Fusion Experiments Research Articles

Fabrication of nanocrystalline diamond capsules by hot-filament chemical vapor deposition for direct-drive inertial confinement fusion experiments

Fabrication of nanocrystalline diamond capsules by hot-filament chemical vapor deposition for direct-drive inertial confinement fusion experiments

Polishing of Metal, Foam, and Si-Doped GDP Capsules for Use as ICF Targets

Spherical targets with a smooth uniform surface are required for inertial confinement fusion experiments. This paper examines polishing as a method of decreasing the surface roughness of tungsten (W) capsules, chromium (Cr) capsules, SiCH [Si-doped glow discharge polymer (GDP)] capsules, and GDP-coated General Atomics–Carbon Hydrogen (GA-CH) foam beads. As expected, increasing the time spent polishing metal (W, Cr) capsules corresponded to decreasing roughness. Despite the decrease in overall surface roughness of Cr capsules, defects present in the batch initially were amplified through polishing. For SiCH capsules, increasing polishing time decreased the surface roughness, though the yield of usable capsules was affected by cracks induced through polishing. While polishing results for GDP-coated foam beads did not show consistent decrease in roughness, the polishing process did not result in the collapse of any of the foams, demonstrating the potential for polishing as a method of decreasing roughness.

Aesthetic and Philosophical Basis of Contemporary Dance

The purpose of the article is to reveal the aesthetic and philosophical foundations of contemporary dance. Research methodology is based on the analysis of scientific sources related to the topic, the application of cultural optics in the clarification of the aesthetic and philosophical foundations of contemporary dance. Scientific novelty. The main approaches of the aesthetic-philosophical foundations of contemporary dance are revealed, and emphasis is placed on consideration of physicality as a specific feature of contemporary dance. Conclusions. Contemporary dance can be qualified as an intellectual choreographic direction, a kind of tool for self-awareness and self-reflection of modern culture. Physicality is a specific feature of contemporary dance, which is due to the desire to establish connections with historical and cultural transformations of the attitude to the human body. The formation of the aesthetic and philosophical foundations of contemporary dance is based on the ideas and approaches of the founders of modern dance. A. Duncan, D. Humphrey, R. Laban, M. Cunningham, J. Skinner, T. Brown, S. Paxton, D. Zambrano, and others are among the choreographers who started new philosophical currents. Philosophical understanding of dance by choreographers consisted in advocating the ideas of a holistic approach in determining the conditions for the fullness of human existence and in effective experiments of fusion of Zen Buddhism and dance. The priority of universal human values and the importance of awareness of one's bodily existence were proclaimed, and the life-affirming meaning of aesthetic culture focused on the need for harmonious development of the individual. Contemporary dance techniques are aimed to develop somatic experience and human physicality, contributing to the formation of a body-oriented philosophy of dance.
 Key words: contemporary dance, modern dance, modern culture, culturology, philosophy of dance, choreography.

Polishing and Local Planarization High-Precision HDC Capsules by Four-Cup-Type Technology for Inertial Confinement Fusion

In inertial confinement fusion (ICF) experiments, high-density carbon (HDC) is being evaluated as an alternative to the current point-design ablator material (glow discharge plasma) due to its high density and optimal opacity, which leads to a higher energy efficiency and implosion stability. Chemical vapor deposition–coated HDC capsules have a near-perfect surface figure but a microscopically rough surface, so polishing is needed to achieve the required nanometer surface finish. Herein, HDC capsule polishing is investigated with modified four-cup-type polishing technology. The surface morphology, microstructures, and wall thicknesses of the polished capsules were examined by multiple techniques, such as an optical microscope, scanning electron microscope, X-ray radiography, and so on. The results show that the HDC capsules can be polished to a surface roughness less than 15 nm and a wall thickness nonuniformity of about 0.5 μm. The Raman spectra indicated that four-cup polishing had no obvious influence on the original surface crystallinity and phase composition of the HDC capsules. The crystallographic of the HDC capsules with different four-cup polishing times had no deterioration. This work plays an important role for the application of HDC capsules in ICF research.

Advances, Challenges, and Future Perspectives of Microwave Reflectometry for Plasma Position and Shape Control on Future Nuclear Fusion Devices.

Providing energy from fusion and finding ways to scale up the fusion process to commercial proportions in an efficient, economical, and environmentally benign way is one of the grand challenges for engineering. Controlling the burning plasma in real-time is one of the critical issues that need to be addressed. Plasma Position Reflectometry (PPR) is expected to have an important role in next-generation fusion machines, such as DEMO, as a diagnostic to monitor the position and shape of the plasma continuously, complementing magnetic diagnostics. The reflectometry diagnostic uses radar science methods in the microwave and millimetre wave frequency ranges and is envisaged to measure the radial edge density profile at several poloidal angles providing data for the feedback control of the plasma position and shape. While significant steps have already been given to accomplish that goal, with proof of concept tested first in ASDEX-Upgrade and afterward in COMPASS, important, ground-breaking work is still ongoing. The Divertor Test Tokamak (DTT) facility presents itself as the appropriate future fusion device to implement, develop, and test a PPR system, thus contributing to building a knowledge database in plasma position reflectometry required for its application in DEMO. At DEMO, the PPR diagnostic's in-vessel antennas and waveguides, as well as the magnetic diagnostics, may be exposed to neutron irradiation fluences 5 to 50 times greater than those experienced by ITER. In the event of failure of either the magnetic or microwave diagnostics, the equilibrium control of the DEMO plasma may be jeopardized. It is, therefore, imperative to ensure that these systems are designed in such a way that they can be replaced if necessary. To perform reflectometry measurements at the 16 envisaged poloidal locations in DEMO, plasma-facing antennas and waveguides are needed to route the microwaves between the plasma through the DEMO upper ports (UPs) to the diagnostic hall. The main integration approach for this diagnostic is to incorporate these groups of antennas and waveguides into a diagnostics slim cassette (DSC), which is a dedicated complete poloidal segment specifically designed to be integrated with the water-cooled lithium lead (WCLL) breeding blanket system. This contribution presents the multiple engineering and physics challenges addressed while designing reflectometry diagnostics using radio science techniques. Namely, short-range dedicated radars for plasma position and shape control in future fusion experiments, the advances enabled by the designs for ITER and DEMO, and the future perspectives. One key development is in electronics, aiming at an advanced compact coherent fast frequency sweeping RF back-end [23-100 GHz in few μs] that is being developed at IPFN-IST using commercial Monolithic Microwave Integrated Circuits (MMIC). The compactness of this back-end design is crucial for the successful integration of many measurement channels in the reduced space available in future fusion machines. Prototype tests of these devices are foreseen to be performed in current nuclear fusion machines.

Analysis of the LaCl3(Ce) scintillator response function to fast neutrons

LaCl3(Ce) scintillator is a novel solution to the task of the fast neutron spectrometry applicable primarily for the nuclear fusion experiments. In the interest of proper neutron spectrum reconstruction, the detector response function has to be studied in detail. This work is focused on the detector response measurement and modelling under fast neutrons born in the 9Be(α, n)12C reaction at Ioffe Institute cyclotron. Comparative analysis of measured spectra versus model is done, the energy resolution and the p/β ratio are estimated for neutron energies of up to 8.5 MeV. The energy resolution is calculated to be 7–8% at 5–8 MeV. The p/β coefficient is estimated, growing from ∼0.75 at 2 MeV to ∼0.85 at 8.5 MeV. These results demonstrate the usability of the LaCl3(Ce) crystal as a neutron spectrometer at DD-neutron energies under γ-ray irradiation. At higher energies, due to low cross-sections and a multitude of possible reaction channels, the suitability of this crystal as a spectrometer is lowered.

Fabrication of a single-crystal diamond neutron detector and its application in 14.1 MeV neutron detection in deuterium–tritium fusion experiments

A single-crystal diamond detector is fabricated to diagnose 14.1 MeV deuterium–tritium (D-T) fusion neutrons. The size of its diamond film is 4.5 mm × 4.5 mm × 500 μm. This film is sandwiched by a flat, strip-patterned gold electrode. The dark current of this detector is experimentally measured to be lower than 0.1 nA under an electric field of 30 kV cm−1. This diamond detector is used to measure D-T fusion neutrons with a flux of about 7.5 × 105 s–1 cm–2. The pronounced peak with a central energy of 8.28 MeV characterizing the reaction in the neutron energy spectrum is experimentally diagnosed, and the energy resolution is better than 1.69%, which is the best result reported so far using a diamond detector. A clear peak with a central energy of 6.52 MeV characterizing the reaction is also identified with an energy resolution of better than 7.67%.

Fingerprinting methods for origin and variety assessment of rice: development, validation and data fusion experiments

Several analytical techniques, i.e. Near Infrared (NIR) and Mid-Infrared (MIR) spectroscopy, Hyper Spectral Imaging (HSI), Gas Chromatography coupled to Mass Spectrometry (GC-MS) and Proton-transfer Reaction Time-of-Flight Mass spectrometry (PTR-TOF-MS), combined with chemometrics, are examined to evaluate their potential for solving food authenticity questions on the case of rice. In total, 237 rice samples were analyzed in this study to examine origin and variety assessment and sourced from producing countries (Italy, Spain, Vietnam, Pakistan and Thailand). The Gaussian Process Latent Variable Model (GP-LVM) was applied as technique to obtain a meaningful compressed representation of the data in a two-dimensional space followed by a classification with a nearest neighbour algorithm. What concerns the origin assessment, GC-MS results score good across all countries, resulting in the most accurate method, with prediction rates ranging from 86% to 94%. Data fusion experiments of combination of GC-MS with NIR, or GC-MS with HSI resulted in prediction rates on origin assessment of more than 90%. Variety assessment was performed with these analytical techniques. Using single techniques, HSI achieved prediction values above 90% for all classes (96%–99%). For data fusion experiments of variety assessment combining GC-MS and NIR all prediction values were equal or higher than 92%; for GC-MS combined with HSI, prediction values were all 98%. The presented methodology can be successfully used for the authentication of rice.

Ray-based cross-beam energy transfer modeling for broadband lasers

Broadband lasers have the potential to mitigate cross-beam energy transfer (CBET) in direct-drive inertial confinement fusion (ICF) experiments. A quantitative assessment of the bandwidth required for CBET mitigation necessitates the development of broadband ray-based CBET models that can be implemented in the radiation-hydrodynamic codes that are used to design ICF experiments. Two different approaches to broadband ray-based CBET modeling (discrete and fixed spectrum) are developed and compared to wave-based calculations. Both approaches give good agreement with wave-based calculations in ICF-relevant configurations. Full-scale 3D calculations show that the bandwidth required for adequate CBET mitigation increases with increasing scale and drive intensity.

Modeling of a spatially resolved ion temperature diagnostic for inertial confinement fusion

The performance of modern laser-driven inertial confinement fusion (ICF) experiments is degraded by contamination of the deuterium–tritium (DT) fuel with high-Z material during compression. Simulations suggest that this mix can be described by the ion temperature distribution of the implosion, given that such contaminants deviate in temperature from the surrounding DT plasma. However, existing neutron time-of-flight (nTOF) diagnostics only measure the spatially integrated ion temperature. This paper describes the techniques and forward modeling used to develop a novel diagnostic imaging system to measure the spatially resolved ion temperature of an ICF implosion for the first time. The technique combines methods in neutron imaging and nTOF diagnostics to measure the ion temperature along one spatial dimension at yields currently achievable on the OMEGA laser. A detailed forward model of the source and imaging system was developed to guide instrument design. The model leverages neutron imaging reconstruction algorithms, radiation hydrodynamics and Monte Carlo simulations, optical ray tracing, and more. The results of the forward model agree with the data collected on OMEGA using the completed diagnostic. The analysis of the experimental data is still ongoing and will be discussed in a separate publication.

Gamma-ray measurements for inertial confinement fusion applications

High-energy γ rays generated from inertial confinement fusion (ICF) experiments have become an important signature for studying the dynamics of implosion processes. Due to their high-energy and penetrating nature, γ rays are the most unperturbed fusion products, which can preserve the original birth information of the fusion process. Fusion γ rays provide a direct measure of nuclear reaction rates (unlike x rays) without being compromised by Doppler spreading (unlike neutrons). However, unambiguous γ-ray measurements for ICF study further required a decade-long period of technological development, which included a deepening understanding of fusion γ-ray characteristics and innovations in instrument performance. This review article introduces the production mechanism of the prompt and secondary γ rays and various ICF performance parameters (e.g., bang time and burn width), which can be derived from γ-ray measurement. A technical overview will be followed by summarizing γ-ray detectors fielded or proposed, especially for high-yield ICF experiments at the Omega Laser Facility and National Ignition Facility. Over the past few years, γ-ray diagnostic technologies have been extended beyond ICF research. A few examples of non-ICF applications of γ-ray detectors are introduced at the end of this article.

Time-dependent saturation and physics-based nonlinear model of cross-beam energy transfer

The nonlinear physics of cross-beam energy transfer (CBET) for multi-speckled laser beams is examined using large-scale particle-in-cell simulations for a range of laser and plasma conditions relevant to indirect-drive inertial confinement fusion (ICF) experiments. The time-dependent growth and saturation of CBET involve complex, nonlinear ion and electron dynamics, including ion trapping-induced enhancement and detuning, ion acoustic wave (IAW) nonlinearity, oblique forward stimulated Raman scattering (FSRS), and backward stimulated Brillouin scattering (BSBS) in a CBET-amplified seed beam. Ion-trapping-induced detuning of CBET is captured in the kinetic linear response by a new δf-Gaussian-mixture algorithm, enabling an accurate characterization of trapping-induced non-Maxwellian distributions. Ion trapping induces nonlinear processes, such as changes to the IAW dispersion and nonlinearities (e.g., bowing and self-focusing), which, together with pump depletion, FSRS, and BSBS, determine the time-dependent nature and level of CBET gain as the system approaches a steady state. Using VPIC simulations at intensities at and above the onset threshold for ion trapping and the insight from the time-dependent saturation analyses, we construct a nonlinear CBET model from local laser and plasma conditions that predicts the CBET gain and the energy deposition into the plasma. This model is intended to provide a more accurate, physics-based description of CBET saturation over a wide range of conditions encountered in ICF hohlraums compared with linear CBET gain models with ad hoc saturation clamps often used in laser ray-based methods in multi-physics codes.

The competing effects of wave amplitude and collisions on multi-ion species suppression of stimulated Brillouin scattering in inertial confinement fusion Hohlraums

Reduction in stimulated Brillouin scattering (SBS) from National Ignition Facility Hohlraums has been predicted through the use of multi-ion species materials on Hohlraum walls. This approach to controlling SBS is based upon introducing a lighter ion species to the heavier ion species Hohlraum wall in order to greatly increase the ion Landau damping of ion acoustic waves (IAWs). In a collisionless plasma, if the IAWs driven by SBS reach sufficient amplitudes, this increased damping is reduced or even eliminated by ion trapping in the IAWs. Here, the nonlinear behavior of IAWs is simulated with a multi-ion species Vlasov code, including interspecies ion–ion collisions, self-collisions, and electron–ion pitch-angle collisions. The effect of collisions on the trapping of ions and electrons in a large-amplitude IAW is studied in a regime of relevance to current Inertial Confinement Fusion experiments. Our simulations show that collisions can scatter trapped particles out of resonance with the IAW, suppressing trapping and helping to maintain an effective Landau damping of the IAW. The IAW amplitude required to trap particles in the presence of strong collisions is estimated analytically. These estimates are tested for strongly damped IAWs in tantalum oxide and pure helium plasmas. Our simulations show that, above a threshold amplitude, the damping is reduced by an amount inversely proportional to the wave amplitude. Thus, the success of controlling SBS using a multispecies plasma may depend sensitively on laser power and pulse length.

Investigating boosted decision trees as a guide for inertial confinement fusion design

Inertial confined fusion experiments at the National Ignition Facility have recently entered a new regime approaching ignition. Improved modeling and exploration of the experimental parameter space were essential to deepening our understanding of the mechanisms that degrade and amplify the neutron yield. The growing prevalence of machine learning in fusion studies opens a new avenue for investigation. In this paper, we have applied the Gradient-Boosted Decision Tree machine-learning architecture to further explore the parameter space and find correlations with the neutron yield, a key performance indicator. We find reasonable agreement between the measured and predicted yield, with a mean absolute percentage error on a randomly assigned test set of 35.5%. This model finds the characteristics of the laser pulse to be the most influential in prediction, as well as the hohlraum laser entrance hole diameter and an enhanced capsule fabrication technique. We used the trained model to scan over the design space of experiments from three different campaigns to evaluate the potential of this technique to provide design changes that could improve the resulting neutron yield. While these data-driven model cannot predict ignition without examples of ignited shots in the training set, it can be used to indicate that an unseen shot design will at least be in the upper range of previously observed neutron yields.

On characterization of shock propagation and radiative preheating in x-ray driven high-density carbon foils

Recently, much effort has been dedicated to the high-density carbon ablator coated fuel capsule in indirect drive inertial confinement fusion experiments due to its higher density compared to other ablators. By using detailed radiation hydrodynamic simulations over a broad range of drive and target parameters, a thorough analysis is performed on shock speed, shock breakout, and maximum preheating temperature in pure and tungsten doped high density carbon foils. The ablators are irradiated by a non-equilibrium x-ray temperature drive consisting of the usual Planckian plus an additionally imposed Gaussian distribution lying in the high frequency M-band region of the incident spectrum. All variables have shown a complex interdependence on strength of the drive, its spectral distribution, and the thickness of the target. Maximum preheating temperature, an important parameter in designing experiments, reduces up to 34% for thicker high-density carbon (HDC) foils, whereas a mere 0.44% doping of tungsten in pure HDC is able to reduce preheating up to 17% for extreme drive conditions. The results are explained on the basis of variation of average albedo/wall loss behavior in foils, an outcome of the interplay between total extinction coefficient and spectral intensity variation with photon energy. For a better understanding and comparison among different types of ablators, multi-parameter scaling relations are proposed for above-mentioned variables, which govern the dynamics of shock propagation and preheating phenomena in HDC based foils.

CDRNet: Cascaded dense residual network for grayscale and pseudocolor medical image fusion

ObjectiveMultimodal medical fusion images have been widely used in clinical medicine, computer-aided diagnosis and other fields. However, the existing multimodal medical image fusion algorithms generally have shortcomings such as complex calculations, blurred details and poor adaptability. To solve this problem, we propose a cascaded dense residual network and use it for grayscale and pseudocolor medical image fusion. MethodsThe cascaded dense residual network uses a multiscale dense network and a residual network as the basic network architecture, and a multilevel converged network is obtained through cascade. The cascaded dense residual network contains 3 networks, the first-level network inputs two images with different modalities to obtain a fused Image 1, the second-level network uses fused Image 1 as the input image to obtain fused Image 2 and the third-level network uses fused Image 2 as the input image to obtain fused Image 3. The multimodal medical image is trained through each level of the network, and the output fusion image is enhanced step-by-step. ResultsAs the number of networks increases, the fusion image becomes increasingly clearer. Through numerous fusion experiments, the fused images of the proposed algorithm have higher edge strength, richer details, and better performance in the objective indicators than the reference algorithms. ConclusionCompared with the reference algorithms, the proposed algorithm has better original information, higher edge strength, richer details and an improvement of the four objective SF, AG, MZ and EN indicator metrics.

Control strategy for the magnetic energy storage and transfer system (MEST)

The Magnetic Energy Storage and Transfer system (MEST) aims at improving the power handling in supplying the SuperConducting (SC) coils of fusion experiments. It is based on smart use of Superconducting Magnetic Energy Storage technology and allows the introduction of a certain degree of decoupling between the grid and the load. The MEST operation is based on the storage and transfer of the needed energy between the Load Coil (LC) and an additional storage inductor named Sink Coil (KC); the energy transfer is realized via capacitors switched by fully controllable semiconductors.This paper focuses on the control system of the MEST and proposes a control strategy, based on two decoupled control loops, with the aim both to guarantee the desired current on the load coil and the compensation of the system losses. A model of the MEST with the proposed control system has been developed to analyze the performance through numerical simulations. The control strategy and the simulation results will be presented and discussed in the paper.

Improving maritime traffic surveillance in inland waterways using the robust fusion of AIS and visual data

To guarantee vessel traffic safety in inland waterways, the automatic identification system (AIS) and shore-based cameras have been widely adopted to monitor moving vessels. The AIS data could provide the unique maritime mobile service identity (MMSI), position coordinates (i.e., latitude and longitude), course over ground, and speed over ground for the vessels of interest. In contrast, the cameras could directly display the visual appearance of vessels but fail to accurately grasp the vessels’ identity information and motion parameters. In this paper, we propose to improve the maritime traffic surveillance in inland waterways using the robust fusion of AIS and visual data. It is able to obtain more accurate vessel tracking results and kinematic characteristics. In particular, to robustly track the visual vessels under complex scenarios, we first propose an anti-occlusion vessel tracking method based on the simple online and real-time tracking with a deep association metric (DeepSORT) method. We then preprocess and predict the vessel positions to obtain synchronous AIS and visual data. Before the implementation of AIS and visual data fusion, the AIS position coordinates in the geodetic coordinate system will be projected into the image coordinate system via the coordinate transformation. A multi-feature similarity measurement-based Hungarian algorithm is finally proposed to robustly and accurately fuse the AIS and visual data in the image coordinate system. For the sake of repeating fusion experiments, we have also presented a new multi-sensor dataset containing AIS data and shore-based camera imagery. The quantitative and qualitative experiments show that our fusion method is capable of improving the maritime traffic surveillance in inland waterways. It can overcome the vessel occlusion problem and fully utilizes the advantages of multi-source data to promote the maritime surveillance, resulting in enhanced vessel traffic safety and efficiency. In this work, the presented multi-sensor dataset and source code are available at https://github.com/QuJX/AIS-Visual-Fusion.

Focus Fusion: Overview of Progress Towards p-B11 Fusion with the Dense Plasma Focus

LPPFusion is developing a source of fusion energy using the dense plasma focus device and p-B11 fuel, a combination we call Focus Fusion. So far, this project has led to the achievement of the highest confined ion energies of any fusion experiment (> 200 keV) as well as, recently, the lowest impurities of any fusion plasma. Among privately-funded fusion efforts, our experiments have achieved the highest ratio of fusion energy generation to device energy input (wall-plug efficiency) and the highest nτT product of 3.4 × 1020 keV-s/m3. Our calculations and simulations indicate that the quantum magnetic field effect will allow a great reduction in bremsstrahlung radiation with p-B11 fuel. For commercial fusion, this approach has several major advantages. The small size and simplicity of design of the DPF can lead to 5 MW generators that are much cheaper than any existing energy source, that can be manufactured by mass production and that can be located close to loads. It shares with other p-B11 approaches a lack of neutron damage and radioactive waste. Direct energy conversion of the ion beam and x-rays produced by the device avoids the high costs associated with thermal cycles. With adequate, but still modest, financial resources we anticipate working prototype generators could be ready for production by 2026–2030.

An Experimental Study Measuring the Image Field Angle of an Electron Beam Using a Streak Tube

The final stage of an inertial confinement fusion (ICF) experiment requires the diagnostic instruments to have the ability to obtain multiple images with high spatiotemporal resolution due to its extremely short duration. However, the influence of field curvature in the streak tube may lead to resolution differences between each image from single line-of-sight (SLOS) technology. In order to achieve high-precision adaptive adjustments, the direction and depth of adjustment should be determined rapidly, which means that the diagnostic instrument must work within the image depth of field of its detector imaging system, requiring it to measure the image field angle of the electron beam. Here, a method based on the streak tube using the combination of planar and spherical fluorescent screens to directly calculate the image field angle of the electron beam from the rear image quality has been proposed for the first time, and its effectiveness has been proved by experiments. It is expected to provide a basis for the diagnostic equipment in ICF experiments to achieve adaptive high-precision adjustment of the focusing voltage to obtain a series of high-resolution images.