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Feasibility study of heavy ion beam probe in CFQS quasi-axisymmetric stellarator
Get PDF0000-0003-3764-3184The world's first quasi-axisymmetric stellarator, CFQS, is now under construction. The CFQS will be dedicated to studies on the interaction between flow and turbulence, and confinement improvement by suppression of turbulence in connection with proof-of-principle experiment of quasi-axisymmetry. In order to conduct this experimental research, a heavy ion beam probe (HIBP) system is planned to be installed and utilized to measure the radial electric field and its fluctuation in a CFQS plasma. In this paper, an orbit calculation for a probe beam is performed to verify feasibility of the HIBP in the CFQS. The required beam energy, possible ion species, and the observable region in a CFQS plasma are investigated. The beam attenuation by a CFQS plasma is also estimated for different beam ion species. If we use 133Cs+ as a primary probe beam, the required beam energy is expected to be 30∼50 keV, which is relatively easy to handle. In this case the beam attenuation, evaluated by the ratio between the injected and detected beam currents, is 10−3∼10−2 in a CFQS plasma with a line-averaged electron density of <1.0 × 1019 m−3. For a higher density plasma, usage of 85Rb+ is better in terms of low-beam-attenuation, and a high signal-to-noise ratio. The HIBP in the CFQS will provide a great opportunity to study physics experimentally, related to the radial electric field, poloidal flow, and turbulence suppression.journal articl
Behavior of Gas Injected Fast Ignition Targets
Get PDF0000-0002-5008-7285Gas target injection system is newly fabricated to observe behaviors of injected fast ignition targets. It can eject a mimic fast ignition target by pressured nitrogen gas and magnetic separator. The flight attitude of injected target is observed by high-speed cameras. Analysis of high-speed camera images indicates that the target velocity is increased with the injection gas pressure up to around 100 m/s which meets the demanded specification of a reactor and the target flight angle is varied in wide range shot by shot. The technical problem how to control flight angle is recognized for a fast ignition reactor.journal articl
Neural Network Data Analysis in the Large Helical Device Thomson Scattering System
Get PDF0000-0002-7023-1539In Thomson scattering diagnostics systems, a combination of the lookup table and the minimum χ2 methods has been widely used to determine electron temperature. The concept of the minimum χ2 method is based on clearly defined mathematical statistics. However, the minimum χ2 method calculation requires a large amount of time because all χ2 values have to be calculated at all temperatures included in the lookup table. Thus, this method is unsuitable for the real-time data analysis required for the next generation of fusion devices, e.g., the International Thermonuclear Experimental Reactor in France. To establish real-time data analysis for Thomson scattering diagnostics, we have developed a neural network program for the large helical device (LHD) Thomson scattering (TS) system. First, we systematically studied the number of nodes and training cycles required to obtain satisfactory results, and then applied them to the LHD TS system. The calculation time was successfully reduced by approximately 1/50 - 1/100 of the χ2 method calculation time. In addition, experimental error estimation has been performed according to the concept of the neural network method used in this study.journal articl
Chromatographic Purification of Lithium, Vanadium, and Uranium from Seawater Using Organic Composite Adsorbents Composed of Benzo-18-Crown-6 and Benzo-15-Crown-5 Embedded in Highly Porous Silica Beads
Get PDF0000-0003-4530-1459The use of the composite adsorbents composed of benzo-15-crown-5 (abbreviated as BC15) and benzo-18-crown-6 (BC18) for the simultaneous recovery of vanadium (V), uranium (U), and lithium (Li) from seawater has been proposed for industrial applications. The adsorption and desorption behavior of these elements on BC15 and BC18 has been examined in various types of aqueous solutions over a wide temperature range. As a result, it was shown that BC15 and BC18 have sufficient adsorption ability for the simultaneous recovery of V, U, and Li from seawater. Moreover, it was seen that the distribution coefficients (Kd) of V decrease with an increase in [HCl]T (subscript T: total concentration), indicating that the anionic V species such as H2V4O134– are exponentially changed into the cationic V species such as V3+, VO2+, and VO2+ under the condition [HCl]T = 1.0 M, and the complexation reactions between BC15 (or BC18) and the initial V structures are inhibited. Besides, it was reasonably shown that the adsorption mechanism is the path through the electrostatic interaction between the anionic V species such as H2V4O134–, and the −C–O–C– single bond that the electron density is eccentrically located in ether functional groups in crown ether rings in BC15 and BC18 (or the −C–OH single bond that the electron density is eccentrically located in bisphenol A in BC15 and BC18). Then, the chromatography experiment of V, U, and Li on BC15 (or BC18) at 298 K was carried out by flowing seawater, 1.0 × 10–2 M HCl, and 1.0 M HCl in sequence. The first peak of V can be separated from the plateau of Li and the first and second peaks of U in the case of the BC15 system. The recovery ratios of V and U were more than 80%. On the other hand, entirely overlapping chromatograms were obtained in the case of the BC18 system, and accordingly, the recovery ratios of V and U were much lower. In short, the separation efficiency of V with BC15 is more pre-eminent than that with BC18. Judging from these results, the durability of BC15 was finally assessed for industrial applications, that is, the aforementioned chromatography experiment was repeatedly carried out to check whether V, U, and Li were stably and mutually separated from seawater or not. The evidence that the recovery performances of V, U, and Li from seawater do not decrease at all after at least five cycle tests was provided. This indicates that this information will be valuable for the development of a practical chromatographic technology to simultaneously recover V, U, and Li from seawater.journal articl
3D metal powder additive manufacturing phased array antenna for multichannel Doppler reflectometer
Get PDF0000-0001-5473-2109Measuring the time variation of the wavenumber spectrum of turbulence is important for understanding the characteristics of high-temperature plasmas, and the application of a Doppler reflectometer with simultaneous multi-frequency sources is expected. To implement this diagnostic in future fusion devices, the use of a phased array antenna (PAA) that can scan microwave beams without moving antennas is recommended. Since the frequency-scanning waveguide leaky-wave antenna-type PAA has a complex structure, we have investigated its characteristics by modeling it with 3D metal powder additive manufacturing (AM). First, a single waveguide is fabricated to understand the characteristics of 3D AM techniques, and it is clear that there are differences in performance depending on the direction of manufacture and surface treatment. Then, a PAA is made, and it is confirmed that the beam can be emitted in any direction by frequency scanning. The plasma flow velocity can be measured by applying the 3D manufacturing PAA to plasma measurement.journal articl
Growth of fiberform nanostructures on metal surfaces by helium plasma irradiation
Get PDF0000-0003-0543-5241Helium plasma irradiation to various metals leads to peculiar morphology changes as forming fiberform nanostructures called fuzz when a certain set of conditions is satisfied. In this Tutorial, we overview experimental observations about the fuzz growth process, conditions, growth rate, etc. on tungsten (W), and fuzz growth observed on other various metals. The fuzz growth mechanism, open questions about fuzz growth, and current understandings on these issues are discussed based on simulation and theoretical works. Several applications (gas sensors and photocatalytic application) with fuzz are shown. We hope that this Tutorial will help new researchers in this field to perform experiments and simulations to reveal new perspectives of fuzz.journal articl
Three-dimensional structure of radiative cooling in impurity seeded plasmas in the Large Helical Device
Get PDF0000-0003-1586-1084Three-dimensionally localization of radiative cooling due to nitrogen (N2) seeding for divertor detachment was detected experimentally. Since the localization along some magnetic field lines induces toroidal asymmetry of heat load reduction on divertor plates, it should be avoided for fusion reactors. The three-dimensionally localized structure was extracted using Principal Component Analysis (PCA) from two-dimensional radiation images measured with an InfraRed imaging Video Bolometer (IRVB). By applying PCA to 34 images each in N2 seeded plasmas with toroidally-asymmetric heat load reduction and in neon (Ne) seeded plasmas with toroidally-symmetric heat load reduction, a radiation feature in N2 seeded plasmas was found as one of the principal components (PC). The three-dimensional transport code EMC3-EIRENE indicated that the ionization in one of the divertor legs is enhanced in nitrogen seeding compared with Ne seeding due to the difference in the first ionization energy. The magnetic field lines from the divertor leg were along the extracted radiation structure and were terminated by the divertor where the heat load decreased due to the N2 seeding. These results indicate that three-dimensionally localized structure of radiative cooling was detected experimentally.journal articl
燃料粒子制御に向けた磁場閉じ込め核融合プラズマにおける 粒子排気のこれまでとこれから
Get PDF0000-0001-5522-3082本解説では，粒子制御に向けたこれまでの取り組みとして，主として粒子排気という視点に立ち，プラズマ対向壁の燃料粒子吸蔵，放出現象のほか，ダイバータによる効率的な燃料排出について筆者が行ってきた研究を中心に紹介する．また，粒子制御を行うための重要な計測手法として，中性粒子圧力計測の一つである高速イオンゲージ開発の進展についても触れる．そのほか，燃焼プラズマで想定される水素同位体，ヘリウム混合プラズマ中の同位体分離や，効率的な粒子排出を可能にする粒子制御手法についても紹介し，これからの粒子制御に向けた展望を述べる．journal articl
Gas puff imaging system for edge plasma fluctuation measurements in large helical device
Get PDF0000-0002-0990-7093A gas puff imaging system has been developed to measure edge fluctuations in large helical device. The optical system splits the image of the plasma into four wavelengths, Hα/Dα (656 nm), HeI (1s2p–1s3d; 587.6; 1s2p–1s3d, 667.8; and 1s2p–1s3s, 706.5 nm), enabling simultaneous measurement of the spatial distribution of line ratios of He I. The image of the plasma is amplified with an image intensifier and recorded with a fast-framing camera. The measurement area has a diameter of 20 cm just outside of the last closed flux surface. The spatial resolution of the optical system is about 3 mm, and the frame rate is 100 kHz for acquisition of the four wavelength images. Signal-to-noise ratio is evaluated for the system, and further improvement is discussed. Clear images are obtained for all wavelengths and a slightly different pattern is recognized, depending on the wavelength. A singular value decomposition analysis can decompose the image clearly to one perpendicular and parallel to the magnetic field lines.journal articl
Feasibility Study of Deuterium-Deuterium Fusion Profile Diagnostics Using Fusion Born 3 MeV Proton for CFQS
Get PDFA feasibility study for measuring a deuterium-deuterium (D-D) fusion reaction radial profile by promptly lost D-D fusion born 3 MeV protons, whose energy Larmor radius is the same as the minor radius of CFQS, was performed. The Lorentz orbit code was utilized to estimate the predicted signals of collimated proton detectors using the D-D fusion radial profile calculated by the analytical Fokker-Planck code for steady-state plasma FIT3D-DD code. The inversion of the D-D fusion profile using the estimated signals was performed using a linear matrix solution library. The coarse agreement between input and inverted profiles shows the possibility of D-D fusion profile diagnostics by a 3 MeV proton in CFQS.journal articl