EAST上离子回旋波与中性束注入协同加热产生的高能粒子分布及输运研究

Investigation of ICRF-NBI synergetic heating induced fast ion distribution and transport in EAST tokamak

在磁约束聚变等离子体中,离子回旋共振加热(ICRF)与中性束注入(NBI)是两种主要的加热方法.它们的协同加热一直都是聚变领域研究的重点.本文首先阐明了ICRF高次谐波加热以及ICRF与NBI协同加热的基本原理.通过EAST托卡马克上实验和相应的TRANSP模拟,发现了ICRF与NBI的协同加热不仅可以显著提高等离子体参数(极向比压、等离子体储能、离子温度、中子产额等),而且能产生大量高能粒子,形成高能粒子尾巴.例如,1 MW的ICRF三次谐波可将初始能量为60 keV的NBI高能氘离子加速至600 keV.通过改变氢少子含量、提高ICRF和NBI加热功率、使用ICRF在轴加热、优化NBI注入角度等,可以有效地提高协同加热效率以及高能粒子的能量.进一步地,将协同加热产生的高能粒子分布代入粒子轨道程序中,计算了高能粒子的输运以及其在第一壁上的损失.结果表明,损失的高能粒子的初始位置位于低场侧,且损失轨道大部分为捕获粒子轨道.高能粒子损失位置主要位于主限制器以及ICRF和低杂波限制器的中上平面.这些损失的高能粒子被认为是造成限制器上热斑的主要原因之一.

In magnetic confinement fusion plasmas,radio-frequency wave heating in the ion cyclotron range of frequencies(ICRF)and neutral beam injection(NBI)are two main heating methods.Their synergetic heating has long been a key topic in fusion research.In this work,we clarify the basic principles of ICRF high harmonic heating and the synergetic heating between ICRF and NBI.Then,we perform a series of experiments on EAST tokamak and carry out the corresponding TRANSP simulations.The results indicate that the ICRF-NBI synergetic heating not only significantly increases the plasma parameters(including poloidal beta,plasma stored energy,ion temperature and neutron yield),but also generates a large number of energetic particles and develops an energetic particle tail in its distribution function.For instance,the ICRF third harmonic heating with 1 MW of power can increase the energy of NBI fast ions from 60 to 600 keV.By changing the hydrogen minority concentration,improving the ICRF and NBI heating power,using the on-axis ICRF heating or optimizing the NBI injection angle,the ICRF-NBI synergetic heating effect can be further enhanced,accompanied with an increase of fast ion energy.Moreover,by using the fast ion distribution as input in the orbit tracing code,the transport and loss of energetic particles are calculated.The results show that the initial positions of the lost energetic particles are on the low field side,and their orbits are mainly trapped orbits.The loss of energetic particles is mainly located in the middle and upper plane of the main limiter,ICRF and LH antenna limiters.The lost of these energetic particles are considered as one of the main reasons why hot spots occur on the limiters.