Pub Date : 2024-10-10DOI: 10.1016/j.nme.2024.101756
V. Quadri , P. Tamain , Y. Marandet , H. Bufferand , N. Rivals , G. Ciraolo , G.L. Falchetto , R. Düll , S. Sureshkumar , N. Varadarajan , H. Yang , H. Reimerdes , D.S. Oliveira , D. Mancini
Experimental results from several tokamaks suggest a strong impact of divertor density regimes on turbulent transport in the edge plasma. Reciprocally, the change in cross- field transport and Scrape-Off-Layer (SOL) width affects the access to density regimes, making it a fundamental topic for heat exhaust issue. Addressing this issue self- consistently requires numerical modeling tools including, both, turbulent transport and neutrals recycling physics. In this study, the SOLEDGE3X multi-fluid edge plasma code is used to conduct a first analysis of turbulent transport in a long-leg diverted plasma in high density regimes. A fluid neutrals model is used to model particle recycling as well as fueling by gas puff. A dedicated pulse run in the TCV tokamak is modeled in which a density scan from attached to detached plasma conditions was performed. The following results demonstrate the achievement of a turbulence simulation in the detached regime, explicitly highlighting a change in turbulence properties between low and high density, which are responsible of a change in the SOL widths.
几个托卡马克反应堆的实验结果表明，分流器的密度制度对边缘等离子体的湍流输运有很大影响。反过来，跨场输运和刮除层（SOL）宽度的变化也会影响密度制度的进入，从而使其成为排热问题的一个基本主题。要持续解决这一问题，需要包括湍流传输和中性回收物理在内的数值建模工具。本研究使用 SOLEDGE3X 多流体边缘等离子体代码，首次分析了高密度区长腿分流等离子体中的湍流输运。流体中性模型用于模拟粒子循环以及气体喷发的助燃。对 TCV 托卡马克中的专用脉冲运行进行了建模，其中进行了从附着到分离等离子体条件的密度扫描。以下结果展示了在分离状态下的湍流模拟成果，明确强调了低密度和高密度之间湍流特性的变化，这也是 SOL 宽度变化的原因。
{"title":"Edge plasma turbulence simulations in detached regimes with the SOLEDGE3X code","authors":"V. Quadri , P. Tamain , Y. Marandet , H. Bufferand , N. Rivals , G. Ciraolo , G.L. Falchetto , R. Düll , S. Sureshkumar , N. Varadarajan , H. Yang , H. Reimerdes , D.S. Oliveira , D. Mancini","doi":"10.1016/j.nme.2024.101756","DOIUrl":"10.1016/j.nme.2024.101756","url":null,"abstract":"<div><div>Experimental results from several tokamaks suggest a strong impact of divertor density regimes on turbulent transport in the edge plasma. Reciprocally, the change in cross- field transport and Scrape-Off-Layer (SOL) width affects the access to density regimes, making it a fundamental topic for heat exhaust issue. Addressing this issue self- consistently requires numerical modeling tools including, both, turbulent transport and neutrals recycling physics. In this study, the SOLEDGE3X multi-fluid edge plasma code is used to conduct a first analysis of turbulent transport in a long-leg diverted plasma in high density regimes. A fluid neutrals model is used to model particle recycling as well as fueling by gas puff. A dedicated pulse run in the TCV tokamak is modeled in which a density scan from attached to detached plasma conditions was performed. The following results demonstrate the achievement of a turbulence simulation in the detached regime, explicitly highlighting a change in turbulence properties between low and high density, which are responsible of a change in the SOL widths.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101756"},"PeriodicalIF":2.3,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142552430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-10DOI: 10.1016/j.nme.2024.101763
Chunyu He , Dahuan Zhu , Baoguo Wang , Binfu Gao , Gaoting Chen , Lingyi Meng , Rong Yan , Yang Wang , Yongqi Gu , Guoliang Xu , Qingquan Yang , Rui Ding , Junling Chen , EAST Team
Heat flux is a key issue in tokamak devices. The non-uniform high heat flux on Plasma-Facing Components (PFCs) has led to local severe damage, including cracks and melting, in current tokamaks such as EAST and WEST. To characterize the non-uniform heat flux loading on the divertor surfaces, the parallel incident heat flux the decay length along the radial direction and the Gaussian spreading width S are used. The can lead to a very high peak heat flux loading on the divertor surfaces, which may cause critical heat flux problems. Additionally, the decay length is a key consideration for future tokamak designs like ITER. Every effort on the present tokamak devices contributes to updating the scaling of the heat flux. In EAST, a calculation method based on a high spatial resolution IR camera is employed to obtain the heat flux and decay length. The main process involves comparing the surface temperature distribution calculated by Fluent simulation with that measured by an infrared camera. Taking a high heating source discharge (#123059 ∼ 10 MW heating source) as an example, the heat flux is as follows: MW/m2, with mm, and mm; it is in line with Langmuir probe data. The infrared-based heat flux calculation method can calculate the peak incident heat flux and the decay length simultaneously, its result can help to update the scaling model of heat flux, thus not only helping to improve the present device but also offering important reference for future tokamaks.
{"title":"Calculation of in-situ steady-state heat flux on EAST lower divertor","authors":"Chunyu He , Dahuan Zhu , Baoguo Wang , Binfu Gao , Gaoting Chen , Lingyi Meng , Rong Yan , Yang Wang , Yongqi Gu , Guoliang Xu , Qingquan Yang , Rui Ding , Junling Chen , EAST Team","doi":"10.1016/j.nme.2024.101763","DOIUrl":"10.1016/j.nme.2024.101763","url":null,"abstract":"<div><div>Heat flux is a key issue in tokamak devices. The non-uniform high heat flux on Plasma-Facing Components (PFCs) has led to local severe damage, including cracks and melting, in current tokamaks such as EAST and WEST. To characterize the non-uniform heat flux loading on the divertor surfaces, the parallel incident heat flux <span><math><mrow><msub><mrow><mi>q</mi></mrow><mrow><mo>‖</mo></mrow></msub><mo>,</mo></mrow></math></span> the decay length <span><math><mrow><msub><mrow><mi>λ</mi></mrow><mrow><mi>q</mi></mrow></msub></mrow></math></span> along the radial direction and the Gaussian spreading width S are used. The <span><math><mrow><msub><mi>q</mi><mo>‖</mo></msub></mrow></math></span> can lead to a very high peak heat flux loading on the divertor surfaces, which may cause critical heat flux problems. Additionally, the decay length is a key consideration for future tokamak designs like ITER. Every effort on the present tokamak devices contributes to updating the scaling of the heat flux. In EAST, a calculation method based on a high spatial resolution IR camera is employed to obtain the heat flux and decay length. The main process involves comparing the surface temperature distribution calculated by Fluent simulation with that measured by an infrared camera. Taking a high heating source discharge (#123059 ∼ 10 MW heating source) as an example, the heat flux is as follows: <span><math><mrow><msub><mi>q</mi><mo>‖</mo></msub><mo>=</mo><msubsup><mrow><mn>216</mn><mspace></mspace></mrow><mrow><mo>-</mo><mn>14</mn></mrow><mrow><mo>+</mo><mn>19</mn></mrow></msubsup></mrow></math></span> MW/m<sup>2</sup>, with <span><math><mrow><msub><mi>λ</mi><mi>q</mi></msub><mo>=</mo><msubsup><mrow><mn>6.2</mn><mspace></mspace></mrow><mrow><mo>-</mo><mn>1.1</mn></mrow><mrow><mo>+</mo><mn>1</mn></mrow></msubsup></mrow></math></span> mm, and <span><math><mrow><mi>S</mi><mo>=</mo><mn>1.2</mn><mo>±</mo><mn>0.4</mn></mrow></math></span> mm; it is in line with Langmuir probe data. The infrared-based heat flux calculation method can calculate the peak incident heat flux and the decay length simultaneously, its result can help to update the scaling model of heat flux, thus not only helping to improve the present device but also offering important reference for future tokamaks.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101763"},"PeriodicalIF":2.3,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-09DOI: 10.1016/j.nme.2024.101757
Vicente Araullo-Peters, Yong Dai
Tungsten is a key material for applications of spallation targets and fusion reactors. Irradiation-induced transmutation products can significantly affect the mechanical and thermal properties of tungsten. However, detailed quantitative analysis of transmutation elements of irradiated tungsten has not been reported and is therefore in high demand, especially in the cases of spallation targets where a large amounts of transmutation elements are produced. In this work, we analyzed the transmutation products in pure tungsten samples irradiated in a target of Swiss Spallation Neutron Source (SINQ) at doses of 6.4 and 28 dpa, the latter being the highest dose ever achieved in spallation targets. Quantitative measurements of 40 nuclides ranging from 144Sm to 188Os were performed using the atom probe tomography (APT) technique. The measured concentrations of transmutation elements are in good agreement with those of neutronic calculations. The APT analysis also revealed clusters of transmutation elements. Due to low irradiation temperature (<500 °C) and low concentration of transmutation elements, the clusters are 1–2 nm in diameter.
{"title":"Quantitative analysis of transmutation nuclides in pure tungsten irradiated with high-energy protons and spallation neutrons at 6.4 and 28 dpa","authors":"Vicente Araullo-Peters, Yong Dai","doi":"10.1016/j.nme.2024.101757","DOIUrl":"10.1016/j.nme.2024.101757","url":null,"abstract":"<div><div>Tungsten is a key material for applications of spallation targets and fusion reactors. Irradiation-induced transmutation products can significantly affect the mechanical and thermal properties of tungsten. However, detailed quantitative analysis of transmutation elements of irradiated tungsten has not been reported and is therefore in high demand, especially in the cases of spallation targets where a large amounts of transmutation elements are produced. In this work, we analyzed the transmutation products in pure tungsten samples irradiated in a target of Swiss Spallation Neutron Source (SINQ) at doses of 6.4 and 28 dpa, the latter being the highest dose ever achieved in spallation targets. Quantitative measurements of 40 nuclides ranging from <sup>144</sup>Sm to <sup>188</sup>Os were performed using the atom probe tomography (APT) technique. The measured concentrations of transmutation elements are in good agreement with those of neutronic calculations. The APT analysis also revealed clusters of transmutation elements. Due to low irradiation temperature (<500 °C) and low concentration of transmutation elements, the clusters are 1–2 nm in diameter.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101757"},"PeriodicalIF":2.3,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-09DOI: 10.1016/j.nme.2024.101760
Muhammad Amir Shabbir, Ran Hai, Zhonglin He, Zehua Liu, Fahad Rehman, Xue Bai, Jianping Mu, Ding Wu, Cong Li, Hongbin Ding
ITER is designed for a burning plasma operation in which Tungsten (W) tiles are used as the first wall and diverter materials. Studying He dynamics in B-coated W wall is essential to understanding the effect of boronized plasma-facing components in fusion reactors, as these post-conditioning materials significantly influence helium retention and release. Plasma-wall interactions (PWI) are an important issue in ITER fusion reactors. PWI would lead to wall erosion and impurity redeposition. As a product of the D-T burning plasma, helium (He) ash would be retained or co-deposited on plasma-facing components (PFCs), affecting the stable operation of burning plasma. Laser-induced breakdown spectroscopy (LIBS) is proposed as a promising in-situ diagnostic approach for monitoring D/T and He retention and impurity deposition on PFCs of tokamak devices. In this study, the LIBS technique was used to investigate the helium retention feature in the boron (B) layer on tungsten substrate in 10−5 mbar. Five He-retention samples on the boron deposition layer on tungsten substrates were prepared by pulsed laser deposition (PLD) method at different ambient pressures in our lab. The investigations indicate that the atomic spectral line of helium (He-I 587.56 nm) was observed in the spectra of the first three laser shots. The depth profiles of He, B, and W in the boron-deposited layer on tungsten substrate were performed by LIBS to determine the co-deposition layer thickness. The concentration of He in the co-deposition layer samples measured by TDS is 7 × 1020 He/m2. The plasma parameters, such as plasma electron temperature and electron number density, were calculated to validate the local thermodynamic equilibrium. Machine learning (ML) algorithms are used to classify the co-deposits and substrates. The first three principal components (PC1, PC2 & PC3) of the unsupervised ML algorithm (PCA) give a classification accuracy of 91.7 %. The supervised ML algorithm neural network achieved training and testing accuracy of 100 % and 96.7 %, respectively.
国际热核聚变实验堆设计用于燃烧等离子体运行，其中钨（W）瓦被用作第一壁和分流器材料。研究硼涂层 W 壁中的氦动力学对于了解聚变反应堆中面向等离子体的硼化组件的效果至关重要，因为这些后处理材料会显著影响氦的保留和释放。等离子体-壁相互作用（PWI）是热核聚变实验堆中的一个重要问题。等离子体-壁相互作用会导致壁侵蚀和杂质再沉积。作为 D-T 燃烧等离子体的产物，氦（He）灰将保留或共同沉积在面向等离子体的部件（PFC）上，从而影响燃烧等离子体的稳定运行。激光诱导击穿光谱（LIBS）被认为是一种很有前途的原位诊断方法，可用于监测托卡马克装置 PFC 上的 D/T 和 He 残留及杂质沉积。在本研究中，我们使用 LIBS 技术研究了钨基底上硼（B）层在 10-5 毫巴条件下的氦滞留特征。本实验室在不同的环境压力下，采用脉冲激光沉积（PLD）方法制备了钨衬底上硼沉积层的五个氦保留样品。研究结果表明，在前三次激光发射的光谱中观察到了氦的原子光谱线（He-I 587.56 nm）。利用 LIBS 对钨基板上硼沉积层中 He、B 和 W 的深度剖面进行了分析，以确定共沉积层的厚度。通过 TDS 测量的共沉积层样品中 He 的浓度为 7 × 1020 He/m2。计算了等离子体参数，如等离子体电子温度和电子数密度，以验证局部热力学平衡。使用机器学习（ML）算法对共沉积层和基底进行分类。无监督 ML 算法（PCA）的前三个主成分（PC1、PC2 & PC3）的分类准确率为 91.7%。有监督 ML 算法神经网络的训练和测试准确率分别为 100 % 和 96.7 %。
{"title":"Helium retention feature in the boron deposited layer on tungsten substrate by laser-induced breakdown spectroscopy and machine learning approach","authors":"Muhammad Amir Shabbir, Ran Hai, Zhonglin He, Zehua Liu, Fahad Rehman, Xue Bai, Jianping Mu, Ding Wu, Cong Li, Hongbin Ding","doi":"10.1016/j.nme.2024.101760","DOIUrl":"10.1016/j.nme.2024.101760","url":null,"abstract":"<div><div>ITER is designed for a burning plasma operation in which Tungsten (W) tiles are used as the first wall and diverter materials. Studying He dynamics in B-coated W wall is essential to understanding the effect of boronized plasma-facing components in fusion reactors, as these post-conditioning materials significantly influence helium retention and release. Plasma-wall interactions (PWI) are an important issue in ITER fusion reactors. PWI would lead to wall erosion and impurity redeposition. As a product of the D-T burning plasma, helium (He) ash would be retained or co-deposited on plasma-facing components (PFCs), affecting the stable operation of burning plasma. Laser-induced breakdown spectroscopy (LIBS) is proposed as a promising in-situ diagnostic approach for monitoring D/T and He retention and impurity deposition on PFCs of tokamak devices. In this study, the LIBS technique was used to investigate the helium retention feature in the boron (B) layer on tungsten substrate in 10<sup>−5</sup> mbar. Five He-retention samples on the boron deposition layer on tungsten substrates were prepared by pulsed laser deposition (PLD) method at different ambient pressures in our lab. The investigations indicate that the atomic spectral line of helium (He-I 587.56 nm) was observed in the spectra of the first three laser shots. The depth profiles of He, B, and W in the boron-deposited layer on tungsten substrate were performed by LIBS to determine the co-deposition layer thickness. The concentration of He in the co-deposition layer samples measured by TDS is 7 × 10<sup>20</sup> He/m<sup>2</sup>. The plasma parameters, such as plasma electron temperature and electron number density, were calculated to validate the local thermodynamic equilibrium. Machine learning (ML) algorithms are used to classify the co-deposits and substrates. The first three principal components (PC1, PC2 & PC3) of the unsupervised ML algorithm (PCA) give a classification accuracy of 91.7 %. The supervised ML algorithm neural network achieved training and testing accuracy of 100 % and 96.7 %, respectively.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101760"},"PeriodicalIF":2.3,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-08DOI: 10.1016/j.nme.2024.101753
J. Moritz , S. Heuraux , M. Lesur , E. Gravier , F. Brochard , L. Marot , P. Hiret
In fusion devices like ITER, plasma-wall interactions are a significant concern due to the high heat fluxes, often tens of MW/m, impacting the first wall. These intense heat fluxes can lead to the formation of hot spots on components facing the plasma, such as tungsten, used in divertor plates and antennas. This results in material erosion and plasma core contamination. Our study investigates the thermal behavior of tungsten surfaces under these conditions using fluid modeling and Particle-In-Cell (PIC) simulations. We examine the effects of thermionic electron emission on the sheath potential and heat transmission. The simulations reveal that thermionic emission can decrease the sheath voltage, increasing the surface temperature due to enhanced heat flux due to electrons. Additionally, we explore how the ratio between the spot size () and the surrounding surface length () influences the surface temperature. We find that a higher ratio allows the surface to reach higher temperatures before the system enters the space-charge-limited regime, where thermionic current is maximized and considerably larger than the case where the entire surface is emissive ().
{"title":"Simulated temperature of a tungsten spot facing large plasma heat loads","authors":"J. Moritz , S. Heuraux , M. Lesur , E. Gravier , F. Brochard , L. Marot , P. Hiret","doi":"10.1016/j.nme.2024.101753","DOIUrl":"10.1016/j.nme.2024.101753","url":null,"abstract":"<div><div>In fusion devices like ITER, plasma-wall interactions are a significant concern due to the high heat fluxes, often tens of MW/m<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span>, impacting the first wall. These intense heat fluxes can lead to the formation of hot spots on components facing the plasma, such as tungsten, used in divertor plates and antennas. This results in material erosion and plasma core contamination. Our study investigates the thermal behavior of tungsten surfaces under these conditions using fluid modeling and Particle-In-Cell (PIC) simulations. We examine the effects of thermionic electron emission on the sheath potential and heat transmission. The simulations reveal that thermionic emission can decrease the sheath voltage, increasing the surface temperature due to enhanced heat flux due to electrons. Additionally, we explore how the ratio between the spot size (<span><math><mi>S</mi></math></span>) and the surrounding surface length (<span><math><msub><mrow><mi>L</mi></mrow><mrow><mi>y</mi></mrow></msub></math></span>) influences the surface temperature. We find that a higher <span><math><mrow><msub><mrow><mi>L</mi></mrow><mrow><mi>y</mi></mrow></msub><mo>/</mo><mi>S</mi></mrow></math></span> ratio allows the surface to reach higher temperatures before the system enters the space-charge-limited regime, where thermionic current is maximized and considerably larger than the case where the entire surface is emissive (<span><math><mrow><msub><mrow><mi>L</mi></mrow><mrow><mi>y</mi></mrow></msub><mo>=</mo><mi>S</mi></mrow></math></span>).</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101753"},"PeriodicalIF":2.3,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-06DOI: 10.1016/j.nme.2024.101755
T. Okamoto , N. Ezumi , S. Takahashi , R. Perillo , S. Togo , K. Kouno , T. Seto , R. Miyauchi , H. Kawahara , J. Kohagura , M. Yoshikawa , M. Sakamoto
In a divertor simulation experimental module (D-module) of GAMMA 10/PDX, additional hydrogen seeding induces molecular-activated recombination (H-MAR). However, when seeding of hydrogen and nitrogen is combined, Nitrogen MAR (N-MAR) is observed in D-module. In this work, we experimentally investigate plasma detachment processes in D-module by seeding hydrogen-only and hydrogen + nitrogen in order to de-couple MARs contribution to the measured particle flux reduction. Nitrogen is seeded after the electron density, measured with Langmuir probes installed in D-module, begins to decrease due to hydrogen seeding. In both cases, the electron temperature near the V-shaped target decreases from ∼23 eV to ∼2 eV. A clear rollover is observed in the ion flux to the V-shaped target. When only hydrogen is seeded, the Balmer lines emission ratio (i.e. the intensity of Hα emission line (IHα)/the intensity of Hβ emission line (IHβ)), an indicator of H-MAR, is observed to increase between V-shaped targets installed in D-module as the amount of hydrogen gas increases. However, when both hydrogen and nitrogen are seeded, IHα/ IHβ increase is suppressed, and the region of the largest IHα/ IHβ signal shifts upstream of D-module, as observed by a high-speed camera. These results show for the first time the transition from H-MAR-dominated phase to N-MAR-dominated phase and the coexistence of both MARs in D-module. It is found that nitrogen seeding increases plasma detachment even at already relatively low Te (∼5 eV). The high-speed camera measurements suggest this effect to be related to the increase of NHx neutral density, in line with previous modeling works.
在 GAMMA 10/PDX 的分流器模拟实验模块（D 模块）中，额外的氢气播种会诱发分子活化重组（H-MAR）。然而，当氢和氮结合在一起时，在 D 模块中会观察到氮分子重组（N-MAR）。在这项工作中，我们通过只播种氢气和氢气+氮气，对 D 模块中的等离子体脱离过程进行了实验研究，以消除 MAR 对所测粒子通量减少的贡献。在 D 模块中安装的朗缪尔探针测量到的电子密度由于氢气的加入而开始下降后，氮气被加入。在这两种情况下，V 型靶附近的电子温度都从∼23 eV 下降到∼2 eV。V 形靶的离子通量出现了明显的翻转。当只加入氢气时，随着氢气量的增加，在 D 模块中安装的 V 形靶之间观察到作为 H-MAR 指标的巴尔默线发射比（即 Hα 发射线强度 (IHα)/Hβ 发射线强度 (IHβ)）也在增加。然而，当同时加入氢气和氮气时，IHα/ IHβ的增加受到抑制，高速相机观测到的最大 IHα/ IHβ信号区域转移到了 D 模块的上游。这些结果首次显示了从 H-MAR 主导阶段到 N-MAR 主导阶段的转变，以及两种 MAR 在 D 模块中的共存。研究发现，即使在相对较低的 Te（∼5 eV）条件下，氮的加入也会增加等离子体的脱离。高速照相机测量结果表明，这种效应与 NHx 中性密度的增加有关，与之前的建模工作相一致。
{"title":"Coexistence of H-MAR and N-MAR in divertor simulation experimental module of GAMMA 10/PDX","authors":"T. Okamoto , N. Ezumi , S. Takahashi , R. Perillo , S. Togo , K. Kouno , T. Seto , R. Miyauchi , H. Kawahara , J. Kohagura , M. Yoshikawa , M. Sakamoto","doi":"10.1016/j.nme.2024.101755","DOIUrl":"10.1016/j.nme.2024.101755","url":null,"abstract":"<div><div>In a divertor simulation experimental module (D-module) of GAMMA 10/PDX, additional hydrogen seeding induces molecular-activated recombination (H-MAR). However, when seeding of hydrogen and nitrogen is combined, Nitrogen MAR (N-MAR) is observed in D-module. In this work, we experimentally investigate plasma detachment processes in D-module by seeding hydrogen-only and hydrogen + nitrogen in order to de-couple MARs contribution to the measured particle flux reduction. Nitrogen is seeded after the electron density, measured with Langmuir probes installed in D-module, begins to decrease due to hydrogen seeding. In both cases, the electron temperature near the V-shaped target decreases from ∼23 eV to ∼2 eV. A clear rollover is observed in the ion flux to the V-shaped target. When only hydrogen is seeded, the Balmer lines emission ratio (i.e. the intensity of H<sub>α</sub> emission line (<em>I</em><sub>Hα</sub>)/the intensity of H<sub>β</sub> emission line (<em>I</em><sub>Hβ</sub>)), an indicator of H-MAR, is observed to increase between V-shaped targets installed in D-module as the amount of hydrogen gas increases. However, when both hydrogen and nitrogen are seeded, <em>I</em><sub>Hα</sub>/ <em>I</em><sub>Hβ</sub> increase is suppressed, and the region of the largest <em>I</em><sub>Hα</sub>/ <em>I</em><sub>Hβ</sub> signal shifts upstream of D-module, as observed by a high-speed camera. These results show for the first time the transition from H-MAR-dominated phase to N-MAR-dominated phase and the coexistence of both MARs in D-module. It is found that nitrogen seeding increases plasma detachment even at already relatively low <em>T<sub>e</sub></em> (∼5 eV). The high-speed camera measurements suggest this effect to be related to the increase of NH<sub>x</sub> neutral density, in line with previous modeling works.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101755"},"PeriodicalIF":2.3,"publicationDate":"2024-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-05DOI: 10.1016/j.nme.2024.101752
J.D. Mateja , S.A. Zamperini , T. Odstrcil , J.H. Nichols , T.E. Ray , A. Cacheris , T. Abrams , A.G. McLean , G. Sinclair , S.H. Messer , R. Maurizio , D.M. Thomas , D.C. Donovan
Experiments using the V-shaped closed slot tungsten (W) coated SAS-VW divertor in DIII-D studied the effects of the BT direction on core contamination of eroded tungsten from a closed slot divertor configuration. Core W content is inferred using soft-X ray tomography (SXR) and vacuum ultraviolet spectroscopy (SPRED), while W divertor erosion is inferred from visible spectroscopy of W emission (400.9 nm) measured by in-slot filterscopes (filtered photo-multipliers). Post-mortem analysis from the campaign discovered tile misalignment leading to suspected pronounced leading-edge erosion in the unfavorable BT direction (ion drift away from divertor) likely not captured by diagnostics. However, empirical findings show up to ∼ 2-3x larger core contamination in the favorable BT direction even considering no additional W erosion from leading edges. A “source-to-core efficiency factor” is derived to estimate the effects of leading-edge erosion and compare W contamination for two pairs of H-mode discharges in opposite BT directions. While having differing absolute parameters, similar core impurity density gradients suggest comparable core impurity transport. These results show that favorable BT may have stronger source-to-core pathways for W impurities sourced from the outer divertor region. Possible explanations could include the effects of drifts on W transport in the scrape-off-layer (SOL) as well as previously determined fast SOL inner target directed flows in favorable BT.
在 DIII-D 中使用 V 形封闭槽钨 (W) 涂层 SAS-VW 分流器进行的实验研究了 BT 方向对封闭槽分流器配置侵蚀钨的堆芯污染的影响。通过软 X 射线断层扫描（SXR）和真空紫外光谱（SPRED）推断出堆芯中的钨含量，而通过槽内滤波器（滤波光电倍增管）测量的钨发射可见光谱（400.9 纳米）推断出钨分流器的侵蚀情况。活动结束后的分析发现，瓦片错位导致前缘在不利的 BT 方向（离子 B→×∇B→ 漂离偏转器）出现明显的侵蚀，而诊断仪很可能无法捕捉到这种侵蚀。然而，经验研究结果表明，即使不考虑来自前缘的额外 W 侵蚀，在有利的 BT 方向上，堆芯污染也会增加 2-3 倍。为了估算前缘侵蚀的影响，并比较 BT 方向相反的两对 H 模式放电的 W 污染情况，得出了一个 "源到堆芯效率系数"。虽然绝对参数不同，但相似的堆芯杂质密度梯度表明堆芯杂质传输具有可比性。这些结果表明，对于来自外侧分流器区域的 W 杂质来说，有利的 BT 可能具有更强的源到堆芯的路径。可能的解释包括 E→×B→ 漂移对 W 在刮离层（SOL）中的传输的影响，以及先前确定的在有利 BT 中快速 SOL 内靶定向流的影响。
{"title":"Investigating the effect of BT direction on W source-to-core pathways during the SAS-VW campaign on DIII-D","authors":"J.D. Mateja , S.A. Zamperini , T. Odstrcil , J.H. Nichols , T.E. Ray , A. Cacheris , T. Abrams , A.G. McLean , G. Sinclair , S.H. Messer , R. Maurizio , D.M. Thomas , D.C. Donovan","doi":"10.1016/j.nme.2024.101752","DOIUrl":"10.1016/j.nme.2024.101752","url":null,"abstract":"<div><div>Experiments using the V-shaped closed slot tungsten (W) coated SAS-VW divertor in DIII-D studied the effects of the B<sub>T</sub> direction on core contamination of eroded tungsten from a closed slot divertor configuration. Core W content is inferred using soft-X ray tomography (SXR) and vacuum ultraviolet spectroscopy (SPRED), while W divertor erosion is inferred from visible spectroscopy of W emission (400.9 nm) measured by in-slot filterscopes (filtered photo-multipliers). Post-mortem analysis from the campaign discovered tile misalignment leading to suspected pronounced leading-edge erosion in the unfavorable B<sub>T</sub> direction (ion <span><math><mrow><mover><mi>B</mi><mo>→</mo></mover><mo>×</mo><mi>∇</mi><mover><mi>B</mi><mo>→</mo></mover></mrow></math></span> drift away from divertor) likely not captured by diagnostics. However, empirical findings show up to ∼ 2-3x larger core contamination in the favorable B<sub>T</sub> direction even considering no additional W erosion from leading edges. A “source-to-core efficiency factor” is derived to estimate the effects of leading-edge erosion and compare W contamination for two pairs of H-mode discharges in opposite B<sub>T</sub> directions. While having differing absolute parameters, similar core impurity density gradients suggest comparable core impurity transport. These results show that favorable B<sub>T</sub> may have stronger source-to-core pathways for W impurities sourced from the outer divertor region. Possible explanations could include the effects of <span><math><mrow><mover><mi>E</mi><mo>→</mo></mover><mo>×</mo><mover><mi>B</mi><mo>→</mo></mover></mrow></math></span> drifts on W transport in the scrape-off-layer (SOL) as well as previously determined fast SOL inner target directed flows in favorable B<sub>T</sub>.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101752"},"PeriodicalIF":2.3,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-05DOI: 10.1016/j.nme.2024.101751
F. Pappalardo , L. Rayneau , C. Martin , M. Cabie , E. Salomon , T. Angot , G. Cartry , R. Bisson , M. Minissale
In this work, we investigate the optical properties variation of thermally grown W oxides during the exposure to low energy deuterium (D) plasma. In-situ ellipsometry in the 400–1000 nm range was coupled to ex-situ diagnostics, such as X-ray photoelectron spectroscopy (XPS) and focused ion beam coupled to scanning electron microscopy (FIB-SEM), to probe the evolution of chemical and morphological properties of the W oxides. First, a 70 nm thick layer was exposed to D plasma at a surface temperature of 650 K. An important reduction of the oxide layer was observed by FIB-SEM, and in-situ ellipsometry showed the evolution of the optical constants n and k of the oxide towards the ones of pure W metal. Secondly, a 300 nm thick layer was exposed to D plasma at a surface temperature below 373 K. In order to follow the oxide evolution step by step, we alternated in-situ ellipsometry and XPS surface characterization. A quite similar evolution of the optical constants was observed, in particular an increase of the extinction coefficient k in the near infrared, which was linked to a progressive reduction of the oxidation level at the surface, as seen by XPS. Interestingly, the reduction of the oxide at 373 K was below the resolution of the FIB-SEM. This observation indicates that ellipsometry in the 400–1000 nm range is able to follow in-situ the reduction of oxides by D plasma with high surface sensitivity.
在这项工作中，我们研究了热生长 W 氧化物在暴露于低能氘（D）等离子体期间的光学特性变化。将 400-1000 nm 范围内的原位椭偏仪与 X 射线光电子能谱 (XPS) 和聚焦离子束耦合扫描电子显微镜 (FIB-SEM) 等原位诊断技术相结合，探究了 W 氧化物化学和形态特性的演变。首先，将 70 nm 厚的 WO3 层暴露在表面温度为 650 K 的 D 等离子体中。FIB-SEM 观察到氧化层明显减少，原位椭偏仪显示氧化物的光学常数 n 和 k 向纯 W 金属的光学常数演变。其次，将 300 nm 厚的 WO3 层暴露在表面温度低于 373 K 的 D 等离子体中。为了逐步跟踪氧化物的演变，我们交替使用了原位椭偏仪和 XPS 表面表征。我们观察到光学常数的演变非常相似，尤其是近红外消光系数 k 的增加，这与 XPS 观察到的表面氧化程度逐渐降低有关。有趣的是，373 K 时氧化物的减少低于 FIB-SEM 的分辨率。这一观察结果表明，400-1000 纳米范围内的椭偏仪能够以较高的表面灵敏度原位跟踪 D 等离子体对 WO3 氧化物的还原。
{"title":"In-situ monitoring of tungsten oxides reduction during deuterium plasma exposure by spectroscopic ellipsometry","authors":"F. Pappalardo , L. Rayneau , C. Martin , M. Cabie , E. Salomon , T. Angot , G. Cartry , R. Bisson , M. Minissale","doi":"10.1016/j.nme.2024.101751","DOIUrl":"10.1016/j.nme.2024.101751","url":null,"abstract":"<div><div>In this work, we investigate the optical properties variation of thermally grown W oxides during the exposure to low energy deuterium (D) plasma. <em>In-situ</em> ellipsometry in the 400–1000 nm range was coupled to <em>ex-situ</em> diagnostics, such as X-ray photoelectron spectroscopy (XPS) and focused ion beam coupled to scanning electron microscopy (FIB-SEM), to probe the evolution of chemical and morphological properties of the W oxides. First, a 70 nm thick <span><math><mrow><mi>W</mi><msub><mrow><mi>O</mi></mrow><mrow><mn>3</mn></mrow></msub></mrow></math></span> layer was exposed to D plasma at a surface temperature of 650 K. An important reduction of the oxide layer was observed by FIB-SEM, and <em>in-situ</em> ellipsometry showed the evolution of the optical constants n and k of the oxide towards the ones of pure W metal. Secondly, a 300 nm thick <span><math><mrow><mi>W</mi><msub><mrow><mi>O</mi></mrow><mrow><mn>3</mn></mrow></msub></mrow></math></span> layer was exposed to D plasma at a surface temperature below 373 K. In order to follow the oxide evolution step by step, we alternated <em>in-situ</em> ellipsometry and XPS surface characterization. A quite similar evolution of the optical constants was observed, in particular an increase of the extinction coefficient k in the near infrared, which was linked to a progressive reduction of the oxidation level at the surface, as seen by XPS. Interestingly, the reduction of the oxide at 373 K was below the resolution of the FIB-SEM. This observation indicates that ellipsometry in the 400–1000 nm range is able to follow <em>in-situ</em> the reduction of <span><math><mrow><mi>W</mi><msub><mrow><mi>O</mi></mrow><mrow><mn>3</mn></mrow></msub></mrow></math></span> oxides by D plasma with high surface sensitivity.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101751"},"PeriodicalIF":2.3,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-04DOI: 10.1016/j.nme.2024.101754
Hongxin Ding , Jin Guo , Shifeng Mao , Xinglei Ruan , Yuchen Xu , Minyou Ye
The core tungsten (W) concentration must be limited to an extremely low level for future fusion reactors. It was found that the effects of E × B drift can lead to a dramatic increase in the core W concentration in our recent work [J. Guo et al., Nucl. Fusion 63 (2023) 126033], in which the simulation study is performed for the divertor geometry with both inner and outer vertical targets. In this work, the influence of the outer target geometry is further investigated by numerical simulations under the direction of toroidal field BT favorable for H-mode access based on a typical EAST upper single-null configuration with two different outer target geometries, i.e. horizontal target (HT) and vertical target (VT). The background plasmas are simulated using SOLPS-ITER, and the W transport is simulated separately using DIVIMP. For the HT case, it is found that detachment in the outer divertor is promoted relative to the VT case, which leads to the suppression of W sputtering flux from the outer target. In contrast, the W sputtering flux from the outer target dominates for the VT case. The plasma profiles are similar for both cases at the inner vertical target, where detachment is achieved due to the drift effects under favorable BT except for the region near the inner strike point. Because the plasma detaches across most of the inner and outer target, the upstream W flux is significantly reduced for the HT case, and the core W concentration is about 2 orders of magnitude lower compared to the VT case. According to the analysis of the W transport for the HT case, two leakage pathways through the inner and outer scrap-off layer near the separatrix are indicated for the W impurities sputtered near the inner strike point.
对于未来的聚变反应堆，堆芯钨（W）浓度必须限制在极低水平。在我们最近的工作[J. Guo 等，Nucl. Fusion 63 (2023) 126033]中发现，E × B 漂移的影响会导致堆芯钨浓度急剧增加。在这项工作中，基于典型的 EAST 上部单空配置和两种不同的外靶几何形状，即水平靶（HT）和垂直靶（VT），通过数值模拟进一步研究了在有利于 H 模式接入的环形场 BT 方向下外靶几何形状的影响。使用 SOLPS-ITER 模拟了背景等离子体，并使用 DIVIMP 分别模拟了 W 的传输。结果发现，在 HT 情况下，相对于 VT 情况，外侧分流器中的脱落得到了促进，从而抑制了外侧靶的 W 溅射通量。相反，在 VT 情况下，来自外靶的 W 溅射通量占主导地位。在内侧垂直靶上，两种情况下的等离子体剖面相似，除内侧撞击点附近区域外，在有利的 BT 条件下，由于漂移效应，等离子体都能脱离。由于等离子体脱离了内外靶的大部分区域，HT 情况下的上游 W 通量显著减少，核心 W 浓度比 VT 情况下低约 2 个数量级。根据 HT 情况下的 W 传输分析，在内侧撞击点附近溅射的 W 杂质有两条通过分离矩阵附近内外废料层的泄漏途径。
{"title":"Simulation study of the influence of the outer target geometry on tungsten contamination: Horizontal vs. vertical target","authors":"Hongxin Ding , Jin Guo , Shifeng Mao , Xinglei Ruan , Yuchen Xu , Minyou Ye","doi":"10.1016/j.nme.2024.101754","DOIUrl":"10.1016/j.nme.2024.101754","url":null,"abstract":"<div><div>The core tungsten (W) concentration must be limited to an extremely low level for future fusion reactors. It was found that the effects of <em>E</em> × <em>B</em> drift can lead to a dramatic increase in the core W concentration in our recent work [J. Guo et al., Nucl. Fusion 63 (2023) 126033], in which the simulation study is performed for the divertor geometry with both inner and outer vertical targets. In this work, the influence of the outer target geometry is further investigated by numerical simulations under the direction of toroidal field <em>B</em><sub>T</sub> favorable for H-mode access based on a typical EAST upper single-null configuration with two different outer target geometries, i.e. horizontal target (HT) and vertical target (VT). The background plasmas are simulated using SOLPS-ITER, and the W transport is simulated separately using DIVIMP. For the HT case, it is found that detachment in the outer divertor is promoted relative to the VT case, which leads to the suppression of W sputtering flux from the outer target. In contrast, the W sputtering flux from the outer target dominates for the VT case. The plasma profiles are similar for both cases at the inner vertical target, where detachment is achieved due to the drift effects under favorable <em>B</em><sub>T</sub> except for the region near the inner strike point. Because the plasma detaches across most of the inner and outer target, the upstream W flux is significantly reduced for the HT case, and the core W concentration is about 2 orders of magnitude lower compared to the VT case. According to the analysis of the W transport for the HT case, two leakage pathways through the inner and outer scrap-off layer near the separatrix are indicated for the W impurities sputtered near the inner strike point.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101754"},"PeriodicalIF":2.3,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-02DOI: 10.1016/j.nme.2024.101750
M. Scotto d’Abusco , I. Kudashev , G. Giorgiani , A. Glasser-Medvedeva , F. Schwander , E. Serre , J. Bucalossi , H. Bufferand , G. Ciraolo , P. Tamain
This work explores the Limiter–Divertor transition (L–D) during the current ramp-up of ITER’s Q = 10 baseline plasma scenario at various central line-integrated density values. The analysis, based on transport simulations performed with the latest version of SoleEdge-HDG, focuses on the time evolution of heat and ion particle fluxes, revealing regions of elevated temperature on the inner wall and plasma-facing components (PFCs) despite moderate loads. The investigation also delves into the effects of perpendicular convection flux terms on density build-up, comparing different formulations and their interplay with auxiliary heating sources. Furthermore, the paper shows the impact of taking into account the evolution of the parallel neutral momentum on plasma and neutral density at the targets in the context of an ITER steady-state scenario.
{"title":"First integrated core-edge fluid simulation of ITER’s Limiter–Divertor transition with SolEdge-HDG","authors":"M. Scotto d’Abusco , I. Kudashev , G. Giorgiani , A. Glasser-Medvedeva , F. Schwander , E. Serre , J. Bucalossi , H. Bufferand , G. Ciraolo , P. Tamain","doi":"10.1016/j.nme.2024.101750","DOIUrl":"10.1016/j.nme.2024.101750","url":null,"abstract":"<div><div>This work explores the Limiter–Divertor transition (L–D) during the current ramp-up of ITER’s Q = 10 baseline plasma scenario at various central line-integrated density <span><math><msub><mrow><mi>n</mi></mrow><mrow><mi>l</mi><mi>i</mi></mrow></msub></math></span> values. The analysis, based on transport simulations performed with the latest version of SoleEdge-HDG, focuses on the time evolution of heat and ion particle fluxes, revealing regions of elevated temperature on the inner wall and plasma-facing components (PFCs) despite moderate loads. The investigation also delves into the effects of perpendicular convection flux terms on density build-up, comparing different formulations and their interplay with auxiliary heating sources. Furthermore, the paper shows the impact of taking into account the evolution of the parallel neutral momentum on plasma and neutral density at the targets in the context of an ITER steady-state scenario.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101750"},"PeriodicalIF":2.3,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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