[en] The complete channeling of energy from alpha particles is likely to be realized only through the excitation of a variety of waves, rather than by one wave alone. While one wave constrains more firmly the direction of the energy transfer, the necessary wave characteristics are far more easily achieved through a combination of waves, even at the expense of less restrictive motion of the α-particles

[en] Alpha particles, the byproducts of the DT reaction in tokamak fusion reactor, might be cooled through interactions with waves. Numerical simulations employing two waves,one with frequency about the alpha cyclotron frequency, and one at much lower frequency, show the existence of parameter regimes where more than half of the α-particle power can be diverted to the waves

[en] The utility of extracting α-particle power, and then diverting this power to fast fuel ions, is investigated. As power is diverted to fast ions and then to ions, a number of effects come into play, as the relative amounts of pressure taken up by electrons, fuel ions, and fast α-particles shift. In addition, if the α-particle power is diverted to fast fuel ions, there is an enhanced fusion reactivity because of the nonthermal component of the ion distribution. Some useful expressions for describing these effects are derived, and it is shown that fusion reactors with power density about twice what otherwise might be obtained can be contemplated, so long as a substantial amount of the α-particle power can be diverted. Interestingly, in this mode of operation, once the electron heat is sufficiently confined, further improvement in confinement is actually not desirable. A similar improvement in fusion power density can be obtained for advanced fuel mixtures such as D-He³, where the power of both the energetic α-particles and the energetic protons might be diverted advantageously

[en] Progress in heavy ion target design over the past few years has focused on relaxing the target requirements for the driver and for target fabrication. We have designed a plastic (CH) ablator capsule that is easier to fabricate and fill than the beryllium ablator we previously used. In addition, 2-d Rayleigh-Taylor instability calculations indicate that this capsule can tolerate ablator surface finishes up to ten times rougher than the NIF specification. We have also explored the trade-off between surface roughness and yield as a method for finding the optimum capsule. We have also designed two new hohlraums: a ''hybrid'' target and a large angle, distributed radiator target. The hybrid target allows a beam spot radius of almost 5 mm while giving gain of 55 from 6.7 MJ of beam energy in integrated Lasnex calculations. To achieve the required symmetry with the large beam spot, internal shields were used in the target to control the P2 and P4 asymmetry. The large-angle, distributed radiator target is a variation on the distributed radiator target that allows large beam entrance angles (up to 24 degrees). Integrated calculations have produced 340 MJ from 6.2 MJ of beam energy in a design that is not quite optimal. In addition, we have done a simple scaling to understand the peak ion beam power required to compress fuel for fast ignition using a short pulse laser

[en] If the energy of charged fusion products can be diverted directly to fuel ions, non-Maxwellian fuel ion distributions and temperature differences between species will result. To determine the importance of these nonthermal effects, the fusion power density is optimized at constant-β for nonthermal distributions that are self-consistently maintained by channeling of energy from charged fusion products. For D-T and D-³He reactors, with 75% of charged fusion product power diverted to fuel ions, temperature differences between electrons and ions increase the reactivity by 40-70%, while non- Maxwellian fuel ion distributions and temperature differences between ionic species increase the reactivity by an additional 3-15%

[en] In this paper a two pronged approach is taken to investigating the energy required for ignition of inertial confinement fusion capsules. A series of one dimensional LASNEX simulations is performed to create a database of barely ignited capsules that span the parameter regime Of interest. This database is used to develop scaling laws for the ignition energy in terms of both the stagnated capsule parameters and the inflight capsule parameters, and explore the connection between these two parameter sets. The second part of this paper examines how much extra energy is required to overcome the effect of the inevitable surface imperfections that are amplified during the implosion process and can lead to capsule break up in flight or to mix of cold fuel into the hotspot, both of which can cause the capsule to fail to ignite. By means of an example, the optimization of a capsule with fixed adiibat, drive pressure, and absorbed energy is performed; the capsule that is maximally robust to these failure modes is found

[en] If the energy of charged fusion products can be diverted directly to fuel ions, non-Maxwellian fuel ion distributions and temperature differences between species will result. To determine the importance of these nonthermal effects, the fusion power density is optimized at constant-β for non-thermal distributions that are self-consistently maintained by channeling of energy from charged fusion products. For D-T and D-³He reactors, with 75% of charged fusion product power diverted to fuel ions, temperature differences between electrons and ions increase the reactivity by 40-70%, while non-Maxwellian fuel ion distributions and temperature differences between ionic species increase the reactivity by an additional 3-15%

[en] The utility of extracting α particle power, an then diverting this power to fast fuel ions, is investigated. As power is diverted to fast ions and then to ions, a number of effects come into play, as the relative amounts of pressure taken up by electrons, fuel ions and fast α particles shift. In addition, if the α particle power is diverted to fast fuel ions, there is an enhanced fusion reactivity because of the non-thermal component of the ion distribution. Some useful expressions for describing these effects are derived, and it is shown that fusion reactors with power density about twice what otherwise might be obtained can be contemplated, so long as a substantial amount of the α particle power can be diverted. Interestingly, in this mode of operation, once the electron heat is sufficiently confined, further improvement in confinement is actually not desirable. A similar improvement in fusion power density can be obtained for advanced fuel mixtures such as D-³He, where the power of both the energetic α particles and the energetic protons might be diverted advantageously. (author). 26 refs, 3 figs, 7 tabs

[en] The complete channelling of energy from α particles is likely to be realized only through the excitation of a variety of waves, rather than by one wave alone. While one wave constraints more firmly the direction of the energy transfer, the necessary wave characteristics are far more easily achieved through a combination of waves, even at the expense of less restrictive motion of the α particles. (author). 27 refs, 7 figs

[en] Numerical simulations show that for a reactor-sized tokamak, a combination of excited toroidal Alfven eigenmodes (TAE) and mode-converted ion Bernstein waves (IBW) might extract more than half the energy from a birth distribution of α particles in a tokamak DT reactor. Preliminary results on TFTR are analyzed with a view towards addressing the underlying assumptions in these simulations. The data support several of the necessary conditions for realizing the alpha channeling effect. (author). 16 refs, 6 figs