Journal of Fusion Energy最新文献

{"title":"Polywell Revisited","authors":"Jaeyoung Park,&nbsp;Nicholas A. Krall,&nbsp;Giovanni Lapenta,&nbsp;Masayuki Ono","doi":"10.1007/s10894-026-00566-y","DOIUrl":"10.1007/s10894-026-00566-y","url":null,"abstract":"<div>\u0000 \u0000 <p>The Polywell fusion concept, originally proposed by Robert W. Bussard in 1985, has been investigated for over four decades as a potential solution for achieving net fusion energy in a compact and economically viable reactor. It combines two distinct approaches: high-beta magnetic cusp confinement of electrons using polyhedral coil configurations and electrostatic ion confinement via a potential well formed by injected electron beams. While the hybrid nature of the Polywell system offers advantages in plasma stability and engineering simplicity, previous efforts have been limited by persistent challenges in achieving sufficient plasma confinement required to generate a net energy gain. In this study, we examine previous works and identify limitations of several Polywell embodiments that have historically impeded progress. We present an updated Polywell physics model incorporating experimental findings and recent first-principles particle-in-cell simulations. This updated model outlines a credible path toward overcoming confinement losses and achieving net energy gain using deuterium-tritium (D-T) fuels. Our findings provide a renewed scientific basis for the continued development of the Polywell fusion concept as a practical and scalable approach to fusion energy.</p>\u0000 </div>","PeriodicalId":634,"journal":{"name":"Journal of Fusion Energy","volume":"45 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147561600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Challenge for Adiabatically Heated FRC Based D-(^3)He Fusion","authors":"Timothée Nicolas,&nbsp;Christophe Goupil,&nbsp;Eric Herbert,&nbsp;Justin Ball","doi":"10.1007/s10894-026-00565-z","DOIUrl":"10.1007/s10894-026-00565-z","url":null,"abstract":"<div>\u0000 \u0000 <p>The performance requirements of fusion reactors based on FRC adiabatic compression with a D-<span>(^3!)</span>He fuel are discussed. Assuming thermonuclear reaction rates, confinement times exceeding 10 ms are required for peak magnetic fields below 25 T. The typical thermodynamic cycle of such reactors in current/flux variables is computed. The fact that most magnetic energy is channeled to vacuum magnetic energy, instead of heating the plasma, translates into a very elongated thermodynamical cycle. The consequences for the viability of this type of reactors are discussed.</p>\u0000 </div>","PeriodicalId":634,"journal":{"name":"Journal of Fusion Energy","volume":"45 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10894-026-00565-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147561682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neutron Spectroscopy of Deuterium-deuterium Reactions in Neutral Beam-heated Plasmas on the Large Helical Device","authors":"Siriyaporn Sangaroon,&nbsp;Kunihiro Ogawa,&nbsp;Longyong Liao,&nbsp;Guoqiang Zhong,&nbsp;Mitsutaka Isobe","doi":"10.1007/s10894-026-00564-0","DOIUrl":"10.1007/s10894-026-00564-0","url":null,"abstract":"<div>\u0000 \u0000 <p>The compact neutron emission spectrometers (CNES) system has enabled detailed and comprehensive characterization of fast ion confinement during the neutral beam injection heating in the Large Helical Device (LHD). Using high resolution neutron spectroscopy along both tangential and perpendicular lines-of-sight, CNES provides direct experimental access to deuterium–deuterium (D–D) reaction dynamics in velocity space, reflecting the behavior of fast ions injected by neutral beam injections. Significant Doppler shifts in D-D neutron energy were observed during intense tangential neutral beam injection, revealing the impact of the relative motion of the D-D reaction center-of-mass (CoM) with respect to the CNES sightline. An upshift in neutron energy was detected when the CoM moved toward the sightline, while a downshift occurred when it move away from the sighline. In plasmas heated by perpendicular neutral beam injection, a distinct double-humped neutron energy spectrum was observed, corresponding to the Larmor motion of helically trapped beam ions within the LHD’s magnetic ripple structure. The results demonstrate the capability of CNES to detect Doppler shifts in neutron energy associated with the direction and confinement of fast ions. By comparing experimental results with numerical simulations, the study confirms the reliability of both tangential and perpendicular CNESs sightline configuration in D-D neutron emission spectroscopy in LHD. The results improve our understanding of how fast ions generated by neutral beam injection affect D-D reaction.</p>\u0000 </div>","PeriodicalId":634,"journal":{"name":"Journal of Fusion Energy","volume":"45 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10894-026-00564-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147441382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ultra-High Neutral Pressures in the Helical Divertor of the Large Helical Device","authors":"U. Wenzel,&nbsp;G. Motojima,&nbsp;S. Masuzaki,&nbsp;M. Kobayashi,&nbsp;M. Goto,&nbsp;B. Peterson,&nbsp;M. Shohji,&nbsp;M. Marquardt,&nbsp;V. Haak","doi":"10.1007/s10894-026-00563-1","DOIUrl":"10.1007/s10894-026-00563-1","url":null,"abstract":"<div>\u0000 \u0000 <p>In the Large Helical Device (LHD), plasma operation is possible with a helical divertor and inward-shifted configurations. For plasmas with a small distance between the divertor and the plasma, ultra-high neutral pressures of up to 2.4 Pa were measured in the helical divertor–ten times higher than theoretically predicted. This enables high particle exhaust rates, comparable to tokamaks such as ASDEX Upgrade and DIII-D, and is caused by a condensation instability near the divertor targets. Like a classical Marfe, it exhibits an asymmetric radiation pattern, but the new phenomenon is dominated by hydrogen radiation. We denote it as HYDRA, which stands for HYdrogen Dominated Radiation Asymmetry. The appearance of the HYDRA induces detachment of the divertor plasma, which, together with the ultra-high divertor neutral pressure, leads to a favorable divertor state for a fusion reactor based on the stellarator concept.</p>\u0000 </div>","PeriodicalId":634,"journal":{"name":"Journal of Fusion Energy","volume":"45 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10894-026-00563-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Progress in Long Pulse ECH Discharges in LHD","authors":"Yasuo Yoshimura,&nbsp;Hiroshi Kasahara,&nbsp;Shin Kubo,&nbsp;Takashi Shimozuma,&nbsp;Hiroe Igami,&nbsp;Hiromi Takahashi,&nbsp;Toru Tsujimura,&nbsp;Ryoma Yanai,&nbsp;Masaki Nishiura,&nbsp;Naoki Kenmochi,&nbsp;Sakuji Kobayashi,&nbsp;Satoshi Ito,&nbsp;Yoshinori Mizuno,&nbsp;Toshiki Takeuchi,&nbsp;Hidenori Takubo,&nbsp;Tsuyoshi Kariya,&nbsp;Takashi Mutoh","doi":"10.1007/s10894-026-00562-2","DOIUrl":"10.1007/s10894-026-00562-2","url":null,"abstract":"<div><p>This is a review paper as a part of the special issue dedicated for Large Helical Device (LHD). The topic of this paper is long pulse discharges performed by Electron Cyclotron Heating (ECH) in LHD, and it is described based on the previously published papers related to the topic. The ECH system on LHD has been upgraded step by step, applying state of the art gyrotrons at the steps. The first long pulse discharge was achieved by applying 84 GHz, 110 kW continuous wave gyrotron. The pulse width was 65 min, with rather low line average electron density <i>n</i>_{e_ave} of 0.15 × 10¹⁹ m^− 3 and the central electron temperature <i>T</i>_e0 of 1.7 keV. Gradually applied 5 gyrotrons (three 77 GHz and two 154 GHz) took the place of the power source for the long pulse ECH discharges. Owing to the improvement in the ECH system, a stable 39 min discharge with much improved parameters, <i>n</i>_{e_ave} of 1.1 × 10¹⁹ m^− 3, <i>T</i>_e0 of over 2.5 keV, and a central ion temperature <i>T</i>_i0 of 1.0 keV was successfully performed with ~ 350 kW ECH power. Also, long pulse experiments have made progress in sustainment of improved electron confinement states (e-ITB) at the plasma core region. Sustainment of a plasma having e-ITB with <i>n</i>_{e_ave} of 1.1 × 10¹⁹ m^− 3 and <i>T</i>_e0 of ∼3.5 keV for longer than 5 min with 340 kW ECH power was successfully demonstrated.</p></div>","PeriodicalId":634,"journal":{"name":"Journal of Fusion Energy","volume":"45 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147362755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anomaly Detection of Radiative Collapse in Impurity Seeding Experiment Using Imaging Bolometer and Autoencoder","authors":"Kiyofumi Mukai,&nbsp;Suguru Masuzaki,&nbsp;Byron J. Peterson,&nbsp;Masahiro Kobayashi,&nbsp;Gakushi Kawamura,&nbsp;Yuki Hayashi,&nbsp;Hirohiko Tanaka,&nbsp;Koyo Munechika","doi":"10.1007/s10894-026-00556-0","DOIUrl":"10.1007/s10894-026-00556-0","url":null,"abstract":"<div><p>Radiative collapse in neon (Ne) seeded plasmas has been detected using a two-dimensional radiation measurement (InfraRed imaging Video Bolometer, IRVB) and an AutoEncoder (AE) on the Large Helical Device (LHD). In divertor detachment for fusion reactors, while the divertor heat load is mitigated using impurity injection, excessive impurity injection induces radiative collapse. Therefore, it is important to detect the precursor of the radiative collapse for the control of the impurity injection amount to maintain stable divertor detachment. In this study, 1219 images measured with the IRVB were used for training. By using the AE model, in the discharges with moderate Ne pulses, radiative collapse was successfully detected as an increase of abnormality earlier than the Ne pulse just before the radiative collapse. Moreover, by investigating the anomalous radiation structure, it was found to remain at the edge plasma region when radiation increased without radiative collapse, whereas the anomalous radiation structure progressed toward the core plasma when radiative collapse occurred.</p></div>","PeriodicalId":634,"journal":{"name":"Journal of Fusion Energy","volume":"45 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10894-026-00556-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147340268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal Assessment of the DTT Bolometric Camera","authors":"V. D’Agostino,&nbsp;A. Belpane,&nbsp;E. Peluso,&nbsp;S. Palomba,&nbsp;A. Murari,&nbsp;L. Gabellieri,&nbsp;L. Senni,&nbsp;G. M. Apruzzese,&nbsp;M. Gelfusa","doi":"10.1007/s10894-026-00559-x","DOIUrl":"10.1007/s10894-026-00559-x","url":null,"abstract":"<div>\u0000 \u0000 <p>The Divertor Tokamak Test facility (DTT) is a fusion device under construction at the ENEA Research Centre in Frascati, Italy. DTT’s primary mission is to explore and test the physics and technology of concepts for the exhaust of the plasma thermal power, especially in the divertor region, in support to ITER and DEMO design. From this perspective, careful control of the total radiation emission will be essential for the operation of these next generation devices. This work focuses on the DTT bolometry system, which is currently in the design phase. Commercial foil bolometers have been selected to provide line-integrated measurements and enable tomographic reconstructions at this stage. The mechanical layout and integration into the machine have been defined, and the line-of-sights (LoS) configuration has been validated. However, preliminary thermo-mechanical analyses have revealed that the initial design did not fully meet all specifications. To address this, an actively cooled protective housing has been included to withstand the high thermal loads from the plasma, approximately 0.5 MW/m² for about 100 s in DTT. In this study, the equatorial bolometric camera simulations have been further refined, and the protective housing has been designed and fully integrated in the diagnostic port. A parametric thermal analysis has been performed, and the final design has been validated through finite elements simulations.</p>\u0000 </div>","PeriodicalId":634,"journal":{"name":"Journal of Fusion Energy","volume":"45 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10894-026-00559-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147339948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study of High Energy Ions Generated by Ion Cyclotron Range of Frequency Heating in Deuterium Plasma","authors":"Ryosuke Seki,&nbsp;Tetsuo Seki,&nbsp;Shuji Kamio,&nbsp;Hiroshi Kasahara,&nbsp;Kenji Saito,&nbsp;Hideo Nuga,&nbsp;Kunihiro Ogawa,&nbsp;Mitsutaka Isobe,&nbsp;Jialei Wang,&nbsp;Gorou Nomura,&nbsp;Motonari Kanda,&nbsp;Masaki Osakabe","doi":"10.1007/s10894-026-00561-3","DOIUrl":"10.1007/s10894-026-00561-3","url":null,"abstract":"<div>\u0000 \u0000 <p>Second harmonic deuteron heating in the ion cyclotron range of frequency (ICRF) was evaluated based on neutron measurements newly installed before a deuterium experimental campaign of the LHD. In deuteron plasmas, it was confirmed that the neutron emission rate increased with higher ICRF injection power. Fast deuterons with energy above 500 keV could be measured by a diamond neutral particle analyzer, when the minority proton ratio was less than 1%. On the other hand, a significant increase in the neutron emission rate, due to fast deuterons produced by ICRF second harmonic heating, was not observed, even in the case of ICRF superimposing on neutral beam injection (NBI). In experiments when the ICRF resonance layer was located near the magnetic axis, fast-ion driven instabilities due to the ICRF heating were observed for the first time at the LHD.</p>\u0000 </div>","PeriodicalId":634,"journal":{"name":"Journal of Fusion Energy","volume":"45 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10894-026-00561-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147339949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"EUV Spectroscopic Analysis of Highly Charged (text {Kr}^{24+}) Ion for Impurity Seeding Studies in Fusion Plasmas via Electron-Impact Excitation and Collisional-Radiative Modeling","authors":"Shivam Gupta,&nbsp;Tetsutarou Oishi,&nbsp;Motoshi Goto,&nbsp;Tomoko Kawate,&nbsp;Yasuko Kawamoto,&nbsp;Yao-Li Liu,&nbsp;Izumi Murakami","doi":"10.1007/s10894-026-00552-4","DOIUrl":"10.1007/s10894-026-00552-4","url":null,"abstract":"<div><p>This study presents a spectroscopic investigation of <span>(text {Kr}^{24+})</span> ion, generated via a krypton impurity seeding experiment in the Large Helical Device, aimed at supporting Extreme Ultraviolet (EUV) diagnostics of high-temperature fusion plasma. EUV spectral lines corresponding to fine-structure transitions among the <span>(text {2p}^{6}text {3s}^{2}text {,} , text {2p}^{6}text {3s3p,} , text {2p}^{6}text {3s3d,})</span> and <span>(text {2p}^{6}text {3p}^{2})</span> configurations were observed in the 12–25 nm wavelength range. To systematically analyze the measured emission lines, extensive relativistic atomic structure calculations were carried out over a broad configuration space, spanning more than 40 configurations, including core-excited and correlation-dominated states up to <span>(text {n}le {7})</span> and <span>(ell le {4})</span>. Bound-state wave functions were obtained using the relativistic many-body perturbation theory and configuration interaction method, implemented via the Flexible Atomic Code. Parallel calculations based on the relativistic multiconfiguration Dirac-Hartree-Fock method with configuration interaction were performed using the GRASP-2018 code to ensure numerical consistency. This article presents fine-structure-resolved excitation energies and transition parameters, including oscillator strengths and transition probabilities, for the relevant spectroscopic configurations up to <span>(3ell)</span>. Moreover, electron impact excitation and ionization cross-sections from the ground state (<span>(text {2p}^{6}text {3s}^{2} , {}^{1}text {S}_{0})</span>) as well as from selected excited states to higher-lying levels were calculated using the relativistic distorted wave method from the respective thresholds over a wide energy range. The corresponding Maxwellian averaged rate coefficients for excitation, de-excitation, ionization, and three-body recombination were evaluated over fusion-relevant electron temperatures. The results are presented for the prominent spectroscopic transitions up to <span>(3ell)</span>. These complete atomic and electron-collision datasets were incorporated into a suitable collisional-radiative model, accounting for the dominant population and depopulation processes, including electron impact excitation, de-excitation, ionization, radiative decay, and three-body recombination. The theoretically modeled EUV spectrum, calculated at <span>(text {n}_text {e}text {=5.5}times text {10}^text {19} , text {m}^text {-3})</span> and <span>(text {T}_text {e}text {=578} , text {eV})</span>, shows good agreement with experimental observations, validating the accuracy of the calculated atomic structure, and electron-collision parameters. The resulting atomic dataset and modeling framework enable detailed spectral analysis of highly charged <span>(text {Kr}^{24+})</span> ion under magnetically confined fusion plasma conditions.</p></div>","PeriodicalId":634,"journal":{"name":"Journal of Fusion Energy","volume":"45 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10894-026-00552-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147340030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Valuing Maintenance Strategies for Fusion Plants as Part of a Future Electricity Grid","authors":"Jacob A. Schwartz,&nbsp;Wilson Ricks,&nbsp;Egemen Kolemen,&nbsp;Jesse D. Jenkins","doi":"10.1007/s10894-026-00551-5","DOIUrl":"10.1007/s10894-026-00551-5","url":null,"abstract":"<div>\u0000 \u0000 <p>Scheduled maintenance is likely to be lengthy and therefore consequential for the economics of fusion power plants. The maintenance strategy that maximizes the economic value of a plant depends on internal factors such as the cost and durability of the replaceable components, the frequency and duration of the maintenance blocks, and the external factors of the electricity system in which the plant operates. This paper examines the value of fusion power plants with various maintenance properties in a decarbonized United States Eastern Interconnection circa 2050. Seasonal variations in electricity supply and demand mean that certain times of year, particularly spring to early summer, are best for scheduled maintenance. Seasonality has two important consequences. First, the value of a plant can be 15% higher than what one would naively expect if value were directly proportional to its availability. Second, in some cases, replacing fractions of a component in shorter maintenance blocks spread over multiple years is better than replacing it all at once during a longer outage, even through the overall availability of the plant is lower in the former scenario.</p>\u0000 </div>","PeriodicalId":634,"journal":{"name":"Journal of Fusion Energy","volume":"45 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2026-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147340031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}