inside the target. For a spherical ICF tar get, the central position of the
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