1997 Fiscal Year Final Research Report Summary
WAVE SCATTERING AND RELATIVISTIC ELECTRON BEAM ACCELERATION AND HEATING INDUCED BY NONLINEAR LANDAU DAMPING
| Project/Area Number |
08680508
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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 |
プラズマ理工学
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| Research Institution | EHIME UNIVERSITY |
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Principal Investigator |
SUGAYA Reiji EHIME UNIVERSITY,FACULTY OF SCIENCE, DEPARTMENT OF PHYSICS PROFESSOR, 理学部, 教授 (30036397)
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| Co-Investigator(Kenkyū-buntansha) |
MAEHARA Tsunehiro EHIME UNIVERSITY,FACULTY OF SCIENCE,DEPARTMENT OF PHYSICS ASSISTANT, 理学部, 助手 (40274302)
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| Project Period (FY) |
1996 – 1997
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| Keywords | nonlinear Landau damping / cascade process / Compton scattering / relativistic electron bean / particle acceleration / perpendicular ion acceleration / Potential formation / anomalous transport |
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| Research Abstract |
(1) Acceleration and heating of a relativistic electron beam by cascading nonlinear Landau damping involving three or four (ten) intense electromagnetic waves in a plasma were studied theoretically based on kinetic wave equations derived from relativistic Vlasov-Maxwell equations. Three or four (ten) electromagnetic waves exite successively two or three (nine) nonresonant beat-wave-driven relativistic electron plasma waves with a phase velocity near the speed of light[nu_p=c(1-gamma_P^<-2>)^<1/2>, gamma_p=omega/omega_<pe>]. Three (nine) beat-waves interact nonlinearly with the electron beam and accelerate it to a highly relativistic energy gamma_pm_ec^2 more effectively than by the usual nonlinear Landau damping of two electromagnetic waves.
(2) We used a test-particle to investigate numerically relativistic electron acceleration by the beat-wave excited by nonlinear Landau damping of two electromagnetic wave in plasma. It suggests that some electrons can be accelerated to the energy of
… More
-2gamma_pm_ec^2, as has been predicted theoretically.
(3) The momentum-space diffusion equation and the kinetic wave equation for resonant wave-wave scattering of electromagnetic and electrostatic waves in relativistic magnetized plasma were derived from the relativistic Vlasov-Maxwell equations. The p-dependent diffusion coefficient and the nonlinear wave-wave coupling coefficient are given in terns of third-order tensors which are amenable to analysis. The transport equations describing energy and momentum transfer between waves and particles were obtained by momentum space integration of the momentum-space diffusion equation, and are expressed in terms of nonlinear wave-wave coupling coefficient in the kinetic wave equation. The conservation laws for total energy and momentum densities of waves and particles are verified from the kinetic wave equation and the transport equations. These equations are very usuful for the theoretical analysis of transport phenomena or the acceleration and generation of high-energy or relativistic particles caused by quasi-linear and resonant wave-wave scattering.
(4) Acceleration and heating of a relativistic electron beam induced by nonlinear Landau damping of lower-hybrid waves in a magnetized plasma ware investigated theoretically based on kinetic wave equations and transport equations derived from relativistic Vlasov-Maxwell equations. It was proved that a relativistic electron beam can be efficiently by two lower-hybrid waves.
(5) Acceleration and heating of a high-energy or relativistic electron beam due to Compton scattering induced by nonlinear Landau damping of extraordinary waves propagating almost perpendicularly to the magnetic field were investgated theoretically by numerical analysis of the nonlinear wave-particle coupling coefficients. It is verified that the efficient acceleration occurs when the phase velocity of the beat-wave exceeds the velocity of the electron beam and the frequency of the extraordinary wave is larger than the right-hand cutoff frequency. The same results were derived from the single-particle theory.
(6) In an electron beam-plasma system, we observed experimentally that the electron heating occurs via Landau damping by electrostatic waves excited by nonlinear Landau damping and that the hollow radial profile of the electron density and the radial and axial electric field are produced. This is induced by the acceleration of plasma electrons due to quasilinear Landau damping of electrostatic waves and is thought to be phenomena of the anomalous transport which is observed in a fusion plasma.
(7) Particle transport along and across a magnetic field and an electric field across a magnetic field which are induced by almost perpendicularly propagating electrostatic waves in a magnetized plasma have been investigated theoretically based on quasilinear transport equations derived from Valsov-Maxwell equations. This theory is capable of explaining the fluctuation-induced anomalous transport occuring in sawtooth crashes or edge plasmas in tokamaks and the perpendicular ion acceleration in tokamaks and space plasmas as well as the anomalous electron transport observed in an electron beam-plasma system. Less
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