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中国物理学会期刊

零维系统模型改进及其对EAST稳态运行区的分析和预测

CSTR: 32037.14.aps.72.20230364

Improvement of zero-dimensional system model and its analysis and prediction of steady-state operating regime on EAST

CSTR: 32037.14.aps.72.20230364
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  • 零维系统模型已广泛应用于下一代托卡马克装置设计以及聚变反应堆等离子体性能的预测和分析, 但普遍采用物理近似和经验公式会导致较大的系统性误差. 本文通过引入等离子体平衡程序使主要等离子体分布参数及其计算基于磁面信息, 引入Sauter模型的自举电流系数与碰撞率变化关系改进自举电流计算, 利用EAST上的实验结果对改进后的模型进行验证, 零维系统模型计算结果与动理学平衡分析结果基本符合. 利用改进模型从已有实验结果出发, 对EAST上实现500 kA等离子体电流的稳态、长脉冲运行区所需要的加热/电流驱动功率及其能够达到的归一化比压进行了分析和预测. 计算结果表明, EAST在7.0—9.5 MW加热/驱动功率, 约束改善因子 H_98 为1.25—1.35, 归一化密度 f_\rmn\rmG 约为0.9的参数范围内可以实现500 kA等离子体电流且自举电流份额在50%以上的稳态运行; 9.5 MW加热/驱动功率, H_98 为1.0—1.4, f_\rmn\rmG 为0.8—1.0的参数范围可以实现较高性能的长脉冲或稳态运行. 综合来说, 提升等离子体约束性能, 可在较低的加热/驱动功率下实现同样等离子体参数的完全非感应运行, 扩展等离子体运行区, 是实现高参数等离子体稳态运行最为有效的途径.

     

    The zero-dimensional system model has been widely used for predicting and analyzing plasma performance in fusion reactors and designing next-generation tokamaks. These models can quickly scan and calculate various parameter, and can be used for the design of device reference operation point and preparation for more accurate one-dimensional numerical simulations. They can also be used to predict device operational parameters and heating/ current drive conditions, providing a quick reference for experimental design. However, relying on physical approximations and empirical formulas can lead to significant systematic errors. In this work we introduce a plasma equilibrium program to obtain the main plasma profile parameters and their calculations based on magnetic surface information. The bootstrap current calculation is improved by introducing the relationship between the bootstrap current coefficient of the Sauter model and the collision rate change. The improved model is validated by using experimental results from EAST, and the results of the zero-dimensional system model calculations are found to be consistent with the results of kinetic equilibrium analysis. Based on the improved model and existing experimental results, the required heating/current drive power and achievable normalized beta for steady-state, long-pulse operation of the 500 kA plasma current on EAST are analyzed and predicted. The calculation results show that EAST can achieve steady-state operation at the 500 kA plasma current with bootstrap current fraction over 50% in the parameter range of 7.0–9.5 MW heating/driving power, H_98 is 1.25–1.35, and f_\rmn\rmG ~0.9. Additionally, to maintain the total non-inductive current, the total heating/current drive power needs to be highly sensitive to plasma confinement and density, which is the most effective way to increase the bootstrap current fraction and reduce the peak heat loads on the divertor. Improving plasma confinement is the most effective way to achieve high bootstrap current fraction and reduce the peak heat load on the divertor. In this work, we also analyze the effect of heating power ratio on the bootstrap current, showing that adjusting the power ratio can change the bootstrap current fraction, and we further analyze the long-pulse operating region of EAST with a plasma current of 500 kA. In the range of 9.5 MW total heating/current driving power, H_98 is 1.0–1.4, and normalized electron density f_\rmn\rmG is 0.8–1.0, high-performance long-pulse or fully non-inductive steady-state operation can be achieved, supporting the research on the physics of ITER and CFETR steady-state operation modes. In general, improving the plasma confinement performance can achieve fully non-inductive operation at lower heating/driving power while maintaining the same plasma parameters, and expand the plasma operating regime, which is the most effective way to achieve high-parameter steady-state operation of the plasma.

     

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