2007 Fiscal Year Final Research Report Summary
Development of Synergetic Fueling Control Compatible with Confinement Improvement and Sustainability of High-Temperature Plasma
| Project/Area Number |
17206095
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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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 | National Institute for Fusion Science |
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Principal Investigator |
YAMADA Hiroshi National Institute for Fusion Science, Department of Large Helical Device Project, Professor (20200735)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAMOTO Ryuichi National Institute for Fusion Science, 准教授 (10290917)
MIYAZAWA Junichi National Institute for Fusion Science, Department of Large Helical Device Project, Associate Professor (50300728)
TANAKA Kenji National Institute for Fusion Science, Department of Large Helical Device Project, Associate Professor (50260047)
MORISAKI Tomohiro National Institute for Fusion Science, Department of Large Helical Device Project, Associate Professor (60280591)
MASUZAKI Suguru National Institute for Fusion Science, Department of Large Helical Device Project, Associate Professor (80280593)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Fusion plasma / Experimental physics / Fueling efficiency / Pellet injection / Particle pumping / Magnetic confinement |
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| Research Abstract |
Establishment of a control scheme of high-temperature plasmas is prerequisite for a future fusion reactor. This research has paid attention to a synergetic effect of external control of refueling and intrinsic property of confinement and sustainability in plasmas. Based on the accumulated knowledge of physics and developed technology on fueling, experimental studies to develop a fueling scheme have been conducted in the Large Helical Device (LHD). LHD is a good experimental platform since it can generate steady-state magnetic field to confine high temperature plasmas only by external coils. Effect of external fueling on internal variables (temperature, density, pressure, etc.) is attributed to generation of particle source. Heat and particle transports are linked with each other, where direct charge exchange loss, indirect charge exchange loss due to recycling, radiation loss and momentum loss are non-linearly coupled. While core fueling by pellet injection has good efficiency and cons
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equently reduces recycling particles significantly, degradation of confinement and fueling efficiency in the high density regime and large perturbation in the core temperature are concerned. In this research, cooperative operation of pellet injection and gas puff has been explored carefully and their synergetic effect has been quantified. This study indicates the relation between local increase of neural pressure in the plasma boundary and performance of core confinement. Particle diffusion is suppressed even with extremely large density gradient when fueling by pellet injection is combined with the condition to enable low neutral pressure at the plasma boundary. Combination of wall conditioning to enhance pumping capability and magnetic configuration to avoid plugging of neutrals is a key element. In this operation, density profile becomes highly peaked and consequently the central density reached 1.2 times 10 to the 21st per cubic meters which is several times larger than a regular requirement for a fusion reactor. This finding suggests an innovative scenario of a fusion reactor with super-high density and relative low temperature. It should be noted that high density operation mitigates, engineering demand. Documentation of this new operational regime has progressed, which suggests that both central density and temperature can be kept constant with repetitive pellet fueling with penetration inside the particle diffusion barrier. Less
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