Damages induced on the tungsten surface at two different operating conditions of a kilojoule plasma focus device are studied. In one condition, the tungsten samples were exposed to axial plasma shocks that are formed after pinch disruption, and in the other condition, the pinch phenomenon was absent or weak. Melting, craters, and cracking on the surfaces were observed in both cases. In the former case, the charged particle beams and post-pinch material ejection will play a role in impacting the surface; however, in the latter case those phenomena will have small contributions because of the absence or weak formation of the pinch. A damage factor of ∼109 W m−2 s0.5 was estimated at a distance of 3 cm from the pinch exit using the method given in Akel et al. [J. Fusion Energy 35, 694–701 (2016)] and Klimov et al. [J. Nucl. Mater. 390, 721–726 (2009)] for the former case. The present work suggests that at pressures lower than the pinch-occurring pressure, only axial plasma shock effects on the targeted surface can be studied and that they can be separated from the effects produced by the charged particle beams mixed with axial plasma shocks in the case of pinch occurrence.
{"title":"Plasma-induced damage on the tungsten surface using a kilojoule plasma focus device: Applicable to study the damages on nuclear fusion reactor related materials","authors":"Jalaj Jain, Marcos Flores Carrasco, Jose Moreno, Sergio Davis, Cristian Pavez, Biswajit Bora, Leopoldo Soto","doi":"10.1063/5.0211839","DOIUrl":"https://doi.org/10.1063/5.0211839","url":null,"abstract":"Damages induced on the tungsten surface at two different operating conditions of a kilojoule plasma focus device are studied. In one condition, the tungsten samples were exposed to axial plasma shocks that are formed after pinch disruption, and in the other condition, the pinch phenomenon was absent or weak. Melting, craters, and cracking on the surfaces were observed in both cases. In the former case, the charged particle beams and post-pinch material ejection will play a role in impacting the surface; however, in the latter case those phenomena will have small contributions because of the absence or weak formation of the pinch. A damage factor of ∼109 W m−2 s0.5 was estimated at a distance of 3 cm from the pinch exit using the method given in Akel et al. [J. Fusion Energy 35, 694–701 (2016)] and Klimov et al. [J. Nucl. Mater. 390, 721–726 (2009)] for the former case. The present work suggests that at pressures lower than the pinch-occurring pressure, only axial plasma shock effects on the targeted surface can be studied and that they can be separated from the effects produced by the charged particle beams mixed with axial plasma shocks in the case of pinch occurrence.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"14 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vicente Valenzuela-Villaseca, Jacob M. Molina, Derek B. Schaeffer, Sophia Malko, Jesse Griff-McMahon, Kirill Lezhnin, Michael J. Rosenberg, S. X. Hu, Dan Kalantar, Clement Trosseille, Hye-Sook Park, Bruce A. Remington, Gennady Fiksel, Dmitri Uzdensky, Amitava Bhattacharjee, William Fox
We present results from x-ray imaging of high-aspect-ratio magnetic reconnection experiments driven at the National Ignition Facility. Two parallel, self-magnetized, elongated laser-driven plumes are produced by tiling 40 laser beams. A magnetic reconnection layer is formed by the collision of the plumes. A gated x-ray framing pinhole camera with micro-channel plate detector produces multiple images through various filters of the formation and evolution of both the plumes and current sheet. As the diagnostic integrates plasma self-emission along the line of sight, two-dimensional electron temperature maps ⟨Te⟩Y are constructed by taking the ratio of intensity of these images obtained with different filters. The plumes have a characteristic temperature ⟨Te⟩Y=240 ± 20 eV at 2 ns after the initial laser irradiation and exhibit a slow cooling up to 4 ns. The reconnection layer forms at 3 ns with a temperature ⟨Te⟩Y=280 ± 50 eV as the result of the collision of the plumes. The error bars of the plumes and current sheet temperatures separate at 4 ns, showing the heating of the current sheet from colder inflows. Using a semi-analytical model, we survey various heating mechanisms in the current sheet. We find that reconnection energy conversion would dominate at low density (ne≲7×1018 cm−3) and electron-ion collisional drag at high-density (≳1019 cm−3).
{"title":"X-ray imaging and electron temperature evolution in laser-driven magnetic reconnection experiments at the national ignition facility","authors":"Vicente Valenzuela-Villaseca, Jacob M. Molina, Derek B. Schaeffer, Sophia Malko, Jesse Griff-McMahon, Kirill Lezhnin, Michael J. Rosenberg, S. X. Hu, Dan Kalantar, Clement Trosseille, Hye-Sook Park, Bruce A. Remington, Gennady Fiksel, Dmitri Uzdensky, Amitava Bhattacharjee, William Fox","doi":"10.1063/5.0213598","DOIUrl":"https://doi.org/10.1063/5.0213598","url":null,"abstract":"We present results from x-ray imaging of high-aspect-ratio magnetic reconnection experiments driven at the National Ignition Facility. Two parallel, self-magnetized, elongated laser-driven plumes are produced by tiling 40 laser beams. A magnetic reconnection layer is formed by the collision of the plumes. A gated x-ray framing pinhole camera with micro-channel plate detector produces multiple images through various filters of the formation and evolution of both the plumes and current sheet. As the diagnostic integrates plasma self-emission along the line of sight, two-dimensional electron temperature maps ⟨Te⟩Y are constructed by taking the ratio of intensity of these images obtained with different filters. The plumes have a characteristic temperature ⟨Te⟩Y=240 ± 20 eV at 2 ns after the initial laser irradiation and exhibit a slow cooling up to 4 ns. The reconnection layer forms at 3 ns with a temperature ⟨Te⟩Y=280 ± 50 eV as the result of the collision of the plumes. The error bars of the plumes and current sheet temperatures separate at 4 ns, showing the heating of the current sheet from colder inflows. Using a semi-analytical model, we survey various heating mechanisms in the current sheet. We find that reconnection energy conversion would dominate at low density (ne≲7×1018 cm−3) and electron-ion collisional drag at high-density (≳1019 cm−3).","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"27 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Kubes, L. Marciniak, M. J. Sadowski, M. Paduch, B. Cikhardtova, J. Cikhardt, J. Kravarik, J. Malir, V. Munzar, J. Novotný, K. Rezac
This paper presents the filamentary structure of the pinched column in a smaller plasma focus device filled with deuterium. The deflections were observed using schlieren and differential interferometry techniques. The observed filaments have a transverse diameter of 40–200 μm, which could be interpreted based on the electric current hypothesis as local concentrations of electric current. The evolution of filaments was compared with global structures recorded by extra ultraviolet frames. These results provide a basis for considering the possibility of a filamentary composition of the poloidal current in compact structures. The model of filaments with a helical shape of electrical current may be able to explain the central narrow and dense cord in the axis of the column, the different lifetimes of the structures, and the submillimeter sources of fast electrons and ions.
{"title":"Evolution of filament-like compact structures in small 3 kJ dense plasma focus discharges","authors":"P. Kubes, L. Marciniak, M. J. Sadowski, M. Paduch, B. Cikhardtova, J. Cikhardt, J. Kravarik, J. Malir, V. Munzar, J. Novotný, K. Rezac","doi":"10.1063/5.0187304","DOIUrl":"https://doi.org/10.1063/5.0187304","url":null,"abstract":"This paper presents the filamentary structure of the pinched column in a smaller plasma focus device filled with deuterium. The deflections were observed using schlieren and differential interferometry techniques. The observed filaments have a transverse diameter of 40–200 μm, which could be interpreted based on the electric current hypothesis as local concentrations of electric current. The evolution of filaments was compared with global structures recorded by extra ultraviolet frames. These results provide a basis for considering the possibility of a filamentary composition of the poloidal current in compact structures. The model of filaments with a helical shape of electrical current may be able to explain the central narrow and dense cord in the axis of the column, the different lifetimes of the structures, and the submillimeter sources of fast electrons and ions.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"17 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Marcos Navarro, Jonathan Van Blarcum, Heinke Frerichs, Juri Romazanov, Andreas Kirschner, Jong-Kyu Park, Seong-Moo Yang, Oliver Schmitz
A 3D analysis of plasma wall interactions and global impurity transport for the edge localized mode suppression window in KSTAR during H-Mode discharges has shown that carbon erosion at the divertor plates is a strong function of the resonant magnetic perturbation (n = 1) coil current and relative phasing. The Generalized Perturbation Equilibrium Code was used to determine a realistic initial perturbed plasma equilibrium, and EMC3-EIRENE was used to calculate the resulting scrape-off layer plasma used in this study as a fixed background for the ERO2.0 plasma–material interaction model. The resulting transport leads to deposition of impurities along the targets positioned at the high-field side of the device. An attempt at calculating the resulting effective charge state has demonstrated a similar dependence on the perturbation coil current and has been able to determine a window for the experimentally observed values of Zeff by including contributions of all ionized carbon charge states and deuterium.
{"title":"Erosion and impurity transport for the edge localized mode suppression window in KSTAR","authors":"Marcos Navarro, Jonathan Van Blarcum, Heinke Frerichs, Juri Romazanov, Andreas Kirschner, Jong-Kyu Park, Seong-Moo Yang, Oliver Schmitz","doi":"10.1063/5.0213155","DOIUrl":"https://doi.org/10.1063/5.0213155","url":null,"abstract":"A 3D analysis of plasma wall interactions and global impurity transport for the edge localized mode suppression window in KSTAR during H-Mode discharges has shown that carbon erosion at the divertor plates is a strong function of the resonant magnetic perturbation (n = 1) coil current and relative phasing. The Generalized Perturbation Equilibrium Code was used to determine a realistic initial perturbed plasma equilibrium, and EMC3-EIRENE was used to calculate the resulting scrape-off layer plasma used in this study as a fixed background for the ERO2.0 plasma–material interaction model. The resulting transport leads to deposition of impurities along the targets positioned at the high-field side of the device. An attempt at calculating the resulting effective charge state has demonstrated a similar dependence on the perturbation coil current and has been able to determine a window for the experimentally observed values of Zeff by including contributions of all ionized carbon charge states and deuterium.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"7 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Weaam Alhejaili, Subrata Roy, Santanu Raut, Ashim Roy, Alvaro H. Salas, Tarek Aboelenen, S. A. El-Tantawy
This article investigates the propagation of different types of nonlinear ion-acoustic waves, including periodic waves, solitons, and breathers in non-Maxwellian magnetized plasma. The plasma model consists of inertial cold ions, inertialess cold electrons that obey a Boltzmann distribution, and inertialess non-Maxwellian hot electrons that follow the generalized (r, q) distribution. The reductive perturbation technique is utilized to obtain the Korteweg–de Vries–Zakharov–Kuznetsov equation (KdV-ZK) from the fluid equations that govern plasma dynamics. Furthermore, the modified KdV-ZK equation is derived due to the limited capability of the KdV-ZK model to represent the dynamics of the nonlinear structures at specific critical values of the relevant physical variables in the investigated system. The periodic solutions to the two models (KdV-ZK and mKdV-ZK models) are derived using Jacobi elliptic functions. This approach directly links periodic waves (cnoidal waves) and soliton solutions. Hirota's bilinear method generates breathers for both models. Finally, we examine the quantitative understanding of the effects of several physical parameters replicated by the Swedish satellite Viking incorporated in the model. The findings reported in this study enhance our comprehension of the properties of the electron distribution function's high- and low-energy segments and the development of periodic, soliton, multi-soliton, and breather phenomena in space and astrophysical plasmas.
{"title":"Analytical solutions to (modified) Korteweg–de Vries–Zakharov–Kuznetsov equation and modeling ion-acoustic solitary, periodic, and breather waves in auroral magnetoplasmas","authors":"Weaam Alhejaili, Subrata Roy, Santanu Raut, Ashim Roy, Alvaro H. Salas, Tarek Aboelenen, S. A. El-Tantawy","doi":"10.1063/5.0220798","DOIUrl":"https://doi.org/10.1063/5.0220798","url":null,"abstract":"This article investigates the propagation of different types of nonlinear ion-acoustic waves, including periodic waves, solitons, and breathers in non-Maxwellian magnetized plasma. The plasma model consists of inertial cold ions, inertialess cold electrons that obey a Boltzmann distribution, and inertialess non-Maxwellian hot electrons that follow the generalized (r, q) distribution. The reductive perturbation technique is utilized to obtain the Korteweg–de Vries–Zakharov–Kuznetsov equation (KdV-ZK) from the fluid equations that govern plasma dynamics. Furthermore, the modified KdV-ZK equation is derived due to the limited capability of the KdV-ZK model to represent the dynamics of the nonlinear structures at specific critical values of the relevant physical variables in the investigated system. The periodic solutions to the two models (KdV-ZK and mKdV-ZK models) are derived using Jacobi elliptic functions. This approach directly links periodic waves (cnoidal waves) and soliton solutions. Hirota's bilinear method generates breathers for both models. Finally, we examine the quantitative understanding of the effects of several physical parameters replicated by the Swedish satellite Viking incorporated in the model. The findings reported in this study enhance our comprehension of the properties of the electron distribution function's high- and low-energy segments and the development of periodic, soliton, multi-soliton, and breather phenomena in space and astrophysical plasmas.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"27 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. McClenaghan, C. Akçay, T. B. Amara, X. Sun, S. Madireddy, L. L. Lao, S. E. Kruger, O. M. Meneghini
This work presents a method for predicting plasma equilibria in tokamak fusion experiments and reactors. The approach involves representing the plasma current as a linear combination of basis functions using principal component analysis of plasma toroidal current densities (Jt) from the EFIT-AI equilibrium database. Then utilizing EFIT's Green's function tables, basis functions are created for the poloidal flux (ψ) and diagnostics generated from the toroidal current (Jt). Similar to the idea of a physics-informed neural network (NN), this physically enforces consistency between ψ, Jt, and the synthetic diagnostics. First, the predictive capability of a least squares technique to minimize the error on the synthetic diagnostics is employed. The results show that the method achieves high accuracy in predicting ψ and moderate accuracy in predicting Jt with median R2 = 0.9993 and R2 = 0.978, respectively. A comprehensive NN using a network architecture search is also employed to predict the coefficients of the basis functions. The NN demonstrates significantly better performance compared to the least squares method with median R2 = 0.9997 and 0.9916 for Jt and ψ, respectively. The robustness of the method is evaluated by handling missing or incorrect data through the least squares filling of missing data, which shows that the NN prediction remains strong even with a reduced number of diagnostics. Additionally, the method is tested on plasmas outside of the training range showing reasonable results.
{"title":"Augmenting machine learning of Grad–Shafranov equilibrium reconstruction with Green's functions","authors":"J. McClenaghan, C. Akçay, T. B. Amara, X. Sun, S. Madireddy, L. L. Lao, S. E. Kruger, O. M. Meneghini","doi":"10.1063/5.0213625","DOIUrl":"https://doi.org/10.1063/5.0213625","url":null,"abstract":"This work presents a method for predicting plasma equilibria in tokamak fusion experiments and reactors. The approach involves representing the plasma current as a linear combination of basis functions using principal component analysis of plasma toroidal current densities (Jt) from the EFIT-AI equilibrium database. Then utilizing EFIT's Green's function tables, basis functions are created for the poloidal flux (ψ) and diagnostics generated from the toroidal current (Jt). Similar to the idea of a physics-informed neural network (NN), this physically enforces consistency between ψ, Jt, and the synthetic diagnostics. First, the predictive capability of a least squares technique to minimize the error on the synthetic diagnostics is employed. The results show that the method achieves high accuracy in predicting ψ and moderate accuracy in predicting Jt with median R2 = 0.9993 and R2 = 0.978, respectively. A comprehensive NN using a network architecture search is also employed to predict the coefficients of the basis functions. The NN demonstrates significantly better performance compared to the least squares method with median R2 = 0.9997 and 0.9916 for Jt and ψ, respectively. The robustness of the method is evaluated by handling missing or incorrect data through the least squares filling of missing data, which shows that the NN prediction remains strong even with a reduced number of diagnostics. Additionally, the method is tested on plasmas outside of the training range showing reasonable results.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"53 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. P. Artyomov, V. I. Oreshkin, A. G. Rousskikh, D. V. Rybka, A. V. Fedyunin, S. A. Chaikovsky, N. A. Ratakhin
It was studied how the geometrical parameters of an X-pinch (the angle of inclination of the wires to the X-pinch vertical axis and the length of the electrode gap) affected the number of hot spots, formed in the region of the X-pinch neck, and the x-ray yield. The experiment was performed on the XPG-3 compact current pulse generator (180 kA, 180 ns). The highest values of the x-ray energy per pulse were observed when the angle of inclination of the wires to the X-pinch load vertical axis (z-axis) was 40°–45° at an electrode gap length of 6–7 mm. In these cases, the energy of the x-ray pulse in the spectral range hν = 1.5–5 keV was 1.1 ± 0.4 J. The angle of inclination of the X-pinch wires to the z-axis equal to 45° was a threshold above which the conditions for the formation of a hot spot changed significantly. It was observed that, regardless of the wire inclination angle, two hot spots formed with a high degree of probability in the neck region at the final stage of implosion.
研究了 X 射线夹的几何参数（导线与 X 射线夹垂直轴的倾斜角度和电极间隙的长度）如何影响在 X 射线夹颈部区域形成的热点数量和 X 射线产量。实验是在 XPG-3 紧凑型电流脉冲发生器（180 kA、180 ns）上进行的。当电极间隙长度为 6-7 mm 时，导线与 X 射线夹钳负载垂直轴（z 轴）的倾斜角为 40°-45° 时，每个脉冲的 X 射线能量值最高。在这些情况下，频谱范围 hν = 1.5-5 keV 的 X 射线脉冲能量为 1.1 ± 0.4 J。X-夹线与 Z 轴的倾斜角等于 45°，超过这个临界值，形成热点的条件就会发生显著变化。据观察，无论导线倾角如何，在内爆的最后阶段，都很有可能在颈部区域形成两个热点。
{"title":"Effect of the geometrical parameters of an X-pinch on the characteristics of the soft x-ray source","authors":"A. P. Artyomov, V. I. Oreshkin, A. G. Rousskikh, D. V. Rybka, A. V. Fedyunin, S. A. Chaikovsky, N. A. Ratakhin","doi":"10.1063/5.0214382","DOIUrl":"https://doi.org/10.1063/5.0214382","url":null,"abstract":"It was studied how the geometrical parameters of an X-pinch (the angle of inclination of the wires to the X-pinch vertical axis and the length of the electrode gap) affected the number of hot spots, formed in the region of the X-pinch neck, and the x-ray yield. The experiment was performed on the XPG-3 compact current pulse generator (180 kA, 180 ns). The highest values of the x-ray energy per pulse were observed when the angle of inclination of the wires to the X-pinch load vertical axis (z-axis) was 40°–45° at an electrode gap length of 6–7 mm. In these cases, the energy of the x-ray pulse in the spectral range hν = 1.5–5 keV was 1.1 ± 0.4 J. The angle of inclination of the X-pinch wires to the z-axis equal to 45° was a threshold above which the conditions for the formation of a hot spot changed significantly. It was observed that, regardless of the wire inclination angle, two hot spots formed with a high degree of probability in the neck region at the final stage of implosion.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"78 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Goodarzi, I. Sagert, J. P. Sauppe, P. A. Keiter, E. N. Loomis, R. F. Sacks, Z. L. Mohamed, S. Palaniyappan, E. C. Merritt, B. M. Haines, B. M. Patterson, D. D. Meyerhofer, D. S. Montgomery, D. W. Schmidt
This work provides a numerical study of how double shell capsule deformations caused by drive asymmetries and fabrication imperfections affect implosion symmetry and neutron yield. Hydrodynamics simulations are performed in two dimensions and focus on low-mode deformations that are caused by corresponding asymmetries in the Hohlraum drive, component offsets, and ablator joint gaps. By providing a parameter study of these features, our goal is to understand the dominant sources for inner shell deformation and yield degradation. The discussed capsules are composed of an aluminum ablator with a chromium inner shell. The latter encloses a carbon-deuterium foam ball that serves as fuel. We find that for clean capsules, even-numbered low-mode asymmetries in the drive are imprinted on the ablator and smoothly transferred to the inner shell during shell collision. The resulting deformation of the inner shell is more pronounced with larger fuel radius, while the yield is inversely proportional to the amplitude of the drive asymmetry and varies by factors ≤4 in comparison with clean simulations. Capsule component offsets in the vertical direction and ablator thickness nonuniformity result in p1-type deformations of the imploding inner shell. Finally, joint gaps have the largest effect in deforming the ablator and inner shell and degrading yield. While small gap widths (1 μm) result in prolate inner shells, larger gap widths (4 μm) cause an oblate deformation. More importantly, capsules with a small outer gap (1 μm) experience a dramatic drop in yield, typically <3% of a clean simulation.
{"title":"Characterizing the effects of drive asymmetries, component offsets, and joint gaps in double shell capsule implosions","authors":"S. Goodarzi, I. Sagert, J. P. Sauppe, P. A. Keiter, E. N. Loomis, R. F. Sacks, Z. L. Mohamed, S. Palaniyappan, E. C. Merritt, B. M. Haines, B. M. Patterson, D. D. Meyerhofer, D. S. Montgomery, D. W. Schmidt","doi":"10.1063/5.0195454","DOIUrl":"https://doi.org/10.1063/5.0195454","url":null,"abstract":"This work provides a numerical study of how double shell capsule deformations caused by drive asymmetries and fabrication imperfections affect implosion symmetry and neutron yield. Hydrodynamics simulations are performed in two dimensions and focus on low-mode deformations that are caused by corresponding asymmetries in the Hohlraum drive, component offsets, and ablator joint gaps. By providing a parameter study of these features, our goal is to understand the dominant sources for inner shell deformation and yield degradation. The discussed capsules are composed of an aluminum ablator with a chromium inner shell. The latter encloses a carbon-deuterium foam ball that serves as fuel. We find that for clean capsules, even-numbered low-mode asymmetries in the drive are imprinted on the ablator and smoothly transferred to the inner shell during shell collision. The resulting deformation of the inner shell is more pronounced with larger fuel radius, while the yield is inversely proportional to the amplitude of the drive asymmetry and varies by factors ≤4 in comparison with clean simulations. Capsule component offsets in the vertical direction and ablator thickness nonuniformity result in p1-type deformations of the imploding inner shell. Finally, joint gaps have the largest effect in deforming the ablator and inner shell and degrading yield. While small gap widths (1 μm) result in prolate inner shells, larger gap widths (4 μm) cause an oblate deformation. More importantly, capsules with a small outer gap (1 μm) experience a dramatic drop in yield, typically &lt;3% of a clean simulation.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"23 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Following Greene et al. [Phys. Fluids 14, 671 (1971)] and Connor et al. [Phys. Plasmas 31, 577 (1988); Plasma Phys. Control. Fusion 34, 161 (1992); and Nucl. Fusion 33, 1533 (1993)], the Grad-Shafranov equation for an axisymmetric tokamak plasma equilibrium is solved via an expansion in the, supposedly small, inverse aspect-ratio of the plasma, ϵ. The displacements of equilibrium magnetic flux-surfaces due to plasma shaping are assumed to be O(ϵ) smaller than the minor radii of the surfaces, but no other restriction is placed on the nature of the shaping. The solution of the Grad-Shafranov equation is matched to a vacuum solution that extends to infinity, and consists of an expansion in toroidal functions. The external poloidal magnetic field generated by a finite set of discrete external poloidal magnetic field-coils is calculated, and incorporated into the toroidal function expansion. In this manner, the shape of a large aspect-ratio tokamak plasma is directly related to the currents flowing in the external poloidal field-coils. Finally, a pedestal in the plasma pressure, and the associated spike in the bootstrap current, are incorporated into the model.
{"title":"Inverse aspect-ratio expanded tokamak equilibria","authors":"R. Fitzpatrick","doi":"10.1063/5.0215345","DOIUrl":"https://doi.org/10.1063/5.0215345","url":null,"abstract":"Following Greene et al. [Phys. Fluids 14, 671 (1971)] and Connor et al. [Phys. Plasmas 31, 577 (1988); Plasma Phys. Control. Fusion 34, 161 (1992); and Nucl. Fusion 33, 1533 (1993)], the Grad-Shafranov equation for an axisymmetric tokamak plasma equilibrium is solved via an expansion in the, supposedly small, inverse aspect-ratio of the plasma, ϵ. The displacements of equilibrium magnetic flux-surfaces due to plasma shaping are assumed to be O(ϵ) smaller than the minor radii of the surfaces, but no other restriction is placed on the nature of the shaping. The solution of the Grad-Shafranov equation is matched to a vacuum solution that extends to infinity, and consists of an expansion in toroidal functions. The external poloidal magnetic field generated by a finite set of discrete external poloidal magnetic field-coils is calculated, and incorporated into the toroidal function expansion. In this manner, the shape of a large aspect-ratio tokamak plasma is directly related to the currents flowing in the external poloidal field-coils. Finally, a pedestal in the plasma pressure, and the associated spike in the bootstrap current, are incorporated into the model.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"2013 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A weakly nonlinear theoretical model is established for the two-dimensional incompressible Rayleigh–Taylor–Kelvin–Helmholtz instability (RT–KHI). The evolution of the perturbation interface is analytically studied by the third-order solution of the planar RT–KHI induced by a single-mode surface perturbation. The difference between the weakly nonlinear growth for Rayleigh–Taylor instability (RTI), Kelvin–Helmholtz instability (KHI), and RT–KHI in plane geometry is discussed. The trend of bubble and spike amplitudes with the Atwood number and the Richardson number is discussed in detail. The bubble and spike amplitudes of RT–KHI change from the KHI case to the RTI case as the Richardson number increases. The deflecting distance of bubble and spike vertices becomes smaller compared to the KHI case as the Richardson number increases. The dependence of the nonlinear saturation amplitude of RT–KHI on the Atwood number, the Richardson number, and the initial perturbation is obtained. The Richardson number is as vital to the nonlinear saturation amplitude as the Atwood number. It is found that the variation of the nonlinear saturation amplitude with the Atwood number at different Richardson numbers is divided into three parts, namely, “RTI-like part,” “transition part,” and “KHI-like part.” In the transition part, the trend of the nonlinear saturation amplitude increasing with the Atwood number is completely opposite to the RTI and KHI cases. Finally, the theory is compared to the numerical simulation under identical initial conditions and displays good correspondence in the linear and weakly nonlinear stages.
为二维不可压缩的雷利-泰勒-开尔文-赫姆霍兹不稳定性（RT-KHI）建立了一个弱非线性理论模型。通过对单模表面扰动引起的平面 RT-KHI 的三阶解，分析研究了扰动界面的演变。讨论了雷利-泰勒不稳定性（RTI）、开尔文-赫姆霍兹不稳定性（KHI）和平面 RT-KHI 的弱非线性增长之间的差异。详细讨论了气泡和尖峰振幅随阿特伍德数和理查德森数变化的趋势。随着理查德森数的增加，RT-KHI 的气泡和尖峰振幅从 KHI 情况变为 RTI 情况。随着理查森数的增加，气泡和尖峰顶点的偏转距离与 KHI 情况相比变得更小。得出了 RT-KHI 的非线性饱和振幅与 Atwood 数、Richardson 数和初始扰动的关系。理查德森数与阿特伍德数一样对非线性饱和振幅至关重要。研究发现，在不同理查森数下，非线性饱和振幅随阿特伍德数的变化分为三个部分，即 "类 RTI 部分"、"过渡部分 "和 "类 KHI 部分"。在过渡部分，非线性饱和振幅随阿特伍德数增加的趋势与 RTI 和 KHI 情况完全相反。最后，在初始条件相同的情况下，将理论与数值模拟进行了比较，结果表明在线性和弱非线性阶段两者之间具有良好的对应关系。
{"title":"Weakly nonlinear incompressible Rayleigh–Taylor–Kelvin–Helmholtz instability in plane geometry","authors":"Zhen-Qi Zou, Jun-Feng Wu, Guo-Wei Yang, Li-Feng Wang, Wei-Yan Zhang","doi":"10.1063/5.0216178","DOIUrl":"https://doi.org/10.1063/5.0216178","url":null,"abstract":"A weakly nonlinear theoretical model is established for the two-dimensional incompressible Rayleigh–Taylor–Kelvin–Helmholtz instability (RT–KHI). The evolution of the perturbation interface is analytically studied by the third-order solution of the planar RT–KHI induced by a single-mode surface perturbation. The difference between the weakly nonlinear growth for Rayleigh–Taylor instability (RTI), Kelvin–Helmholtz instability (KHI), and RT–KHI in plane geometry is discussed. The trend of bubble and spike amplitudes with the Atwood number and the Richardson number is discussed in detail. The bubble and spike amplitudes of RT–KHI change from the KHI case to the RTI case as the Richardson number increases. The deflecting distance of bubble and spike vertices becomes smaller compared to the KHI case as the Richardson number increases. The dependence of the nonlinear saturation amplitude of RT–KHI on the Atwood number, the Richardson number, and the initial perturbation is obtained. The Richardson number is as vital to the nonlinear saturation amplitude as the Atwood number. It is found that the variation of the nonlinear saturation amplitude with the Atwood number at different Richardson numbers is divided into three parts, namely, “RTI-like part,” “transition part,” and “KHI-like part.” In the transition part, the trend of the nonlinear saturation amplitude increasing with the Atwood number is completely opposite to the RTI and KHI cases. Finally, the theory is compared to the numerical simulation under identical initial conditions and displays good correspondence in the linear and weakly nonlinear stages.","PeriodicalId":20175,"journal":{"name":"Physics of Plasmas","volume":"87 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141946330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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