1997 Fiscal Year Final Research Report Summary
Alpha-Particle Effect in Ignition-Experiment-Grade Laser Fusion Pellets
| Project/Area Number |
08680538
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Nuclear fusion studies
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| Research Institution | Kyushu University |
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Principal Investigator |
NAKAO Yasuyuki Kyushu University, Department of Nuclear Engineering, Associate Professor, 工学部, 助教授 (00164129)
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| Co-Investigator(Kenkyū-buntansha) |
KUDO Kazuhiko Kyushu University, Department of Nuclear Engineering, Professor, 工学部, 教授 (40039681)
ODA Akinori Kyushu University, Department of Nuclear Engineering, Research Associate, 工学部, 助手 (60224234)
NAKASHIMA Hideki Kyushu University, Department of Energy Conversion Engineering, Professor, 総合理工学研究科, 教授 (60112306)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Laser fusion / Ignition experiment / alpha-particle / Energy deposition / Electron degneracy / Burn property / Diffusion approximation / Two-dimensional code |
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| Research Abstract |
(1) Effect of EIectron Degeneracy on alpha-Particle Heating
The configuration of ICF fuel pellets at the final stage of compression consists of a central hot (<greater than or equal>4keV) spark with low density and a remaining "cold" (<1keV) main fuel with high density. Most of the electrons in the fuel plasma are in degenerate state, being governed by the Fermi-Dirac statistics. In this study we first examined the transport of 3.52-MeV alpha-particles in degenerate plasma spheres. Compared with the case of classical (i.e.Maxwellian) plasmas, the electronic stopping power substantially decreases and hence the range of the alpha-particles increases. The slowing-down of individual alpha-particle is thus strongly influenced by the state of e
In actual burning ICF pellets, however, the alpha-particles produced in the central ignited spark deposit must of their energy near the ignited region. They do not enter deeply into the cold main fuel where most of the electrons are degenerate. On the other hand, neutrons deposit a certain fraction of their energy in the main fuel region, thereby resolving the degeneracy. Thus, the electron degeneracy at he final stage of fuel compression does not affect the thermonuclear burning.
(2) Validity of Diffusion Approximation for alpha-Particle Transport
It was found that the alpha-particle heating in ICF plasma can be well calculated using approximate diffusion model, if we adopt Levermore's diffusion coefficient and appropriately discretize the energy variable. We have also developed a two-dimensional alpha-particle diffusion code.
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