Thermonuclear gain and parameters of fast ignition ICF-targets

Abstract

The requirements of matching shell ICF target parameters, parameters of compressing, and triggering drivers under direct~fast! ignition are developed. Thin shell target, which represents a shell-ablator with a DT-ice layer, frosted on the inner surface of the shell are considered. Design of a target which ensures the energy supply from the triggering driver to the central part of thermonuclear fuel, in both spherical and cylindrical geometry is developed. Spherical target is furnished with one or two conical channels for the injection of the triggering driver radiation. The ends of the cylindrical target are protected by heavy material walls that have the holes of the radius equal to the final radius of compressed fuel. It was found that the parameters of fast ignition spherical and cylindrical targets, which provide high thermonuclear gain of 500-2000 in the range of the compressing driver energy of 1-10 MJ, may be matched with the drivers parameters at low aspect ratios of the targets, 10-20. The operation of spherical targets at the moderate radius convergence ratio of 15-20, may be provided at the triggering driver energy not higher than 30 kJ. The operation of cylindrical target with spin-oriented DT-fuel at radius convergence ratio of 20-25 may be provided at 150-200 kJ of the triggering driver energy.

The effect of density gradient on the growth rate of relativistic Weibel instability

“…The fast ignition scenario is a very promising approach to inertial fusion, because it can significantly reduce the required laser energy. [1][2][3] Various approaches such as jet collision or shell impact concepts are now available, and the original scenario is a two-step process implying two drivers. 4 The deuterium tritium pellet is first precompressed by a laser without being ignited.…”

GARPUN-MTW: A hybrid Ti:Sapphire/KrF laser facility for simultaneous amplification of subpicosecond/nanosecond pulses relevant to fast-ignition ICF concept

“…Among them there are generation of high-order short-wavelength harmonics (Isakov et al, 2005;Kuroda et al, 2005;Ozaki et al, 2006) and attosecond pulses of X-ray radiation, acceleration of electrons, and protons over GeV energies (Glinec et al, 2005;Borghesi et al, 2005Borghesi et al, , 2007Lifshitz et al, 2006;Mangles et al, 2006;Flippo et al, 2007;Yin et al, 2006), investigations in high-energy-density physics of relativistic plasma (Hoffmann et al, 2005), laboratory modeling of astrophysical phenomena, isochoric heating of solid matter for strong shock wave generation, and equation of state studies, development of coherent and non-coherent soft X-ray sources for radiography, microlithography, and biomedical applications, etc. In the fast-ignition concept (Basov et al, 1992;Tabak et al, 1994), which is considered today as the most promising way for the inertial confinement fusion (ICF) (Gus'kov, 2005;Sakagami et al, 2006), (thermonuclear reaction is implemented in two steps: a conventional "long" nanosecond laser pulse (typically t long $ 5 ns) produces an implosion of a shell pellet and the following short UHI laser pulse (t sh $ 1-20 ps) heats and ignites the collapsed fuel before it begins to expand. For a novel target design where 0.5-PW, 0.6-ps UHI pulse was delivered through a cone to the center of a spherical target preliminary compressed by 2.5-kJ, 1.2-ns pulse, 1000-fold increase in the neutron yield and 20-30% efficiency of UHI pulse coupling to the plasma energy were demonstrated by Kodama et al (2002).…”

The density gradient effect on quantum Weibel instability

“…Then, ignition is performed through a petawatt laser shot on the side of the fuel pellet. [2][3][4] The beams of relativistic electrons are produced at the critical density surface when an ultrahigh-intensity shortpulse ($10 ps) laser interacts with dense plasma of fuel. The energetic MeV electron beam is pushed out of the pellet core and ignites the compressed deuterium tritium fuel.…”