Physics of Plasmas最新文献

{"title":"X-point radiator and power exhaust control in configurations with multiple X-points in TCV","authors":"S. Gorno, O. Février, C. Theiler, T. Ewalds, F. Felici, T. Lunt, A. Merle, F. Bagnato, C. Colandrea, J. Degrave, R. Ducker, G. Durr-Legoupil-Nicoud, B. Duval, K. Lee, L. Martinelli, D. S. Oliveira, A. Perek, H. Reimerdes, L. Simons, G. Sun, B. Tracey, M. Wischmeier, C. Wüthrich","doi":"10.1063/5.0201401","DOIUrl":"https://doi.org/10.1063/5.0201401","url":null,"abstract":"Novel power exhaust solutions are being developed to address the challenge of integrating a high performance fusion core plasma with a well-protected divertor, if the single null configuration does not scale to a reactor device. This work aims to elucidate the physics mechanisms responsible for the reduction in peak target heat flux in configurations with multiple X-points. Experimental studies on tokamak à configuration variable in the Snowflake Minus configuration are extended to a novel configuration with three nearby divertor X-points, termed a Jellyfish, allowing us to enhance the expected effects of an additional divertor X-point. These studies are complemented by simplified 1D scrape-off layer (SOL) modeling with the SPLEND1D code and by interpretative modeling with the edge transport code EMC3-EIRENE applied to the Snowflake Minus, to further elucidate some of the key underlying processes. We find that configurations with multiple nearby X-points, and increased near-SOL connection length, exhibit reductions in peak target heat flux and an earlier detachment onset compared to a reference single null configuration, consistent with expectations from SPLEND1D. A strong correlation is experimentally observed between the radially localized radiated power and connection length. While this does not necessarily map to higher total divertor radiative losses for configurations with multiple X-points, it can, at least, provide some control over the radial position of the spatial radiation distribution. Experiments are shown to exhibit radial striations in the emissivity of multiple spectral lines in the inter-null region in these configurations. Although comparisons with EMC3-EIRENE simulations support enhanced cross field transport in the inter-null region, additional transport physics is required in the model to obtain a quantitative match with experiment. No significant differences in divertor-core compatibility are attributed to the presence of additional divertor X-points. However, impurity source optimization is required in such geometries to ensure a low core impurity content is maintained.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"19 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141710831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analytical derivation and numerical simulation of the ablation rate of a spherical target","authors":"Yan-Zhao Han, Yun-Xing Liu, Ying-Jun Li","doi":"10.1063/5.0196305","DOIUrl":"https://doi.org/10.1063/5.0196305","url":null,"abstract":"This paper presents a quasi-steady-state analytical model of the plasma conduction region of a spherical target, and the model is used to analyze the factors that influence the mass ablation rate during laser ablation. Unlike in the case of planar geometry, the mass ablation rate changes as the distance to the ablation front increases. For the plasma in the heat-conduction region of the spherical target under certain conditions, the new analytical model provides relevant parameters such as the density, pressure, and sound velocity, and its results align with those from one-dimensional hydrodynamic simulations. The model and results presented here are valuable resources for investigating mass ablation rates in laser fusion processes.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"3 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141714039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Early internal detection of magnetic tearing and implications for tokamak magnetohydrodynamic stability","authors":"M. D. Pandya, B. Chapman, K. McCollam, R. A. Myers, J. Sarff, B. S. Victor, D. P. Brennan, D. Brower, J. Chen, W. X. Ding, C. T. Holcomb, N. Logan, E. Strait","doi":"10.1063/5.0205964","DOIUrl":"https://doi.org/10.1063/5.0205964","url":null,"abstract":"Internal fluctuation measurements with Faraday-effect polarimetry in the DIII-D tokamak reveal the onset of a tearing mode with toroidal mode number n = 3 well before it is detected by the sensing coils external to the plasma. This mode appears before the n = 2, 1 modes and is first detected with internal measurements at a lower value of the ideal-wall kink beta limit than is indicated at the time of first detection by the sensing coils. When the mode is first detected, the linear resistive stability parameter, Δ′, indicates marginal stability and continues to do so until later when the mode amplitude begins increasing linearly with time—together suggesting a neoclassical origin for this mode.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"376 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141707957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fundamental difference between the mechanisms of electrostatic field screening in dense and thoroughly collisionless plasmas","authors":"E. V. Rosenfeld","doi":"10.1063/5.0200148","DOIUrl":"https://doi.org/10.1063/5.0200148","url":null,"abstract":"When an external electric field appears in a homogeneous plasma, ions move into regions where their electrostatic energy is lower. Simultaneously, forces arise that counteract this effect, causing the plasma to reach equilibrium when the field disappears completely. In collisional plasma, the resulting charge inhomogeneities decrease both Coulomb energy and entropy. Randomly induced diffusion flows tend to hinder their growth, minimizing free energy at any point. Accordingly, in the Debye–Hückel theory, the external field strength decreases exponentially with distance within the plasma. In a collisionless plasma, an antiscreening mechanism operates differently. Each ion moves in a self-consistent field along distinct trajectories, following classical dynamics laws. An external field bends these trajectories, bringing ions into regions where their Coulomb energy is lower. The antiscreening mechanism occurs when ions accelerate into potential wells, increasing the distances between them along their trajectories and decreasing their number densities along these paths. The law of energy conservation for any single ion governs this principally nonlocal process, and the dependence of field strength on distance is not necessarily exponential. This paper demonstrates that the Debye–Hückel theory should not be used to describe the charge density distribution within an unrestricted stream of collisionless plasma, such as the solar wind. It also analyzes non-exponential solutions of the Poisson equation for plasma sheaths above flat surfaces, from which such a flow takes off and on which it falls, obtained in quadratures.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"414 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141707765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Plasma dynamics and collisional magnetic presheath structure in unmagnetized divertor plasma in fusion devices","authors":"I. Baranovsky, E. Kaveeva, V. Rozhansky","doi":"10.1063/5.0211632","DOIUrl":"https://doi.org/10.1063/5.0211632","url":null,"abstract":"A model of strongly ionized plasma dynamics in a slightly inclined magnetic field with ions, unmagnetized with respect to ion–ion collisions, typical for detached regimes, is presented. It is demonstrated that far from the material surface, the parallel dynamics remains almost the same as in the magnetized plasma. In the wall vicinity, parallel plasma motion is transformed into perpendicular classical diffusion originating from electron–ion collisions, forming a diffusive layer. At a distance of few ion gyroradii from the material surface, a collisional magnetic presheath is formed, where ions move toward the surface with the velocity of the order of the sound speed, in spite of the fact that an ion exhibits many collisions before reaching the surface. For typical inclination angles of magnetic field of the order of few degrees, the electrostatic potential in the diffusive layer and in the presheath deviates considerably from the Boltzmann potential for electrons, which is typical for collisionless magnetic presheath. Moreover, the normal electric field in some regions is directed away from the surface, which is important for impurities to interact with the surface.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"9 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141277540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Divergence of the energy-losing rate of charged particles in plasmas","authors":"B. Du, Dongguo Kang, Kai Li, Wen-shuai Zhang, Shiyang Zou, Luan Deng, Hongbo Cai, Shaoping Zhu","doi":"10.1063/5.0207504","DOIUrl":"https://doi.org/10.1063/5.0207504","url":null,"abstract":"In modeling the charged alpha particle transport in hot-spot plasmas of inertial confinement fusion, the energy-losing rate is a major concern in the Monte Carlo simulations of alpha particle transport of a radiative-hydrodynamic code. However, the traditionally used energy stopping-power only describes the averaged energy-losing rate of the incident charged particles, whereas the variance of the energy exchange with the background particles is generally ignored. In this paper, the variance of charged particle collisions is studied by both analytical derivation and Monte Carlo simulations. An expression of the divergence of the charged particle energy-losing rate is given for the first time, which can be directly used for practical estimations. It indicates that when the areal density of the target particles along the incident particle path length is low, the divergence of the lost energy would be much larger than the average value, and the traditionally used energy stopping-power would be no longer sufficient to describe the charged particle Coulomb collisions. It helps to obtain a more comprehensive understanding about the charged particle transport in plasmas.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"22 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141278940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Time-of-flight technique for estimation of the energy of runaway electron bunches formed in magnetized gas diodes","authors":"L. N. Lobanov, K. Sharypov, V. Shpak, S. Shunailov, M. I. Yalandin, N. M. Zubarev","doi":"10.1063/5.0213344","DOIUrl":"https://doi.org/10.1063/5.0213344","url":null,"abstract":"Time-of-flight estimates of the kinetic energy of magnetically insulated bunches of moderately relativistic runaway electrons (RAEs) were obtained with the use of an air diode equipped with a drift section. The measurements have demonstrated that the bunch energy can be controlled by changing the conditions for RAE emission in an air diode with a sharply inhomogeneous electric field, which can be done by varying the cathode geometry and material and the length of the cathode-anode gap. It has been demonstrated that if the measured electron current peaks are resolved to within 10 ps, and the bunch duration and spread in RAE emission moments are close to this resolution, the characteristic energies of the bunches can be estimated with an accuracy of ≈10%. Examples of energy measurements are given for paraxial and tubular bunches accelerated at cathode potentials of up to −250 kV. The estimated characteristic energies of the bunches, even not corrected for drift losses in the fill gas, turned out to be greater than the energies that could be achieved for bunches accelerated in a vacuum diode with due account for the variations in diode voltage.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"52 23","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141275340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diagnosis of solid–liquid phase transition using hopping particles in 2D dusty plasmas","authors":"Shaoyu Lu, Dong Huang, Zhuang Ma, Yan Feng","doi":"10.1063/5.0211119","DOIUrl":"https://doi.org/10.1063/5.0211119","url":null,"abstract":"Based on the statistical analysis of particles hopping outside the cages formed by their nearest neighboring particles, a new diagnostic of the hopping particle (HP) percentage is proposed to identify the solid–liquid phase transition in two-dimensional (2D) dusty plasmas. To demonstrate the effectiveness of the HP percentage, Langevin dynamical simulations of 2D Yukawa systems under various conditions are performed to mimic 2D dusty plasmas. It is found that the HP percentage exhibits a significant jump while decreasing the coupling parameter around the melting point, just corresponding to the solid–liquid phase transition. As compared with other traditionally used diagnostics, the HP percentage diagnostic is sensitive enough, and the dynamical information is incorporated inside. By comparing to the most widely used diagnostic of the bond-angular order parameter, the melting criterion of this HP percentage diagnostic is determined to be about 30% for the suitable time interval, which is general for the 2D Yukawa systems with different screening parameters.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"64 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141277495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computation of transport properties of warm dense matter using Abinit","authors":"A. Blanchet, V. Recoules, F. Soubiran, M. Tacu","doi":"10.1063/5.0204198","DOIUrl":"https://doi.org/10.1063/5.0204198","url":null,"abstract":"The dynamics of an inertial confinement fusion capsule, or of a stellar or planet interior, obey a very similar set of equations: magneto-radiative-hydrodynamic equations. The solutions of these equations, however, depend entirely on the transport properties associated with the different materials at play. To properly model the dynamics of these systems, it is necessary to determine with high accuracy the transport coefficients of several materials over a large range of thermodynamic conditions. Experimental capabilities in this respect are still limited due to the nature of the microphysics at play and the extreme conditions involved. Numerical simulations are thus necessary, and in this respect, molecular dynamics simulations based on density functional theory offer exquisite possibilities to constrain the transport properties in the warm to hot dense matter regime. In this paper, we report the methodology used to extract different transport properties based on molecular dynamics performed with the software Abinit. The examples shown are based on the specific cases identified for the purpose of the second charged-particle transport code comparison workshop.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"2 20","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141277439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simulation studies of tungsten impurity behaviors in helium plasma in comparison with deuterium plasma via SOLPS-ITER","authors":"Xiaoju Liu, Shanlu Gao, Qiqi Shi, Tingfeng Ming, Guoqiang Li, Xiang Gao","doi":"10.1063/5.0191960","DOIUrl":"https://doi.org/10.1063/5.0191960","url":null,"abstract":"The sputtering and transport of tungsten (W) impurities in helium (He) and deuterium (D) plasma discharges are compared using the SOLPS-ITER code. To reduce the computational resources of modeling, W ions are treated using the bundled charge state model. The results show that the W erosion flux of He plasma is almost a factor of two higher than that of D plasma under the same upstream electron density and heating power due to the higher W sputtering yield in He plasma. Moreover, the W self-sputtering flux is significantly higher than the W flux sputtered by the main ions. The leakage and retention of W impurities in the divertor region is also analyzed. W ions mainly escape from the near scrape-off layer (SOL) region through the divertor entrance as the stagnation point of the average W impurity poloidal velocity is considerably closer to the target plates in the near SOL region. Furthermore, the leakage flux of W ions in He plasma is higher than that in D plasma, mainly because of the higher W sputtering level in He plasma, which results in a larger W density. W ions with low-lying charge states, mostly comprising the charge state of W10–12+, easily escape from the divertor through the near SOL flux tubes in both D and He plasmas. In addition, the effects of upstream electron density on W sputtering and retention in He and D plasma discharges are presented.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"34 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141280282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}