Nuclear Materials and Energy最新文献

{"title":"Density compensation with pellet fueling during ELM suppression with n = 4 RMP on metal-wall EAST tokamak","authors":"Jilei Hou ,&nbsp;Jie Zhang ,&nbsp;Kaibo Nan ,&nbsp;Liqing Xu ,&nbsp;Guizhong Zuo ,&nbsp;Manni Jia ,&nbsp;Haotian Qiu ,&nbsp;Guangle Lin ,&nbsp;Yifei Jin ,&nbsp;Jia Huang ,&nbsp;Kaixuan Ye ,&nbsp;Yue Chen ,&nbsp;Jiansheng Hu","doi":"10.1016/j.nme.2024.101749","DOIUrl":"10.1016/j.nme.2024.101749","url":null,"abstract":"<div><div>Pellet injection is the most promising fueling method to achieve a deep particle deposition for future fusion reactors. On metal-wall EAST tokamak, a full density compensation has been achieved by the pellet fueling during ELM suppression with n = 4 RMP which will be used in ITER’s operation. During the pellet injection, ELM suppression is terminated and small ELMs reappear. The plasma stored energy does not have a reduction with the pellet injection. Meanwhile, large sawtooth accompanied with RMP application is modified by the pellet injection. The amplitude of sawtooth crash decreases and high frequency small sawtooth crashes appear during the pellet fueling. The concentration of heavy impurities in the plasma core, such as tungsten and molybdenum, has an obvious reduction with the ELM reappearance and sawtooth modification. Although the same ELM behaviors also appears after divertor gas fueling, pellet fueling can modify the core plasma more significantly. All these experimental results will provide a good support to the ITER operation in the future.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101749"},"PeriodicalIF":2.3,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142356868","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}

{"title":"Experimental characterization of leading edge cracking on bulk tungsten divertor components during 2017–2019 WEST operation","authors":"M. Diez ,&nbsp;J. Demiane ,&nbsp;P. Reilhac ,&nbsp;D. Dorow-Gerspach ,&nbsp;M.Lemetais ,&nbsp;J. Gerardin ,&nbsp;J. Gaspar ,&nbsp;C. Martin ,&nbsp;A. Durif ,&nbsp;M. Wirtz ,&nbsp;T. Loewenhoff ,&nbsp;the WEST team","doi":"10.1016/j.nme.2024.101746","DOIUrl":"10.1016/j.nme.2024.101746","url":null,"abstract":"<div><div>During the 2017–2019 WEST operation, a set of ITER-like plasma-facing units consisting of tungsten monoblocks was installed on the lower divertor. Despite modest heating power, 27 % of these monoblocks had cracks on their poloidal leading edges, which were not protected by a toroidal bevel. A comprehensive experimental characterization of the 133 cracked monoblocks indicates that damage occurs near the plasma strike point areas where neat cracks separated by 0.15–0.5 mm in the poloidal direction were observed. Cracks are up to 1 mm long and 1 mm deep and did not affect the lower divertor ability to sustain long pulses. The most important parameter affecting crack formation is the relative vertical misalignment between components.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101746"},"PeriodicalIF":2.3,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142320369","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}

{"title":"Experimental study on metallic impurity behavior with boronization wall conditioning in EAST tokamak","authors":"Yunxin Cheng ,&nbsp;Ling Zhang ,&nbsp;Ailan Hu ,&nbsp;Shigeru Morita ,&nbsp;Wenmin Zhang ,&nbsp;Chengxi Zhou ,&nbsp;Darío Mitnik ,&nbsp;Fengling Zhang ,&nbsp;Jiuyang Ma ,&nbsp;Zhengwei Li ,&nbsp;Yiming Cao ,&nbsp;Haiqing Liu","doi":"10.1016/j.nme.2024.101744","DOIUrl":"10.1016/j.nme.2024.101744","url":null,"abstract":"<div><div>Operation of EAST tokamak with full metal wall without any wall conditioning are attempted in 2023 and 2024 experimental campaign to address the issues related to ITER tungsten wall operation. It is found that H-mode plasma could be sustained even with a substantial increase in metallic impurity content caused by strong plasma-wall interaction under uncoated metal wall. Boronization wall conditioning is therefore performed to improve the plasma performance with higher injected power. This study aims to quantitatively assess the impact of boronization wall conditioning on metallic impurity concentration and behavior in the EAST tokamak. It is then proved to be an effective wall conditioning approach for significantly controlling high-Z impurity content. In this work, the impurity spectra at extreme ultraviolet (EUV) wavelength range measured by sets of fast-time-response and space-resolved EUV spectrometers are widely used in the data analysis. The variation in the boron content in plasma after boronization are investigated by monitoring the 2nd order of B V line at 48.59 Å. It is found that the persistence time of boron in EAST device after a boronization with 10 g of carborane (C₂B₁₀H₁₂) is about 2000 s (∼150 shots) of discharge duration. The impact of different wall conditions (uncoated metal wall and boron coated wall) on metallic impurity content are then quantitatively studied. After boronization, the concentration of tungsten (<em>C</em>_W) and molybdenum (<em>C</em>_Mo) dropped by 85 %, e. g., from 2.0 × 10^-4 to 4.1 × 10^-5 and from 4.6 × 10^-5 to 6.3 × 10^-6, respectively. While the concentration of copper (<em>C</em>_Cu) and iron (<em>C</em>_Fe) decreased by approximately 50 % and 65 %, respectively, e. g., from 4.3 × 10^-5 to 2.1 × 10^-5 and from 2.0 × 10^-4 to 6.9 × 10^-5. A comparison of the line emission profiles from tungsten ions of W²⁶⁺ − W³²⁺ and W⁴³⁺ before and after boronization reveals an overall reduction in the intensity while without obvious change in the profile shape, which suggests a reduction in metallic impurities source after boronization instead of altering impurity transport in core plasma significantly.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101744"},"PeriodicalIF":2.3,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2352179124001674/pdfft?md5=6a2b133be0bfd2966e6d5ec516990d8f&pid=1-s2.0-S2352179124001674-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312276","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}

{"title":"Thermal and statistical analysis of the high-Z tungsten-based UFOs observed during the first deuterium high fluence campaign of the WEST tokamak","authors":"J. Gaspar ,&nbsp;Y. Anquetin ,&nbsp;Y. Corre ,&nbsp;X. Courtois ,&nbsp;M. Diez ,&nbsp;A. Ekedahl ,&nbsp;N. Fedorczak ,&nbsp;A. Gallo ,&nbsp;J-L. Gardarein ,&nbsp;J. Gerardin ,&nbsp;J. Gunn ,&nbsp;A. Grosjean ,&nbsp;K. Krieger ,&nbsp;T. Loarer ,&nbsp;P. Manas ,&nbsp;C. Martin ,&nbsp;P. Maget ,&nbsp;R. Mitteau ,&nbsp;P. Moreau ,&nbsp;F. Rigollet ,&nbsp;E. Tsitrone","doi":"10.1016/j.nme.2024.101745","DOIUrl":"10.1016/j.nme.2024.101745","url":null,"abstract":"<div><div>This paper summarizes the observations on the Unidentified Flying Object (UFO) observed during the first high fluence campaign performed in WEST. The campaign was characterized by high erosion and deposition rates, generating dusts and deposits prone to flaking during plasma operation. A total of 686 UFOs have been detected for 384 discharges executed, in which 133 UFOs lead to a disruption. These UFOs appear mostly during the low hybrid heating ramp-up early in the discharges. The mechanisms leading to a disruption is described as well as the delay available to react after the UFO entering in the plasma. The UFOs originate mostly from the high field side corresponding to the thick deposit area. These UFOs can be debris from a preceding disruption (≈27 %) or come from progressive loss of adherence of the thick deposits (≈55 %) under plasma cycling or more likely by disruption on this area. Finally, the thermal resistance of the poorly attached deposits has been calculated in the range from 2.10⁻⁴ °C m²/W to 1.10⁻³ °C m²/W coherent with previous observations in the high field side of the JET divertor.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101745"},"PeriodicalIF":2.3,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142320370","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}

{"title":"ICRF-specific W sources: Advances in minimization in ASDEX Upgrade and near-field based extrapolations to ITER with W-wall","authors":"V. Bobkov ,&nbsp;R. Bilato ,&nbsp;F. Calarco ,&nbsp;L. Colas ,&nbsp;R. Dux ,&nbsp;G. Grenfell ,&nbsp;W. Helou ,&nbsp;D. Milanesio ,&nbsp;R. Ochoukov ,&nbsp;F. Paulus ,&nbsp;Th. Pütterich ,&nbsp;G. Urbanczyk ,&nbsp;M. Usoltseva ,&nbsp;the ASDEX Upgrade Team","doi":"10.1016/j.nme.2024.101742","DOIUrl":"10.1016/j.nme.2024.101742","url":null,"abstract":"<div><div>Experimental data from the 2022 ASDEX Upgrade (AUG) helium (He) campaign reveals that a lower tungsten (W) content can be achieved during operation of the 3-strap antennas with the W-coated limiters. By fine-tuning of electrical feeding of the 3-strap antennas, the core W content was reduced by about a factor of 2 compared to that during operation of the 2-strap antennas with boron coated limiters at the same power and target plasma. This is in contrast to what is observed in deuterium (D) plasmas, where both types of antennas perform similarly in terms of the W release. A higher significance of remote W sources in He than in D is one plausible explanation.</div><div>Special AUG experiments in D plasmas, with a density in the SOL reduced to the level relevant for some of the predicted profiles for ITER, show similar characteristics of the near-fields and the sputtering even when the slow wave is propagative. Nevertheless, it is advised for ITER to tailor the SOL profiles by the foreseen local gas injection close to the antenna, to avoid the conditions when the lower hybrid resonance position is approximately aligned with the position the leading edges of the plasma facing components.</div><div>Based on near-field calculations for the AUG 3-strap and the ITER ICRF antennas using the HFSS code under the same conditions, the experimentally validated RF-sheath rectified voltages of the AUG 3-strap antenna were scaled to the ITER ICRF antenna. Using conservative assumptions, the estimations of the ICRF-specific W sources for ITER were then made for the D-T case with neon seeding. The extrapolation shows that by carefully choosing the electrical feeding, the increment of the W sputtering rate during ITER ICRF operation at up to 20 MW, can be kept (in the worst case) below 10 % of the total W wall rate without ICRF, as well as below 25 % of the W rate at the outboard wall without ICRF.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101742"},"PeriodicalIF":2.3,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142320371","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}

{"title":"Impurity behaviour in JET high-current baseline scenario for Deuterium, Tritium and Deuterium-Tritium plasmas","authors":"N. Wendler ,&nbsp;A. Chomiczewska ,&nbsp;W. Gromelski ,&nbsp;E. Kowalska-Strzęciwilk ,&nbsp;G. Telesca ,&nbsp;I. Ivanova–Stanik ,&nbsp;L. Garzotti ,&nbsp;D. Van Eester ,&nbsp;V.K. Zotta ,&nbsp;D. Frigione ,&nbsp;F. Rimini ,&nbsp;G. Pucella ,&nbsp;JET Contributors ,&nbsp;The Eurofusion Tokamak Exploitation Team","doi":"10.1016/j.nme.2024.101743","DOIUrl":"10.1016/j.nme.2024.101743","url":null,"abstract":"<div><div>To support future ITER operation, experimental campaigns at the Joint European Torus (JET) with an ITER-like wall (tungsten divertor and beryllium main chamber) in pure deuterium (D), tritium (T) and Deuterium-Tritium (D-T) were performed. One of the most important challenges in recent years was the development of two main scenarios that investigated different approaches to achieve the high fusion power as well as good plasma confinement (Garzotti et al., 2023). The first one, so-called baseline scenario is relying on high plasma current (I_p≈3.5 MA), normalized beta β_N &lt; 2 and safety factor q₉₅ ≈ 3 (Garzotti et al., 2023). On the other hand, the second one, so-called Hybrid scenario is operating at lower plasma current (flat-top I_p ≤ 2.6 MA) and density with respect to the baseline, higher normalized beta β_N &gt; 2 and safety factor q₉₅ ≈ 4.8 (Hobirk et al., 2023).</div><div>In this paper we focus on the impurity behaviour analysis for the baseline discharges at I_p = 3.5 MA and B_T = 3.3 T with D, T and DT plasmas, in which the gas and power waveform were optimized to achieve the best possible performance. In particular, we study the impact of total heating power (P_tot + P_alpha), flat-top gas flow and ELM (edge localized modes) frequency on mid-Z (Nickel (Ni), Copper (Cu)) and high-Z (Tungsten (W)) impurities. In addition, we compared the two best performing pulses of the baseline scenario (I_p = 3.5MA, B_T = 3.3 T and P_in ≈ 35 MW) in D and DT in order to identify the causes responsible for the increase in radiation during the DT pulse, which led to an early plasma termination. All presented results rely on the data collected by the VUV as well as the bolometry system. Detailed analysis indicates that in the baseline scenario, higher radiation, which is most likely due to the tungsten (W), is observed for T and DT plasmas in comparison to D. Moreover, for the two best performing baseline pulses, tomographic reconstructions show that the radiated power density is mainly emitted from the low field side (LFS) of the plasma and W does not accumulate in the plasma center (Telesca et al., 2024).</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101743"},"PeriodicalIF":2.3,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2352179124001662/pdfft?md5=c7133c51d229a5d47790bed3107001da&pid=1-s2.0-S2352179124001662-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312907","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}

{"title":"Wall conditions in WEST during operations with a new ITER grade, actively cooled divertor","authors":"A. Gallo ,&nbsp;Ph. Moreau ,&nbsp;D. Douai ,&nbsp;T. Alarcon ,&nbsp;K. Afonin ,&nbsp;V. Anzallo ,&nbsp;R. Bisson ,&nbsp;J. Bucalossi ,&nbsp;E. Caprin ,&nbsp;Y. Corre ,&nbsp;M. De Combarieu ,&nbsp;C. Desgranges ,&nbsp;P. Devynck ,&nbsp;A. Ekedahl ,&nbsp;N. Fedorczak ,&nbsp;J. Gaspar ,&nbsp;A. Grosjean ,&nbsp;C. Guillemaut ,&nbsp;R. Guirlet ,&nbsp;J.P. Gunn ,&nbsp;A. Widdowson","doi":"10.1016/j.nme.2024.101741","DOIUrl":"10.1016/j.nme.2024.101741","url":null,"abstract":"<div><div>Future fusion reactors like ITER and DEMO will have all-tungsten (W) walls and long pulses. These features will make wall conditioning more difficult than in most of the existing devices. The W Environment Steady-state Tokamak (WEST) is one of the few long pulse (364 s) fusion devices with actively cooled W plasma-facing components in the world. WEST is a unique test bed to study impurity migration and plasma density control via reactor relevant wall conditioning techniques. The phase II of WEST operations began in 2022, after the installation of a new lower divertor, now entirely equipped with actively cooled, ITER grade, W monoblocks. After pump down, we baked WEST between 90 °C and 170 °C for ∼2 weeks. After 82.5 h at 90 °C and 33 h at 170 °C, vacuum conditions were stable with a vessel pressure of 6x10^-5 Pa and mass spectra dominated by H₂ molecules. While at 170 °C, we performed ∼40 h of D₂ glow discharge cleaning (GDC) and ∼5 h of glow discharge boronization (GDB), using a 15 %-85 % B₂D₆-He mix and a total boron mass of ∼12 g. This was the very first GDB at such high temperature for WEST. The whole wall conditioning sequence led to a ∼10 times reduction of the H₂O signal as well as to a ∼3 times reduction of the O₂ signal, according to mass spectra. Once back to 70 °C, the vessel pressure was 5.5x10^-6 Pa and plasma restart was seamless with ∼30 s cumulated over the very first 5 pulses and an Ohmic radiated power fraction F_rad = 0.6, showing successful conditioning of the new ITER grade divertor. The effect of the first, ‘hot’ GDB faded with a characteristic cumulative injected energy of 2.45 GJ and saturation towards F_rad ∼0.8. After 1.4 h and 7.5 GJ of cumulative plasma time and injected energy, we carried out a second GDB, this time at 70 °C. This ‘cold’ GDB initially led to a much lower Ohmic F_rad = 0.3–0.4 but the effect lasted ∼7 times less, with a characteristic cumulative injected energy of 0.37 GJ. At the end of the campaign, we cumulated ∼3h and ∼30 GJ through repetitive, minute long pulses without any boronization. Throughout this 4-weeks-long experiment, F_rad in the 4 MW heating phase evolved only marginally (from 0.5 to 0.55). This increase is mostly due to the build-up of re/co-deposited layers on both lower divertor targets.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101741"},"PeriodicalIF":2.3,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2352179124001649/pdfft?md5=3912a6c3700db6f4c6469e71864a572c&pid=1-s2.0-S2352179124001649-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314194","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}

{"title":"The dominant roles of “electron-density-mechanism” and “chemical-bonding-mechanism” for hydrogen in molybdenum and lithium","authors":"Quan-Fu Han ,&nbsp;Zongru Li ,&nbsp;Keying Cheng ,&nbsp;Peng Shao ,&nbsp;Kun Jie Yang ,&nbsp;Yue-Lin Liu","doi":"10.1016/j.nme.2024.101739","DOIUrl":"10.1016/j.nme.2024.101739","url":null,"abstract":"<div><div>Using first-principles calculations, we have systematically studied structures and thermodynamic stability of interstitial H as well as the H-vacancy interaction in molybdenum (Mo) and lithium (Li). Single H atom prefers to occupy tetrahedral interstitial position (TIP) and octahedral interstitial position (OIP) in Mo and Li, respectively, and the solution energies are 0.87 eV and −0.66 eV, respectively. In Mo, mono-vacancy can capture as many as seven H atoms and each H atom prefers to bind onto an isosurface of valence electron density. However, H atoms detach from vacancy to occupy the OIPs outside vacancy in Li. Based on these results, we reveal that the electron-density-mechanism (EDM) and chemical-bonding-mechanism (CBM) cause different properties of H in Mo and Li, respectively. In Mo, since the valence electron density everywhere in interstitial lattice is much high, H atom has to search a place where the valence electron density must be suitable. Accordingly, vacancy can provide an optimal valence electron density region for H dissolution, and the optimal valence electron density is 0.10 electron/ų at vacancy. In Li, H atom exhibits the negative solution energy in the interstitial lattice, which promotes H atom to form ionic bond with neighboring Li atom. H atoms do not combine inside vacancy but stay at the OIPs outside vacancy to form ionic bonds with neighboring Li atoms. We believe that the EDM and CBM can be generalized to other transition metals and other alkali metals, respectively.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101739"},"PeriodicalIF":2.3,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142320368","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}

{"title":"Collisional-Radiative modeling of unresolved transition array spectra near 200AA from W17+-W25+ emissions for diagnostics of ITER edge plasma","authors":"R. Nishimura ,&nbsp;T. Oishi ,&nbsp;I. Murakami ,&nbsp;D. Kato ,&nbsp;H.A. Sakaue ,&nbsp;S. Gupta ,&nbsp;H. Ohashi ,&nbsp;M. Goto ,&nbsp;Y. Kawamoto ,&nbsp;T. Kawate ,&nbsp;H. Takahashi ,&nbsp;K. Tobita","doi":"10.1016/j.nme.2024.101740","DOIUrl":"10.1016/j.nme.2024.101740","url":null,"abstract":"<div><div>Tungsten (W) is one of the major impurities in ITER and future DEMO reactors. However,</div><div>diagnosing the ion density, temperature, and spatial distribution of tungsten ions in intermediate charge states, such as W⁸⁺-W²⁷⁺, is difficult because of the lack of spectral line data. In this study, we observed a tungsten Unresolved Transition Array (UTA) spectrum, which has a pseudo-continuum structure, around W²⁰⁺ in the Extreme Ultraviolet wavelength region in the Large Helical Device (LHD). We conducted Collisional-Radiative (CR) modeling for W¹⁷⁺-W²⁵⁺. Two pseudo-continuum peaks corresponding to 5 s-5p transition and transition between doubly excited states of 5 s²-5s5p, are strongly emitted around 200AA for each ion. The synthesized spectrum of W¹⁷⁺-W²⁵⁺ ions reproduced the observed LHD spectrum near 200AA. From the electron temperature dependence of the UTA spectral shape, the UTA shifted toward longer wavelength region with several pseudo-continuum peaks appearing for ions in lower charge states, with decreasing electron temperature from 0.4 keV to 0.2 keV. This result qualitatively explained the observed time evolution of the spectrum.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101740"},"PeriodicalIF":2.3,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2352179124001637/pdfft?md5=9685d3e603ad5cfce6a814c34eda0620&pid=1-s2.0-S2352179124001637-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314417","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}

{"title":"Normal high velocity solid dust impacts on tiles of tokamak-relevant temperature","authors":"Marco De Angeli ,&nbsp;Panagiotis Tolias ,&nbsp;Francisco Suzuki-Vidal ,&nbsp;Dario Ripamonti ,&nbsp;Tim Ringrose ,&nbsp;Hugo Doyle ,&nbsp;Giambattista Daminelli ,&nbsp;Jay Shadbolt ,&nbsp;Peter Jarvis ,&nbsp;Monica De Angeli","doi":"10.1016/j.nme.2024.101735","DOIUrl":"10.1016/j.nme.2024.101735","url":null,"abstract":"<div><p>Runaway electron incidence on plasma facing components triggers explosive events that are accompanied by the expulsion of fast solid debris. Subsequent dust-wall high speed impacts constitute a mechanism of wall damage and dust destruction. Empirical damage laws that can be employed for erosion estimates are based on room-temperature impact experiments. We use light-gas gun shooting systems to accelerate solid tungsten dust to near-supersonic speeds towards bulk tungsten targets that are maintained at different temperatures. This concerns targets cooled down to <span><math><mrow><mo>−</mo><mn>100</mn><mo>°</mo></mrow></math></span>C with liquid nitrogen and targets resistively heated up to 400 °C. Post-mortem surface analysis reveals that the three erosion regimes (plastic deformation, bonding, partial disintegration) weakly depend on the target temperature within the investigated range. It is concluded that empirical damage laws based on room-temperature measurements can be safely employed for predictions.</p></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101735"},"PeriodicalIF":2.3,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2352179124001583/pdfft?md5=8ebb6e275c20f595ab26057a8f70c27f&pid=1-s2.0-S2352179124001583-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142238085","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}