等离子体物理
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- [1] arXiv:2507.19668 [中文pdf, pdf, html, 其他]
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标题： 探索聚变堆设计空间：通过优化比较正三角形性和负三角形性托卡马克的分析标题： Exploring the fusion power plant design space: comparative analysis of positive and negative triangularity tokamaks through optimizationT. Slendebroek, A. O. Nelson, O. M. Meneghini, G. Dose, A. G. Ghiozzi, J. Harvey, B. C. Lyons, J. McClenaghan, T. F. Neiser, D. B. Weisberg, M. G. Yoo, E. Bursch, C. Holland评论： 37页，15图主题： 等离子体物理 (physics.plasm-ph)
在聚变能电厂中，正三角形 (PT) 和负三角形 (NT) 托卡马克之间的最佳配置选择取决于应对不同的运行约束，而不是达到特定的等离子体性能指标。 本研究使用集成融合合成引擎 (FUSE) 框架，通过受约束的多目标优化进行了系统比较。 进行了超过 200,000 次集成设计评估，探索了资本成本最小化与运行可靠性（最大化$q_{95}$）之间的权衡，同时满足工程约束条件，包括 250$\pm$50 兆瓦净电功率、氚增殖比$>$1.1、功率排出限制和一小时平顶时间。 两种配置通过对比的设计理念实现了类似的成本-性能帕累托前沿。 PT 在表现出对边缘梯度退化（补偿高达 40% 的减少）的弹性的同时，由于 L-H 阈值要求与研究确立的功率排出限制（$P_{sol}/R$ $<$ 15 兆瓦/平方米）之间的狭窄运行窗口，被限制为更大的机器（$R_0$ $>$ 6.5 米）。 这迫使通过相对较低的磁场进行优化（$\sim$8T）。 NT配置利用其不受这些限制的自由度，以获得紧凑且高场的设计（$R_0 \sim 5.5$m，$B_0$ $>$ 12 T），与先进的HTS技术产生自然协同效应。 敏感性分析表明，PT的经济可行性在很大程度上取决于L-H阈值尺度和功率处理极限的不确定性。 值得注意的是，任一参数50%的变化都可能消除可行的设计或使进入紧凑设计空间成为可能。 这些结果表明，配置选择应基于风险：当操作约束可以自信预测时，PT提供了最低成本的路径，而NT对约束和物理不确定性的大幅变化具有鲁棒性。
The optimal configuration choice between positive triangularity (PT) and negative triangularity (NT) tokamaks for fusion power plants hinges on navigating different operational constraints rather than achieving specific plasma performance metrics. This study presents a systematic comparison using constrained multi-objective optimization with the integrated FUsion Synthesis Engine (FUSE) framework. Over 200,000 integrated design evaluations were performed exploring the trade-offs between capital cost minimization and operational reliability (maximizing $q_{95}$) while satisfying engineering constraints including 250 $\pm$ 50 MW net electric power, tritium breeding ratio $>$1.1, power exhaust limits and an hour flattop time. Both configurations achieve similar cost-performance Pareto fronts through contrasting design philosophies. PT, while demonstrating resilience to pedestal degradation (compensating for up to 40% reduction), are constrained to larger machines ($R_0$ $>$ 6.5 m) by the narrow operational window between L-H threshold requirements and the research-established power exhaust limit ($P_{sol}/R$ $<$ 15 MW/m). This forces optimization through comparatively reduced magnetic field ($\sim$8T). NT configurations exploit their freedom from these constraints to access compact, high-field designs ($R_0 \sim 5.5$ m, $B_0$ $>$ 12 T), creating natural synergy with advancing HTS technology. Sensitivity analyses reveal that PT's economic viability depends critically on uncertainties in L-H threshold scaling and power handling limits. Notably, a 50% variation in either could eliminate viable designs or enable access to the compact design space. These results suggest configuration selection should be risk-informed: PT offers the lowest-cost path when operational constraints can be confidently predicted, while NT is robust to large variations in constraints and physics uncertainties.
- [2] arXiv:2507.19729 [中文pdf, pdf, html, 其他]
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标题： 弱碰撞平行输运的半隐式连续动力学建模标题： Semi-Implicit Continuum Kinetic Modeling of Weakly Collisional Parallel Transport in a Magnetic Mirror主题： 等离子体物理 (physics.plasm-ph)
我们使用连续代码\textsc{COGENT}对磁镜配置中的弱碰撞平行等离子体输运进行隐式-显式 (IMEX) 动力学模拟。 数值方案采用无雅可比矩阵的牛顿-克里洛夫方法，并结合代数多重网格预处理，以克服完全显式方案中由强镜像力引起的严重时间步限制。 应用于与 WHAM 镜实验相关的参数，IMEX 方法使时间步长达到显式方法允许的$2.5 \times 10^4$倍，从而在包含动力学离子和玻尔兹曼电子的平行输运一维-二维模拟中实现了 2500 倍的速度提升。 此外，实现了一个用于方形镜的简化的回旋平均模型，以支持计算密集的全动力学模拟。 回旋平均公式用于评估速度空间离散化算法的数值收敛性，并通过比较采用非线性福克-普朗克和简化伦德-伯恩斯坦-多吉蒂碰撞算子的模拟来评估碰撞模型的作用。
We present implicit-explicit (IMEX) kinetic simulations of weakly collisional parallel plasma transport in magnetic mirror configurations using the continuum code \textsc{COGENT}. The numerical scheme employs a Jacobian-free Newton--Krylov method with algebraic multigrid preconditioning to overcome the severe time-step limitations imposed by strong mirror forces in fully explicit schemes. Applied to parameters relevant to the WHAM mirror experiment, the IMEX approach enables time steps up to $2.5 \times 10^4$ times larger than those permitted by explicit methods, resulting in a 2500x speedup in 1D--2V simulations of parallel transport with kinetic ions and Boltzmann electrons. Additionally, a reduced bounce-averaged model for a square mirror is implemented to support the computationally intensive fully kinetic simulations. The bounce-averaged formulation is used to evaluate the numerical convergence of the velocity-space discretization algorithms and to assess the role of the collision model by comparing simulations employing the nonlinear Fokker--Planck and the simplified Lenard--Bernstein--Dougherty collision operators.
- [3] arXiv:2507.20244 [中文pdf, pdf, html, 其他]
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标题： 等离子体三角形度与微撕裂湍流之间的相互作用标题： On the interplay between plasma triangularity and micro-tearing turbulence主题： 等离子体物理 (physics.plasm-ph)
在本工作中，我们使用线性和非线性通量管GENE模拟研究了三角形和微撕裂湍流之间的相互作用。 我们考虑了来自现有托卡马克装置（TCV、DIII-D、MAST-U和SMART）和EU-DEMO的负三角形和正三角形等离子体形状情景。 所有这些托卡马克的研究揭示了一个连贯的画面。 负三角形几何结构更容易受到微撕裂模式（MTM）的影响，当存在时，其输运比正三角形情况差得多。 在足够大的$\beta$（等离子体压强与磁压强的比值）、磁剪切和电子与离子温度梯度比值下，所有负三角形情景都由MTM湍流主导。 相比之下，相应的正三角形情景仍然由静电湍流主导，MTM是次主导或稳定的。 我们观察到，常规托卡马克通常运行在远离负三角形MTM主导区域的参数空间中，从而保持了负三角形对湍流输运的有益影响。 相反，球形托卡马克运行接近这一区域，并可能最终在负三角形情况下表现出比正三角形更差的输运。 我们发现，在球形托卡马克中降低磁剪切可以保持负三角形对静电湍流的有益影响，并防止强烈的MTM输运。 最后，线性和非线性模拟揭示了更强MTM的原因：在负三角形几何结构中，磁漂移更快。
In this work, we study the interplay between triangularity and micro-tearing turbulence using linear and nonlinear flux tube GENE simulations. We consider scenarios with negative and positive triangularity plasma shaping taken from existing tokamaks (TCV, DIII-D, MAST-U and SMART) and EU-DEMO. The study of all these tokamaks reveals a coherent picture. Negative triangularity geometry is more susceptible to micro-tearing modes (MTM), which, when present, make transport much worse than in positive triangularity. At sufficiently large $\beta$ (the ratio of plasma pressure over magnetic pressure), magnetic shear and ratio of electron to ion temperature gradient, all the scenarios with negative triangularity are dominated by MTM turbulence. In contrast, the corresponding scenarios with positive triangularity remain dominated by electrostatic turbulence and MTMs are subdominant or stable. We observe that conventional tokamaks usually operate in a parameter space far away from the onset of this MTM-dominated regime in negative triangularity, thus preserving the beneficial effect of negative triangularity on turbulent transport. In contrast, spherical tokamaks operate close to this regime and may ultimately exhibit worse transport at negative triangularity than positive triangularity. We find that lowering the magnetic shear in spherical tokamaks can preserve the beneficial effect of negative triangularity on electrostatic turbulence and prevent strong MTM transport. Finally, linear and nonlinear simulations reveal the reason for stronger MTMs: the magnetic drifts are faster in the negative triangularity geometry.
- [4] arXiv:2507.20248 [中文pdf, pdf, html, 其他]
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标题： 具有轴向背景磁场的混合流体-动力学圆柱平衡标题： Hybrid fluid-kinetic cylindrical equilibria with axial background magnetic field主题： 等离子体物理 (physics.plasm-ph)
自洽的一维准中性螺管平衡在一种混合模型中被构建，该模型将流体电子与由Vlasov方程描述的动能离子耦合在一起。 平衡依赖于垂直于圆柱轴的径向坐标，并包含一个轴向背景磁场。 采用一个依赖于能量以及与两个可忽略坐标共轭的规范动量的三参数离子分布函数，问题被简化为一组四阶准线性常微分方程，这些方程通过数值方法求解。 得到了静态平衡和具有宏观离子剪切速度的平衡。 电子流体的压力是各向同性的，电子对电流密度的贡献与磁场方向平行，而动能离子则与非回转对称的压力张量相关。 通过解计算了各种平衡量，并研究了自由参数对平衡特性的影响。
Self-consistent, one-dimensional quasineutral screw-pinch equilibria are constructed within a hybrid model that couples fluid electrons with kinetic ions governed by the Vlasov equation. The equilibria depend on the radial coordinate perpendicular to the cylindrical axis and include an axial background magnetic field. Adopting a three-parameter ion distribution function depending on the energy and the canonical momenta conjugate to the two ignorable coordinates, the problem is reduced to a set of four quasilinear ODEs which are solved numerically. Both static equilibria and equilibria with macroscopic ion sheared velocities are obtained. The pressure of the electron fluid is isotropic and the electron contribution to the current density is parallel to the magnetic field, while the kinetic ions are associated with a non-gyrotropic pressure tensor. By means of the solutions the various equilibrium quantities are calculated and the impact of the free parameters on the equilibrium characteristics is examined.
- [5] arXiv:2507.20523 [中文pdf, pdf, 其他]
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标题： 多机器燃料和杂质注入速率的扩展定律，足以实现分离：磁约束聚变装置的系统综述标题： Multi-Machine Scaling Laws for Fuel and Impurity Puffing Rates Sufficient for Detachment Access: a Systematic Review of Magnetic Confinement Fusion DevicesM. Moscheni, A. Herrmann, R. Kembleton, M. Kryjak, S. Lazerson, F. Levi, M. Siccinio, P. Staniec, T. Giegerich, C. Tantos, the Gauss Fusion GmbH Team主题： 等离子体物理 (physics.plasm-ph)
从32台实心壁托卡马克装置、stellarators和线性等离子体装置的457个实验和数值数据数据库中，我们推导出物理信息多机器尺度定律，这些定律可预测足够的燃料和杂质注入速率以实现等离子体分离——这是解决等离子体-壁相互作用这一开放问题的候选方案。 在最多40个低约束和高约束模式等离子体以及先进配置中的验证表明，在多达50%的情况下准确度在1.5倍以内，平均在2倍以内。 仅偏滤器体积就被发现与燃料注入相关。 添加等离子体不透明度导致经验校准的公式$\Gamma_{\text{D}}\propto [n_{\text{sep}}\times a\times(S_{\text{div}}/V_{\text{div}})^{-1.5}]^{1.05}$在所有环形装置中有效。 将其简化为$\Gamma_{\text{D}}^{\text{HDL}}\propto 0.43\times a^{1.58}\times\lambda_q^{-0.89}$避免了对$n_{\text{sep}}$的依赖，并由H/L密度极限和功率衰减长度提供了内在意义。 杂质动力学的非线性体现在种子率中——本研究既确定了一般公式，也确定了Greenwald-Eich-Scarabosio简化公式$\Gamma_{\text{Z}}^{\text{GES}}\propto a^{1.51}\times\lambda_q^{-0.27}$。 对于stellarators定义了类似关系，紧密跟随主流但未提供验证数据——这应激发进一步的研究。 在核聚变反应堆设计时代，这些结果立即适用于指导反应堆燃料循环设计和边缘等离子体建模。 更广泛地说，这项研究证明了能够将分离与工程执行器相关联的基于物理的定律存在，并为连接实验操作真实输入的分析模型铺平了道路。
From a database of 457 experimental and numerical data from 32 machines among solid-walled tokamaks, stellarators and linear plasma devices, we derive physics-informed multi-machine scaling laws predictive of fuel and impurity puffing rates sufficient to access plasma detachment -- leading candidate for a reactor-relevant solution to the open issue of plasma-wall interaction. Validation of our laws in up to 40 plasmas in low- and high-confinement mode also featuring advanced configurations demonstrates accuracy within a factor 1.5 in up to 50% of the instances, and within a factor 2 on average. Divertor volume alone is found to correlate to fuelling. The addition of plasma opaqueness leads to the empirically-calibrated law $\Gamma_{\text{D}}\propto [n_{\text{sep}}\times a\times(S_{\text{div}}/V_{\text{div}})^{-1.5}]^{1.05}$ valid across all toroidal devices. Its simplification to $\Gamma_{\text{D}}^{\text{HDL}}\propto 0.43\times a^{1.58}\times\lambda_q^{-0.89}$ avoids a dependence on $n_{\text{sep}}$ and bears intrinsic significance provided by the H/L density limit and the power fall-off length. Non-linearities of the impurity dynamics manifest in the seeding rate -- which the present work identifies both a generalised formula for, and the Greenwald-Eich-Scarabosio simplification $\Gamma_{\text{Z}}^{\text{GES}}\propto a^{1.51}\times\lambda_q^{-0.27}$. Similar relationships are defined for stellarators, closely following the mainstream but without providing data for validation -- which should stimulate further investigations. In the era of nuclear fusion reactor design, these results find immediate applicability in informing reactor fuel cycle design and edge plasma modelling. More generally, this study demonstrates that physics-based laws able to relate detachment to engineering actuators exist, and pave the way for analytical models bridging to the true inputs of experimental operation.
- [6] arXiv:2507.20626 [中文pdf, pdf, 其他]
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标题： 表征火星多组分等离子体环境中的离子声波冲击波碰撞标题： Characterizing ion-acoustic shock wave collisions in Martian multicomponent plasma environments主题： 等离子体物理 (physics.plasm-ph) ; 数学物理 (math-ph)
我们对火星多组分等离子体中碰撞的离子声波（IA）激波进行了理论研究，该等离子体由氢（$H^+$）离子、氧（$O^+$）离子和氧分子（$O_2^+$）离子组成，包括背景超热电子（用$\kappa$-（kappa）分布函数建模）。通过采用改进的Poincaré-Lighthill-Kuo（PLK）摄动方法，得到一组Burgers方程，以描述耗散非线性IA波结构的正面碰撞动力学。我们利用MAVEN探测器在火星大气中通常观测到的参数估计了时空尺度，理论上预期在多组分等离子体中激波会发生相互碰撞。探讨了正面碰撞对由一次和两次IA激波相互作用产生的静电势分布的影响。我们的数值分析表明，碰撞导致激波结构明显展宽，并伴随着运动粘度的增强。
We present theoretical investigation of colliding ion-acoustic (IA) shock waves in Martian multicomponent plasmas consisting of hydrogen ($H^+$), oxygen ($O^+$) and oxygen molecule ($O_2^+$) ions, including background superthermal electrons (modeled by a $\kappa$-(kappa) distribution function). A set of Burgers' equations is obtained by adopting a modified Poincar\'e-Lighthill-Kuo (PLK) perturbation method to describe the head-on-collision dynamics of dissipative nonlinear IA wave structures. We have estimated the spatio-temporal scales using parameters typically observed in the Martian atmosphere by the MAVEN spacecraft, for which shock waves are theoretically expected to undergo mutual collisions in the multicomponent plasma. The effects of head-on collisions on the electrostatic potential profiles arising from one-fold and two-fold IA shock interactions are explored. Our numerical analysis reveals that the collision leads to a noticeable broadening of the shock structures with the enhancement of kinematic viscosity.
- [7] arXiv:2507.20691 [中文pdf, pdf, 其他]
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标题： 欧普拉西亚@SPARC_LAB 等离子体束驱动工作点的数值研究标题： Numerical Studies for EuPRAXIA@SPARC\_LAB Plasma Beam Driven Working PointStefano Romeo, Alessio Del Dotto, Massimo Ferrario, Anna Giribono, Andrea Renato Rossi, Gilles Jacopo Silvi, Cristina Vaccarezza评论： 6页，1图期刊参考： J. Phys.: Conf. Ser. 2687 (2024) 042008主题： 等离子体物理 (physics.plasm-ph) ; 加速器物理 (physics.acc-ph)
基于EuPRAXIA@SPARC_LAB模型的等离子体用户设施的实现需要设计一个工作点，该工作点允许获得高加速梯度，同时保持加速束流的低发射度和低能量散布。这种束流预计用于波长为2-\SI{4}{\nano\meter}的软X射线自由电子激光器。在本工作中，展示了多种模拟扫描，同时改变等离子体密度和驱动器-见证粒子分离距离，以表明在EuPRAXIA@SPARC_LAB的实际工作点下，可以找到一个理想的权衡方案，使得具有峰值电流>1kA的见证粒子能够将核心（80%的电荷）的能量散布保持在0.1%以下，同时在等离子体模块内保持约1 GV/m的加速梯度。该研究还通过参数分析完成，旨在确定RF工作点和等离子体通道的稳定性要求，以保持能量抖动与能量散布处于同一水平。
The realization of a plasma based user facility on the model of EuPRAXIA@SPARC\_LAB requires to design a working point for the operation that allows to get an high accelerating gradient preserving a low emittance and low energy spread of the accelerated beam. Such beam is supposed to pilot a soft x-ray free electron laser with a wavelength of 2-\SI{4}{\nano\meter}. In this work several simulation scans are presented, varying at the same time the plasma density and driver-witness separation in order to show that, in a realistic working point for EuPRAXIA@SPARC\_LAB, it is possible to find an ideal compromise for a witness with a peak current >1kA that allows to preserve the energy spread of the core (80\% of the charge) below 0.1\%, while maintaining an accelerating gradient inside the plasma module around of 1 GV/m. The study is completed with a parametric analysis with the aim of establishing the stability requirements of the RF working point and the plasma channel in order to preserve the energy jitter at the same level of the energy spread.
- [8] arXiv:2507.20748 [中文pdf, pdf, 其他]
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标题： 通过可调谐二极管激光吸收光谱法在大气压射频等离子体喷流中对氦亚稳态密度进行二维空间分辨测量标题： Two-dimensional spatially resolved measurements of helium metastable densities by tunable diode laser absorption spectroscopy in atmospheric pressure RF plasma jets主题： 等离子体物理 (physics.plasm-ph)
氦亚稳态粒子在通过Penning电离维持射频(RF)驱动的微大气压等离子体喷流以及生成活性氧和氮物种(RONS)中起着关键作用。它们的密度通常使用可调谐二极管激光吸收光谱(TDLAS)进行测量。大多数空间分辨的TDLAS方法依赖于窄激光束在等离子体上的机械扫描，这耗时且限制了空间分辨率。在本工作中，我们提出了一种先进的二维(2D) TDLAS方法，能够在不需要机械扫描的情况下直接对氦亚稳态密度进行空间映射。采用旋转光学扩散器来抑制斑点干扰并在等离子体区域产生均匀照明。使用配备远心镜头的短波长红外相机捕捉吸收谱图，在整个视场内实现了高空间分辨率(约10 {\mu }m)。这种方法显著提高了数据质量和采集速度。改进的二维TDLAS系统被用于测量由不同定制电压波形驱动的结构电极等离子体喷流中的氦亚稳态密度。结果与流体模拟和以前报道的实验数据有很好的定性一致性。
Helium metastable species play a critical role in sustaining radio-frequency (RF) driven micro atmospheric pressure plasma jets through Penning ionization and for the generation of reactive oxygen and nitrogen species (RONS). Their densities are typically measured using tunable diode laser absorption spectroscopy (TDLAS). Most spatially resolved TDLAS approaches rely on mechanical scanning of a narrow laser beam across the plasma, which is time-consuming and limits spatial resolution. In this work, we present an advanced two-dimensional (2D) TDLAS method that enables direct spatial mapping of helium metastable densities without the need for mechanical scanning. A rotating optical diffuser is employed to suppress speckle interference and generate uniform illumination across the plasma region. The absorption profile is captured using a short-wavelength infrared camera equipped with a telecentric lens, achieving high spatial resolution (approximately 10 {\mu}m) across the entire field of view. This approach significantly enhances both data quality and acquisition speed. The improved 2D TDLAS system is applied to measure helium metastable densities in plasma jets with structured electrodes driven by different tailored voltage waveforms. The results show very good qualitative agreement with fluid simulations and previously reported experimental data.
- [9] arXiv:2507.20771 [中文pdf, pdf, 其他]
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标题： 等离子体压力对轴对称粘性电阻MHD稳态中非感应电流驱动的响应标题： Plasma pressure response to non-inductive current drive in axisymmetric visco-resistive MHD steady-states主题： 等离子体物理 (physics.plasm-ph)
我们使用粘性电阻磁流体动力学模型，研究不可压缩托卡马克等离子体的自洽、稳态轴对称解。 这项工作的关键贡献是推导出控制压力分布的泊松方程。 我们的分析表明，当前的电流建模无法产生现实的压力水平。 为了克服这一限制，我们引入了额外的非感应电流驱动，类似于中性束注入或射频加热产生的电流，作为环向电流的修改。 数值模拟验证了我们的增强模型，显示出压力分布特性的显著改进。 在所研究的情况下，这些电流驱动对速度分布的影响是适度的，除非非感应电流驱动引起总环向电流密度的反转，从而导致具有内部分隔面的非嵌套通量面。
We investigate self-consistent, steady-state axisymmetric solutions of incompressible tokamak plasma using a visco-resistive magnetohydrodynamic model. A key contribution of this work is the formulation of Poisson's equation that governs the pressure profile. Our analysis reveals that the current modeling fails to produce realistic pressure levels. To overcome this limitation, we introduce additional non-inductive current drives, akin to those generated by neutral beam injection or radio frequency heating, modeled as modifications to the toroidal current. Numerical simulations validate our enhanced model, showing significant improvements in pressure profile characteristics. In the cases examined, the effect of these current drives on the velocity profiles is moderate, except when the non-inductive current drives induce reversals in the total toroidal current density, leading to non-nested flux surfaces with internal separatrices.
- [10] arXiv:2507.20948 [中文pdf, pdf, html, 其他]
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标题： 通过多级加速器中的空间电荷抑制实现增强的束流传输用于聚变等离子体诊断标题： Enhanced beam transport via space charge mitigation in a multistage accelerator for fusion plasma diagnostics主题： 等离子体物理 (physics.plasm-ph)
高效传输高电流负离子束对于在磁约束聚变等离子体中使用重离子束探针（HIBP）系统进行准确的等离子体电位诊断至关重要。 然而，强烈的空间电荷效应通常会降低传输效率，尤其是对于金离子（Au-）等重离子。 在本研究中，我们通过在多级加速系统中优化电压分配引入静电透镜效应，显著提高了束流传输效率。 利用IGUN进行的数值模拟，以及LHD-HIBP系统的实验结果表明，这种方法有效抑制了由空间电荷引起的束流发散和损失。 无需对束流管进行机械改造，优化后的配置使注入双级加速器的Au-束流电流增加了2-3倍。 因此，等离子体电位测量扩展到了更高密度的等离子体，实现了高达1.75e19 m^-3的线平均电子密度，并提高了信噪比。 该技术为在空间电荷主导条件下传输高电流重离子束提供了一种紧凑、实用且高效的解决方案。 除了对等离子体诊断的影响外，该方法还可广泛应用于各种加速器系统，包括科学和工业应用中需要高强束流传输的系统。
Efficient transport of high-current negative ion beams is critical for accurate plasma potential diagnostics using heavy-ion beam probe (HIBP) systems in magnetically confined fusion plasmas. However, strong space-charge effects often degrade transport efficiency, particularly for heavy ions such as Au-. In this study, we demonstrate a substantial improvement in beam transport by introducing an electrostatic lens effect through optimized voltage allocation in a multistage acceleration system. Numerical simulations using IGUN, supported by experiments with the LHD-HIBP system, show that this approach effectively suppresses space-charge-induced beam divergence and loss. Without requiring mechanical modifications to the beamline, the optimized configuration enables a 2-3 fold increase in Au- beam current injected into the tandem accelerator. Consequently, plasma potential measurements were extended to higher-density plasmas, reaching line-averaged electron densities up to 1.75e19 m^-3 with improved signal-to-noise ratio. This technique offers a compact, practical, and highly effective solution for transporting high-current heavy-ion beams under space-charge-dominated conditions. Beyond its impact on plasma diagnostics, the method is broadly applicable to a wide range of accelerator systems, including those used in scientific and industrial applications where high-intensity beam transport is required.
- [11] arXiv:2507.21003 [中文pdf, pdf, html, 其他]
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标题： 优化准等离子体星形环中的粒子输运以提高约束性能标题： Optimizing Particle Transport for Enhanced Confinement in Quasi-Isodynamic Stellarators主题： 等离子体物理 (physics.plasm-ph)
尽管在减少湍流热损失方面取得了显著进展，现代准不变磁通（QI）托卡马克——如Stellaris——仍然受到较差的粒子约束的困扰，这从根本上限制了它们的整体性能。 使用GENE-Tango框架内的gyrokinetic模拟，我们确定由于不利的磁几何结构导致的抑制向内热扩散是主要原因。 为了克服这一限制，我们设计了一种新的配置，其镜像比降低，这增强了通过电子对向内粒子通量的贡献。 这有助于形成强烈尖峰密度分布，抑制湍流，并带来约束性能的显著提升。 我们的优化配置相比Stellaris实现了能量约束近两倍的提高，突显了在下一代托卡马克设计中优化粒子输运的关键作用。
Despite significant advances in reducing turbulent heat losses, modern quasi-isodynamic (QI) stellarators -- such as Stellaris -- continue to suffer from poor particle confinement, which fundamentally limits their overall performance. Using gyrokinetic simulations within the GENE--Tango framework, we identify suppressed inward thermodiffusion, caused by unfavorable magnetic geometry, as the primary cause. To overcome this limitation, we design a new configuration with a reduced mirror ratio, which enhances the contribution of passing electrons to the inward particle flux. This facilitates the formation of strongly peaked density profiles, suppresses turbulence, and leads to a substantial improvement in confinement. Our optimized configuration achieves nearly a twofold increase in energy confinement compared to Stellaris, highlighting the crucial role of optimizing particle transport in next-generation stellarator designs.
新提交 (展示 11 之 11 条目 )
- [12] arXiv:2507.20663 (交叉列表自 physics.optics) [中文pdf, pdf, 其他]
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标题： 太赫兹频率转换在等离子体诱导的时间边界处标题： Terahertz frequency conversion at plasma-induced time boundaryYindong Huang, Bin Zhou, Aijun Xuan, Mingxin Gao, Jing Lou, Xiaomin Qu, Zengxiu Zhao, Ce Shang, Xuchen Wang, Chao Chang, Viktar Asadchy主题： 光学 (physics.optics) ; 等离子体物理 (physics.plasm-ph)
我们报告了通过飞秒激光诱导的空气到等离子体相变在超快时间边界处产生的太赫兹（THz）波的频率转换。 我们的实验和理论相结合的方法揭示了在超快时间边界处折射率的突然变化由于色散等离子体导致了宽带THz谱的红移和蓝移，具有显著的振幅变化。 本研究将这些效应与空间边界的效果进行对比，突出了时间操纵在光谱工程中的优越性。 这些发现不仅加深了对时变介质中光-物质相互作用的理解，也为太赫兹技术的创新应用铺平了道路，并为观察时间反射效应、光子时间晶体以及时空调制物质的观测奠定了基础。
We report on the frequency conversions of terahertz (THz) waves at ultrafast time boundaries created via femtosecond laser-induced air-to-plasma phase transitions. Our combined experimental and theoretical approach reveals that the abrupt change in refractive index at the ultrafast time boundaries drives both the red and blue shifts over the broadband THz spectrum due to the dispersive plasma, with distinctive amplitude variations. The present study contrasts these effects with those from spatial boundaries, highlighting the superior efficacy of temporal manipulations for spectral engineering. These findings not only deepen the understanding of light-matter interactions in time-varying media but also pave the way for innovative applications in THz technology and lay the groundwork for the observation of temporal reflection effects, photonic time crystals, and spatio-temporally modulated matter.
交叉提交 (展示 1 之 1 条目 )
- [13] arXiv:2412.15823 (替换) [中文pdf, pdf, html, 其他]
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标题： LHD等离子体中芯部密度坍缩事件的三维非线性MHD模拟标题： 3D non-linear MHD simulations of core density collapse event in LHD plasma主题： 等离子体物理 (physics.plasm-ph)
一种新的三维非线性磁流体动力学（MHD）模型已被扩展到MIPS代码中，结合了平行热扩散率。 该模型已与MIPS代码中以前使用的MHD模型进行了对比测试。 利用开发的模型对在大型 helical 装置（LHD）等离子体中观测到的核心密度塌缩事件（CDC）进行了初步研究。 使用HINT代码为LHD中的典型高密度核心放电构建了平衡状态，真空磁场轴配置为RaxV = 3.85 m，磁场轴beta\beta 0 = 4%等离子体。 该配置对应于具有陡峭压力梯度和强Shafranov位移的等离子体，这使得等离子体在LHD中可能不稳定。 该模型展示了CDC事件的初步特征。 在低场侧区域的线性阶段，高n球形模态使等离子体失稳，最终导致压力和密度剖面的塌缩，同时伴随着磁场的随机化以及在松弛阶段非线性耦合后集中在等离子体核心的低n模态的转移。
A new three-dimensional, non-linear Magnetohydrodynamics (MHD) model has been extended in MIPS code, incorporating parallel heat dif- fusivity. The model has been benchmarked against the former MHD model used in MIPS code. A preliminary study of the core density collapse event (CDC) observed in the Large Helical Device (LHD) plasma has been performed using the developed model. The equilibrium has been constructed using HINT code for a typical super dense core discharge in LHD, with vacuum magnetic axis configuration RaxV = 3.85 m and magnetic axis beta \beta0 = 4% plasma. This configuration corresponds to a plasma with a steep pressure gradient and strong Shafranov shift, which makes the plasma potentially unstable in the LHD. The model shows preliminary characteristics of the CDC event. The plasma is destabilized by high-n ballooning modes in the low-field side region during the linear regime, eventually leading to the collapse of the pressure and density profiles, together with the stochastization of the magnetic field and a shift to low-n modes centered at the core of the plasma after the non-linear coupling at the relaxation regime.
- [14] arXiv:2503.05674 (替换) [中文pdf, pdf, 其他]
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标题： MAST-U上静态前向自由边界Grad-Shafranov问题的多个解标题： Multiple solutions to the static forward free-boundary Grad-Shafranov problem on MAST-U主题： 等离子体物理 (physics.plasm-ph) ; 数值分析 (math.NA)
广义-沙法诺夫（GS）方程是一个非线性椭圆偏微分方程，它描述了托卡马克等离子体的理想磁流体动力学平衡。 以往的研究已经证明，在理想几何结构中使用简化的等离子体电流密度剖面和边界条件求解GS方程时，存在多个解。 到目前为止，关于在具有更复杂电流密度剖面和积分自由边界条件（通常用于生产级平衡代码）的实际托卡马克几何中是否存在多个平衡状态的问题仍然没有答案。 在本工作中，我们使用经过验证的演化平衡求解器FreeGSNKE和阻尼延续算法，在MAST-U托卡马克几何中发现了静态正向自由边界GS问题的多个解。 通过改变GS方程中的等离子体电流、电流密度剖面系数或线圈电流，我们识别并表征了不同的平衡解，包括深度约束和较浅约束的等离子体状态。 我们认为，积分自由边界条件的限制性质可能阻止了更多平衡状态的存在，该条件在全球范围内将计算边界上的环向通量与内部的环向通量耦合在一起。 最后，我们讨论了这些发现对更广泛的平衡建模的影响，并强调需要探索其他平衡代码和托卡马克中是否存在多个解，以及它们对依赖GS平衡的下游模拟的潜在影响。
The Grad-Shafranov (GS) equation is a nonlinear elliptic partial differential equation that governs the ideal magnetohydrodynamic equilibrium of a tokamak plasma. Previous studies have demonstrated the existence of multiple solutions to the GS equation when solved in idealistic geometries with simplified plasma current density profiles and boundary conditions. Until now, the question of whether multiple equilibria might exist in real-world tokamak geometries with more complex current density profiles and integral free-boundary conditions (commonly used in production-level equilibrium codes) has remained unanswered. In this work, we discover multiple solutions to the static forward free-boundary GS problem in the MAST-U tokamak geometry using the validated evolutive equilibrium solver FreeGSNKE and the deflated continuation algorithm. By varying the plasma current, current density profile coefficients, or coil currents in the GS equation, we identify and characterise distinct equilibrium solutions, including both deeply and more shallowly confined plasma states. We suggest that the existence of even more equilibria is likely prohibited by the restrictive nature of the integral free-boundary condition, which globally couples poloidal fluxes on the computational boundary with those on the interior. We conclude by discussing the implications of these findings for wider equilibrium modelling and emphasise the need to explore whether multiple solutions are present in other equilibrium codes and tokamaks, as well as their potential impact on downstream simulations that rely on GS equilibria.
- [15] arXiv:2505.10669 (替换) [中文pdf, pdf, html, 其他]
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标题： 通过超光速相位速度的直接激光加速中更高阶共振带来的增强能量增益标题： Enhanced energy gain through higher-order resonances during direct laser acceleration with superluminal phase velocity主题： 等离子体物理 (physics.plasm-ph) ; 加速器物理 (physics.acc-ph) ; 光学 (physics.optics)
超高强度激光等离子体相互作用可以通过直接激光加速产生超相对论电子，这一过程由准静态等离子体磁场和电场辅助。这些场横向约束电子运动并引发贝塔龙振荡。净能量增益受到两个频率之间相互作用的强烈影响：贝塔龙频率和电子经历的激光场振荡频率。先前的研究表明，能量增益是通过贝塔龙振荡与激光场振荡之间的共振实现的。特别是，当激光场在一个贝塔龙振荡期间完成多个周期时，会发生高阶共振，从而允许超越基本（贝塔龙）共振的额外能量传递区域。在本工作中，我们证明，当激光的相速度为超光速时，这种共振变得特别有效。尽管随着电子能量的增加，这两个频率通常以不同的方式演变，导致失谐，但超光速相速度引入了一个具有全局最小值的非单调频率比。这个最小值使得在广泛的能量范围内能够持续的频率匹配，从而实现增强的能量增益。随着相速度的增加，贝塔龙共振由于过早的频率失谐而变得无效。同时，高阶共振变得越来越有效，在这种直接激光加速的区域内成为增强能量增益的主要机制。
Ultra-high intensity laser-plasma interactions can produce ultra-relativistic electrons via direct laser acceleration, assisted by quasi-static plasma magnetic and electric fields. These fields transversely confine electron motion and induce betatron oscillations. The net energy gain is strongly influenced by the interplay between two frequencies: the betatron frequency and the frequency of laser field oscillations experienced by the electron. Prior work has shown that energy gain is enabled by a resonance between the betatron oscillations and the oscillations of the laser field. In particular, higher-order resonances occur when the laser field completes multiple cycles during one betatron oscillation, allowing additional regimes of energy transfer beyond the fundamental (betatron) resonance. In this work, we demonstrate that such resonances become particularly effective when the laser's phase velocity is superluminal. Although the two frequencies generally evolve differently with increasing electron energy, which leads to detuning, a superluminal phase velocity introduces a non-monotonic frequency ratio with a global minimum. This minimum allows sustained frequency matching over a broad energy range, thereby enabling enhanced energy gain. As the phase velocity increases, the betatron resonance becomes ineffective due to premature frequency detuning. At the same time, higher-order resonances become increasingly effective, emerging as the dominant mechanisms for enhanced energy gain in this regime of direct laser acceleration.
- [16] arXiv:2506.05553 (替换) [中文pdf, pdf, html, 其他]
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标题： 通过渐近匹配技术研究托卡马克反应堆中电子回旋辐射测温法对新经典撕裂模式的检测标题： Investigation of Neoclassical Tearing Mode Detection by ECE Radiometry in Tokamak Reactors via Asymptotic Matching Techniques主题： 等离子体物理 (physics.plasm-ph)
TJ环形撕裂模式代码用于对ITER类似托卡马克等离子体平衡中由经典撕裂模式(NTMs)产生的电子回旋辐射(ECE)信号进行现实预测。 在所谓的"外区"，即等离子体的大部分区域，具有与NTM相同环向模式数但不同极向模式数的磁场螺旋谐波通过Shafranov位移和平衡磁通面的形状相互耦合。 在"内区"，即NTM有理表面附近的区域，其极向和环向模式数比例与NTM相同的螺旋谐波非线性地相互耦合，以产生径向不对称的磁岛链。 内区和外区的解彼此进行渐近匹配。 渐近匹配过程确定了NTM的整体磁结构，以及该模式引起的电子温度的全局扰动。 开发了一种模拟的ECE诊断方法，该方法考虑了由于发射电子的相对论质量增加而导致的信号频率下移和展宽。
The TJ toroidal tearing mode code is used to make realistic predictions of the electron cyclotron emission (ECE) signals generated by neoclassical tearing modes (NTMs) in an ITER-like tokamak plasma equilibrium. In the so-called "outer region'', which comprises the bulk of the plasma, helical harmonics of the magnetic field with the same toroidal mode number as the NTM, but different poloidal mode numbers, are coupled together by the Shafranov shifts and shaping of the equilibrium magnetic flux-surfaces. In the "inner region'', which is localized in the vicinity of the NTM rational surface, helical harmonics whose poloidal and toroidal mode numbers are in the same ratio as those of the NTM are coupled together nonlinearly to produce a radially asymmetric magnetic island chain. The solutions in the inner and outer regions are asymptotically matched to one another. The asymptotic matching process determines the overall magnetic structure of the NTM, as well as the global perturbation to the electron temperature caused by the mode. A simulated ECE diagnostic is developed that accounts for the downshifting and broadening in frequency of the signal due to the relativistic mass increase of the emitting electrons.
- [17] arXiv:2409.07015 (替换) [中文pdf, pdf, html, 其他]
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标题： 低$β$等离子体中离子加热的统一现象学：粒子模拟标题： A Unified Phenomenology of Ion Heating in Low-$β$ Plasmas: Test-Particle Simulations评论： 已被《物理评论快报》接受发表。14页，5幅图；包含补充材料（6幅图）主题： 太阳与恒星天体物理学 (astro-ph.SR) ; 等离子体物理 (physics.plasm-ph) ; 空间物理 (physics.space-ph)
我们认为，在低$\beta$碰撞等离子体中通常被视为不同过程的随机和准线性离子加热，是受湍流波动非线性展宽控制的连续体的远端极限，因此也由归一化交叉螺旋度所控制。 我们提出一个简单的经验公式，能够捕捉这两种情况，推广了通常用于描述随机加热的公式。 测试离子与湍流相互作用的模拟结果在不同离子和湍流特性范围内确认了我们的标度关系，包括在太阳风中观察到的陡峭离子动力学过渡范围。 我们的结果提供了一个统一的框架，以理解从黑洞吸积盘到太阳日冕的各种天体物理环境中的离子加热过程，同时也为更大尺度的模拟提供了一个紧凑且通用的亚网格模型。
We argue that stochastic and quasi-linear ion heating, often viewed as distinct processes in low-$\beta$ collisionless plasmas, are the far limits of a continuum controlled by nonlinear broadening of turbulent fluctuations, and thus by the normalized cross helicity. We propose a simple empirical formula that captures both regimes, generalizing that commonly used to describe stochastic heating. Simulations of test ions interacting with turbulence confirm our scalings across a wide range of different ion and turbulence properties, including with a steep ion-kinetic transition range as seen in the solar wind. Our results provide a unified framework for understanding ion heating processes across diverse astrophysical environments from black-hole accretion disks to the solar corona, also providing a compact and versatile subgrid model for larger-scale simulations.
- [18] arXiv:2505.00288 (替换) [中文pdf, pdf, html, 其他]
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标题： Nyström型指数积分器用于强磁场中的带电粒子动力学标题： Nyström Type Exponential Integrators for Strongly Magnetized Charged Particle Dynamics主题： 计算物理 (physics.comp-ph) ; 数值分析 (math.NA) ; 等离子体物理 (physics.plasm-ph)
计算带电粒子在电磁场中的动力学（即粒子推进问题）是等离子体物理模拟中粒子-网格（PIC）方法中最计算密集的组成部分之一。当等离子体强烈磁化时，这一任务尤其具有挑战性，因为在这种情况下，粒子运动包含从高度振荡的快速回旋运动到缓慢宏观行为的广泛时间尺度， resulting 的数值模型非常刚性。目前用于模拟粒子运动的最先进的时间积分器由于问题的严重数值刚性而存在局限性，因此需要更高效的 方法。最近，指数积分器被提出作为一种有前景的新方法用于这些模拟，并显示出相对于常用方案的计算优势。指数方法可以精确求解线性问题，并且是$A$稳定的。在本文中，标准指数算法框架被扩展，以推导出一种将牛顿运动方程作为二阶微分方程集成的 Nyström 型指数方法。推导出了二阶和三阶的特定 Nyström 型方案，并应用于强磁化粒子推进问题。数值实验表明，Nyström 型指数积分器在计算效率方面相比标准指数方法有显著提升。
Calculating the dynamics of charged particles in electromagnetic fields (i.e. the particle pushing problem) is one of the most computationally intensive components of particle-in-cell (PIC) methods for plasma physics simulations. This task is especially challenging when the plasma is strongly magnetized, since in this case the particle motion consists of a wide range of temporal scales from highly oscillatory fast gyromotion to slow macroscopic behavior and the resulting numerical model is very stiff. Current state-of-the-art time integrators used to simulate particle motion have limitations given the severe numerical stiffness of the problem and more efficient methods are of interest. Recently, exponential integrators have been proposed as a promising new approach for these simulations and shown to offer computational advantages over commonly used schemes. Exponential methods can solve linear problems exactly and are $A$-stable. In this paper, the standard exponential algorithms framework is extended to derive Nystr\"om-type exponential methods that integrate the Newtonian equations of motion as a second-order differential equation. Specific Nystr\"om-type schemes of second and third orders are derived and applied to strongly magnetized particle pushing problems. Numerical experiments are presented to demonstrate that the Nystr\"om-type exponential integrators can provide significant improvement in computational efficiency over the standard exponential methods.