Denys Moskal, Jiri Martan, Vladislav Lang, Milan Honner
Laser-induced water ablation triggers various physical effects, including atom ionization, optical breakdown of the liquid, phase explosion, cavitation, and shockwave propagation. These effects can be further amplified in heavy water by deuterium-deuterium fusion reactions, which require extremely high energy levels. Laser pulses can be grouped in bursts to achieve the necessary energy within the ablation plasma plume. This study aims to compare the ablation plasma glow and thermal effects in light and heavy water under both single-pulse and burst-mode ultrashort laser irradiation. Notably, this research introduces the novel application of burst laser ablation in heavy water for the first time. The ablation was conducted beneath the water surface along a circular, laser-scanned trajectory, with two distinct ablation regimes: burst mode and single-pulse mode, utilizing lenses with varying focal lengths and different pulse durations. Absorption processes and plasma glow were monitored using visible and infrared detectors, a fast silicon detector, and a thermocouple. The study revealed that the burst regime in heavy water produced the most intense plasma glow when 1 ps laser pulses were used, with shorter pulses yielding less intense glow and the longest pulses yielding the least. Surprisingly, plasma glow at a lower initial power density of 2.6e13 W/cm2 was four times higher than at a higher power density of 8e13 W/cm2. These findings were compared with existing theories on plasma formation in water by ultrashort laser pulses. The observed increase in pulse-to-pulse plasma glow in burst mode was attributed to thermo-electron accumulation effects. The density of excited and hydrated electrons was calculated using both strong-field ionization and avalanche ionization models. Additionally, the influence of pulse parity on burst ablation glow in heavy water was discussed.
{"title":"Thermo-electron accumulation in light and heavy water during MHz-burst laser ablation","authors":"Denys Moskal, Jiri Martan, Vladislav Lang, Milan Honner","doi":"arxiv-2409.03311","DOIUrl":"https://doi.org/arxiv-2409.03311","url":null,"abstract":"Laser-induced water ablation triggers various physical effects, including\u0000atom ionization, optical breakdown of the liquid, phase explosion, cavitation,\u0000and shockwave propagation. These effects can be further amplified in heavy\u0000water by deuterium-deuterium fusion reactions, which require extremely high\u0000energy levels. Laser pulses can be grouped in bursts to achieve the necessary\u0000energy within the ablation plasma plume. This study aims to compare the\u0000ablation plasma glow and thermal effects in light and heavy water under both\u0000single-pulse and burst-mode ultrashort laser irradiation. Notably, this\u0000research introduces the novel application of burst laser ablation in heavy\u0000water for the first time. The ablation was conducted beneath the water surface\u0000along a circular, laser-scanned trajectory, with two distinct ablation regimes:\u0000burst mode and single-pulse mode, utilizing lenses with varying focal lengths\u0000and different pulse durations. Absorption processes and plasma glow were\u0000monitored using visible and infrared detectors, a fast silicon detector, and a\u0000thermocouple. The study revealed that the burst regime in heavy water produced the most\u0000intense plasma glow when 1 ps laser pulses were used, with shorter pulses\u0000yielding less intense glow and the longest pulses yielding the least.\u0000Surprisingly, plasma glow at a lower initial power density of 2.6e13 W/cm2 was\u0000four times higher than at a higher power density of 8e13 W/cm2. These findings\u0000were compared with existing theories on plasma formation in water by ultrashort\u0000laser pulses. The observed increase in pulse-to-pulse plasma glow in burst mode\u0000was attributed to thermo-electron accumulation effects. The density of excited\u0000and hydrated electrons was calculated using both strong-field ionization and\u0000avalanche ionization models. Additionally, the influence of pulse parity on\u0000burst ablation glow in heavy water was discussed.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"396 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196045","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}
S. C. Singh, C. Fallon, P. Yeates, C. McLoughlin, J. T. Costello
The expansion dynamics of laser produced plasma plumes in gaseous atmospheres exhibit information on plasma-ambient gas interactions which result in plume splitting, shock formation, sharpening and confinement. We investigate laser spot size variation on shock wave, plume, and ion dynamics from laser produced YBa2Cu3O7 (YBCO) plasmas using fast photography and Langmuir probe diagnosis. Changes in plume geometry are observed with varying focal spot size. At smaller spot sizes, lateral expansion of the plume is found to be larger, and plume expansion is spherical, while at larger spot sizes plume expansion is more cylindrical. Shock front formation time, relative intensity, spatial extent and total charge yield (TCY) are all dependent on laser spot size. Total charge yield (TCY) increases as the spot area increases, but decreases beyond a certain value. The width of the ion velocity distribution and the peak velocity decrease with increasing spot size, demonstrate that ions corresponding to larger spot sizes are somewhat more monoenergetic.
{"title":"Spot size dependent shock wave, plume and ion expansion dynamics of laser produced YBCO plasma","authors":"S. C. Singh, C. Fallon, P. Yeates, C. McLoughlin, J. T. Costello","doi":"arxiv-2409.03846","DOIUrl":"https://doi.org/arxiv-2409.03846","url":null,"abstract":"The expansion dynamics of laser produced plasma plumes in gaseous atmospheres\u0000exhibit information on plasma-ambient gas interactions which result in plume\u0000splitting, shock formation, sharpening and confinement. We investigate laser\u0000spot size variation on shock wave, plume, and ion dynamics from laser produced\u0000YBa2Cu3O7 (YBCO) plasmas using fast photography and Langmuir probe diagnosis.\u0000Changes in plume geometry are observed with varying focal spot size. At smaller\u0000spot sizes, lateral expansion of the plume is found to be larger, and plume\u0000expansion is spherical, while at larger spot sizes plume expansion is more\u0000cylindrical. Shock front formation time, relative intensity, spatial extent and\u0000total charge yield (TCY) are all dependent on laser spot size. Total charge\u0000yield (TCY) increases as the spot area increases, but decreases beyond a\u0000certain value. The width of the ion velocity distribution and the peak velocity\u0000decrease with increasing spot size, demonstrate that ions corresponding to\u0000larger spot sizes are somewhat more monoenergetic.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196039","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}
Turbulence is a complex physical process that emerges in multiple areas of modern physics, and in ionized environments such as interstellar gas, the magnetic field can be dynamically important. However, the exact function of the magnetic field in the ionized gas remains unclear. We use the $M_{rm A} = sqrt{E_{rm k}/E_B} $ to describe the importance of the magnetic field measured to the turbulent motion, and reveal diverse ways of mutual interaction. At low $M_{rm A}$ (magnetic regime), the magnetic field is well-described as force-free. Despite the strong magnetic field, the motion of gas does not stay aligned with the magnetic field. At the regime of intermediate $M_{rm A}$ (magnetic-kinetic transition regime), the velocity field and the magnetic field exhibit the highest degree of alignment, which is likely the result of a rapid relaxation. At high $M_{rm A}$ (kinetic regime), both the magnetic field and the velocity field are irregular, with no alignment. We find observational counterparts to these regimes in observations of interstellar gas. The results highlight the diverse behavior of gas in MHD turbulence and guide future interpretations of the role of the magnetic field in astrophysical observations.
{"title":"Magnetic, Kinetic, and Transition regime: Spatially-segregated structure of compressive MHD turbulence","authors":"Guang-Xing Li, Mengke Zhao","doi":"arxiv-2409.02769","DOIUrl":"https://doi.org/arxiv-2409.02769","url":null,"abstract":"Turbulence is a complex physical process that emerges in multiple areas of\u0000modern physics, and in ionized environments such as interstellar gas, the\u0000magnetic field can be dynamically important. However, the exact function of the\u0000magnetic field in the ionized gas remains unclear. We use the $M_{rm A} =\u0000sqrt{E_{rm k}/E_B} $ to describe the importance of the magnetic field measured to the turbulent\u0000motion, and reveal diverse ways of mutual interaction. At low $M_{rm A}$\u0000(magnetic regime), the magnetic field is well-described as force-free. Despite\u0000the strong magnetic field, the motion of gas does not stay aligned with the\u0000magnetic field. At the regime of intermediate $M_{rm A}$ (magnetic-kinetic\u0000transition regime), the velocity field and the magnetic field exhibit the\u0000highest degree of alignment, which is likely the result of a rapid relaxation.\u0000At high $M_{rm A}$ (kinetic regime), both the magnetic field and the velocity\u0000field are irregular, with no alignment. We find observational counterparts to\u0000these regimes in observations of interstellar gas. The results highlight the\u0000diverse behavior of gas in MHD turbulence and guide future interpretations of\u0000the role of the magnetic field in astrophysical observations.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"64 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142195847","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}
William Tang, Eliot Feibush, Ge Dong, Noah Borthwick, Apollo Lee, Juan-Felipe Gomez, Tom Gibbs, John Stone, Peter Messmer, Jack Wells, Xishuo Wei, Zhihong Lin
In addressing the Department of Energy's April, 2022 announcement of a Bold Decadal Vision for delivering a Fusion Pilot Plant by 2035, associated software tools need to be developed for the integration of real world engineering and supply chain data with advanced science models that are accelerated with Machine Learning. An associated research and development effort has been introduced here with promising early progress on the delivery of a realistic Digital Twin Tokamak that has benefited from accelerated advances by the Princeton University AI Deep Learning innovative near-real-time simulators accompanied by technological capabilities from the NVIDIA Omniverse, an open computing platform for building and operating applications that connect with leading scientific computing visualization software. Working with the CAD files for the GA/DIII-D tokamak including equilibrium evolution as an exemplar tokamak application using Omniverse, the Princeton-NVIDIA collaboration has integrated modern AI/HPC-enabled near-real-time kinetic dynamics to connect and accelerate state-of-the-art, synthetic, HPC simulators to model fusion devices and control systems. The overarching goal is to deliver an interactive scientific digital twin of an advanced MFE tokamak that enables near-real-time simulation workflows built with Omniverse to eventually help open doors to new capabilities for generating clean power for a better future.
{"title":"AI-Machine Learning-Enabled Tokamak Digital Twin","authors":"William Tang, Eliot Feibush, Ge Dong, Noah Borthwick, Apollo Lee, Juan-Felipe Gomez, Tom Gibbs, John Stone, Peter Messmer, Jack Wells, Xishuo Wei, Zhihong Lin","doi":"arxiv-2409.03112","DOIUrl":"https://doi.org/arxiv-2409.03112","url":null,"abstract":"In addressing the Department of Energy's April, 2022 announcement of a Bold\u0000Decadal Vision for delivering a Fusion Pilot Plant by 2035, associated software\u0000tools need to be developed for the integration of real world engineering and\u0000supply chain data with advanced science models that are accelerated with\u0000Machine Learning. An associated research and development effort has been\u0000introduced here with promising early progress on the delivery of a realistic\u0000Digital Twin Tokamak that has benefited from accelerated advances by the\u0000Princeton University AI Deep Learning innovative near-real-time simulators\u0000accompanied by technological capabilities from the NVIDIA Omniverse, an open\u0000computing platform for building and operating applications that connect with\u0000leading scientific computing visualization software. Working with the CAD files\u0000for the GA/DIII-D tokamak including equilibrium evolution as an exemplar\u0000tokamak application using Omniverse, the Princeton-NVIDIA collaboration has\u0000integrated modern AI/HPC-enabled near-real-time kinetic dynamics to connect and\u0000accelerate state-of-the-art, synthetic, HPC simulators to model fusion devices\u0000and control systems. The overarching goal is to deliver an interactive\u0000scientific digital twin of an advanced MFE tokamak that enables near-real-time\u0000simulation workflows built with Omniverse to eventually help open doors to new\u0000capabilities for generating clean power for a better future.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"66 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196044","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}
L. Casali, D. Eldon, T. Odstrcil, R. Mattes, A. Welsh, K. Lee, A. O. Nelson, C. Paz-Soldan, F. Khabanov, T. Cote, A. G. McLean, F. Scotti, K. E. Thome
The first achievement of highly radiating plasmas in negative triangularity is shown with an operational space featuring high core radiation at high Greenwald fraction obtained with the injection of reactor-relevant seeded gases. These negative triangularity (NT) shape diverted discharges reach high values of normalized plasma pressure (BetaN > 2) at high radiation fraction with no ELMs. We demonstrate that as long as the impurity level in the core is kept low to avoid excessive fuel dilution and impurity accumulation, integration of NT configuration with high radiation fraction not only is achievable but it can lead to confinement improvement with stabilization effects originating from collisionality, ExB shear and profiles changes due to impurity radiation cooling. The underlying physics mechanism is robust and holds for a variety of impurity species. The absence of the requirement to stay in H-mode translates in a higher core radiation fraction potentially allowed in NT shape effectively mitigating the power exhaust issue. The results presented here demonstrate a path to high performance, ELM free and highly radiative regime with rector-relevant seeding gases making this regime a potential new scenario for reactor operation.
通过注入与反应堆相关的种子气体，在高格林瓦尔德分率下实现了高核心辐射的运行空间，显示了负三角形高辐射等离子体的首次成就。这些负三角形（NT）形状的分流放电在高辐射分率下达到很高的归一化等离子体压力值（BetaN > 2），而且没有 ELM。我们证明，只要内核中的杂质含量保持在较低水平，以避免燃料的过度稀释和杂质的积累，在高辐射分率下整合 NT 配置不仅是可行的，而且还能通过碰撞性、ExB 剪切和杂质辐射冷却引起的剖面变化所产生的稳定效应来改善约束。其基本物理机制是稳健的，适用于各种杂质。由于不需要保持 H 模式，NT 形状中可能允许更高的堆芯辐射分数，从而有效地缓解了功率耗尽问题。本文介绍的结果展示了一条通往高性能、无 ELM 和高辐射状态的道路，与反应堆相关的种子气体使这一状态成为反应堆运行的潜在新方案。
{"title":"Achievement of highly radiating plasma in negative triangularity and effect of reactor-relevant seeded impurities on confinement and transport","authors":"L. Casali, D. Eldon, T. Odstrcil, R. Mattes, A. Welsh, K. Lee, A. O. Nelson, C. Paz-Soldan, F. Khabanov, T. Cote, A. G. McLean, F. Scotti, K. E. Thome","doi":"arxiv-2409.02377","DOIUrl":"https://doi.org/arxiv-2409.02377","url":null,"abstract":"The first achievement of highly radiating plasmas in negative triangularity\u0000is shown with an operational space featuring high core radiation at high\u0000Greenwald fraction obtained with the injection of reactor-relevant seeded\u0000gases. These negative triangularity (NT) shape diverted discharges reach high\u0000values of normalized plasma pressure (BetaN > 2) at high radiation fraction\u0000with no ELMs. We demonstrate that as long as the impurity level in the core is\u0000kept low to avoid excessive fuel dilution and impurity accumulation,\u0000integration of NT configuration with high radiation fraction not only is\u0000achievable but it can lead to confinement improvement with stabilization\u0000effects originating from collisionality, ExB shear and profiles changes due to\u0000impurity radiation cooling. The underlying physics mechanism is robust and\u0000holds for a variety of impurity species. The absence of the requirement to stay\u0000in H-mode translates in a higher core radiation fraction potentially allowed in\u0000NT shape effectively mitigating the power exhaust issue. The results presented\u0000here demonstrate a path to high performance, ELM free and highly radiative\u0000regime with rector-relevant seeding gases making this regime a potential new\u0000scenario for reactor operation.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"62 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227738","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}
Propagation of ultrarelativistically intense laser pulse in a self-trapping mode in a near critical density plasma makes it possible to produce electron bunches of extreme parameters appropriate for different state of art applications. Based on the 3D PIC simulations, it has been demonstrated how the best efficiency of electron acceleration in terms of the total charge of high-energy electrons and laser-to-electrons conversion rate can be achieved. For given laser pulse energy the universal way is a proper matching of laser hot spot size and electron plasma density to the laser pulse duration. The recommendation to achieve the highest yield of high-energy electrons is to compress laser pulse as much as possible. As example, compression of the few tens fs pulse to the 10 fs pulse leads to generation of the high-energy electron bunch with the highest total charge to exhibit conversion efficiency exceeding 50% for the Joule-level laser pulse energies.
{"title":"Compression of high-power laser pulse leads to increase of electron acceleration efficiency","authors":"O. E. Vais, M. G. Lobok, V. Yu. Bychenkov","doi":"arxiv-2409.02671","DOIUrl":"https://doi.org/arxiv-2409.02671","url":null,"abstract":"Propagation of ultrarelativistically intense laser pulse in a self-trapping\u0000mode in a near critical density plasma makes it possible to produce electron\u0000bunches of extreme parameters appropriate for different state of art\u0000applications. Based on the 3D PIC simulations, it has been demonstrated how the\u0000best efficiency of electron acceleration in terms of the total charge of\u0000high-energy electrons and laser-to-electrons conversion rate can be achieved.\u0000For given laser pulse energy the universal way is a proper matching of laser\u0000hot spot size and electron plasma density to the laser pulse duration. The\u0000recommendation to achieve the highest yield of high-energy electrons is to\u0000compress laser pulse as much as possible. As example, compression of the few\u0000tens fs pulse to the 10 fs pulse leads to generation of the high-energy\u0000electron bunch with the highest total charge to exhibit conversion efficiency\u0000exceeding 50% for the Joule-level laser pulse energies.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225088","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}
The electromagnetic field is a fundamental force in nature that regulates the formation of stars in the universe. Despite decades of efforts, a reliable assessment of the importance of the magnetic fields in star formation relations remains missing. In star-formation research, our acknowledgment of the importance of magnetic field is best summarized by the Cruther+ 2010 B-rho relation. The relation is either interpreted as proof of the importance of a magnetic field in the collapse, or the result of self-similar collapse where the role of the magnetic is secondary to gravity. Using simulations, we find a fundamental relation, ${cal M}_{rm A}$-k$_{B-rho}$(slope of $B-rho$ relation) relation. This fundamental B-$rho$-slope relation enables one to measure the Alfv'enic Mach number, a direct indicator of the importance of the magnetic field, using the distribution of data in the B-$rho$ plane. It allows us to drive the following empirical $B-rho$ relation begin{equation} frac{B}{B_c} = {rm exp}left(left(frac{gamma}{{cal K}}right)^{-1}left( frac{rho}{rho_c}right)^frac{gamma}{{cal K}}right)nonumber, end{equation} which offers an excellent fit to the Cruther et al. data, where we assume ${cal M}_{rm A}-rho$ relation. The foundational ${cal M}_{rm A}-{rm k}_{B-rho}$ relation provides an independent way to measure the importance of magnetic field against the kinematic motion using multiple magnetic field measurements. Our approach offers a new interpretation of Cruther+2010, where a gradual decrease in the importance of B at higher densities is implied.
{"title":"Slope of Magnetic Field-Density Relation as An Indicator of Magnetic Dominance","authors":"Mengke Zhao, Guang-Xing Li, Keping Qiu","doi":"arxiv-2409.02786","DOIUrl":"https://doi.org/arxiv-2409.02786","url":null,"abstract":"The electromagnetic field is a fundamental force in nature that regulates the\u0000formation of stars in the universe. Despite decades of efforts, a reliable\u0000assessment of the importance of the magnetic fields in star formation relations\u0000remains missing. In star-formation research, our acknowledgment of the\u0000importance of magnetic field is best summarized by the Cruther+ 2010 B-rho\u0000relation. The relation is either interpreted as proof of the importance of a\u0000magnetic field in the collapse, or the result of self-similar collapse where\u0000the role of the magnetic is secondary to gravity. Using simulations, we find a\u0000fundamental relation, ${cal M}_{rm A}$-k$_{B-rho}$(slope of $B-rho$\u0000relation) relation. This fundamental B-$rho$-slope relation enables one to\u0000measure the Alfv'enic Mach number, a direct indicator of the importance of the\u0000magnetic field, using the distribution of data in the B-$rho$ plane. It allows\u0000us to drive the following empirical $B-rho$ relation begin{equation} frac{B}{B_c} = {rm exp}left(left(frac{gamma}{{cal\u0000K}}right)^{-1}left( frac{rho}{rho_c}right)^frac{gamma}{{cal\u0000K}}right)nonumber, end{equation} which offers an excellent fit to the\u0000Cruther et al. data, where we assume ${cal M}_{rm A}-rho$ relation. The\u0000foundational ${cal M}_{rm A}-{rm k}_{B-rho}$ relation provides an\u0000independent way to measure the importance of magnetic field against the\u0000kinematic motion using multiple magnetic field measurements. Our approach\u0000offers a new interpretation of Cruther+2010, where a gradual decrease in the\u0000importance of B at higher densities is implied.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"62 6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196060","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}
Fabio Federici, Matthew L. Reinke, Bruce Lipschultz, Jack J. Lovell, Kevin Verhaegh, Cyd Cowley, Mike Kryjak, Peter Ryan, Andrew J. Thornton, James R. Harrison, Byron J. Peterson, Bartosz Lomanowski, Jeremy D. Lore, Yacopo Damizia
Plasma detachment involves interactions of the plasma with impurities and neutral particles, leading to significant losses of plasma power, momentum, and particles. Accurate mapping of plasma emissivity in the divertor and X-point region is essential for assessing the relationship between particle flux and radiative detachment. The recently validated InfraRed Video Bolometer (IRVB) diagnostic, in MAST-U enables this mapping with higher spatial resolution than more established methods like resistive bolometers. In previous preliminary work, the evolution of radiative detachment was characterised in L-mode (power entering the scrape-off layer, PSOL ~0.4MW). With a conventional divertor the inner leg consistently detached ahead of the outer leg, and radiative detachment preceded particle flux detachment. This work presents results also from the third MAST-U experimental campaign, fuelled from the low field side instead of the high field side, including Ohmic and beam heated L-mode shots (with a power exiting the core up to PSOL ~1-1.5MW). The radiation peak moves upstream from the target at lower upstream densities than the ion target flux roll-over (typically considered the detachment onset), while the inner leg detaches before the outer one. The movement of the radiation is in partial agreement with the expectations from the DLS model, predicting a sudden shift from the target to the X-point. The energy confinement is found to be related to detachment, but there seems to be some margin between the radiation on the inner leg reaching the X-point and confinement being affected, a beneficial characteristic if it could be extrapolated to future reactors. For increasing PSOL the particle flux roll over is almost unaffected, while radiative detachment occurs at higher density in both legs, but much higher on the outer, suggesting an uneven distribution of the power exiting the core.
等离子体脱离涉及等离子体与杂质和中性粒子的相互作用，导致等离子体功率、动量和粒子的大量损失。要评估粒子通量与辐射脱离之间的关系，就必须精确绘制分流器和X点区域的等离子体发射率图。MAST-U中最近通过验证的红外视频辐射计（IRVB）诊断能够以比电阻式辐射计等更成熟的方法更高的空间分辨率进行这种测绘。在以前的初步工作中，辐射脱离的演变是在 L 模式下进行的（对刮除层供电，PSOL ~0.4MW）。使用传统分流器时，内侧支管始终先于外侧支管脱离，辐射脱离先于粒子流脱离。这项工作还展示了 MAST-U 第三次实验活动的结果，这次活动从低场侧而不是高场侧进行燃料注入，包括欧姆和束流加热 L 模式射流（流出堆芯的功率高达 PSOL ~1-1.5MW）。辐射峰在上游密度低于离子靶通量翻转（通常被认为是脱离的起始点）时从靶上向上游移动，而内侧腿先于外侧腿脱离。辐射的移动与 DLS 模型的预期部分吻合，该模型预测了从目标到 X 点的突然移动。研究发现，能量限制与脱离有关，但在内侧辐射到达 X 点和限制受到影响之间似乎存在一定的余量，如果能将其推断到未来的反应堆，则这是一个有益的特征。对于不断增大的 PSOL，粒子通量的翻滚几乎不受影响，而辐射脱落则发生在密度较高的两个支脚上，但外侧支脚的密度要高得多，这表明流出堆芯的功率分布不均匀。
{"title":"Evolution of radiation profiles in a strongly baffled divertor on MAST Upgrade","authors":"Fabio Federici, Matthew L. Reinke, Bruce Lipschultz, Jack J. Lovell, Kevin Verhaegh, Cyd Cowley, Mike Kryjak, Peter Ryan, Andrew J. Thornton, James R. Harrison, Byron J. Peterson, Bartosz Lomanowski, Jeremy D. Lore, Yacopo Damizia","doi":"arxiv-2409.02837","DOIUrl":"https://doi.org/arxiv-2409.02837","url":null,"abstract":"Plasma detachment involves interactions of the plasma with impurities and\u0000neutral particles, leading to significant losses of plasma power, momentum, and\u0000particles. Accurate mapping of plasma emissivity in the divertor and X-point\u0000region is essential for assessing the relationship between particle flux and\u0000radiative detachment. The recently validated InfraRed Video Bolometer (IRVB)\u0000diagnostic, in MAST-U enables this mapping with higher spatial resolution than\u0000more established methods like resistive bolometers. In previous preliminary\u0000work, the evolution of radiative detachment was characterised in L-mode (power\u0000entering the scrape-off layer, PSOL ~0.4MW). With a conventional divertor the\u0000inner leg consistently detached ahead of the outer leg, and radiative\u0000detachment preceded particle flux detachment. This work presents results also\u0000from the third MAST-U experimental campaign, fuelled from the low field side\u0000instead of the high field side, including Ohmic and beam heated L-mode shots\u0000(with a power exiting the core up to PSOL ~1-1.5MW). The radiation peak moves\u0000upstream from the target at lower upstream densities than the ion target flux\u0000roll-over (typically considered the detachment onset), while the inner leg\u0000detaches before the outer one. The movement of the radiation is in partial\u0000agreement with the expectations from the DLS model, predicting a sudden shift\u0000from the target to the X-point. The energy confinement is found to be related\u0000to detachment, but there seems to be some margin between the radiation on the\u0000inner leg reaching the X-point and confinement being affected, a beneficial\u0000characteristic if it could be extrapolated to future reactors. For increasing\u0000PSOL the particle flux roll over is almost unaffected, while radiative\u0000detachment occurs at higher density in both legs, but much higher on the outer,\u0000suggesting an uneven distribution of the power exiting the core.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225087","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}
Timothy Johnson, Graeme Sutcliffe, Jacob Pearcy, Andrew Birkel, Gabriel Rigon, Neel Kabadi, Brandon Lahmann, Patrick Adrian, Benjamin Reichelt, Justin Kunimune, Skylar Dannhoff, Matt Cufari, Frank Tsung, Hui Chen, Joseph Katz, Vladimir Tikhonchuk, Chikang Li
This letter reports the first complete observation of magnetized collisionless shock precursors formed through the compression of Biermann-battery magnetic fields in laser produced plasmas. At OMEGA, lasers produce a supersonic CH plasma flow which is magnetized with Biermann-battery magnetic fields. The plasma flow collides with an unmagnetized hydrogen gas jet plasma to create a magnetized shock precursor. The situation where the flowing plasma carries the magnetic field is similar to the Venusian bow shock. Imaging 2$omega$ Thomson scattering confirms that the interaction is collisionless and shows density and temperature jumps. Proton radiographs have regions of strong deflections and FLASH magnetohydrodynamic (MHD) simulations show the presence of Biermann fields in the Thomson scattering region. Electrons are accelerated to energies of up to 100 keV in a power-law spectrum. OSIRIS particle-in-cell (PIC) simulations, initialized with measured parameters, show the formation of a magnetized shock precursor and corroborate the experimental observables.
{"title":"Biermann-battery driven magnetized collisionless shock precursors in laser produced plasmas","authors":"Timothy Johnson, Graeme Sutcliffe, Jacob Pearcy, Andrew Birkel, Gabriel Rigon, Neel Kabadi, Brandon Lahmann, Patrick Adrian, Benjamin Reichelt, Justin Kunimune, Skylar Dannhoff, Matt Cufari, Frank Tsung, Hui Chen, Joseph Katz, Vladimir Tikhonchuk, Chikang Li","doi":"arxiv-2409.03076","DOIUrl":"https://doi.org/arxiv-2409.03076","url":null,"abstract":"This letter reports the first complete observation of magnetized\u0000collisionless shock precursors formed through the compression of\u0000Biermann-battery magnetic fields in laser produced plasmas. At OMEGA, lasers\u0000produce a supersonic CH plasma flow which is magnetized with Biermann-battery\u0000magnetic fields. The plasma flow collides with an unmagnetized hydrogen gas jet\u0000plasma to create a magnetized shock precursor. The situation where the flowing\u0000plasma carries the magnetic field is similar to the Venusian bow shock. Imaging\u00002$omega$ Thomson scattering confirms that the interaction is collisionless and\u0000shows density and temperature jumps. Proton radiographs have regions of strong\u0000deflections and FLASH magnetohydrodynamic (MHD) simulations show the presence\u0000of Biermann fields in the Thomson scattering region. Electrons are accelerated\u0000to energies of up to 100 keV in a power-law spectrum. OSIRIS particle-in-cell\u0000(PIC) simulations, initialized with measured parameters, show the formation of\u0000a magnetized shock precursor and corroborate the experimental observables.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196074","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}
H. S. Wilson, A. O. Nelson, J. McClenaghan, P. Rodriguez-Fernandez, J. Parisi, C. Paz-Soldan
NT experiments have demonstrated core performance on par with positive triangularity (PT) H-mode without edge-localized modes (ELMs), encouraging further study of an NT reactor core. In this work, we use integrated modeling to scope the operating space around two NT reactor strategies: a high-field, compact fusion pilot plant concept and a low field, high aspect ratio concept. By integrating equilibrium, core transport, and edge ballooning instability models, we establish a range of operating points with less than 50 MW scrape-off layer power and fusion power comparable to positive triangularity (PT) H-mode reactor concepts. Heating and seeded impurities are leveraged to accomplish the same fusion performance and scrape-off layer exhaust power for various pressure edge boundary conditions. Scans over these pressure edge conditions accommodate any current uncertainty of the properties of the NT edge and show that the performance of an NT reactor will be extremely dependent on the edge pressure. The high-field case is found to enable lower scrape-off layer power because it is capable of reaching high fusion powers at a relatively compact size, which allows increased separatrix density without exceeding the Greenwald density limit. An increase in fusion power density is seen at weaker NT. Infinite-n ballooning instability models indicate that an NT reactor core can reach fusion powers comparable to leading PT H-mode reactor concepts while remaining ballooning-stable. Seeded krypton is leveraged to further lower scrape-off layer power since NT does not have a requirement to remain in H-mode. We contextualize the NT reactor operating space by comparing to popular PT H-mode reactor concepts, and find that NT exhibits competitive ELM-free performance with these concepts for a variety of edge conditions while maintaining relatively low scrape-off layer power.
NT实验表明，堆芯性能与无边缘定位模式（ELM）的正三角柱体（PT）H模式相当，这鼓励了对NT反应堆堆芯的进一步研究。在这项工作中，我们利用综合建模来确定两种 NT 反应堆策略的运行空间范围：一种是高场强、紧凑型聚变试验装置概念，另一种是低场强、高纵横比概念。通过整合平衡、堆芯输运和边缘气球不稳定性模型，我们确定了一系列运行点，其刮离层功率小于 50 兆瓦，聚变功率与正三角（PT）H 型反应堆概念相当。在不同的压力边缘边界条件下，利用加热和种子杂质来实现相同的聚变性能和刮除层排气功率。在这些压力边缘条件下进行的扫描，考虑到了目前新界边缘特性的任何不确定性，并表明新界反应堆的性能将极其依赖于边缘压力。研究发现，高场情况能够降低刮擦层的功率，因为它能够以相对紧凑的尺寸达到较高的聚变功率，从而在不超过格林沃尔德密度极限的情况下提高分离矩阵密度。在较弱的 NT 下，聚变功率密度会增加。无限正气球不稳定性模型表明，NT 反应堆堆芯可以达到与领先的 PT H 模式反应堆概念相当的聚变功率，同时保持气球稳定。由于 NT 并不要求保持 H 模式，因此可以利用种子氪进一步降低刮离层功率。通过与流行的 PT H 模式反应堆概念进行比较，我们确定了 NT 反应堆的操作空间，并发现在各种边缘条件下，NT 与这些概念相比具有具有竞争力的无ELM 性能，同时还能保持相对较低的刮除层功率。
{"title":"Characterizing the negative triangularity reactor core operating space with integrated modeling","authors":"H. S. Wilson, A. O. Nelson, J. McClenaghan, P. Rodriguez-Fernandez, J. Parisi, C. Paz-Soldan","doi":"arxiv-2409.03038","DOIUrl":"https://doi.org/arxiv-2409.03038","url":null,"abstract":"NT experiments have demonstrated core performance on par with positive\u0000triangularity (PT) H-mode without edge-localized modes (ELMs), encouraging\u0000further study of an NT reactor core. In this work, we use integrated modeling\u0000to scope the operating space around two NT reactor strategies: a high-field,\u0000compact fusion pilot plant concept and a low field, high aspect ratio concept.\u0000By integrating equilibrium, core transport, and edge ballooning instability\u0000models, we establish a range of operating points with less than 50 MW\u0000scrape-off layer power and fusion power comparable to positive triangularity\u0000(PT) H-mode reactor concepts. Heating and seeded impurities are leveraged to\u0000accomplish the same fusion performance and scrape-off layer exhaust power for\u0000various pressure edge boundary conditions. Scans over these pressure edge\u0000conditions accommodate any current uncertainty of the properties of the NT edge\u0000and show that the performance of an NT reactor will be extremely dependent on\u0000the edge pressure. The high-field case is found to enable lower scrape-off\u0000layer power because it is capable of reaching high fusion powers at a\u0000relatively compact size, which allows increased separatrix density without\u0000exceeding the Greenwald density limit. An increase in fusion power density is\u0000seen at weaker NT. Infinite-n ballooning instability models indicate that an NT\u0000reactor core can reach fusion powers comparable to leading PT H-mode reactor\u0000concepts while remaining ballooning-stable. Seeded krypton is leveraged to\u0000further lower scrape-off layer power since NT does not have a requirement to\u0000remain in H-mode. We contextualize the NT reactor operating space by comparing\u0000to popular PT H-mode reactor concepts, and find that NT exhibits competitive\u0000ELM-free performance with these concepts for a variety of edge conditions while\u0000maintaining relatively low scrape-off layer power.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"185 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196043","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}
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