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 Journal of Fusion EnergyJournal Prestige (SJR): 0.411 Citation Impact (citeScore): 1Number of Followers: 2      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1572-9591 - ISSN (Online) 0164-0313 Published by Springer-Verlag  [2469 journals]
• Giga-sample Pulse Acquisition and Digital Processing for Photomultiplier
Detectors

Abstract: Abstract Digital Pulse Processing offers multiple advantages over traditional analogue processing chains. As a disadvantage, produce gigabytes of data every second. Storing and processing such data rates in real-time still remains a challenge. Analogue solutions are not riddled with this issue, however, they offer limited flexibility and modifiability. This work highlights the advantages of Digital Pulse Processing over Analogue Pulse Processing and describes a successful implementation of a digital pulse detection and acquisition system based on Field Programmable Gate Arrays. The system is tasked with processing pulses generated by a Photo Multiplier Tube nuclear detector. Incoming signals are sampled at a 1 GS/s rate, so to enable full acquisition resolution, throughput is reduced with digital detection filters and leading-edge triggering or with a derivative zero-crossing detector. Three different fast timing filters are adapted to high-speed real-time acquisition and compared in a simulated scenario. A trapezoidal filter is implemented in firmware alongside the detection channel for pulse height analysis. Thanks to the use of reprogrammable devices, the system remains versatile and can be remotely adapted to different needs with no additional hardware costs.
PubDate: 2022-05-12

• The Magnetized Indirect Drive Project on the National Ignition Facility

Abstract: Abstract A new project is underway at the National Ignition Facility with the goal of applying a seed magnetic field to the fusion fuel in an indirect drive hohlraum implosion and quantifying the effect on the hot-spot temperature, shape and neutron yield. Magnetizing fusion fuel is calculated to reduce heat loss from the implosion core by constraining the motion of electrons and fusion-generated alpha particles; this can improve the chances of achieving high-gain fusion in a laboratory plasma. We describe the goals of this project and the significant scientific and technological challenges which must be overcome for this project to succeed.
PubDate: 2022-05-10

• Predicted Behaviour of Helium in ITER by the Multi-Mode Transport Model

Abstract: Abstract Computer simulations of 1.5D BALDUR predictive transport code which is coupled with empirically predictive boundary models for the pedestal densities and temperatures are carried out to investigate the plasma characteristics in ITER with the helium environment. In each simulation, the transports of particles and energy in the confined volume are predicted by both neoclassical and anomalous transports in which the latter is based on multi-mode model. The boundaries of the confined plasma are defined at the top of the pedestal and the width of the pedestal is assumed to be fixed. The pedestal temperatures are predicted based on the magnetic and flow shear stabilization. The pedestal densities of hydrogenic and impurity particles are empirically determined from experimental data taken from the International Pedestal Database. Based on these boundary models, the simulations show that the amount of the helium content is 9.9%. The fusion gains predicted by the model is about 3.5. However, as the helium fraction increases to 18%, the fusion gains are further reduced to 1.0 due to the fuel dilution and increasing radiative power loss. Moreover, micro-instability analysis of the ITER plasmas for different level of the helium content is also explored. The results show that, as the amount of helium content increases, the ion-temperature gradient mode is stabilized due to the decrease of the temperature gradient. The trapped-electron mode is also reduced because of increasing the electron collisionality.
PubDate: 2022-04-21

• Analysis of Two Fusion Reactor Designs Based on Magnetic Electrostatic
Plasma Confinement

Abstract: Abstract Two fusion reactor designs based on electrostatic plugging of a magnetic cusp system—known as electromagnetic or magnetic electrostatic plasma confinement (MEPC)—are analyzed for feasibility. Both designs use the linear set of ring cusps geometry. The first design, proposed by Dolan (Current trends in international fusion research, Springer, 1997), utilizes low-temperature superconductor technology and is comparable in size to the ITER or DEMO tokamaks, while producing 500–1000 MW $$_{\text {th}}$$ of fusion power. The second design is more compact, assuming more powerful magnetic fields are now conceivable with high-temperature superconductor technology, and produces 50–150 MW $$_{\text {th}}$$ of fusion power. Using scaling equations from Dolan, both reactors have an estimated energy gain $$Q\approx 10$$ when neglecting impurities and alpha heating. A different model of conduction and diffusion losses, including the effect of minor impurities, is developed. This model predicts Q values about 3–5 times smaller than Dolan. Reactor engineering considerations such as the first wall, blanket, and magnetic forces in a linear set of ring cusps geometry are discussed. An experimental program to resolve outstanding questions and verify scaling laws is needed to determine the feasibility of an MEPC fusion reactor.
PubDate: 2022-04-18

• Flow Boiling Burnout in a Hypervapotron Channel Under High Heat Flux and
High Sub-Cooling Conditions

Abstract: Abstract In this study, a subcooled flow boiling experiment was conducted to analyze the critical heat flux (CHF) of a hypervapotron (HV) channel based on the one-side high-heat load condition. The experimental loop used in this study was operated at high values of pressure (20 bar), flow rate (1.5 kg/s), and fluid temperature (150 °C) with a one-side joule heating system capable of loading a high heat of 14.8 MW/m2. We analyzed the effect of the system parameters on the CHF of the HV channel and determined that the CHF increased at high subcooling and flow rate. This can be attributed to the strengthening of forced convective heat transfer and rapid condensation of the vapor under the aforementioned conditions. Additionally, the CHF tended to increase with the increasing pressure, owing to the decreased bubble size under pressure ranges of 1 to 10 bar. Furthermore, we evaluated the prediction performance of the existing subcooled flow boiling correlations considering the CHF of HV. However, most correlations tended to underpredict as they were developed based on smooth channels. Therefore, we modified the Inasaka and Nariai CHF correlation and developed a novel HV CHF correlation using PYTHON and the artificial intelligence regression method. The mean absolute error and root mean square error of the proposed correlation are 10.68% and 11.99%, respectively, which are significantly lower than those of existing correlations. It is recommended that the newly developed CHF correlation be utilized at an inlet bulk temperature of 40–140 °C, a mass flow rate of 0.071–0.284 kg/s, and a pressure of 1–10 bar.
PubDate: 2022-04-04

• An Approach to a Lee Model for Rotating Plasma

Abstract: Abstract The Dense Plasma Focus (DPF) is such a simple device that it has awakened deep interest as a source of neutrons and as a possible alternative to the generation of energy by nuclear fusion. In essence, a DPF consists of two concentric electrodes between which a plasma sheet is formed by the action of an electrical discharge. Then, this sheet is accelerated until it collapses at the end of the device, generating a hot and extremely dense plasma. One of the most widely theoretical models used for describing the physical processes taking place in the DPF is Lee’s as it fits very well to the experimental data. This model divides the operation of the DPF into five phases. On the other hand, the poisoning of the plasma by particles from the electrodes can be reduced by rotating the plasma through the presence of an axial magnetic field. However, this generates a series of processes that were not taken into account in Lee’s original model. In this work, a variant of the Lee Model describing the rotational effects of plasma is presented. The new model brings new parameters and phenomena to be analyzed, such as the angular velocity and the swirl acceleration effect. The reduction of plasma temperature and also the reduction in neutron yield as observed experimentally, are also explained.
PubDate: 2022-03-10
DOI: 10.1007/s10894-022-00315-x

Posture

Abstract: Abstract The China Fusion Engineering Test Reactor (CFETR) multipurpose overload robot was designed to inspect and maintain important internal components. More specifically, the CFETR multipurpose overload robot (CsMOR) must deal with the complex tokamak torus environment and transport the toolbox to inspect and maintain the blanket and divertor components that are closest to the CFETR core. In this paper, an optimal design algorithm is proposed to optimize the size of the CMOR. This method takes maximum workspace and best advantage posture as the objective function. A Genetic Algorithm was used for the optimization. The total length of CMOR is reduced from 10.7 to 9.8 m, increasing the overall CMOR workspace in the CFETR vacuum vessel by 71.4%. The posture manipulability was improved by 2.1 times.
PubDate: 2022-03-04
DOI: 10.1007/s10894-022-00314-y

• Development of Rapid Simulation Code for NBI Heating Analysis in LHD

Abstract: Abstract We develop a rapid simulation code for neutral beam injection (NBI) heating analysis, FIT3D-RC, to evaluate the power deposition in NBI-heated plasmas of the Large Helical Device (LHD). This code evaluates the beam ion birth profile using the Gaussian process regression (GPR) model applied to precomputation results by the Monte Carlo simulation and calculates the power deposition profile by NBI heating based on the simple analytical solution of the Fokker-Planck equation. We apply this code to the NBI heating in LHD and compare the results with the conventional code (conv-FIT3D). We obtain good agreement in the power deposition profiles calculated by FIT3D-RC and that by conv-FIT3D. Furthermore, the calculation time is significantly reduced compared to the previously available codes. FIT3D-RC is expected to be used for the high-speed analysis and prediction of NBI-heated plasmas.
PubDate: 2021-11-09
DOI: 10.1007/s10894-021-00313-5

• Application Study of Film Capacitor of DC Link Capacitor in EAST Vertical
Stabilization Control Power Supply

Abstract: Abstract A large number of electrolytic capacitors are applied in DC link of EAST vertical stabilization control power supply (VSPS), which become the reliability weak links of the power supply. An appropriate film capacitor is selected to take place of electrolytic capacitor applied in DC link. The criteria for calculation of capacitance according to energy storage and ripple current absorption for sizing the DC link are given. The feasibility of the selection of the capacitor is proven in MATLAB simulation in various operation conditions.
PubDate: 2021-11-01
DOI: 10.1007/s10894-021-00312-6

• Design of Coordination System for Composite Mobile Robot Platform Oriented
to Nuclear Fusion Vessel

Abstract: Abstract Regular maintenance of the nuclear fusion reactor vessel is essential. However, due to the complex physical and geometric conditions inside the reactor vessel, the implementation of this work is facing great difficulties. The existing cantilever robot or in-vessel remote operating system is unable to complete complex tasks because of its single function and poor system coordination. Based on the above research background and the practical application requirements, a composite multi-joint remote operation robot platform which can be used in the internal environment of the nuclear fusion vessel and has the ability of moving, observing and controlling is designed in this paper. The platform consists of three parts: the suspended multi-joint mobile robot system, the peristaltic multi-joint mobile robot system and the multi-robot coordinated control system. First of all, based on the physical model and environmental characteristics of the EAST nuclear fusion vessel, through the analysis of the functional requirements and design specifications of the robot platform, the modular mechanism design and function analysis of each component system are carried out. Secondly, through the analysis of the gravity compensation effect of the multi-robot coordinated control system for the suspended multi-joint manipulator, how to enhance the load capacity of the whole system through a bidirectional coordinated control is studied. Finally, in order to verify the effectiveness of the developed system, the basic motion and load-bearing performance of each component of the prototype are tested by actually building a simulation environment for the EAST nuclear fusion vessel. The experimental results show that the prototype of the robot platform has good kinematic and mechanical properties and load-bearing performance, and meets the design requirements in function.
PubDate: 2021-10-18
DOI: 10.1007/s10894-021-00311-7

• Research on Short Circuit Operation Control Strategy of a Superconducting
Magnet Power Supply for CRAFT

Abstract: Abstract When the power supply of superconducting magnet for Comprehensive Research Facility for Fusion Technology (CRAFT) is operating under short circuit condition and overload, the commutation overlap angle changes dynamically, which greatly increases the complexity in the system modeling and the difficulty in control. To solve these problems, by replacing the circular arc with small bowstring, the dynamic mathematical model under short-circuit operation can be simplified. In order to precisely adjust the impact speed and amplitude of impulse current under short circuit operation, an open-loop control strategy is proposed based on dynamic mathematical model, which can get the excellent performances, inherent stability, fast response and no overshoot. The instantaneous current sharing control strategy using virtual impedance is designed to solve the problem of serious overload and dynamic current sharing under short circuit operation, which thereby ensures the overall overload capacity of superconducting magnet power supply. At last, simulations and experiments are conducted, and results validate the feasibility of the proposed methods.
PubDate: 2021-08-25
DOI: 10.1007/s10894-021-00310-8

• Generalization of the Stability Condition for the Semi–Implicit
Formulation of the Radial Impurity Transport Equation in Tokamak Plasma in
Terms of the Magnetic Flux Surface Coordinate

Abstract: Abstract The present study details the generalization of a stability condition for the semi-implicit formulation of the one-dimensional impurity transport equation for tokamak plasmas in terms of the magnetic flux surface coordinate system (ρ). The radial impurity transport equation for tokamak plasmas is a set of non-linear, parabolic, partial differential equations, solving which generates the radial distributions of all impurity charge states (Z) within the plasma. The present study illustrates the application of a semi-implicit method over the ρ-based impurity transport equation, generated by applying a transformation of the coordinate for the poloidal cross-section of the torus-shaped plasma confinement system, from its geometric radius (r) to the magnetic flux surface coordinate system (ρ). The study further discusses the von Neumann stability analysis of the numerical scheme applied to this transformed (ρ-based) impurity transport equation. The von Neumann stability analysis of the semi-implicit formulation of the radial impurity transport equation has been reported earlier. The stability condition derived in this study is, therefore, a generalization to the earlier reported stability condition now applicable to all ρ(r) including the specific case ρ = r considered in the earlier study. The effects of the impurity transport coefficient (D and v) profiles and the plasma and impurity parameter profiles on the derived ρ-based stability condition are analysed in this study. The impurity element considered is oxygen (1 ≤ Z ≤ 8) and the geometry and plasma parameters of the ADITYA tokamak are applied to the cases studied for consistency.
PubDate: 2021-08-20
DOI: 10.1007/s10894-021-00308-2

• Comparative Study of Boris and He-VPA for a Toroidally Rippled Tokamak

Abstract: Abstract Numerical schemes such as Boris solver and volume preserving algorithm (VPA) enable efficient calculations of plasma particle trajectories under the influence of electromagnetic and collisional forces. In this regard, trajectories of fusion-born alpha particles in an axisymmetric tokamak magnetic configuration have been calculated, using 4th order Runge–Kutta (RK4) technique, the Boris scheme and the VPA. It is observed that Boris scheme and VPA produce accurate trajectories for long ( $$\ge 10^{3}$$ bounce period) simulation time, while the RK4 scheme fails in this regard. Moreover, the total energy is well conserved in Boris and VPA, whereas in RK4, a spurious damping is introduced due to propagation of numerical errors. After demonstrating the superiority of the Boris algorithm and VPA, the computations are extended to magnetically perturbed configuration, namely the toroidal field ripples. It is observed that the resonance interaction, due to toroidal precession of banana orbits and ripple periodicity, causes unwanted radial spread. Whereas, the passing particles, which are not subjected to any resonance interactions, are not affected by ripple magnetic perturbation. In this regard, it is shown that both schemes successfully produce the super banana orbits. However, VPA based computations over-perform as far as energy conservation is concerned.
PubDate: 2021-08-18
DOI: 10.1007/s10894-021-00309-1

• Potential Early Markets for Fusion Energy

Abstract: Abstract We examine potential early markets for fusion energy and their projected cost targets, based on analysis and synthesis of many relevant, recent studies and reports. Seeking to provide guidance to ambitious fusion developers aspiring to enable commercial deployment before 2040, we examine cost requirements for fusion-generated electricity, process heat, and hydrogen production based on today’s market prices but with various adjustments relating to possible scenarios in 2035, such as “business-as-usual,” high renewables penetration, and carbon pricing up to 100 $/ $$\hbox {tCO}_2$$ . Key findings are that fusion developers should consider focusing initially on high-priced global electricity markets and consider including integrated thermal storage, depending on techno-economic factors, in order to maximize revenue and compete in markets with high renewables penetration. Process heat and hydrogen production will be tough early markets for fusion, but may open up to fusion as markets evolve and if fusion’s levelized cost of electricity falls below 50$/ $$\hbox {MWh}_{\mathrm {e}}$$ . Finally, we discuss potential ways for a fusion plant to increase revenue via cogeneration (e.g., desalination, direct air capture, or district heating) and to lower capital costs (e.g., by minimizing construction times and interest or by retrofitting coal plants).
PubDate: 2021-07-10
DOI: 10.1007/s10894-021-00306-4

• The Polarization Shielding Effect on Zonal Flows for Fusion Plasma in the

Abstract: Abstract This paper presents a model for zonal flows (ZFs) generation based on a Chew-Goldberger-Low double equations in the regime of finite banana width (FBW) length-scale creating polarization shielding. The coupled equation is used to investigate the interplay between marginally stable geodesic-acoustic modes (GAM) and low frequency zonal flow (LZF) branch. The effect of safety factor q and dimensionless parameter $$\eta = {\text{p}}_{ \bot } /{\text{p}}_{{ }}$$ on the LZF as well as GAM is investigated. Furthermore, suppression of the growth rate due to polarization shielding is demonstrated. The mechanism of ZFs growth and suppression displays many of the features expected for avalanches in tokamak turbulence.
PubDate: 2021-06-29
DOI: 10.1007/s10894-021-00307-3

• The Implementation of Real-Time Plasma Electron Density Calculation Based
on FPGA for Tokamak Devices

Abstract: Abstract A hydrogen cyanide laser interferometer is mostly used to measure the plasma electron density in many Tokamak devices. The real-time calculation system of the plasma electron density based on a field-programmable gate array is proposed in this work. An Altera EP4CE30F23C8 FPGA chip is selected as the master chip, and an AD9238 chip of 10 MSps is employed for analog-to-digital conversion. The FPGA-based adapted Fast Fourier Transform and the proposed processing algorithm are designed to obtain the plasma electron density. The calculated density is stored in the secure digital card and can also be transmitted to the plasma control system via Ethernet. The experimental results show that the proposed system can effectively obtain the plasma density. The maximum error range is from − 1 to 1 degree and the time resolution is 0.025 ms which is better than that of the convention method 0.1 ms. Meanwhile, this system is highly flexible and reduces design costs to meet the demands of Tokamak devices.
PubDate: 2021-06-15
DOI: 10.1007/s10894-021-00305-5

• Special Issue: 1st China Fusion Energy Conference—Part II

PubDate: 2021-05-24
DOI: 10.1007/s10894-021-00294-5

• The First Experimental Results of Time-of-Flight Neutron Spectrometer at
EAST

Abstract: Abstract Neutron emission spectroscopy (NES) measurements at Experimental Advanced Superconducting Tokamak (EAST) are described. Both measurements and simulations of the neutron energy spectrum were done for the NBI-heated plasma at EAST. The experimental results were measured by the time-of-flight (TOF) neutron spectrometer TOFED, which was moved outside the experimental hall and installed in the newly-built nuclear diagnostics laboratory. A fully digital data acquisition system based on the digitizers was designed and utilized for the TOFED, which satisfied all the primary scintillators and 16 secondary scintillators. The TOFED prototype firstly obtained the neutron time-of-flight spectra with optimized signal-to-noise ratio in the 2017 EAST experiment campaign, when the NBI heating systems were employed. The neutron time-of-flight spectra were distinctly broadened, compared to the simulation of neutron spectra from the thermal plasma with the code GENESIS. These experimental results demonstrate the capability of the time-of-flight neutron spectrometer TOFED to contribute to the studies on fast ion physics at EAST.
PubDate: 2021-05-21
DOI: 10.1007/s10894-021-00304-6

• Stability Analysis of CFETR Distribution Network

Abstract: Abstract The safe operation of distribution network is a prerequisite for the stable operation of CFETR. The electricity load is classified succinctly in this article to identify specific properties. By calculating the influence of CFETR load operation on the distribution network stability in Matlab, a comprehensive analysis of the interaction between load and distribution network is carried out. According to load statistics and stability analysis, the general principle and method of parameters determination for CFETR distribution network is obtained. The power flow is calculated by ETAP 12.6.0 simultaneously to verify the feasibility of the CFETR distribution network configuration.
PubDate: 2021-04-26
DOI: 10.1007/s10894-021-00293-6

• Recent Progress of Optical and Spectroscopic Diagnostics for Turbulence on
the HL-2A tokamak

Abstract: Abstract In the last several years, great progress of optical and spectroscopic diagnostics has been achieved on the HL-2A tokamak. The main physical goal of these diagnostics is to measure plasma parameters for research of turbulence and transport. These diagnostics include: (1) a Phase Contrast Imaging to calculate wavenumber spectra based on a 10.6-μm CO2 laser, (2) a multi-channel (48 channels now and 324 channels for future) Beam Emission Spectroscopy (BES) based on neutral beam injection to measure Doppler-shifted 659.1-nm Dα line for density fluctuation measurement, (3) a four-channel Lyman-Alpha-Based BES (LAB) to measure 121-nm vacuum ultraviolet line for edge density fluctuation measurement, (4) a Gas Puff Imaging (GPI) to measure the intensity of 587.6-nm He I line to investigate plasma evolution, (5) a Multi-Color GPI (MC-GPI) to specify electron temperature and plasma density based on the line-intensity-ratio technique, (6) a Doppler Coherent Imaging Spectroscopy (CIS) to measure two-dimensional plasma velocity, (7) a Near-Infrared PCI (NI-PCI) based on a 1.55-μm fiber laser, (8) a Main-Ion Charge eXchange Recombination Spectroscopy (MI-CXRS) for main ion temperature measurement, and (9) a Fast Ion Dα Imaging (FIDA-I) to image two-dimensional energetic ion profiles. The main characteristic of these diagnostics is the high spatiotemporal resolution which is at the orders of millimeters and microseconds to meet the requirement of turbulence investigation. First experimental results obtained by using some of these new diagnostics, such as poloidal asymmetry of flow velocity during edge localized modes (ELMs), localized pedestal mode in high-β ELM-free H-mode, two-dimensional evolution of density blobs and the quasi-coherent mode in H-mode configuration, are also presented.
PubDate: 2021-04-26
DOI: 10.1007/s10894-021-00302-8

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