Experimental simulation of high temperature plasma confinement using dimensionally similar low temperature plasma

使用尺寸相似的低温等离子体进行高温等离子体约束的实验模拟

• 批准号: 15206107
• 负责人: TOI Kazuo
• 金额: $ 21.63万
• 依托单位: National Institute for Fusion Science
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15206107/
• 关键词: plasma and nuclear fusion; dimensional similarity; turbulent transport; over-dense plasma; electron Bernstein wave heating; whistler wave heating; neoclassical transport; transport barrier; 電子バ-シュタイン波加熱; 閉じ込め改善; 次元的相似プラズマ; ヘリカル装置; 径電場; 電子バーンシ

Better understanding of transport phenomena such as transport barrier formation in high temperature plasma is a key issue for realization of fusion-burn plasma. However, the phenomena are very complex and the understanding is still preliminary. The main reason is difficulty to measure various plasma parameters and turbulent fluctuations with high time and spatial resolutions. To resolve this difficulty, this project aims at simulating transport in high temperature plasma using "dimensionally similar" low temperature plasma where several dimensionless parameters such as normalized collision frequency, plasma toroidal beta and so on are the same as those in high temperature plasma, except normalized ion gyro radius evaluated with electron temperature. In the low temperature plasma, Langmuir probes can be applied for measurements of equilibrium plasma parameters, fluctuations and correlations among various fluctuations with high time and spatial resolutions. This experiment was carried ou … More t in a small sized heliotron/torsatronl device CHS, having two main research objectives : (1) to produce and heat low temperature and density plasmas at low toroidal field condition by launching 2.45GHz electron cyclotron waves (ECWs), and (2) to measure electrostatic fluctuations in this low temperature plasma and clarify turbulent plasma transport. (1) : Plasma production was performed by 2.45GHz ECW launching in the range of the toroidal field from 175 G to 1050 G Over-dense plasmas exceeding the cut-off density for ordinary mode (O-mode) were successfully and routinely generated. In these over-dense plasmas, collisionality regimes of MHD (collisional), plateau and 1/v-regimes were realized over a substantial fraction of a plasma minor radius. This plasma production and heating is thought to be done by electron Bernstein waves (EBWs) converted from launched ECWs. Power absorption profile measured with ECW power modulation technique is concentrated in interior region beyond X-mode cutoff and upper-hybrid layers. This result is consistent with mode-converted EBW heating. (2): When launching microwave power exceeds a certain threshold, electron density profile exhibits a clear transition to a very peaked profile having steep gradient from a usual parabolic one. This indicates formation of internal particle transport barrier. As a new trial, we attempted to heat up a plasma by ramping ECW power from very low(~1kW) to high power (~20kW). In the initial phase with very low heating power, turbulent particle flux is very low but quickly increases toward strongly turbulent state with the increase in WCW power. However, turbulent particle flux immediately saturates at a certain level. With the increase in turbulent particle flux, fluctuations of radial electric field grow clearly, suggesting generation of sheared poloidal flow. Detailed analysis is under way.In parallel to these researches, we also studied characteristics of edge transport barrier formed in high temperature plasmas in CHS and the large helical device LHD. These results support the progress of this project. Less

更好地理解高温等离子体中的输运现象，如输运势垒的形成，是实现聚变燃烧等离子体的关键问题。然而，这些现象非常复杂，认识仍然是初步的。其主要原因是等离子体的各种参数和湍流起伏难以获得高的时间和空间分辨率。为了解决这一难题，本项目的目标是使用“尺寸相似”的低温等离子体来模拟高温等离子体中的输运，其中，除了用电子温度来估计归一化离子陀螺半径之外，诸如归一化碰撞频率、等离子体环形β等几个无量纲参数与高温等离子体中的那些参数相同。在低温等离子体中，朗缪尔探针可以用于测量平衡等离子体参数、涨落以及各种涨落之间的关联，具有很高的时间和空间分辨率。本实验是在 ...更多信息 在小型的Heliotron/Torsatronl装置CHS上进行了实验研究，主要有两个研究目标：（1）通过发射2.45GHz的电子回旋波（ECW），在低环向场条件下产生和加热低温低密度等离子体;（2）测量低温等离子体中的静电涨落，阐明湍流等离子体输运。(1):在175 G ~ 1050 G的环向场范围内，用2.45 GHz的ECW发射进行了等离子体的产生，成功地常规地产生了超过普通模（O模）截止密度的过密等离子体。在这些过密等离子体中，MHD（碰撞），平台和1/V-制度的碰撞制度实现了相当大的一部分等离子体小半径。这种等离子体的产生和加热被认为是通过从发射的ECW转换的电子伯恩斯坦波（EBW）来完成的。用ECW功率调制技术测量的功率吸收分布集中在X模截止层和上混合层以外的内部区域。这一结果与模式转换EBW加热是一致的。(2)当发射微波功率超过一定阈值时，电子密度分布从通常的抛物线型向具有陡峭梯度的非常尖峰的分布表现出明显的过渡。这表明内部颗粒传输屏障的形成。作为一项新的试验，我们试图通过将ECW功率从非常低（~ 1 kW）提升到高功率（~ 20 kW）来加热等离子体。在加热功率很低的初始阶段，湍流粒子通量很低，但随着WCW功率的增加，湍流粒子通量迅速向强湍流状态增加。然而，湍流粒子通量立即饱和在一定的水平。随着湍流粒子通量的增加，径向电场的起伏明显增大，表明剪切极向流的产生。在这些研究的同时，我们还研究了CHS和大螺旋LHD中高温等离子体形成的边缘输运势垒的特性。这些结果支持了该项目的进展。少

项目成果

Two-Dimensional Measurement of Electron Density in LHD plasmas by Sheet-Shaped Thermal Lithium Beam

利用片状热锂束二维测量 LHD 等离子体中的电子密度

• 发表时间: 2006
• 期刊: Journal of the Korean Physical Society 49・1
• 作者: T.Takahashi;T.Morisaki;K.Toi
• 通讯作者: K.Toi

Experimental Simulation of High Temperature Plasma Transport Using Almost Dimensionally Similar Cold Plasmas in the Compact Helical System

在紧凑螺旋系统中使用几乎尺寸相似的冷等离子体进行高温等离子体输运的实验模拟

• 发表时间: 2005
• 期刊: Journal of plasma and fusion research SERIES Vol.6(to be published)
• 作者: K.Toi;R.Ikeda;M.Takeuch;T.Ito;C.Suzuki et al.
• 通讯作者: C.Suzuki et al.

Characteristic Formation of Edge Transport Barrier in the Compact Helical System

紧凑螺旋系统中边缘传输势垒的特征形成

• 发表时间: 2006
• 期刊: Journal of Plasma and Fusion Research 1・2
• 作者: M.Takeuchi;K.Toi;K.Nagaoka;C.Suzuki;T.Minami et al.
• 通讯作者: T.Minami et al.

Production of Over-Dense Plasmas by Launching 2.45GHz Electron Cyclotron Wave in the Compact Helical System

通过在紧凑螺旋系统中发射 2.45GHz 电子回旋波来产生过密等离子体

• 发表时间: 2006
• 期刊: Journal of the Korean Physical Society 49・1
• 作者: R.Ikeda;M.Takeuchi;K.Toi;C.Suzuki;S.Okamura
• 通讯作者: S.Okamura

Formation of edge transport barrier in the ergodic field layer of helical divertor configuration on the Large Helical Device

大型螺旋装置螺旋偏滤器结构遍历场层中边缘传输势垒的形成

• 发表时间: 2006
• 期刊: Plasma Physics and Controlled Fusion 48・5
• 作者: K.Toi;S.Ohdachi;F.Watanabe;K.Narihara;T.Morisaki et al.
• 通讯作者: T.Morisaki et al.