1988 Fiscal Year Final Research Report Summary
Particle Acceleration and Plasma Heating due to Cyclotron Subharmonic Wave
| Project/Area Number |
60580009
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
プラズマ理工学
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| Research Institution | Kyoto University |
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Principal Investigator |
ABE Hirotada Faculty of Engineering, Kyoto University.Lecturer, 工学部, 講師 (30026140)
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| Co-Investigator(Kenkyū-buntansha) |
ITATANI Ryohei Faculty of Engineering,Kyoto University Professor, 工学部, 教授 (90025833)
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| Project Period (FY) |
1985 – 1986
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| Keywords | Subharmonic Frequency / Simulation / Plasma Heating / エネルギー緩和 |
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| Research Abstract |
The purpose of this project is that the property on the resonant heating due to cyclotron subharmonic wave of frequency = (n/2) _i discovered by us is examined in detail.
In 1985 fiscal year, we have carried out the simulation on 5/2 _i resonant heating, succeeding the simulation on 3/2 _i resonant heating, originally studied. This work has been requested by the experimentalists. Any qualitative differences are not found out between the 5/2 and 3/2 resonant heating, and therefore, these two heating mechanisms are the same in essence.
Since 1986, Porkolab at MTT has attempted to explain this heating mechanism from the different aspect from ours. The mechanism proposed by him is named the nonlinear Landau damping and is characterized by appearance of the virtual wave. Therefore, it is controversial in the world and thus we have needed to reexamine our claim on the heating mechanism.
First, we have confirmed that its heating rate in time has shown a feature of the nonlinear process. Second w
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e have an analytical solution of the averaged particle orbit by adopting the method of the multi-time scaling. Third we have observed the existence of the virtual wave. However, its amplitude is about 10 % in the wave energy compared with the pump wave and is so small that the virtual wave affects the heating by only about 10 %. Therefore, the rest part of the heating should be by interpreted in terms of the cyclotron subharmonic heating.
Our original claim is that the wave of frequency = (n/2) _i forms islands resonantly in phase space of the ion particle orbit and ion is accelerated efficiently due to a particle trapping in this island and that the resonant feature of the energy deposition around = (n/2) _i layer is the result of the ion acceleration efficiency enhancement due to this trapping.
If this heating mechanism results from the phenomenon of the single particle trapping, however, heating should be saturated in an early time. If some energy relaxation mechanism exists, on the other hand, this mechanism can be considered as a true heating mechanism.
In order to see whether the energy relaxation mechanism exits in plasma or not, we have carried out the simulations in the simple system where the magnetic field and the plasma density are uniform. We have tested two cases: One is the weak and the other is the large amplitude case. In either case, the saturation of the heating is not observed. This means that the simple system of plasma itself involves some enegy relaxation relaxation mechanism. Finally we have shown that the very small binary collision in plasma owes to this energy relaxation mechanism. Less
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Research Products
(3 results)
