Nuclear Materials and Energy最新文献

{"title":"Compositionally-driven surface nanostructuring on refractory compositionally complex alloys under low energy helium bombardment","authors":"Shane Evans ,&nbsp;Justin Hamil ,&nbsp;Matthew J. Baldwin ,&nbsp;Daisuke Nishijima ,&nbsp;Marlene I. Patino ,&nbsp;Megan J. McCarthy ,&nbsp;Andrew B. Kustas ,&nbsp;Mary Alice Cusentino ,&nbsp;Eric Lang","doi":"10.1016/j.nme.2025.101946","DOIUrl":"10.1016/j.nme.2025.101946","url":null,"abstract":"<div><div>Additive manufacturing enables user-defined control of the compositional complexity, opening new design spaces for complex concentrated alloys (CCAs). Refractory CCAs may offer enhanced performance in the divertor region of a fusion reactor environment where plasma-facing materials will be subject to high temperatures, low energy He and D particles, and 14 MeV neutrons. In this work, specimens with the nominal composition of NbTaMoTi, NbTaMo, NbTaTi, and NbTa were fabricated via directed energy deposition (DED) then bombarded with 40 eV He ions to a fluence of 2x10²⁶ m⁻² at ∼ 1000 K. Post irradiation, the surface morphology and composition were examined with electron microscopy and x-ray photoelectron spectroscopy to offer information on the spatial distribution of surface nano-structuring. Sub-surface He bubbles driving the nano-structuring were examined with electron microscopy techniques. Analysis indicates the local composition directly influences the He bubble and tendril size, while the region with the highest complexity showed the shortest nano-structuring. Molecular Dynamics simulations complement the experimental results, showing comparable helium bubble growth and migration as a function of compositional complexity. This work demonstrates the compositional dependence of surface nanostructure formation of compositionally complex alloys, important for future design of complex plasma facing materials in fusion reactors.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"43 ","pages":"Article 101946"},"PeriodicalIF":2.3,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143924016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-speed camera observation of Hα, Hβ and Hγ associated with mutual neutralization and EIR in GAMMA 10/PDX divertor simulated plasma","authors":"S. Takahashi,&nbsp;N. Ezumi,&nbsp;T. Okamoto,&nbsp;K. Kono,&nbsp;H. Kawahara,&nbsp;T. Seto,&nbsp;R. Miyauchi,&nbsp;S. Togo,&nbsp;M. Hirata,&nbsp;J. Kohagura,&nbsp;M. Yoshikawa,&nbsp;Y. Nakashima,&nbsp;M. Sakamoto","doi":"10.1016/j.nme.2025.101945","DOIUrl":"10.1016/j.nme.2025.101945","url":null,"abstract":"<div><div>For the purpose of gaining a better understanding of detached plasma formation, the transition of the volumetric plasma recombination processes of the end-loss hydrogen plasma of a tandem-mirror, GAMMA 10/PDX, was investigated. In the Divertor Experimental Module (D-module) on the end cell, where the additional hydrogen gas is injected, the plasma flows into the V-shaped tungsten target plates. A 4-branch high-speed camera system was used to observe the 2D distributions of H_α, H_β and H_γ emission intensities simultaneously. As the neutral gas pressure (<em>p</em>_n) in the D-module increased, two distinct emission phases were observed. The first phase was characterized by an initial increase followed by a decrease in H_α emission, coinciding with a rollover of the electron density (<em>n</em>_e). This behavior is associated with the mutual neutralization of H⁺ and H^-, a process associated with molecular activated recombination (MAR). Further increase in <em>p</em>_n led to the second phase, during which a drastic increase in H_β and H_γ emissions alongside H_α was seen and the interferometer indicated a re-increase in <em>n</em>_e up to at least ∼ 4 × 10¹⁸ m⁻³, while the spectrometer observed an increase in Balmer emission intensities from higher excited states (n ≥ 5). The electron temperature (<em>T</em>_e) was estimated to be less than ∼ 0.1 eV using the Boltzmann plot method. These results suggest a shift in the dominant volumetric recombination mechanisms, with mutual neutralization of H₂⁺ and H^- becoming significant alongside electron–ion recombination (EIR), a process previously thought to be negligible in GAMMA 10/PDX.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"43 ","pages":"Article 101945"},"PeriodicalIF":2.3,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143941763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of thermal treatment at various temperatures on structure and radiation-induced effects in advanced ceramic breeder pebbles","authors":"A. Ansone ,&nbsp;A. Antuzevics ,&nbsp;L. Avotina ,&nbsp;E. Sprugis ,&nbsp;A. Trimdale-Deksne ,&nbsp;J.M. Leys ,&nbsp;R. Knitter ,&nbsp;A. Zarins","doi":"10.1016/j.nme.2025.101944","DOIUrl":"10.1016/j.nme.2025.101944","url":null,"abstract":"<div><div>Advanced ceramic breeder (ACB) pebbles consisting of 65 mol% lithium orthosilicate (Li₄SiO₄) and 35 mol% lithium metatitanate (Li₂TiO₃) are currently being developed as the European Union’s reference material for tritium breeding in future thermonuclear fusion reactors. In the present work, the influence of thermal treatment at various temperatures on structure and radiation-induced effects in the ACB pebbles is investigated. The produced ACB pebbles were thermally treated at selected temperatures between 500 and 1000 °C in different atmospheres (air, argon, and vacuum) and afterwards irradiated using X-rays with energies up to 45 keV. The formed and accumulated paramagnetic radiation-induced defect centres in the irradiated ACB pebbles before and after thermal treatment were analysed using electron paramagnetic resonance (EPR) spectroscopy. To determine the exact temperatures of the phase transitions and evaluate the influence of thermal treatment on the crystal structure, chemical bond vibrations, and microstructure of the ACB pebbles before irradiation, several other relevant physico-chemical analytical methods were applied: differential scanning calorimetry/thermogravimetry (DSC/TG), powder X-ray diffraction (PXRD) technique, attenuated total reflectance – Fourier transform infrared (ATR-FTIR) spectroscopy, and scanning electron microscopy (SEM). On the basis of the obtained results, it can be concluded that thermal treatment at temperatures higher than 700 °C influences the distribution of paramagnetic centres generated by exposure to X-rays. This is probably due to the second-order phase transition from “low-temperature” to “high-temperature” structure of the Li₄SiO₄ phase between 600 and 750 °C. The obtained results highlight the importance of considering the thermal treatment temperature of the produced ACB pebbles prior to irradiation when analysing these ceramic materials using EPR spectroscopy techniques.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"43 ","pages":"Article 101944"},"PeriodicalIF":2.3,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143891024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study of line spectra emitted by hydrogen isotopes in tokamaks through Deep-Learning algorithms","authors":"N. Saura,&nbsp;M. Koubiti,&nbsp;S. Benkadda","doi":"10.1016/j.nme.2025.101935","DOIUrl":"10.1016/j.nme.2025.101935","url":null,"abstract":"<div><div>Artificial Intelligence (AI) is increasingly used in various plasma physics topics, including applications in spectroscopy and diagnostics in magnetically confined fusion plasmas. The paper focuses on the application of the convolutional neural network (CNN) algorithm to emission spectroscopy from the divertor regions of magnetic fusion devices. Specifically, we use a CNN to determine hydrogen isotopic ratios from the theoretical emission spectra of the Balmer-α line in hydrogen–deuterium (HD) plasmas. The motivation for coupling AI with spectroscopy is to develop novel frameworks that can outperform existing classical methods based on spectral line fitting, in terms of accuracy, speed, or adaptability. In a previous work, we have used a fully connected neural network algorithm for theoretical Hα/Dα line spectra emitted by HD plasmas which have been generated for conditions relevant to divertor plasmas in tokamaks (magnetic field, neutral temperatures and fractions and hydrogen concentration). The generated spectra were preprocessed to extract few spectroscopic features which were then used as input data by the neural network. In the present work, we apply for the first time a CNN model to raw synthetic Hα/Dα line spectra theoretically emitted by HD plasmas to predict the corresponding isotopic ratios. In this context, we show that the trained CNN predicts hydrogen isotopic ratios with deviations of up to 5% from the true values. Additionally, our model can generalize its predictions to spectra corresponding to any observation angle relative to the magnetic field, despite being trained solely on spectra from parallel observations. The prediction accuracy in these cases is comparable to the training accuracy.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"43 ","pages":"Article 101935"},"PeriodicalIF":2.3,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143882139","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Balmer emission measurements in JET-ILW hydrogen, deuterium, tritium and deuterium-tritium low-confinement mode plasmas","authors":"A.G. Meigs ,&nbsp;M. Groth ,&nbsp;V.-P. Rikala ,&nbsp;B. Lomanowski ,&nbsp;N. Vianello ,&nbsp;M. Wischmeier ,&nbsp;the JET contributors","doi":"10.1016/j.nme.2025.101941","DOIUrl":"10.1016/j.nme.2025.101941","url":null,"abstract":"<div><div>Measurements of Balmer-alpha (B-α) and Balmer-gamma (B-γ), where B = H, D, or T isotopes of hydrogen, emission across the low-field side (LFS) divertor in JET ITER-like Wall (ILW), low-confinement mode (L-mode) plasma indicate that the divertor plasma was more strongly detached in deuterium, tritium and deuterium–tritium than in hydrogen plasmas. These measurements are consistent with the lower degree of detachment in hydrogen versus tritium plasmas inferred from Langmuir probes (Groth et al., 2023) [<span><span>1</span></span>]. The ratio of B-γ to B-α is a suitable indicator of high density/low temperature conditions because B-α emission is dominated by electron impact excitation with a small electron–ion recombination component regardless of electron temperature and density (for conditions in tokamak plasmas) whilst for B-γ the recombination component increases and the excitation component decreases as the electron temperature decreases and the electron density increases. Within the uncertainty of the measurements, the electron density at the low-field side separatrix and the power crossing the separatrix are similar to permit these comparisons. The B-©/B-α ratio is well correlated with the onset of detachment as measured by Langmuir probes (McCracken et al., 1998; Groth et al., 2023). The ratios of B-γ and B-α varied between 0.005 and 0.035 for low-recycling, high-recycling and partially detached conditions, and were 60–70 % higher in partially detached hydrogen than in tritium plasmas. In contrast, the difference between deuterium, tritium and 40–60 % deuterium–tritium is within 10 % and thus within the uncertainties of the measurements. Profiles of the B-α and B-γ emission was measured with two filtered CCDs connected to the visible lost light leg of JET’s mirror link spectroscopy system (Meigs et al., 2010; Lomanowski et al., 2014)[<span><span>4</span></span>,<span><span>5</span></span>]. Spatially (radial) narrower B-α profiles were measured with increasing isotope mass, while similarly broadened B-γ profiles were measured.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"43 ","pages":"Article 101941"},"PeriodicalIF":2.3,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143865093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microstructural characterization and low-cycle fatigue behavior of ODS steel prepared by precursor-assisted cast technology","authors":"Yanyun Zhao ,&nbsp;Boyang Zhang ,&nbsp;Yu Si ,&nbsp;Shiao Ding ,&nbsp;Qijing Sun ,&nbsp;Kunjie Yang ,&nbsp;Qiang Zhen ,&nbsp;Xiaodong Mao","doi":"10.1016/j.nme.2025.101933","DOIUrl":"10.1016/j.nme.2025.101933","url":null,"abstract":"<div><div>The microstructural evolution and cyclic deformation behavior of oxide dispersion-strengthened (ODS) steel fabricated by precursor-assisted cast technology (PACT) were systematically investigated through multi-scale characterization methods. Low-cycle fatigue tests were performed at 650 °C with total strain amplitudes ranging from ± 0.4 % to ± 1.0 % to investigate the deformation mechanisms and the stability of nano-oxides. The evolution of dislocation structures and nano-oxide distributions was characterized using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) at critical fatigue stages. Regions with a high oxide density exhibit enhanced resistance to cyclic softening, indicating a strong correlation between dislocation structure evolution and nano-oxide distribution. Fractographic examination using scanning electron microscopy (SEM) reveals transgranular crack propagation without failure initiation at inclusions, confirming the microstructural homogeneity achieved through PACT. This comprehensive characterization demonstrates that the PACT produces ODS steels with stable nano-oxide dispersions and improved resistance to cyclic deformation at elevated temperatures.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"43 ","pages":"Article 101933"},"PeriodicalIF":2.3,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143868546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The plasma-chemical mechanism of surface destruction of the diagnostic system components inside EAST vacuum vessel","authors":"L.G. Lobanova ,&nbsp;S. Wang ,&nbsp;H. Lian ,&nbsp;X. Cui ,&nbsp;J. Chen ,&nbsp;R. Yan ,&nbsp;L. Zhang ,&nbsp;V.P. Afanas’ev ,&nbsp;H. Liu","doi":"10.1016/j.nme.2025.101938","DOIUrl":"10.1016/j.nme.2025.101938","url":null,"abstract":"<div><div>The study investigates the causes of surface degradation of the retro reflectors, made of polycrystalline molybdenum, used in the optical diagnostic polarimeter/interferometer (POINT) system on the EAST tokamak. The component and depths profiling analysis of the retro reflectors surface was conducted based on the interpretation of X-ray photoelectron spectroscopy (XPS) energy spectra. The depths profiling analysis was performed using argon ion sputtering with an energy of 2 keV to a depth of 60 nm. On the uncleaned retro reflectors surface, the following was observed: the predominant presence of molybdenum trioxide (MoO₃), no presence of unoxidized molybdenum, and the presence of elements from constructional details, including C and B, Zn, Fe, Cu, Ca, Na with quantities not exceeding 1 %. It was established that the main cause of surface degradation of the retro reflectors and, consequently, the degradation of their reflective properties, is the active chemical oxidation of molybdenum during technical breaks and in the absence of plasma discharges, followed by the plasma-chemical removing of molybdenum oxides under plasma discharge conditions. The cyclic process of surface oxidation by water vapor and oxygen and subsequent removing of molybdenum oxides due to the heating and the interaction of the retro reflectors surface with plasma, leads to the formation of a well-developed morphology on the retro reflectors surface and, thus, to the reflectivity degradation. It is noted that similar processes occur with inner vacuum vessel materials, which consist of transition metals, such as W and Mo.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"43 ","pages":"Article 101938"},"PeriodicalIF":2.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143851675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gas puff imaging of plasma turbulence in the magnetic island scrape-off layer of W7-X","authors":"S.G. Baek ,&nbsp;S. Ballinger ,&nbsp;O. Grulke ,&nbsp;C. Killer ,&nbsp;A. von Stechow ,&nbsp;J.L. Terry ,&nbsp;F. Scharmer ,&nbsp;B. Shanahan","doi":"10.1016/j.nme.2025.101937","DOIUrl":"10.1016/j.nme.2025.101937","url":null,"abstract":"<div><div>The turbulence characteristics of the scrape-off-layer (SOL) plasma in the W7-X stellarator are investigated using a gas-puff-imaging (GPI) diagnostic, newly installed and operated during the OP 2.1 campaign. The SOL plasma on W7-X features a set of island divertors for heat and particle exhaust and provides a unique environment for studying SOL turbulence and transport. This paper focuses on the O-point region of the magnetic island divertor SOL in the standard magnetic configuration. Fourier and cross-correlation analyses show that turbulence flows are predominantly in the poloidal direction (i.e., direction tangent to the last closed flux surface) with significantly weaker radial motion. This suggests dominant ExB convection and suppressed filamentary transport compared to those observed in the far scrape-off-layer region of tokamaks, as further supported by high-resolution skewness and kurtosis data that show the absence of intermittent, bursty filamentary events. Additionally, a relationship between the radial profile of the connection length and the sheared poloidal flow structure is reported, suggesting a possible linkage among magnetic topology, turbulence dynamics, and turbulence generation.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"43 ","pages":"Article 101937"},"PeriodicalIF":2.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143874771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impurity study to assess N = 1D ICRF heating scenario in T-rich plasmas with D-beams during JET-ILW DT experimental campaigns","authors":"A. Chomiczewska ,&nbsp;W. Gromelski ,&nbsp;I. Ivanova-Stanik ,&nbsp;E. Kowalska-Strzęciwilk ,&nbsp;N. Wendler ,&nbsp;M. Maslov ,&nbsp;E. Lerche ,&nbsp;G. Pucella ,&nbsp;JET contributors ,&nbsp;the EUROfusion Tokamak Exploitation Team","doi":"10.1016/j.nme.2025.101936","DOIUrl":"10.1016/j.nme.2025.101936","url":null,"abstract":"<div><div>A JET D-T scenario with optimised non-thermal fusion has been developed and successfully demonstrated during the second JET deuterium–tritium campaign (DTE2) at JET-ILW [<span><span>1</span></span>]. By using fundamental deuterium (D) minority ICRF heating scenario (N = 1 D) and pure D-NBI heating in T-rich plasmas, an energy world record for the most fusion energy produced in a single fusion shot has been achieved, by generating 69 MJ of heat from fusion reactions. During scenario optimisation, a systematic study of impurity behaviour has been performed. The impurities were analysed using various diagnostic techniques, e.g. VUV, VIS spectroscopy, and bolometry. The influence of different factors, including the plasma parameters and the heating methods has been investigated. The high-power T-rich hybrid pulses with different D gas puff rates in the main heating phase were compared to determine the influence of the D/T ratio on impurity behaviour. It was found that the intrinsic impurity content and the radiated power increase with the D/T ratio. Additionally, discharges in T-rich plasmas were compared with hybrid-like pulses with 50/50 D/T plasma mixtures and different ICRF heating schemes. It was found that T-rich plasmas, in which the highest fusion power was achieved are characterised by the lowest impurity content and highest ELM frequency (f_ELM ∼ 80–100 Hz), which increases with the fuelling rate. In some cases, the duration of the high-performance phase in T-rich plasmas was limited by impurity accumulation in the plasma core. Experimental and theoretical investigation showed that the high-Z impurity accumulation is related to the impurity transport inside the plasma and not related to the impurity source.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"43 ","pages":"Article 101936"},"PeriodicalIF":2.3,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143847304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of nitrogen molecular breakup on divertor conditions in JET L-mode plasmas using SOLPS-ITER","authors":"R. Mäenpää ,&nbsp;H. Kumpulainen ,&nbsp;M. Groth ,&nbsp;N. Horsten ,&nbsp;D. Reiter ,&nbsp;J. Romazanov ,&nbsp;B. Lomanowski ,&nbsp;S. Brezinsek ,&nbsp;J. Karhunen ,&nbsp;K.D. Lawson ,&nbsp;A.G. Meigs ,&nbsp;S. Menmuir ,&nbsp;A. Shaw ,&nbsp;JET Contributors ,&nbsp;EUROfusion Tokamak Exploitation Team","doi":"10.1016/j.nme.2025.101929","DOIUrl":"10.1016/j.nme.2025.101929","url":null,"abstract":"<div><div>SOLPS-ITER simulations of nitrogen-seeded, low-confinement mode plasmas in the Joint European Torus (JET) predict that the electron temperature in the low-field side (LFS) divertor leg is reduced locally by up to an order of magnitude when nitrogen is assumed to recycle as molecules (N₂) instead of atoms using a fixed nitrogen injection rate. The LFS divertor temperature reduction under the assumption of molecular recycling occurs due to a three-step mechanism: (1) the plasma penetration of nitrogen atoms is increased due to the strong triple bond of the N₂ molecule and the kinetic energy release in the dissociation event, both mechanisms contributing equally, (2) the abundance of (particularly multiply-charged) nitrogen ions in the divertor is increased and (3) the electron temperature is reduced due to the increase in radiation (by up to a factor of 4) from nitrogen ions.</div><div>Setting the volume-integrated nitrogen radiated power to a constant value (0.6<!--> <!-->MW) instead of the nitrogen injection rate, SOLPS-ITER predicts under the molecular nitrogen recycling assumption that the peak line-integrated N II, N III and N IV intensities in the LFS divertor are approximately within 15%, 35% and 5%, respectively, of the reference atomic nitrogen recycling case. The predicted peak N II, N III and N IV intensities under either assumption are within 30%, 65% and 5%, respectively, of measurements using the vertically viewing mirror-link divertor spectrometer (Meigs et al., 2010) in nitrogen-seeded JET L-mode plasmas (Lomanowski et al., 2019). ERO2.0 simulations using a constant nitrogen seeding rate on static background plasma solutions from EDGE2D-EIRENE (previously presented in Mäenpää et al., (2022), revised here to include fast reflections) predict that N II to N IV line emission is increased by 20% to 30% when nitrogen is assumed to recycle as molecules, demonstrating the importance of considering the effect of molecular dissociation reactions on the divertor plasma in a self-consistent manner.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"43 ","pages":"Article 101929"},"PeriodicalIF":2.3,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143833444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}