Statistical Picture of hysteresis characteristics of transition phenomena in steady state current drive plasma

稳态电流驱动等离子体过渡现象滞后特性统计图

基本信息

批准号：
15206105
负责人：
ZUSHI H.
金额：
$ 30.95万
依托单位：
KYUSHU UNIVERCITY
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-15206105/
关键词：
Transition Phenomenon Hysteresis current drive Threshold power PWI driven relaxation oscillations Electron cyclotron current drive Fusion plasma physics plasma wall interaction current drive LHW ECW transition deposition Plasma

项目摘要

The summary of this research is as follows.In the current drive plasma, various transition phenomena have been investigated. Firstly, the transition for the confinement (∝ plasma stored energy/input power) and current drive efficiency (∝ current^★density^★major radius/power) is studied with view point of hysteresis. It is found that there exists a power threshold above which a transition is triggered. At the transition, both ion and electron temperature are increased and the density is also increased. Since driven current is raised, current drive efficiency is enhanced. The transition probability is also studied. The driven power is varied with a time, much longer than the confinement time, and the transition characteristics below the threshold power to above it, called forward-transition. Backward- transition is also studied from the "Enhanced current drive" mode achieved above the threshold down to the L-mode below the threshold power. The transition probability is defined as a delay … More time with which a transition is delayed with respect to a change in power. This transition probability is studied for both forward and backward transitions, and it is found that there is a critical difference between then and this difference leads to a hysteresis.Secondly, a transition in current drive property is studied for bi-directional lower hybrid current drive operation. In this experiments, the forward LHW and backward LHW are superposed and the directivity of the driven current is studied. Namely, the forward current is driven by FW LHW, but the backward current is driven by the BW LHW. The experiments show that a transition of the current directivity from the BW direction to FW direction as a function of the BW/FW power ratio. This transition is triggered when this power ratio exceeds a critical value of 〜 0.8. It is found that the current density profile becomes narrow when the BW-LHW is superposed and the power ratio exceeds above the critical one, and then the transition of the current profile changes from the centrally peaked to a broad one suddenly. A hysteresis is not taken for this experiments.Thirdly, a transition is studied in a long pulse discharge from a view points of plasma wall interaction. Oscillations at the very low frequency are found for the first time. This is called ULF events. In the long pulse operation, there are several processes which dominate discharge characteristics. The input rf power is launched from the out board side via a tunneling process in front of the rf antenna. The rf coupling to the plasma depends strongly on the density gradient in this region. During the long pulse discharge, the heat load from the plasma and escaped energetic electrons are deposited on the wall and antenna. The surface temperature rise changes the wall pumping property of the plasma facing components. Thus the edge or SOL density may vary in the discharge. Then this perturbation changes the reduction of the coupling or increment in the reflected power. A transition occurs during the ULF event, and then the five hour discharge is terminated. The heat load and particle perturbation grow rapidly from the dominant PFC (rail limiter) around the torus and finally they collapse the discharge. The related events are hot spot formation which may caused by the escaped energetic electrons. The local temperature on the hot spot is measured with the IR spectrometer. The hydrogen Balmer and Faulcher band are studied as a function of the surface temperature. It is found that both emission lines start to increase non-linearly as the hot spot temperature exceeds a critical values of 〜2100 K and they are sharply increased with increasing temperature and turns over even when the temperature still increases, and finally they decay to the previous level at the lower temperature. Less

这项研究的摘要如下。在当前的驱动等离子中，已经研究了各种过渡现象。首先，研究了限制的过渡（等离子体存储的能量/输入功率）和电流驱动效率（∝电流^★密度^★大半径/功率）使用滞后视点进行了研究。发现存在触发过渡的功率阈值。在过渡时，离子和电子温度都会增加，并且密度也增加。由于驱动电流升高，因此电流驱动效率提高了。过渡概率也是研究的。驱动能力随时间变化，比禁闭时间更长，并且过渡特性低于其上方的阈值，称为前进。从“增强的电流驱动器”模式下，向后转移的阈值以下到阈值以下的L模式。过渡概率被定义为延迟……随着功率变化而延迟过渡的更多时间。研究了向前和向后转换的这种过渡概率，发现当时和这种差异导致滞后之间存在临界差异。第二，现在研究了当前驱动器属性的过渡属性，以进行双向下降杂交电流驱动器操作。在此实验中，向前LHW和后向LHW是超级伪造的，并且驱动电流的方向性是研究的。也就是说，前向电流由FW LHW驱动，但向后电流由BW LHW驱动。实验表明，当前方向从BW方向转变为FW方向，这是BW/FW功率比的函数。当该功率比超过〜0.8时，触发此转换。发现当BW-LHW超级叠加并且功率比超过临界值时，电流密度曲线变得狭窄，然后电流轮廓的过渡从中心峰突然变为宽阔的峰值。该实验没有进行滞后。三分之二的是，从等离子体壁相互作用的视点长时间研究了过渡。首次发现非常低频率的振荡。这称为ULF事件。在长脉冲操作中，有几种主导放电特性的过程。输入RF功率是通过RF天线前面的隧道工艺从外板侧发射的。与等离子的RF耦合在很大程度上取决于该区域的密度梯度。在长脉冲放电过程中，血浆和逃脱的能量电子的热载荷沉积在墙壁和天线上。表面温度升高改变了等离子体面向组件的壁泵化特性。边缘或溶胶密度可能在放电中有所不同。然后，这种扰动会改变反射功率的耦合或增量的减少。在ULF事件期间发生过渡，然后终止了五个小时的放电。热载荷和颗粒扰动从圆环周围的主要PFC（导轨限制器）迅速生长，最后它们塌陷了排放。相关事件是热点形成，可能由逃脱的能量电子产品产生。使用红外光谱仪测量热点上的局部温度。氢Balmer和Faulcher带是表面温度的函数。发现随着热点温度超过〜2100 K的临界值，两种发射线都开始非线性增加，并且随着温度的升高和变化的升高，它们在较低温度下的温度升高，即使温度仍然升高，它们也随温度升高而急剧增加。较少的