2019年9月12日 五室第116期研讨会

2019912 五室第116期研讨会 

题  目: Numerical study on nonlinear growth of m/n=3/1 double tearing mode in high Lundquist number regime


   间: 2019年9月12日(星期四)  15:00—16:00

   点: 4楼中间会议室


   The nonlinear growth of the m/n=3/1 double tearing mode (DTM) is numerically investigated in cylinder geometry with non-monotonic radial profiles of the equilibrium safety factor, having two q=3 surfaces. The formation of plasmoids is found in high Lundquist number regime in such configurations for the first time. During the nonlinear growth of DTM, long and thin Sweet–Parker current sheets are formed near the original inner and outer rational surfaces and become tearing unstable for a large enough Lundquist number, leading to secondary and tertiary magnetic islands which accelerate the magnetic reconnection. The plasmoids also affect the magnetic topology at nonlinear mode saturation. The system can eventually saturate at a quasistationary state with small island pairs. The simulation results show that the Lundquist number and the distance between two rational surfaces have important effects on plasmoids formation


2019年7月31日 五室第115期研讨会

2019年7月31日 五室第115期研讨会  

题  目:Computing the Double-Gyroaverage Term Incorporating Short-Scale Perturbation and SteepEquilibrium Profile by the Interpolation Algorithm

报告人:张双喜 博士

   间: 2019年7月31日(星期三)  9:00—10:30

   点: 4楼中间会议室


2019年7月26日 五室第114期研讨会

题 目:The Geodesic Acoustic Eigenmode in toroidally rotating tokamaks 报告人: 周登 研究员
时 间: 2019年7月26日(星期五) 14:30—15:20
地 点: 4楼中间会议室

2019年7月17日 五室第113期研讨会

题  目:The correct cutoff vsriable for integrals with the Rutherford differential cross-section.

报告人:常永斌 教授

时  间:2019年7月17日(星期三)  9:00—10:00

地  点:4楼中间会议室


2019年7月5日 五室第112期研讨会

201975 五室第112期研讨会

题  目:日韩模拟会议简单介绍


时  间:2019年7月5日(星期五)  14:30—15:30

地  点:6楼中间会议室

摘  要:

  汇报本次参加Japan-Korea workshop on “Modeling and Simulation of Magnetic Fusion Plasmas”的会议内容。主要是日本方面的报告内容。日本目前的模拟工作基本上都是基于自己开发的程序,本次会议的主要报告内容偏重于动理学问题,具体研究方向涵盖了磁约束等离子体中的湍流,新经典输运以及合成诊断等。希望通过本次介绍,让大家了解日本同行的部分研究进展,并讨论可能开展的合作方向。


2019年7月2日 五室第111期研讨会

201972 五室第111期研讨会

题  目:Plasma Theory Connections to Quantum Information Science

报告人Prof. Scott Parker  ( University of Colorado)

 时  间:2019年7月2日(星期二)  14:00—15:00

地  点:601会议室

摘  要:

The potential impact of quantum information science (QIS) on large-scale computing is tantalizing due to the capability to manipulate 2^N complex numbers where N is the number of qubits.  Even for N=60, one approaches exascale. Additionally, Moore’s law scaling, nearing 5 nm scale, is approaching physical limits. Present day experimental quantum computers are very modest in terms of size and general capability. Whether they may someday be useful for large-scale computation is unknown due to fundamental constraints.  Efficient operations are linear.  Copying data is approximate.  Measurement, or obtaining output is expensive. Here we present two research areas where QIS and plasma theory overlap in interesting ways: 1) quantum algorithms solving the Vlasov equation, and 2) direct numerical simulation of ultra-cold non-neutral ion plasmas used in QIS.  We have developed a quantum algorithm that time evolves the linear Vlasov equation with an exponential speed up, thereby, directly addressing the computational demands of the 6D phase space.  Progress is being made on developing strategies for the nonlinear problem.  A series expansion with good convergence properties using the Homotopy Analysis method (HAM)[1] allows formulation of the nonlinear problem as a large number of matrix multiplies suitable for an efficient quantum algorithm.  Additionally, we will discuss how plasma theory can help support QIS via many-particle simulation of ultra-cold non-neutral ion plasmas.  A Penning trap is being used to simulate 100’s of interacting quantum spins using an ultracold 2D crystal of singly-ionized Beryllium ions[2].  The simulation obtains excellent agreement with linear eigenmode analysis and includes a fairly detailed laser doppler cooling model that allows prediction of the ultracold plasma steady state, and shows agreement with experimentally observed temperatures.


2019年6月29日 五室第110期研讨会

2019629 五室第110期研讨会

题  目:A relativistic model of electron cyclotron current drive efficiency in tokamak plasmas


时  间:2019年6月29日(星期六)  9:00—9:50

摘  要:

Electron cyclotron current drive (ECCD) has been considered an im-portant tool for current profile control to achieve high performance in ITER operation owing to its ability to drive local current on- and off-axis. An accurate and computationally efficient model of ECCD efficiency is highly desirable for the purpose of performing scenario modeling and in-between shots data analysis for EC experiments on ITER. From theoret-ical studies in the past, it is clear that both momentum-conserving and relativistic characteristics are needed in the electron-electron collision op-erator to appropriately describe the collisional relaxation [1, 2, 3]]processes in the high temperature plasmas. In this work, numerical calculations of the current drive efficiency in a tokamak by using the variational approach are performed. A fully relativistic extension of the variational principle with the modified test function for the Spitzer function with momen-tum conservation in the electron-electron collision is described in general tokamak geometry [4, 5, 6]]. The model developed has generalized that of Marushchenko’s[2], which is extended for arbitrary temperatures and covers exactly the asymptotic for u  1 when Zeff  1, and suited to ray-tracing calculations. Also the wave-particle interaction is modeled by the relativistic generalization of the local Kennel-Engelman wave-induced dif-fusion operator in velocity space [7]. The theoretical results obtained here have been used to upgrade the current drive package in the ray-gracing code TORAY-GA, the benchmark has been made and the calculated re-sults were in good agreement with that using CQL3D. The upgraded code can also be used in other EC ray-tracing codes.


2019年6月21日 五室第109期研讨会

2019621 五室第109期研讨会

题  目:回旋动理学粒子模拟与全轨道粒子模拟的比较


 时  间:2019年6月21日(星期五)  14:30—15:30

地  点:6楼中间办公室

摘  要:

从上个世纪90年代开始, 回旋动理学模拟逐渐成为研究托卡马克湍流输运的标准方法。 传统的包含回旋运动的粒子模拟方法对研究高频波现象是常用的方法, 但对研究低频湍流现象, 仍然面临时间步长与数值稳定性等限制,因而未能在这一领域广泛应用。我同时尝试过这两种模拟手段,对二者的区别有一点体会。我想借周五讨论的机会,梳理一些这两种模拟方法。对回旋动理学模拟, 从基本的麦克斯韦方程组出发,采用矢势与标势描述,导出回旋动理学模拟中要求解的场方程的具体形式。 然后定义导心变换,并讨论一下Frieman-Chen的非线性回旋动理学方程的推导步骤,以及回旋动理学模拟中非常重要的极化密度,回旋平均的数值处理及场方程的数值求解。给出回旋动理学模拟出的离子温度梯度模(ITG)与电子温度梯度模(ETG)的结果。讨论绝热电子与动理学电子, 静电模型与电磁模型所带来的处理方法的区别, 以及电磁模拟中的数值抵销误差问题。 对全轨道模拟方法,介绍计算全轨道的Boris算法及其相对于Runge-Kutta方法的优越性。由于没有回旋平均,全轨道粒子模拟的噪声比回旋动理学粒子模拟的噪声大。与回旋动理学模拟不同, 在全轨道模拟中,等离子体温与度密度的空间梯度不显式出现在模型中,如何把梯度效应包含到模拟中的是一个很微妙且很关键的问题。最后给出用全轨道粒子模拟给出的ITG与ETG的结果及仍然面临的一些数值困难。


2019年6月14日 五室第108期研讨会

2019614 五室第108期研讨会

题  目:1.Nonlinear interaction between toroidal Alfven eigenmodes

and tearing modes

2. Sawtooth Oscillation and Fast Core-Crash in Tokamak

报告人 马志为 教授 (浙江大学)

时  间:2019年6月14日(星期五)  10:00—11:30

地  点:4楼中间办公室

摘  要:

  1. Nonlinear interaction between toroidal Alfven eigenmodes and tearing modes

Nonlinear interaction between toroidal Alfven eigenmodes (TAEs) and tearing modes is investigated by using the MHD-Particle hybrid code CLT-K. It is found that the n=1 TAE is first excited by isotropic energetic particles at the linear stage and reaches the first steady state due to wave-particle interaction. After the saturation of the n=1 TAE, the m/n=2/1 tearing mode grows continuously and reaches its steady state due to nonlinear mode-mode coupling. The development of the tearing mode activity could weaken the TAE frequency chirping through the interaction between the p=1 TAE resonance and the p=2 tearing mode resonance for passing particles in the phase space, which is opposite to the classical physical picture of the TAE frequency chirping that is enhanced with increase of dissipation. The tearing mode activity can also cause strong increase of the n=0 zonal component and large decrease of the n=1 TAE mode due to redistribution of energetic particles associated with formation of magnetic islands.  

  • Sawtooth Oscillation and Fast Core-Crash in Tokamak

Sawtooth oscillation and fast core-crash are investigated using a three-dimensional toroidal and nonlinear MHD code CLT. It is found that the behavior of sawtooth oscillations significantly depends on the viscosity of plasma. With a high viscosity, a normal sawtooth oscillation is observed. With low viscosity, the system quickly turns into a small sawtooth after the first pressure crash. When the viscosity falls below the critical value, the system reaches a stationary state, in which the magnetic field, plasma pressure, and q profile remain unchanged. The mode-mode coupling effect plays an crucial role on fast core-crash associated with double tearing mode. The zonal component and all other high n harmonics generated by the mode-mode coupling of the n=1 mode gain more than 40% of the total kinetic energy and become unneglectable at the nonlinear phase. The time scale of the fast core crash is nearly independence of the resistivity.  ��c*

2019年度 五室研讨会人员顺序表

顺序 人员
  1 胡友俊
  2 夏天阳
  3 胡业民
  4 周登
  5 郭文峰
  6 肖小涛
  7 马骏
  8 于治
  9 李德徽
  10 徐颖峰
  11 潘成康
  12 叶磊
  13 甘春芸
  14 申伟
  15 桂彬
  16 杨程
  17 贾国章
  18 杨小庆
  19 陈佳乐
  20 刘晓娟
  21 黄跃恒
  22 欧靖
  23 项农