Journal of Fusion Energy最新文献

In the Tokamak discharge experiment, obtaining the largest possible null field region is a necessary condition for the smooth breakdown of the plasma, and adjusting the poloidal field coil current is key to achieving a better null field region. This paper, based on the Sino-Thai Tokamak cooperation project Thailand Tokamak-1 (TT-1) device, employs an exponentially decreasing Particle Swarm Optimization (PSO) algorithm to optimize the poloidal field coil current to create the desired null field region in the vacuum chamber area. First, a calculation model for the mutual inductance coefficient and the null field region is established according to the characteristics and magnetic structure of the TT-1 device, enabling the calculation of the null field region. Then, an optimization model for the poloidal field coil current is established, aiming to create a sufficiently large null field region (less than 10 Gauss) to facilitate breakdown. The optimization is carried out using both a typical linearly decreasing PSO algorithm and an improved PSO algorithm to determine the optimal poloidal field coil current. Compared to the unmodified PSO algorithm, the improved PSO algorithm reduces the root mean square error by 31.80%. The results show that the improved PSO algorithm is more suitable for the optimization of the poloidal field coil, has stronger optimization capabilities, and can effectively create the desired null field region, providing an important reference for the smooth breakdown of plasma in the TT-1 device.

Direct-drive laser inertial fusion is a potential producer of baseline power that has increased credibility following the achievement at the National Ignition Facility of ignition and net gain using indirect-drive via laser-produced X-rays. Ultraviolet broad band lasers such as argon fluoride, at 193 nm and 10 THz, are predicted by hydrocode simulations to enable energy gains greater than 100 with laser energies less than 0.5 MJ, stimulating renewed reactor design effort in anticipation of experimental verification. The present study attempts to create a reactor design with very few unknowns in materials, corrosion, first wall viability, tritium breeding and ease of servicing. A new variant of magnetic intervention has an increased ion dump surface area combined with a simple structure. Around an inner vacuum vessel an all-ceramic tritium breeder blanket is possible in an unconstrained volume, allowing helium coolant to be used without excessive pressure or flow power. The case is made for development of a lead (Pb) ceramic as the neutron multiplier.

Survival regression models can achieve longer warning times at similar receiver operating characteristic performance than previously investigated models. Survival regression models are also shown to predict the time until a disruption will occur with lower error than other predictors. Time-to-event predictions from time-series data can be obtained with a survival analysis statistical framework, and there have been many tools developed for this task which we aim to apply to disruption prediction. Using the open-source Auton-Survival package we have implemented disruption predictors with the survival regression models Cox Proportional Hazards, Deep Cox Proportional Hazards, and Deep Survival Machines. To compare with previous work, we also include predictors using a Random Forest binary classifier, and a conditional Kaplan-Meier formalism. We benchmarked the performance of these five predictors using experimental data from the Alcator C-Mod and DIII-D tokamaks by simulating alarms on each individual shot. We find that developing machine-relevant metrics to evaluate models is an important area for future work. While this study finds cases where disruptive conditions are not predicted, there are instances where the desired outcome is produced. Giving the plasma control system the expected time-to-disruption will allow it to determine the optimal actuator response in real time to minimize risk of damage to the device.

As an integral part of the European strategy for advancing fusion-generated electricity, IFMIF-DONES represents a high-intensity neutron irradiation plant with the main purpose of assessing the suitability of materials for fusion reactor applications. Its primary mission is to examine how materials respond to irradiation within a neutron flux that mimics the conditions expected in the first wall of the proposed DEMO reactor, which is intended to succeed ITER. Consequently, IFMIF-DONES, whose construction is slated to commence shortly, plays a pivotal role in aiding the development, approval, and safe operation of DEMO, as well as future fusion power plants. This paper provides a quick overview of the current development of the IFMIF-DONES neutron source with a particular snapshot of the present engineering design status for what concerns the instrumentation and control systems together with its complex diagnostics, that guarantees the safe monitoring, supervision and regulation of all operations. The current status of design, after the completion of the preliminary design phase is presented, as well as the existing and future plans for their integration also using some of the new capabilities offered by Artificial Intelligence tools.

This study delves into the impact of the pre-ionization technique, facilitated by an optimal shunt resistor, on a DPF device operating with deuterium gas. The investigation unveils enhancements in critical parameters within the plasma column environment during the pinch phase, specifically the total and plasmoid hard x-ray yields. Employing a combination of time-resolved detectors, such as plastic scintillator and magnetic probe arrays, alongside time-integrated detectors like pinhole camera, and just by using this technique, the research illustrated an augmented plasma sheath velocity during the axial phase. Notably and other than the enhancement of hard x-ray yield, the optimal pressure of DPF device experienced an upward shift to higher working points, accompanied by a reduction in deviation from the optimum point (52.7% and 66.6% for total and plasmoid hard x-rays respectively). This, in turn, bolstered the Lawson criterion, impacting both particle density and temperature in the plasma column. A nuanced examination further discerned that, while the pre-ionization technique amplified the intensities of total and plasmoid hard x-rays, it maintained a consistent contribution to the emitted hard x-ray intensity from the device, refraining from establishing clear superiority between these two kinds of hard x-rays, with or without using the shunt resistor.

One of the primary obstacles faced by spectrometers operating under high counting rates is pile-up, which occurs when two or more events are detected within a timelapse short enough to result in a superposition of the events waveforms. These can not hence be integrated separately in order to get their amplitudes. Piled-up events are typically identified using pile-up rejection or recovery algorithms. In the latter case, the constituent single waveforms and their amplitudes are also restored. However, there are instances in which the pulses overlap so closely that it is impossible to identify the occurrence of pile-up, resulting in the integration of these pulses into a single spurious event. This phenomenon is known as degenerate pile-up. A method to rectify the incorrect reconstruction of degenerate pile-up was developed, based on a statistical approach, which can be directly applied to the pulse height spectra distributions. The approach was tested on a number of synthetic spectra, with counting rates ranging from 20 kHz up to 1 MHz. The recovered spectra were compared to those purely analysed with a pile-up recovery algorithm, demonstrating an improvement of the reconstructed spectrum of several tens of percent when compared to the true synthetic counterpart.

The unusual graphic representation of time series based on Symmetrized Dot Pattern (SDP) helps capturing subtle dynamics in the analyzed signals, otherwise difficult to identify when applying traditional techniques. SDP is creating features and forming a global percept easily readable and recognizable for a human observer. Thanks to this method, local correlations of the signals of any sampled data series can be visualized. This work describes the application of SDP to measurements of tokamak plasma radiation, namely the soft X-ray line-integrated brightness on WEST, where it was thus possible to analyze different phases of the discharge and in particular to identify sawtooth oscillations. In the future, the SDP method could be used to monitor the plasma state and to warn against the appearance of undesirable plasma behavior.

Developing a robust, feasible, and reliable plasma-facing components (PFCs) is a key mission to realize the commercial fusion power reactor. The situation of the divertor targets will be particularly severe because of higher heat and particle flux in the future devices. In order to improve the power handling capacity and lifetime of the divertor target, a solution of covering the plasma-facing surface of the target with liquid metal was proposed owing to the ability of self-healing. However, liquid metal targets are still in early stages of development and there are many issues need to be explored, especially in the context of the plasma environment in a tokamak. Experimental Advanced Superconducting Tokamak (EAST), aiming to investigate scientific and engineering issues for fusion, provides a suitable environment to study the performance of liquid metal divertor. In this paper, the design of a water-cooling system for liquid metal divertor target test module in EAST is presented. It contains four circulation loops to deal with different accidents to ensure enough safety margin while minimizing the impact on the plasma discharge experiment. The corresponding system safety analyses have been performed and verified that the water-cooling system can meet the design requirements for the liquid metal target test under both normal condition and accidental events. Furthermore, the design of the water-cooling system is compatible with the constraints adopted for the high heat flux components, enhancing its potential for serving other test modules with similar water-cooling requirements in EAST.