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中国物理学会期刊

Design of Operational Scenarios for High Fusion Triple Product in the HL-3 Tokamak

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  • 本文面向中国新一代托卡马克装置HL-3在2027–2030年开展氘氚(D-T)聚变实验的物理准备需求,系统设计了一套高聚变三乘积(Fusion triple product, n_i \cdot T_i \cdot \tau_E)运行方案。聚变三乘积是衡量磁约束等离子体性能的核心指标,其数值直接关联聚变增益因子 Q,并决定能否接近点火条件(Lawson 判据要求n_i \cdot T_i \cdot \tau_E \geq 3-5 \times 10^20 KeV \cdot s \cdot m^-3)。为实现n_i \cdot T_i \cdot \tau_E > 1 \times 10^20 KeV \cdot s \cdot m^-3 的阶段性目标,本文构建了一个多尺度、多物理耦合的集成模拟工作流:首先通过0.5D参数扫描(METIS)确定可行运行窗口;继而采用1.5D集成建模平台OMFIT获得自洽的平衡位形与剖面分布;随后利用 CLT、MARS 和 ELITE 代码评估磁流体(MHD)不稳定性;最后通过 SOLPS-ITER 模拟偏滤器热负荷以验证工程可行性。模拟结果表明,在I_p=2.0MA、B_T=2.2T、中性束注入功率P_NBI=3MW、高约束品质因子 H_ITER98,y2=1.14条件下,HL-3可实现芯部聚变三乘积1.02 \times 10^20 KeV \cdot s \cdot m^-3。该方案采用高密度(线平均密度n_bar=9.26 \times 10^19m^-3,达 Greenwald 密度极限的 61\%)、低加热功率策略,同时满足 MHD 稳定性(无内部扭曲模、撕裂模稳定、电阻壁模裕度充足)与偏滤器热负荷限制(峰值平均热负荷小于1.5 MW/m^2,远低于材料极限 7 MW/m^2)。本研究不仅为HL-3迈向高参数运行提供了可实施的物理方案,也为 ITER 及未来聚变堆的先进运行场景积累了关键技术经验。

    This paper presents a systematic and integrated design for a high fusion triple product operational scenario on the HL-3 tokamak, establishing a robust physical and engineering foundation for its planned deuterium-tritium (D-T) experiments between 2027-2030. The fusion triple product (the product of ion density n_i, ion temperature T_i, and energy confinement time \tau_E) serves as a core metric for evaluating tokamak plasma performance, with clear physical significance as it directly relates to the fusion gain factor Q (ratio of fusion output power to input power). Achieving plasma "ignition" or self-sustained burning requires the triple product to exceed the Lawson criterion threshold (approximately 3 - 5 \times 10^20 keV \cdot s \cdot m^-3 for deuterium-tritium reactions). Therefore, pursuing high triple product operation represents not only a critical scientific objective in tokamak plasma physics but also a direct demonstration of the scientific feasibility of fusion energy.To obtain a feasible operational scenario with a triple product exceeding n_i \cdot T_i \cdot \tau_E=1 \times 10^20 keV \cdot s \cdot m^-3, this research innovatively constructs a comprehensive simulation workflow. This approach integrates parameter scanning, integrated modeling, instability analysis, and divertor physics assessment through iterative optimization to comprehensively predict the high-parameter operational states of the HL-3 device. Methodologically, the process begins with basic configuration design using EFIT and 0.5D parameter scanning with METIS to determine feasible ranges for plasma current, magnetic field, density, and heating power. This is followed by 1.5D integrated modeling using OMFIT, which combines EFIT for magnetic equilibrium, ONETWO for heating and current drive, TGYRO for transport calculations, and EPED1-NN for pedestal region analysis to obtain self-consistent plasma equilibria and profile distributions. Finally, magnetohydrodynamic (MHD) instabilities are evaluated using CLT, MARS, and ELITE codes, while SOLPS-ITER calculates divertor heat loads to ensure engineering feasibility.The results demonstrate that under conditions of I_p=2.0 MA, B_T=2.2 T, NBI heating power P_NBI=3 MW, and H_ITER98,y2=1.14, a high-performance operational mode with a core triple product of n_i \cdot T_i \cdot \tau_E=1.02 \times 10^20 keV \cdot s \cdot m^-3 can be achieved. This scenario employs a high-density (line-averaged density n_bar=9.26 \times 10^19/m^3, Greenwald fraction n_bar/n_GW=0.61), low-heating-power strategy, yielding excellent parameters including core electron density n_e(0)=11.53 \times 10^19/m^3, ion temperature T_i(0)=3.22 keV, electron temperature T_e(0)=3.16 keV, normalized beta \beta_N=1.65, and minimum safety factor q_min=1.02. In-depth MHD instability analysis reveals that the scenario effectively avoids internal kink modes due to qmin>1; tearing modes (TM) and neoclassical tearing modes (NTM) remain stable without growth over 1200–1400 Alfvén times; resistive wall mode (RWM) analysis shows the operational beta (\beta_N=1.65) remains well below both no-wall (1.976) and ideal-wall (2.25) limits, ensuring stability; edge-localized modes (ELMs) reside in the marginally stable region (\gamma/(\omega^*/2)=0.5-1.5), with the most unstable toroidal mode number around 25, yet distant from the unstable region, suggesting small or no ELMs are expected during experiments, which is beneficial for maintaining stable plasma parameters. Divertor heat load calculations indicate a peak heat flux not exceeding 1.5 MW/m^2, significantly below the engineering material limit for the lower divertor of 7 MW/m^2; a target plate electron temperature of approximately 16 eV indicates no detachment, but Z_eff distribution analysis confirms that physical-chemical sputtering in the divertor will not increase the core impurity content.This research not only provides detailed procedural recommendations and theoretical support for HL-3's pursuit of high-parameter operation but also accumulates valuable experience for advanced operational scenarios in ITER. Through systematic simulation and analysis, the study confirms HL-3's capability to achieve a triple product at the 10^20 KeV \cdot s \cdot m^-3 level, establishing a solid foundation for subsequent deuterium-tritium experiments and contributing significant scientific and engineering value to the advancement of magnetic confinement fusion energy development.

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