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The recent achievement of fusion ignition—meaning more energy came out of a self-sustaining fusion reaction than was put in—at Lawrence Livermore National Laboratory's National Ignition Facility has brought to the fore long-simmering questions about whether certain experiments violate the Comprehensive Test Ban Treaty on nuclear explosions. Fusion research for peaceful use and military use are highly intertwined, despite attempts to cloak nuclear weapons with the aura of the so-called "peaceful atom." Ignition has been achieved, but there is still a remarkable silence around whether pure fusion weapons—weapons that could kill large numbers of humans with neutron radiation but have blast effects much smaller than current thermonuclear weapons—are an objective of the overall program. Even if not an explicit objective, would they be built if fusion technology makes them feasible? [ABSTRACT FROM AUTHOR]

Fusion reactions on the cathode surface of glow discharge deuterium–deuterium fusion neutron sources contribute significantly to the neutron production rate (NPR). While the NPR shows a linear relationship with current in the low current regime, a rise in cathode temperature in the high-current regime causes stagnation of the NPR. This tendency may be caused by high-temperature-induced desorption of deuterium on the cathode. This study aims to clarify the relationship between NPR and deuterium desorption. The present study utilized a water-cooling system to prevent deuterium desorption on the cathode. A stainless-steel 304 cathode and a diamond-like carbon (DLC)-coated cathode were tested. The cooling system kept the cathode temperature below 315 K throughout the experiment. In the case of the DLC-coated cathode, the water-cooling system improves the NPR in a high-current regime (30 mA or more in the present study). At 50 kV and 60 mA, the NPRs were 1.87 × 106 and 8.39 × 105 (n/s), with and without water cooling, respectively. Furthermore, without the cooling system, the NPR correlation with the cathode temperature indicates good agreement with the estimation model of deuterium desorption on the DLC-coated cathode. This study demonstrates that suppression of deuterium desorption in the cathode improves NPR, especially in the high-current regime. [ABSTRACT FROM AUTHOR]

The tokamak approach, utilizing a toroidal magnetic field configuration to confine a hot plasma, is one of the most promising designs for developing reactors that can exploit nuclear fusion to generate electrical energy1,2. To reach the goal of an economical reactor, most tokamak reactor designs3-10 simultaneously require reaching a plasma line-averaged density above an empirical limit-the so-called Greenwald density11-and attaining an energy confinement quality better than the standard high-confinement mode12,13. However, such an operating regime has never been verified in experiments. In addition, a long-standing challenge in the high-confinement mode has been the compatibility between a high-performance core and avoiding large, transient edge perturbations that can cause very high heat loads on the plasma-facing-components in tokamaks. Here we report the demonstration of stable tokamak plasmas with a line-averaged density approximately 20% above the Greenwald density and an energy confinement quality of approximately 50% better than the standard high-confinement mode, which was realized by taking advantage of the enhanced suppression of turbulent transport granted by high density-gradients in the high-poloidal-beta scenario14,15. Furthermore, our experimental results show an integration of very low edge transient perturbations with the high normalized density and confinement core. The operating regime we report supports some critical requirements in many fusion reactor designs all over the world and opens a potential avenue to an operating point for producing economically attractive fusion energy.

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An equation for estimating the effective diffusivity χ φ eff based on the thermal and frictional forces arising from the interactions with neutral particles is provided. These interactions are primarily attributed to charge-exchange processes between ions and neutral particles. Our analysis indicates that the proposed forces are strong candidates to act as sources or sinks of momentum at the plasma edge. Furthermore, although we only have an estimated profile of neutral particles, the results demonstrate a strong dependence of the effective diffusivity on the ion-neutral collision frequency and a comparatively weaker dependence on ion temperature. We showed that the toroidal rotation profile in the TCABR tokamak is well described by the Helander model for toroidal rotation velocity in the Pfirsch-Schlüter regime, which depends on the ion temperature gradient in the presence of the neutral particles. The toroidal rotation profile has been reconstructed by a sum of Bessel functions, derived from the solution of a second-order differential equation for the toroidal velocity. In this initial study on momentum transport in TCABR, our findings indicate that χ φ eff —which accounts for both the diffusivity and pinch terms in the momentum equation—increases significantly in the outer plasma region. Additionally, it achieves a reasonable maximum value of approximately χ φ eff ≈ 20 m 2 / s near the plasma edge at r / a ≃ 0.87 , in the same radial position of the maximum ion-neutral collision frequency, demonstrating that the applied method successfully captures the general behaviour of this component as reported in other works, and guiding future experimental validation. [ABSTRACT FROM AUTHOR]

The global energy crisis and climate change pose significant challenges for the future of humankind. To address these issues, clean energy sources are being promoted, with nuclear energy being an effective solution. The development of fission reactors and the promising advancements in fusion reactor technology provide potential solutions. However, challenges related to security and costs remain. This study focuses on the interaction between 55Mn and protons at 14.7 MeV using Monte Carlo simulations. Various Monte Carlo codes, including TALYS-1.96, GEANT4 (for GEometry ANd Tracking), PHITS-3.31 (for Particle and Heavy Ion Transport Code System), SRIM-2013 (for Stopping and Range of Ions in Matter), and ATIMA v1 41 (for ATomic Interaction with MAtter), were employed to investigate different interaction mechanisms. The research aims to understand the impact of these interactions on reactor performance, particularly in the context of the fusion facility. Manganese-containing steels play a crucial role in enhancing efficiency, durability, and safety in fusion reactors. The findings contribute to ongoing research and development activities in the field of nuclear energy. [ABSTRACT FROM AUTHOR]

Research into heavy-ion fusion, a key area of modern nuclear reaction physics, has flourished in recent decades pursuant to developments in accelerator technology. The primary goal of studying heavy-ion reactions is to gain knowledge about the underlying processes and how they are affected by entrance channel parameters, such as beam energy, angular momentum and mass asymmetry. The fusion mechanism of non-α-cluster projectiles, such 14N and 19F, has been studied in the low-energy zone. It has been challenging to analyze the contributing degrees of freedom in such reactions due to the absence of experimental data. The present study reports the measurement of residual cross-sections from the 19F induced reaction on 93Nb within the energy range of 3–6 MeV/A. The stack foil activation technique followed by offline γ spectroscopy was employed to measure the cross-sections of residues populated in the reaction. The experimental data were compared with theoretical predictions from statistical model code PACE4 to probe the underlying reaction dynamics. The imitation of xn and pxn channel data grossly by model code suggests the production of residues via the complete fusion (CF) mode, while the enhancement observation in α-channel cross-sections hints at the signatures of incomplete fusion (ICF) in addition to the dominant CF. Thus, the ICF strength fraction (FICF) was calculated. Moreover, the estimated incomplete fusion fraction has been used to study the effect of several entrance channel parameters on incomplete fusion reaction dynamics. The present analysis shows the presence of strong clustering in the 19F projectile as α and 15N. [ABSTRACT FROM AUTHOR]

Upon fertilization, male and female nuclei fuse to form the zygotic nucleus in angiosperms. Karyogamy is considered to be essential for proper embryogenesis; however, the transcriptional dynamics during karyogamy in plant zygotes remain unclear. In this study, we performed a single-cell transcriptome analysis of rice zygotes at six early developmental stages (15 min, 30 min, 1 h, 2 h, 4 h, and 6 h after gamete fusion) to reveal gene expression profiles during karyogamy in plant zygotes. The time-series RNA-sequencing analysis detected possible de novo and altered gene expression in zygotes from 15 min post-fertilization. Fertilization-induced transcription during karyogamy was characterized by protein interaction database and gene ontology (GO) analyses. Furthermore, paternal allele transcription was initiated approximately 30 min to 1 h after gamete fusion, when nuclear fusion begins in the zygote. Some transcripts preferentially expressed in egg cells were downregulated after gamete fusion. Moreover, a dynamic shift from maternal-biased transcripts to bi-parental expression occurred during early zygotic development. These results suggest that transcriptional dynamics during karyogamy plays an initial role in proper and sequential zygotic development and embryogenesis. [ABSTRACT FROM AUTHOR]

Turbulent mixing is a pivotal phenomenon in fusion research with profound implications for energy gain. A Reynolds-averaged Navier–Stokes model capable of predicting realistic mixing transition processes is of significant importance for fusion applications, yet such a model remains elusive. This work addresses the limitations of prevalent global transition criteria, proposing a new idea to quantify local transition characteristics based on the mixing state, recognizing its direct relevance to fusion reaction rates. We delve into the description and analysis of the spatiotemporal evolution of the mixing state and its interplay with the transition process. Then, a local transition indicator is developed and compared with conventional global criteria using the large-eddy simulation (LES) of Rayleigh–Taylor turbulent mixing. Building upon this foundation, we introduce a novel eddy viscosity model based on the local transition indicator. A posterior assessment using LES data validates that it significantly outperforms standard gradient transport models during the transition stage. Consequently, we integrate this new eddy viscosity model with the Besnard–Harlow–Rauenzahn model to construct a comprehensive transition model, which demonstrates reasonably good performance in comparison with LES results. This work paves the way for future research in developing advanced modelling strategies that can effectively address the complexities of transitional flows in fusion engineering applications. [ABSTRACT FROM AUTHOR]

Shape‐persistent conjugated nanobelts (CNBs) are fascinating synthetic targets. However, in most cases these are made in low overall yields by applying strategies of macrocyclization followed by (multiple) ring fusion reactions for nanobelt formation. Here, we describe the high yielding synthesis of enantiopure chiral nanobelts in 84 % yield by applying chirality‐assisted synthesis (CAS). The chiral nanobelts were investigated by UV/Vis and CD spectroscopy. By DFT calculations the aromaticity of these structures is discussed. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Vanadium (V) alloys, such as V-Cr, V-Ti, and V-Cr-Ti alloys, are promising candidates for structural components in fusion energy systems because of their low activation, excellent radiation resistance, good compatibility with liquid lithium, and high ductility. Despite these advantages, the limited high-temperature strength and poor creep performances of V alloys have constrained their operating temperature range, challenging the application of these materials over the past few decades. The mechanical behavior is strongly dependent on microstructural features, including precipitates, intergranular and intragranular boundaries, dislocations, and point defects. At the same time, these features serve as preferable sites for solute or impurity atoms to segregate. The elemental segregation alters the local chemistry and stability of these defects, influencing microstructural evolutions and various materials properties that are essential for fusion energy applications. This review paper aims to provide a comprehensive overview of experimental and computational studies on elemental segregation and solute/impurity effects on the mechanical behaviors and microstructural evolution in V alloys. The conventional and advanced manufacturing processes of V alloys will be also discussed. Finally, this review will provide a concise perspective on the potential research directions of V alloys for future fusion reaction applications. [ABSTRACT FROM AUTHOR]

The Experimental Advanced Superconducting Tokamak (EAST) fast control power supply (FCPS) is an important device for controlling the vertical displacement of plasma during the nuclear fusion power generation process, adopting a multiple H-bridge invertor branch parallel operation structure to output total current. At the beginning of each shot of plasma discharge, FCPS works in open-loop voltage control mode (VCM) or closed-loop current control mode (CCM) determined by the plasma control system to output current for exciting the load coil, to achieve plasma vertical displacement control. VCM has the characteristics of fast dynamic response speed but poor consistency of branch current and insufficient branch current control accuracy and stability because of open-loop control. CCM has the characteristics of high branch current control accuracy but poor dynamic response and robustness because of control delay and control parameters determined based on engineering experience. To achieve fast and robust control, an improved voltage control method (IVCM) is proposed by combining the advantages of VCM and CCM. In the beginning of establishing the output current, FCPS operates in VCM, and rapid establishment of the output current is ensured. After the output current rapidly increases to the critical value, closed-loop current control is added to VCM to ensure the accuracy of output current control. In closed-loop current control, linear super-twisting sliding mode control is designed to achieve fast and robust control, ensuring good consistency and fast dynamic response performance of each branch current. Simulations and experiments verify that the designed IVCM has better compatibility characteristics in output current stability, control accuracy, and consistency of each branch current compared to VCM. [ABSTRACT FROM AUTHOR]

Efforts to capitalize on recent advances in fusion energy hold promise for sustainable clean energy. Realization of this promise will require addressing both technical and social challenges. In this paper we focus on the latter, using survey data from a representative sample of the U.S. public to evaluate prospects for sustainable public support for fusion. We demonstrate that while fusion is broadly viewed in a generally positive light across age, gender, and partisan groups, most people concede that they have little knowledge about the technology. The array of images and emotions currently associated with fusion energy technologies tends to be positive, particularly in comparison with those evoked by traditional fission nuclear energy. Trust for regulators and operators of prospective fusion energy facilities is currently quite high and is strongly associated with support for fusion energy. Positive views of fusion also get a boost from technological optimism, but the persistent connection among some Americans to fears of nuclear technologies tends to reduce that support. Implications are that while fusion currently enjoys broad public support, developers and regulators need to exercise care to assure that accidents, overly optimistic claims, and poorly designed and executed regulations do not inflame perceived risks and distrust. As with nuclear fission, continuing investments in a regulatory process for fusion that is grounded in trust, robust technological designs, and a culture of responsible safety will be needed to sustain public support. [ABSTRACT FROM AUTHOR]

The EU-DEMO (EUropean DEMOnstration Power Plant) fusion reactor is one of the most ambitious energy projects aiming at demonstrating the feasibility of nuclear fusion to be a clean, safe, and sustainable source of energy. The distribution grid of the DEMO facility plays a crucial role in delivering the net generated power to the European transmission grid, so it is imperative for its operation to be reliable. The proper design of the electrical subsystems within the fusion power plant is a fundamental factor that must be considered to guarantee reliable and secure operations. This paper presents the models and the results of a sensitivity analysis on the design and sizing of the components of DEMO electrical power system, under different operating conditions, exploiting a Monte Carlo-based Probabilistic Power Flow methodology. This approach was selected to assess the impact of uncertainties on DEMO steady-state power distribution grid and to identify the critical components, which need special requests in their design. The results of the sensitivity analysis can provide valuable insights for the design and sizing of the distribution system of the facility.

ObjectivesThe preliminary research device of magnetic confinement deuterium-deuterium fusion neutron source is a novel neutron source preliminary research device based on field-reversed configuration (FRC) cascade magnetic compression. It aims to leverage the experiences from the first-phase construction to enhance system design, significantly improve plasma parameters, and further expand research on magnetic compression fusion, laying the foundation for achieving a large-volume high-flux fusion neutron source in the third phase.MethodsThe preliminary research device control system optimized and reconstructed the control framework, provided safety interlocking, pulse control and comprehensive data services, coordinated and integrated each service into the automated discharge process through integrated control, and added a number of resources to expand applications and DevOps tool.ResultsThrough the reconfiguration design, the comprehensive performance of the control system in terms of safety, stability and efficiency had been significantly improved. The safety interlock system ensured the safety of personnel and equipment during the experiment process, the pulse control system achieved high-precision timing control, the comprehensive data service provided full process support from data collection to analysis, and resource expansion applications and DevOps tools further improved the system flexibility and operation and maintenance efficiency.ConclusionsBy optimizing the control framework and introducing advanced operation and maintenance tools, the design can better meet the needs of complex device structure and precise discharge flow, and provide an efficient control system construction plan for the subsequent long-term cooperation construction of the magnetically confined deuterium fusion neutron source preliminary research device.

ObjectivesHigh-field superconducting magnets have great application value in many fields. Due to the immature welding technology, the second-generation high-temperature superconducting magnets cannot achieve persistent current mode operation. A rare earth barium copper oxide (REBCO) closed-loop superconducting gourd-shaped loop stacked magnet can achieve unimpeded closed-loop operation. It has been verified that it has the functions of flux density amplification and flux accumulation, and has the potential to achieve high magnetic field output. Therefore, it is crucial to study whether this magnet can maintain stability under high current and high magnetic field conditions.MethodsA three-dimensional finite element model of this REBCO closed-loop superconducting gourd-shaped loop stacked magnet was established to analyze its electromagnetic response and stress-strain distribution under the field cold excitation method.ResultsThe electromagnetic force per unit volume of the stacked magnet decreases gradually from the inner diameter to the outer diameter of the circular loop, with higher values at both ends and lower values in the middle, it presented a “U” shaped distribution. Additionally, the areas with significant stress are located at the connecting bridge and the junction between the loop and the bridge, making these regions prone to deformation and potential quench risks.ConclusionsThe analysis of the distribution characteristics of stress and strain of the magnet has a reference significance for improving the geometric shape of the gourd-shaped double-hole closed-loop superconducting sheet and the structure of the stacked magnet, and is of great significance to the safe operation of the magnet.

ObjectivesWith the rapid development of the steady high magnetic field, the requirements for the performance and uniformity of superconducting magnets have become increasingly stringent, resulting in the current Bi2Sr2CaCu2Ox (Bi-2212) high-temperature superconducting wires failing to meet the application requirements in terms of comprehensive performance. In order to enhance the performance and uniformity of Bi-2212 superconducting wires and achieve the preparation of wires with superior comprehensive performance, the uniform processing technology for multi-core wires is of utmost importance. Die angle is an important parameter of the wire. Therefore, the influence of different die angles on the wire processing was studied.MethodsMultiple Bi-2212 wires were prepared using the powder-in-tube method and processed with alloy drawing dies with half die angles of 3°, 7° and 14°, respectively. During the experiment, systematic investigations were conducted on the microstructure, powder hardness, and superconducting physical properties of the wires.ResultsThe wires processed with smaller die angles show higher current-carrying capabilities, especially, the current-carrying capacity of the sample with a 3° half die angle is 1.56 times that of the sample with a 14° half die angle. The Wires processed with a large die angle show core wire fractures and silver layer ruptures, leading to decreased performance, while the wires with smaller die angles maintain structural integrity. Furthermore, the choice of die angle significantly affects the smoothness of the Ag/superconductor interface, with wires processed at smaller die angles demonstrating superior interface smoothness. This further influences the texture of the superconducting filaments and the current-carrying capacity of the wires.ConclusionsSmaller half die angles help maintain the structural integrity of the multi-filament Bi-2212 wire cores and improve the current-carrying capacity by enhancing the texture. The research results provide process guidance for the preparation of high-performance Bi-2212 wires.

ObjectivesIn order to support the testing requirements of the international thermonuclear experimental reactor AC/DC converter system and apply to high-precision control standards for future fusion magnet power supplies, a real-time control system suitable for high-power DC test platforms was developed.MethodsChoosing the QNX real-time operating system as the core platform and combining it with reflective memory technology provided by GE company in the United States, a network architecture for real-time high-speed data exchange was built. The system was designed with multiple operation modes to cope with different testing scenarios, while implementing different levels of safety interlocking mechanisms to ensure equipment safety. This system possessed the capabilities of setting converter operating parameters, fault identification, equipment status monitoring, and millisecond-level real-time control and safety protection functions.ResultsExperimental validation has demonstrated the system’s stability and reliability in high-power environments, achieving precise control of 120 kA steady-state current and 500 kA pulse current. Furthermore, the system not only meets the basic requirements of real-time control but also ensures safe interlocking and continuous stable operation of the equipment during multi-mode operation.ConclusionsThe designed real-time control system for the high-power DC test platform achieves efficient multi-module synchronous management and fully complies with strict millisecond-level control cycle requirements.

ObjectivesThe application of high-temperature superconductivity (HTS) magnet system is an important technical route for future tokamak devices. However, the magnetic field anisotropy of the HTS tape and the complex conductor structures greatly increase the complexity of the simulation in the electromagnetic design stage of the HTS magnet system of the fusion device. It is necessary to carry out the corresponding research on the electromagnetic simulation and simplified methods.MethodsThe finite element simulation software COMSOL was used to establish the overall electromagnetic simulation model and various simplified models of the HTS magnet system, and the related electromagnetic properties were simulated and compared.ResultsThe calculation results of the central magnetic field and the maximum ripple of plasma are mainly controlled by the magnetic field generated by the toroidal field (TF) coil. However, the TF coil has little influence on the magnetic field distribution on the central solenoid (CS) coil. When the detailed structure of the conductor is combined and the magnetic field anisotropy of the HTS tape is considered, the calculated results of the vertical magnetic field show a large difference compared with the overall model.ConclusionsThe TF coil can only be considered in the calculation of the relevant electromagnetic parameters in the plasma region, and the TF coil can be ignored in the analysis of the magnetic field on the CS coil. In addition, by combining the average current distribution of the conductor structure, the simulation error of the vertical magnetic field of the HTS tape can be effectively reduced.

The blanket system is a crucial element in nuclear fusion power generation, tasked with tritium production and the efficient dissipation of the high thermal flux from the tokamak. Korea is in the process of developing the Helium Cooled Ceramic Reflector (HCCR) blanket, which stands as the forefront design among the nation's blanket systems. This paper presents accident analysis results of LOOP (Loss Of Offsite Power) accident for the HCCR blanket. Loss of power accident is one of the postulated events in the nuclear fusion system. This event may be caused by common failure of the external electrical grids or electrical faults in the site. The objective of this safety analysis is to assess the impact of the activation of an additional power supply within 90 seconds after an accident on the system temperature, and to evaluate the heat load that can be removed by the stagnated coolant in the CCWS (Component Cooling Water System) connected to the heat exchanger of the blanket system.

For decades, plasma transport simulations in tokamaks have used the finite difference method (FDM), a relatively simple scheme to solve the transport equations, a coupled set of time-dependent partial differential equations. In this FDM approach, typically over O(105) time steps are needed for a single discharge, to mitigate numerical instabilities induced by stiff transport coefficients. It requires significant computing time as costly transport models are repeatedly called in a serial manner, proportional to the number of time steps. Additionally, the unidirectional calculations of FDM make it difficult to predict regions prior to the initial condition or apply additional temporal constraints. In this study, we discuss using a new scheme to solve plasma transport based on physics-informed neural networks (PINNs). PINN iteratively updates a function that maps spatiotemporal coordinates to plasma states, gradually reducing errors in transport equations. The required number of updates in PINNs is several orders of magnitude less than the chronological iterations in FDM. Furthermore, it is free from numerical instabilities arising from finite grids and enables more versatile semi-predictive simulations with arbitrary spatiotemporal constraints. In this paper, we discuss the features and potentials of the tokamak transport solver using PINNs through comparisons with FDM, and also its drawbacks and challenges.