Journal of Fusion Energy最新文献

Electron Cyclotron Emission Imaging(ECEI) is a powerful tool for investigating MHD instabilities and turbulence in magnetically confined plasma. In the LHD, the ECEI system has been developed and successfully obtained two-dimensional images of temperature fluctuations. This paper describes the current V-band and Q-band ECEI systems including developments in their key components. The initial results of the observation of geodesic acoustic mode (GAM) are presented.

Helicon waves (HW) are fast magnetosonic waves that can efficiently drive off-axis plasma current in tokamak plasmas through electron Landau damping (ELD) and transit-time magnetic pumping (TTMP) effect. Simulation of helicon wave current drive (HCD) were conducted for the purpose of increasing the discharge current of the NCST, combined with theoretical analysis of wave absorption based on the dispersion relation. Key findings are as follows: (1) When the wave frequency f > 40 MHz, ELD becomes the dominant absorption mechanism for HW in NCST, which is confirmed by the significant increase in the Landau damping term with frequency (Fig. 1). (2) At a frequency of approximately 65 MHz, HCD effectively supplements the bootstrap current for the NCST scenario. (3) Under the optimal parameter combination (({n_parallel }= - 3.8), (beta ={10^ circ })), the maximum current drive efficiency reaches 136 kA/MW. These results clarify the parameter range for efficient HCD, validate HCD as a feasible non-inductive current drive solution for compact spherical tokamaks, and thereby provide critical theoretical guidance for the design and construction of NCST’s helicon system.

The enhancement of the D(d, n)³He fusion reaction rate, due to the production of energetic deuterons (referred to as the knock-on tail) via nuclear elastic scattering of energetic beam protons, was observed on the large helical device (LHD). The enhanced reaction rate was measured as an increase in the neutron generation rate by more than one order of magnitude. This observed phenomenon was explained through both the Boltzmann–Fokker–Planck analysis and particle simulations that consider three-dimensional particle motion in beam-heated deuterium plasma. The simulations demonstrated a good agreement with the observed phenomenon, leading to the conclusions that the knock-on tail is formed in the deuteron velocity distribution function.

IFMIF-DONES (International Fusion Materials Irradiation Facility-DEMO Oriented Neutron Source) is a key facility for the study and analysis of the materials properties exposed to irradiation conditions characterised by a high neutron flux with high energies up to 55 MeV. These irradiation conditions are expected by the future DEMOnstration fusion power plant (DEMO). Within IFMIF-DONES, the irradiation modules which host the specimens material are placed. Therefore, real-time monitoring of the neutron flux is essential to detect and correct any deviations, ensuring continuous and uniform irradiation. Among the diagnostics taken into account, the Self-Powered Neutron Detector (SPND) appears to offer strong physical characteristics in such an environment. However, they have so far only been used in fission reactors. In this work, a theoretical study has been carried out to analyse the signals that could be measured with these diagnostics.

To advance the understanding of helium transport physics, helium neutral beam (He-NB) experiments were initiated in the Large Helical Device (LHD) during the FY2021 experimental campaign. To facilitate these investigations, modifications were implemented in both the impurity exhaust system and the neutral beam (NB) injection system, enabling the use of the helium beam in a typical fusion experimental environment. In the positive-ion-source-based NB system—originally designed for hydrogen and deuterium beams—the gas supply lines were adapted to introduce helium and argon into the ion sources, while argon was injected into the neutralizer cells. These modifications allowed for the injection of a high current and high focused 78 keV He-NB into the plasma. To improve helium exhaust efficiency at main vessel, turbo-molecular pumps were installed, increasing the effective pumping speed by approximately 1.4 times. During He-NB operation, a gradual decrease in the arc current of the NB ion source was observed with each discharge. This effect was attributed to the formation of helium bubbles on the tungsten filament surface, and a recovery method using argon gas discharges was successfully demonstrated. Plasma heating by He-NB injection was confirmed, and both energetic helium ions and bulk helium ions were successfully measured. Their spatial distributions were also observed. These results contribute to a deeper understanding of helium behavior in fusion plasma and offer valuable insights for future helium transport studies.

The supercritical carbon dioxide (sCO₂) cooled Lithium–Lead (LiPb) dual function blanket is an advanced blanket concept design proposed by Chinese Fusion Engineering and Test Reactor (CFETR), which has the characteristics of high inherent safety and high thermoelectric conversion efficiency. In order to study the operational safety characteristics of the fusion reactor blanket Auxiliary Cooling System (ACS) and ensure the safe and stable operation of the system, this paper establishes a dynamic simulation model of key equipment for the fusion reactor blanket ACS, and develops a system analysis program. Based on the self-programming system program, this paper analyzes the thermal safety effects of various heating powers and flow rates on the sCO₂/LiPb dual function blanket, and conducts research on the operational safety characteristics of the system under expected shutdown transient events and varying degrees of Unprotected Loss of Heat Sink (ULOHS) accidents. The results indicate that sCO₂ and LiPb can effectively remove plasma radiation heat flux and nuclear thermal power, ensuring the thermal safety of the blanket. When the LiPb mass flow rate is 60% of the rated value, the outlet temperature of LiPb in the breeding zone exceeds its design limit of 1273.15K. When the LiPb flow rate is 30% of the rated value, the temperature of the cooling plate material in the blanket exceeds its design limit of 798.15K. Under expected shutdown operating conditions, the system can effectively export residual heat from the blanket. The ultimate operating condition of ULOHS accident is a 95% loss of sCO₂ flow on the secondary side, and after 3000 s, the LiPb temperature inside the blanket exceeds the limit value. This study can provide technical support for system regulation and operation control.

We report the implementation and technical evaluation of a shot-by-shot data transfer system from the GAMMA 10/PDX tandem mirror device to the LHD LABCOM system via SNET, as part of the Fusion Virtual Laboratory project. Since 2008, we have transferred approximately 1.5 TB of experimental data annually. In 2023, we successfully established real-time CAMAC data transfer on a per-shot basis. This paper details the network architecture, data acquisition systems, transfer protocols, and operational reliability. The system enables remote access and supports collaborative research by providing timely and structured data to the LABCOM database. The technical performance and future development plans are also discussed.

The atomic data of heavy elements, especially rare-earth metals, plays a crucial role in enhancing our understanding and interpreting kilonova spectra and underlying astrophysical processes. Among these elements, Erbium (Er) is particularly intriguing because it is important for opacities of the kilonova observed in 2017 (GW170817). In order to assess the atomic data, optical spectra of Er ions were precisely measured in (385-400,hbox {nm}) at Large Helical Device (LHD). In the present experiment, Er was injected into the core plasma of LHD through carbon pellets containing Er powders. The electron density and temperature of the Er-contained C pellet ablation cloud were obtained to be (1.6 times 10^{22},hbox {m}^{-3}) and 1.4 eV using the Stark broadening of a C II line and the Boltzmann plot of Er II lines, respectively. Transition probabilities of observed Er II lines were assessed using the Boltzmann plot analysis. Recent measurements with laser-induced breakdown spectroscopy (LIBS) of an Er II line at 393.86 nm were confirmed by the present work.

Fusion energy is regarded as a promising energy source due to its abundant fuel reserves, high energy efficiency, and reduced radioactive waste compared to fission. However, risks such as radioactive leakage, extreme operational conditions, and hazardous materials (e.g., cryogens, magnets) necessitate thorough safety assessments. Some countries have begun to develop their own fusion experimental devices to gain an advantage in the future energy distribution. Although fusion reactors have their inherent safety, there is still a risk of radioactive leakage that threatens the environment and people around, so it is necessary to perform a risk assessment of fusion devices. The probabilistic safety assessment (PSA) technology currently used in commercial pressurized water reactors is not applicable to fusion devices at this stage due to their structural particularity. To address this issue, this paper analyzes the differences between a fusion device and a fission device from three aspects: structural design, radioactive source term, and safety system, and proposed a preliminary probabilistic safety assessment method for fusion devices, with a case study on the ITER facility, which has been applied to a fusion experimental device under design and achieved good analytical results.Note that this method is currently validated only for ITER-like experimental devices, and its extension to other fusion plants requires further scenario-specific adjustments.In addition, the case study on ITER is based on historical design data and serves as an example application of this framework. The result does not represent the current security assessment of ITER.

We review global gyrokinetic simulation studies on plasma transport in the Large Helical Device using XGC-S. XGC-S is an extended version of X-point Gyrokinetic Code for stellarators and has been progressively verified throughout the code development process. Verification tests of neoclassical transport successfully demonstrate the generation of an ambipolar electric field due to ripple-trapped particles. We perform quasi-linear analyses of the ion temperature gradient mode under the influence of the ambipolar electric field. The results reveal that the ambipolar electric field and the heavy hydrogen component in mixed isotope plasmas can lead to the favorable isotope effect observed in recent deuterium experiments. We also present recent efforts in code development toward whole-volume simulations, including the helical divertor region. A mesh generation scheme based on field-line tracing and the construction of curved surfaces perpendicular to the magnetic field would be promising for global field calculations in the whole-volume simulations.