The behavior of neutral deuterium (D) atoms is important for understanding the physics in the divertor region of nuclear fusion reactors. It is necessary to introduce an active measurement when considering the application to detached plasmas, where recombination processes dominate the processes determining the population distribution. In this work, we have developed a two-photon absorption laser-induced fluorescence (TALIF) system in the toroidal divertor simulator NAGDIS-T to measure D atomic density. The absolute D atomic density was obtained by calibrating the signal with the krypton TALIF signal. The gas pressure and power dependence of the D atomic density is shown. The D atomic density was in the range of 1.6 × 1018–1.4 × 1019 m−3, and the temperature was estimated to be 0.4 . The behavior of the D atoms is discussed in terms of the production process.
{"title":"TALIF measurements of atomic deuterium in toroidal divertor simulator NAGDIS-T","authors":"Shin Kajita , Kota Hiraiwa , Hirohiko Tanaka , Ryuki Iwai , Mitsutoshi Aramaki , Ryo Yasuhara , Noriyasu Ohno","doi":"10.1016/j.nme.2025.101898","DOIUrl":"10.1016/j.nme.2025.101898","url":null,"abstract":"<div><div>The behavior of neutral deuterium (D) atoms is important for understanding the physics in the divertor region of nuclear fusion reactors. It is necessary to introduce an active measurement when considering the application to detached plasmas, where recombination processes dominate the processes determining the population distribution. In this work, we have developed a two-photon absorption laser-induced fluorescence (TALIF) system in the toroidal divertor simulator NAGDIS-T to measure D atomic density. The absolute D atomic density was obtained by calibrating the signal with the krypton TALIF signal. The gas pressure and power dependence of the D atomic density is shown. The D atomic density was in the range of 1.6 × 10<sup>18</sup>–1.4 × 10<sup>19</sup> m<sup>−3</sup>, and the temperature was estimated to be <span><math><mo><</mo></math></span>0.4 <span><math><mi>eV</mi></math></span>. The behavior of the D atoms is discussed in terms of the production process.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"42 ","pages":"Article 101898"},"PeriodicalIF":2.3,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430285","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 : 2025-02-13DOI: 10.1016/j.nme.2025.101903
D.M. Thomas , T. Abrams , R. Ding , D. Donovan , F. Effenberg , J. Herfindal , A. Hyatt , A.W. Leonard , X. Ma , R. Maurizio , A.G. McLean , C. Murphy , J. Ren , M.W. Shafer , D. Truong , H.Q. Wang , J.G. Watkins , J.H. Yu
Recent DIII-D experiments on Small Angle Slot (SAS) divertors have confirmed that a combination of divertor closure and target shaping can enhance cooling across the divertor target and increase energy dissipation, but with significant dependence on BT (toroidal magnetic field) direction. In these novel divertors, the roles of closure, target shaping, drifts, and scale lengths are all interconnected in optimizing dissipation, with the separatrix electron density neSEP being the key parameter associated with the level of dissipation/detachment. After modifying the original flat-targeted graphite SAS to include a V shape with a tungsten coating on the outer side of the divertor (SAS-VW), matched series of discharges were run to compare to detailed SOLPS-ITER modeling. Experimentally, when run as designed with the outer strike point at the slot vertex, SAS-VW requires nearly identical neSEP for detachment as the original SAS, with little difference in dissipation for the new geometry. This is in contrast to (1) earlier modeling predictions that a small change of the SAS geometry to a V shape should enhance dissipation at the same neSEP for magnetic configurations having better H-mode access (ion B × ∇B drift directed into the divertor), and (2) despite the achievement of significantly higher (2-7x) neutral pressures and compression in the SAS-VW slot. Comparisons of experimental density scans to the most recent SOLPS-ITER modeling with ExB drifts show reasonable agreement for dissipation/detachment onset when using separatrix density as the independent parameter. In order to help understand the discrepancy in modeled vs actual performance for the new configuration, additional measurements varying gas injection location and impurity injection were undertaken. In-slot D2 gas fueling is more effective (5–22 %) in promoting detachment, in accord with modeling. In-slot impurity injection (N2 or Ne) can yield 30 % lower core Zeff and 15 % less confinement degradation after detachment compared to main chamber puffing, as well as relatively lower tungsten leakage from the divertor. Modeling can also reproduce the improved detachment seen as the strike point moves inboard of the slot vertex.
While we can explain the effects of the most important parameters causing energy dissipation in these slot divertors, it remains that many aspects of their behavior cannot be accurately modeled using state-of-art codes such as SOLPS-ITER. This is of concern for future model-driven designs utilizing similar V-shaped geometries.
{"title":"Experiment-modeling studies comparing energy dissipation in the DIII-D SAS and SAS-VW divertors","authors":"D.M. Thomas , T. Abrams , R. Ding , D. Donovan , F. Effenberg , J. Herfindal , A. Hyatt , A.W. Leonard , X. Ma , R. Maurizio , A.G. McLean , C. Murphy , J. Ren , M.W. Shafer , D. Truong , H.Q. Wang , J.G. Watkins , J.H. Yu","doi":"10.1016/j.nme.2025.101903","DOIUrl":"10.1016/j.nme.2025.101903","url":null,"abstract":"<div><div>Recent DIII-D experiments on Small Angle Slot (SAS) divertors have confirmed that a combination of divertor closure and target shaping can enhance cooling across the divertor target and increase energy dissipation, but with significant dependence on B<sub>T</sub> (toroidal magnetic field) direction. In these novel divertors, the roles of closure, target shaping, drifts, and scale lengths are all interconnected in optimizing dissipation, with the separatrix electron density n<sub>eSEP</sub> being the key parameter associated with the level of dissipation/detachment. After modifying the original flat-targeted graphite SAS to include a V shape with a tungsten coating on the outer side of the divertor (SAS-VW), matched series of discharges were run to compare to detailed SOLPS-ITER modeling. Experimentally, when run as designed with the outer strike point at the slot vertex, SAS-VW requires nearly identical n<sub>eSEP</sub> for detachment as the original SAS, with little difference in dissipation for the new geometry. This is in contrast to (1) earlier modeling predictions that a small change of the SAS geometry to a V shape should enhance dissipation at the same n<sub>eSEP</sub> for magnetic configurations having better H-mode access (ion B × ∇B drift directed into the divertor), and (2) despite the achievement of significantly higher (2-7x) neutral pressures and compression in the SAS-VW slot. Comparisons of experimental density scans to the most recent SOLPS-ITER modeling with ExB drifts show reasonable agreement for dissipation/detachment onset when using separatrix density as the independent parameter. In order to help understand the discrepancy in modeled vs actual performance for the new configuration, additional measurements varying gas injection location and impurity injection were undertaken. In-slot D<sub>2</sub> gas fueling is more effective (5–22 %) in promoting detachment, in accord with modeling. In-slot impurity injection (N<sub>2</sub> or Ne) can yield 30 % lower core Z<sub>eff</sub> and 15 % less confinement degradation after detachment compared to main chamber puffing, as well as relatively lower tungsten leakage from the divertor. Modeling can also reproduce the improved detachment seen as the strike point moves inboard of the slot vertex.</div><div>While we can explain the effects of the most important parameters causing energy dissipation in these slot divertors, it remains that many aspects of their behavior cannot be accurately modeled using state-of-art codes such as SOLPS-ITER. This is of concern for future model-driven designs utilizing similar V-shaped geometries.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"42 ","pages":"Article 101903"},"PeriodicalIF":2.3,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143436679","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 : 2025-02-13DOI: 10.1016/j.nme.2025.101902
Yan Lyu , Dongye Zhao , Xue Bai , Cong Li , Chengming Wang , Chengzhi Cao , Yi Hu , Wei Qian , Huace Wu , Ding Wu , Laizhong Cai , Hongbin Ding
The retention of hydrogen isotopes in the fusion device is critical due to safety concerns. In this work, the deuterium (D) and helium (He) retention features in the different marked tiles exposed to HL-2A tokamak discharge plasma were quantitatively characterized using long pulse laser induced desorption-quadrupole mass spectrometer (LID-QMS) combined with SEM and EDX. The D retention originates primarily from D plasma discharges of HL-2A during 2021 campaign, and the He retention comes primarily from the helium glow discharge cleaning (He-GDC). The marked tiles materials include pure bulk W, bulk stainless steel (S.S) and W-, C-, Fe-films deposited on titanium-zirconium-molybdenum alloy (TZM) or W substrates. The LID-QMS results indicate that the D and He retention distribution along the poloidal direction of HL-2A device exhibited an overall uniformity. The sequence of the D concentration trapped in the marked tiles is C-film > W-film > Fe-film/bulk S.S > bulk W, whereas the He retention is Fe-film > bulk S.S > W-film > bulk W > C-film. The D retention is higher than the He retention in all measured materials. And the D and He trapped in the film tiles are higher than those in bulk tiles. The probable reasons for the differences were discussed in combination with the changes of the surface micro-morphology and the elemental compositions of the marked tiles. This investigation would provide a reference for future in-situ application of LID-QMS to monitor the D and He retention in bulk tiles and deposited materials, and also gives the data support for fuel particle transport modelling.
{"title":"Quantitative characterization of deuterium and helium retention in the marked tiles with various materials exposed to HL-2A tokamak","authors":"Yan Lyu , Dongye Zhao , Xue Bai , Cong Li , Chengming Wang , Chengzhi Cao , Yi Hu , Wei Qian , Huace Wu , Ding Wu , Laizhong Cai , Hongbin Ding","doi":"10.1016/j.nme.2025.101902","DOIUrl":"10.1016/j.nme.2025.101902","url":null,"abstract":"<div><div>The retention of hydrogen isotopes in the fusion device is critical due to safety concerns. In this work, the deuterium (D) and helium (He) retention features in the different marked tiles exposed to HL-2A tokamak discharge plasma were quantitatively characterized using long pulse laser induced desorption-quadrupole mass spectrometer (LID-QMS) combined with SEM and EDX. The D retention originates primarily from D plasma discharges of HL-2A during 2021 campaign, and the He retention comes primarily from the helium glow discharge cleaning (He-GDC). The marked tiles materials include pure bulk W, bulk stainless steel (S.S) and W-, C-, Fe-films deposited on titanium-zirconium-molybdenum alloy (TZM) or W substrates. The LID-QMS results indicate that the D and He retention distribution along the poloidal direction of HL-2A device exhibited an overall uniformity. The sequence of the D concentration trapped in the marked tiles is C-film > W-film > Fe-film/bulk S.S > bulk W, whereas the He retention is Fe-film > bulk S.S > W-film > bulk W > C-film. The D retention is higher than the He retention in all measured materials. And the D and He trapped in the film tiles are higher than those in bulk tiles. The probable reasons for the differences were discussed in combination with the changes of the surface micro-morphology and the elemental compositions of the marked tiles. This investigation would provide a reference for future <em>in-situ</em> application of LID-QMS to monitor the D and He retention in bulk tiles and deposited materials, and also gives the data support for fuel particle transport modelling.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"42 ","pages":"Article 101902"},"PeriodicalIF":2.3,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422085","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 : 2025-02-12DOI: 10.1016/j.nme.2025.101896
T. Eich , T. Body , M. Faitsch , O. Grover , M.A. Miller , P. Manz , T. Looby , A.Q. Kuang , A. Redl , M. Reinke , A.J. Creely , D. Battaglia , J. Hillesheim , M. Wigram , J.W. Hughes , ASDEX Upgrade team
Fusion power plants require ELM-free, detached operation to prevent divertor damage and erosion. The separatrix operational space (SepOS) is proposed as a tool for identifying access to the type-I ELM-free quasi-continuous exhaust regime. In this work, we recast the SepOS framework using simple parameters and present dedicated ASDEX Upgrade discharges to demonstrate how to interpret its results. Analyzing an extended ASDEX Upgrade database consisting of 6688 individual measurements, we show that SepOS accurately describes how the H-mode boundary varies with plasma current and magnetic field strength. We then introduce a normalized SepOS framework and LH minimum scaling and show that normalized H-Mode boundaries across multiple machines are nearly identical, suggesting that the normalized SepOS can be used to translate results between different machines. The LH minimum density predicted by SepOS is found to closely match an experimentally determined multi-machine scaling, which provides a further indirect validation of SepOS across multiple devices. Finally, we demonstrate how SepOS can be used predictively, identifying a viable type-I ELM free Quasi-Continuous-Exhaust (QCE) operational point for SPARC, at , and — a value solidly within the QCE operational space on ASDEX Upgrade. This demonstrates how SepOS provides a concise, intuitive method for scoping ELM-free operation on next-step devices.
{"title":"The separatrix operational space of next-step fusion experiments: From ASDEX Upgrade data to SPARC scenarios","authors":"T. Eich , T. Body , M. Faitsch , O. Grover , M.A. Miller , P. Manz , T. Looby , A.Q. Kuang , A. Redl , M. Reinke , A.J. Creely , D. Battaglia , J. Hillesheim , M. Wigram , J.W. Hughes , ASDEX Upgrade team","doi":"10.1016/j.nme.2025.101896","DOIUrl":"10.1016/j.nme.2025.101896","url":null,"abstract":"<div><div>Fusion power plants require ELM-free, detached operation to prevent divertor damage and erosion. The separatrix operational space (SepOS) is proposed as a tool for identifying access to the type-I ELM-free quasi-continuous exhaust regime. In this work, we recast the SepOS framework using simple parameters and present dedicated ASDEX Upgrade discharges to demonstrate how to interpret its results. Analyzing an extended ASDEX Upgrade database consisting of 6688 individual measurements, we show that SepOS accurately describes how the H-mode boundary varies with plasma current and magnetic field strength. We then introduce a normalized SepOS framework and LH minimum scaling and show that normalized H-Mode boundaries across multiple machines are nearly identical, suggesting that the normalized SepOS can be used to translate results between different machines. The LH minimum density predicted by SepOS is found to closely match an experimentally determined multi-machine scaling, which provides a further indirect validation of SepOS across multiple devices. Finally, we demonstrate how SepOS can be used predictively, identifying a viable type-I ELM free Quasi-Continuous-Exhaust (QCE) operational point for SPARC, at <span><math><mrow><msub><mrow><mi>n</mi></mrow><mrow><mi>e</mi><mo>,</mo><mi>s</mi><mi>e</mi><mi>p</mi></mrow></msub><mo>=</mo><mn>4</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>20</mn></mrow></msup><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup></mrow></math></span>, <span><math><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>e</mi><mo>,</mo><mi>s</mi><mi>e</mi><mi>p</mi></mrow></msub><mo>=</mo><mn>156</mn><mi>e</mi><mi>V</mi></mrow></math></span> and <span><math><mrow><msub><mrow><mi>α</mi></mrow><mrow><mi>t</mi></mrow></msub><mo>=</mo><mn>0</mn><mo>.</mo><mn>7</mn></mrow></math></span> — a value solidly within the QCE operational space on ASDEX Upgrade. This demonstrates how SepOS provides a concise, intuitive method for scoping ELM-free operation on next-step devices.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"42 ","pages":"Article 101896"},"PeriodicalIF":2.3,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143436680","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 : 2025-02-11DOI: 10.1016/j.nme.2025.101901
D. Moiraf , G. Ciraolo , N. Fedorczak , J. Morales , H. Bufferand , O. Février , J. Gunn , R. Nouailletas , J. Redaud , N. Rivals , P. Tamain , A. Gallo , J. Gaspar , A. Grosjean , P. Hennequin , S. Rienäcker , N. Varadarajan , L. Vermare , the WEST team
The WEST tokamak allows for high power steady-state plasma discharges in Lower Single-Null (LSN), Double-Null (DN) and Upper Single-Null (USN) configurations. In this contribution, first results from experimental L-mode DN discharges with 3.1 MW of additional heating in the WEST tokamak and associated modeling with the SOLEDGE-EIRENE code are presented. The goal is to investigate if the magnetic configuration could help to reduce the peak heat load on the targets, and how sensitive is the power sharing between the strike points to a change in magnetic equilibrium. This study, previously performed on other devices such as DIII-D, Alcator C-mod and MAST-U, provide new data for machines with a compact divertor configuration and tungsten walls. During the experiment, the distance between the two separatrices at the outer midplane dRsep was scanned from –32 mm (USN) to 42 mm (LSN), with the ion Bx∇B drift directed towards the lower divertor. The measured power fall off length mapped at the outer midplane can vary between configurations but is centered around λq = 15.6 ± 2.4 mm. In the DN configuration, Langmuir probes measurements have shown that 86 % of the power is directed towards the outer strike points. This inner/outer imbalance is consistent with the ones measured on DIII-D, Alcator C-mod and MAST-U. The influence of ballooned radial transport, that drives most of the power towards the low field side, has been reproduced in transport simulation with imposed poloidally ballooned cross-field transport. The peak heat flux measured on all strike points is reduced by half in DN compared to LSN configuration. In certain conditions of high radiations (Ohmic discharges or with ICRH), the DN configuration can trigger a MARFE on the High-Field Side (HFS) that moves in opposition to the oscillations of the plasma vertical position. This MARFE has been measured to account for 0.3 % of the particles in the plasma. Temperature and density of the core plasma are unaffected by its presence.
{"title":"Heat and particle exhaust in double-null configuration in WEST: Experimental study and modeling with SOLEDGE-EIRENE","authors":"D. Moiraf , G. Ciraolo , N. Fedorczak , J. Morales , H. Bufferand , O. Février , J. Gunn , R. Nouailletas , J. Redaud , N. Rivals , P. Tamain , A. Gallo , J. Gaspar , A. Grosjean , P. Hennequin , S. Rienäcker , N. Varadarajan , L. Vermare , the WEST team","doi":"10.1016/j.nme.2025.101901","DOIUrl":"10.1016/j.nme.2025.101901","url":null,"abstract":"<div><div>The WEST tokamak allows for high power steady-state plasma discharges in Lower Single-Null (LSN), Double-Null (DN) and Upper Single-Null (USN) configurations. In this contribution, first results from experimental L-mode DN discharges with 3.1 MW of additional heating in the WEST tokamak and associated modeling with the SOLEDGE-EIRENE code are presented. The goal is to investigate if the magnetic configuration could help to reduce the peak heat load on the targets, and how sensitive is the power sharing between the strike points to a change in magnetic equilibrium. This study, previously performed on other devices such as DIII-D, Alcator C-mod and MAST-U, provide new data for machines with a compact divertor configuration and tungsten walls. During the experiment, the distance between the two separatrices at the outer midplane dR<sub>sep</sub> was scanned from –32 mm (USN) to 42 mm (LSN), with the ion Bx∇B drift directed towards the lower divertor. The measured power fall off length mapped at the outer midplane can vary between configurations but is centered around λ<sub>q</sub> = 15.6 ± 2.4 mm. In the DN configuration, Langmuir probes measurements have shown that 86 % of the power is directed towards the outer strike points. This inner/outer imbalance is consistent with the ones measured on DIII-D, Alcator C-mod and MAST-U. The influence of ballooned radial transport, that drives most of the power towards the low field side, has been reproduced in transport simulation with imposed poloidally ballooned cross-field transport. The peak heat flux measured on all strike points is reduced by half in DN compared to LSN configuration. In certain conditions of high radiations (Ohmic discharges or with ICRH), the DN configuration can trigger a MARFE on the High-Field Side (HFS) that moves in opposition to the oscillations of the plasma vertical position. This MARFE has been measured to account for 0.3 % of the particles in the plasma. Temperature and density of the core plasma are unaffected by its presence.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"42 ","pages":"Article 101901"},"PeriodicalIF":2.3,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430284","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 : 2025-02-10DOI: 10.1016/j.nme.2025.101893
Vesa-Pekka Rikala , M. Groth , A.G. Meigs , D. Reiter , B. Lomanowski , A. Shaw , S. Aleiferis , G. Corrigan , I.S. Carvalho , D. Harting , N. Horsten , I. Jepu , J. Karhunen , K.D. Lawson , C. Lowry , S. Menmuir , B. Thomas , D. Borodin , D. Douai , A. Huber
Spectroscopic measurements of the hydrogenic Balmer- and Balmer- line emission in JET-ILW low-confinement mode (L-mode) deuterium plasmas are used to assess the onset of volume recombination in the low-field side (LFS) divertor. The evolution of the EDGE2D-EIRENE predicted Balmer- to Balmer- emission ratio from low-recycling to detached conditions is in qualitative agreement with the measured ratio. In low-recycling conditions the EDGE2D-EIRENE predicted line-emission is within 30% of measured emission, in high-recycling within 20%t, and in detached conditions lower by a factor of 2.5.
{"title":"Characterization of detachment inferred from the Balmer line ratios in JET-ILW low-confinement mode plasmas","authors":"Vesa-Pekka Rikala , M. Groth , A.G. Meigs , D. Reiter , B. Lomanowski , A. Shaw , S. Aleiferis , G. Corrigan , I.S. Carvalho , D. Harting , N. Horsten , I. Jepu , J. Karhunen , K.D. Lawson , C. Lowry , S. Menmuir , B. Thomas , D. Borodin , D. Douai , A. Huber","doi":"10.1016/j.nme.2025.101893","DOIUrl":"10.1016/j.nme.2025.101893","url":null,"abstract":"<div><div>Spectroscopic measurements of the hydrogenic Balmer-<span><math><mi>α</mi></math></span> and Balmer-<span><math><mi>γ</mi></math></span> line emission in JET-ILW low-confinement mode (L-mode) deuterium plasmas are used to assess the onset of volume recombination in the low-field side (LFS) divertor. The evolution of the EDGE2D-EIRENE predicted Balmer-<span><math><mi>γ</mi></math></span> to Balmer-<span><math><mi>α</mi></math></span> emission ratio from low-recycling to detached conditions is in qualitative agreement with the measured ratio. In low-recycling conditions the EDGE2D-EIRENE predicted line-emission is within 30% of measured emission, in high-recycling within 20%t, and in detached conditions lower by a factor of 2.5.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"42 ","pages":"Article 101893"},"PeriodicalIF":2.3,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143388227","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 : 2025-02-10DOI: 10.1016/j.nme.2025.101895
Richard C. Bergmayr , Dirk Wünderlich , Mathias Groth , Liam H. Scarlett , Dmitry V. Fursa , Mark C. Zammit , Igor Bray , Ursel Fantz
EDGE2D-EIRENE profiles characteristic for low recycling, high recycling and detached plasmas are postprocessed applying a vibrationally resolved collisional radiative (CR) model based on the Yacora solver to predict excited state densities and thus the molecular Lyman-, Werner- and Fulcher band emission intensities. These emission intensities are compared to predictions from the AMJUEL database standardly used in EIRENE. Lower Fulcher band and higher Lyman- and Werner band emission is predicted by the Yacora model in comparison to AMJUEL suggesting that inconsistent results from model based evaluation of measured spectra are expected depending on which model and molecular emission band is considered. The implications on detachment rate predictions are discussed.
{"title":"Demonstrating the impact of ro-vibrationally excited H2 on divertor detachment via population modelling","authors":"Richard C. Bergmayr , Dirk Wünderlich , Mathias Groth , Liam H. Scarlett , Dmitry V. Fursa , Mark C. Zammit , Igor Bray , Ursel Fantz","doi":"10.1016/j.nme.2025.101895","DOIUrl":"10.1016/j.nme.2025.101895","url":null,"abstract":"<div><div>EDGE2D-EIRENE profiles characteristic for low recycling, high recycling and detached plasmas are postprocessed applying a vibrationally resolved collisional radiative (CR) model based on the Yacora solver to predict excited state densities and thus the molecular Lyman-, Werner- and Fulcher band emission intensities. These emission intensities are compared to predictions from the AMJUEL database standardly used in EIRENE. Lower Fulcher band and higher Lyman- and Werner band emission is predicted by the Yacora model in comparison to AMJUEL suggesting that inconsistent results from model based evaluation of measured spectra are expected depending on which model and molecular emission band is considered. The implications on detachment rate predictions are discussed.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"42 ","pages":"Article 101895"},"PeriodicalIF":2.3,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143388228","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 : 2025-02-06DOI: 10.1016/j.nme.2025.101897
Xin Zhang , Heng Li , Katsuyoshi Tsumori , Yuhong Xu , Mitsutaka Isobe , Guangjiu Lei , Sanqiu Liu , Masaki Osakabe , Haruhisa Nakano , Akihiro Shimizu , Shoichi Okamura , Kunihiro Ogawa , Hiromi Takahashi , Zilin Cui , Jun Hu , Yiqin Zhu , Xiaolong Li , Xiaoqiao Liu , Huaqing Zheng , Shaofei Geng , Changjian Tang
We conducted ab-initio molecular dynamics simulations to investigate the migration of hydrogen and impurities (oxygen or copper) and their impact on the work function of cesiated surfaces under different cesium coverages. To ensure temperature and energy stability, all simulations were divided into pre-equilibrium and equilibrium phases, with more rigorous computations performed on equilibrium configurations. Our findings indicate that as the cesium coverage increases, the effects of hydrogen and impurities on the work function gradually diminish. When the cesium coverage reaches 20/16 θ, the work function without hydrogen and impurities is approximately 2.07 eV, and the presence of hydrogen and impurities causes a work function change of less than 0.05 eV. Additionally, when hydrogen and oxygen impurities are bound to the Mo (001) substrate (deposited underneath the cesium layer), the range of electron redistribution induced by hydrogen and impurities is limited, terminating at 1.03 Å above the dense cesium layer. When the cesium layer thickness is greater than dense layer, the electronic density perturbations caused by hydrogen and impurities vanish. The dynamic simulation with hydrogen and impurities initially positioned above the cesium layer reveals that they quickly enter the disordered Cs phase but stabilizes at a specific height, without penetrating the dense cesium layer. Impurities close to the top of disordered Cs phase cause electronic density perturbations that cannot be fully screened in this case. Furthermore, hydrogen and impurities remaining bound to the Mo (001) substrate are more energetically stable. This is attributed to the electron-rich environment below the dense cesium layer, which is particularly advantageous for oxygen impurities with strong electronegativity.
{"title":"The influence of hydrogen and impurities on the work function of multilayer Cs atoms on the plasma grid: An ab-initio molecular dynamics study about negative hydrogen ion sources for neutral beam injection systems","authors":"Xin Zhang , Heng Li , Katsuyoshi Tsumori , Yuhong Xu , Mitsutaka Isobe , Guangjiu Lei , Sanqiu Liu , Masaki Osakabe , Haruhisa Nakano , Akihiro Shimizu , Shoichi Okamura , Kunihiro Ogawa , Hiromi Takahashi , Zilin Cui , Jun Hu , Yiqin Zhu , Xiaolong Li , Xiaoqiao Liu , Huaqing Zheng , Shaofei Geng , Changjian Tang","doi":"10.1016/j.nme.2025.101897","DOIUrl":"10.1016/j.nme.2025.101897","url":null,"abstract":"<div><div>We conducted ab-initio molecular dynamics simulations to investigate the migration of hydrogen and impurities (oxygen or copper) and their impact on the work function of cesiated surfaces under different cesium coverages. To ensure temperature and energy stability, all simulations were divided into pre-equilibrium and equilibrium phases, with more rigorous computations performed on equilibrium configurations. Our findings indicate that as the cesium coverage increases, the effects of hydrogen and impurities on the work function gradually diminish. When the cesium coverage reaches 20/16 <em>θ</em>, the work function without hydrogen and impurities is approximately 2.07 eV, and the presence of hydrogen and impurities causes a work function change of less than 0.05 eV. Additionally, when hydrogen and oxygen impurities are bound to the Mo (001) substrate (deposited underneath the cesium layer), the range of electron redistribution induced by hydrogen and impurities is limited, terminating at 1.03 Å above the dense cesium layer. When the cesium layer thickness is greater than dense layer, the electronic density perturbations caused by hydrogen and impurities vanish. The dynamic simulation with hydrogen and impurities initially positioned above the cesium layer reveals that they quickly enter the disordered Cs phase but stabilizes at a specific height, without penetrating the dense cesium layer. Impurities close to the top of disordered Cs phase cause electronic density perturbations that cannot be fully screened in this case. Furthermore, hydrogen and impurities remaining bound to the Mo (001) substrate are more energetically stable. This is attributed to the electron-rich environment below the dense cesium layer, which is particularly advantageous for oxygen impurities with strong electronegativity.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"42 ","pages":"Article 101897"},"PeriodicalIF":2.3,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143403348","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 : 2025-02-04DOI: 10.1016/j.nme.2025.101894
L. Corso , S. Curiotto , F. Cheynis , P. Muller , E. Bernard , M. Cabie , C. Martin , F. Leroy
Nuclear fusion, as a carbon-free energy source, is actively pursued by the international community. However, the irradiation by helium (He) of the walls facing the plasma can lead to important damages at the surface and deeper in the bulk, affecting the properties and life span of the materials. To address the effects of He irradiation, we have studied in real time, during He bombardment at 1273 K, the nucleation and growth of He bubbles nearby the surface of tungsten by grazing incidence small angle X-ray scattering (GISAXS). We could disentangle the surface and bubble contributions on the measured GISAXS patterns by adjusting the X-ray incident angle below and above the critical angle of total external reflection. The occurrence of tilted diffuse scattering rods proves the presence of facetted bubbles buried inside the tungsten matrix. The time evolution of the X-ray diffuse scattering has been used to evaluate the growth kinetics. A close comparison with analytical modelling of the growth process suggests a growth kinetics dominated by the migration-coalescence of bubbles during which the bubble motion is hindered by the nucleation of ledges at the bubble facet surface.
{"title":"Real-time helium bubble growth in tungsten by in-situ GISAXS","authors":"L. Corso , S. Curiotto , F. Cheynis , P. Muller , E. Bernard , M. Cabie , C. Martin , F. Leroy","doi":"10.1016/j.nme.2025.101894","DOIUrl":"10.1016/j.nme.2025.101894","url":null,"abstract":"<div><div>Nuclear fusion, as a carbon-free energy source, is actively pursued by the international community. However, the irradiation by helium (He) of the walls facing the plasma can lead to important damages at the surface and deeper in the bulk, affecting the properties and life span of the materials. To address the effects of He irradiation, we have studied in real time, during He bombardment at 1273 K, the nucleation and growth of He bubbles nearby the surface of tungsten by grazing incidence small angle X-ray scattering (GISAXS). We could disentangle the surface and bubble contributions on the measured GISAXS patterns by adjusting the X-ray incident angle below and above the critical angle of total external reflection. The occurrence of tilted diffuse scattering rods proves the presence of facetted bubbles buried inside the tungsten matrix. The time evolution of the X-ray diffuse scattering has been used to evaluate the growth kinetics. A close comparison with analytical modelling of the growth process suggests a growth kinetics dominated by the migration-coalescence of bubbles during which the bubble motion is hindered by the nucleation of ledges at the bubble facet surface.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"42 ","pages":"Article 101894"},"PeriodicalIF":2.3,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143372478","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 : 2025-02-03DOI: 10.1016/j.nme.2025.101886
N. Maaziz, F. Reimold, V.R. Winters, D. Bold, Y. Feng, V. Perseo, W7-X Team
The island divertor has been proposed for power and particle exhaust in stellarators. It is investigated in the Wendelstein 7-X (W7-X) experiment. The divertor capabilities such as particle exhaust or radiative power dissipation scale with the divertor density. However, significantly lower divertor density has been obtained in W7-X in comparison to tokamaks and no high-recycling scaling is observed. To alleviate the impact of the complicated geometry, a simplified geometry model for the island divertor in EMC3-EIRENE is developed and used to investigate the effect of the divertor target geometry. We show that compared to the open divertor, a closed divertor geometry leads to higher achievable densities and in particular a much stronger scaling of the target density with respect to the separatrix density.
{"title":"Investigating the role of divertor geometry on density build-up in the island divertor","authors":"N. Maaziz, F. Reimold, V.R. Winters, D. Bold, Y. Feng, V. Perseo, W7-X Team","doi":"10.1016/j.nme.2025.101886","DOIUrl":"10.1016/j.nme.2025.101886","url":null,"abstract":"<div><div>The island divertor has been proposed for power and particle exhaust in stellarators. It is investigated in the Wendelstein 7-X (W7-X) experiment. The divertor capabilities such as particle exhaust or radiative power dissipation scale with the divertor density. However, significantly lower divertor density has been obtained in W7-X in comparison to tokamaks and no high-recycling scaling is observed. To alleviate the impact of the complicated geometry, a simplified geometry model for the island divertor in EMC3-EIRENE is developed and used to investigate the effect of the divertor target geometry. We show that compared to the open divertor, a closed divertor geometry leads to higher achievable densities and in particular a much stronger scaling of the target density with respect to the separatrix density.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"42 ","pages":"Article 101886"},"PeriodicalIF":2.3,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143343832","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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