用于燃烧聚变等离子体自洽动力学模拟的多物种反应玻尔兹曼公式
A Multi-Species Reactive-Boltzmann Formulation for Self-Consistent Kinetic Simulation of Burning Fusion Plasmas
AI总结：
针对国家点火设施中燃烧等离子体实验与模型的差异，提出多物种反应 - 弹性动力学框架，用反应玻尔兹曼碰撞算符评估聚变源汇，经快速傅里叶谱方法离散碰撞算符，通过数值实验发现聚变产物加热未产生显著超热群体。
AI中文摘要：
国家点火设施中燃烧等离子体的实验数据与辐射流体动力学模型之间的差异，部分归因于反应物离子分布可能偏离麦克斯韦平衡。具体而言，有人推测高能聚变产物与体等离子体的碰撞弛豫可能产生简化模型未捕获的超热离子群体。为在完全动力学环境中评估这一假设，我们提出一个多物种反应 - 弹性动力学框架，其中聚变源和汇直接从反应物速度分布函数通过反应玻尔兹曼碰撞算符进行评估。为提高计算效率，弹性相互作用在小角度碰撞极限下使用朗道和列纳德 - 伯恩斯坦碰撞算符建模，不过该框架允许大角度弹性散射推广。积分 - 微分碰撞算符用快速傅里叶谱方法离散化，能在三维速度空间高效、高精度评估反应过程，为蒙特卡罗碰撞方法提供确定性替代。对空间均匀的两物种和三物种 D - D 聚变系统在弱耦合、早期阶段进行了数值实验。我们发现聚变产物加热在反应物离子中不会产生显著的超热群体：在弗罗贝尼乌斯范数和聚变反应性方面，与相应麦克斯韦分布的偏差都很小。
英文摘要：
Discrepancies between experimental data and radiation-hydrodynamic models of burning plasmas at the National Ignition Facility have been attributed, in part, to possible deviations of reactant ion distributions from Maxwellian equilibrium. In particular, it has been hypothesized that the collisional relaxation of energetic fusion products with the bulk plasma may generate suprathermal ion populations not captured by reduced models. To assess this hypothesis in a fully kinetic setting, we present a multi-species reactive--elastic kinetic framework, in which fusion sources and sinks are evaluated directly from the reactant velocity distribution function with a reactive Boltzmann collision operator. For computational efficiency, elastic interactions are modeled in the small-angle collision limit using the Landau and Lenard--Bernstein collision operators, although the framework admits large-angle elastic scattering generalizations. The integro-differential collision operators are discretized with a fast Fourier spectral method, enabling efficient, high-order accuracy evaluation of reactive processes in three-dimensional velocity space and providing a deterministic alternative to Monte Carlo collision methods. Numerical experiments are performed for spatially homogeneous two- and three-species D--D fusion systems in weakly coupled, early-time regimes. We find that fusion product heating does not generate a significant suprathermal population in the reactant ions: deviation from the corresponding Maxwellian distribution remains small in both the Frobenius norm and the fusion reactivity.
