Search

The FIREX-1 project, the goal of which is to demonstrate fuel heating up to 5 keV by fast ignition scheme, has been carried out since 2003 including construction and tuning of LFEX laser and integrated experiments. Implosion and heating experiment of Fast Ignition targets have been performed since 2009 with Gekko-XII and LFEX lasers. A deuterated polystyrene shell target was imploded with the 0.53- μm Gekko-XII, and the 1.053- μm beam of the LFEX laser was injected through a gold cone attached to the shell to generate hot electrons to heat the imploded fuel plasma. Pulse contrast ratio of the LFEX beam was significantly improved. Also a variety of plasma diagnostic instruments were developed to be compatible with harsh environment of intense hard x-rays (γ rays) and electromagnetic pulses due to the intense LFEX beam on the target. Large background signals around the DD neutron signal in time-of-flight record of neutron detector were found to consist of neutrons via (γ,n) reactions and scattered gamma rays. Enhanced neutron yield was confirmed by carefully eliminating such backgrounds. Neutron enhancement up to 3.5 × 107 was observed. Heating efficiency was estimated to be 10–20% assuming a uniform temperature rise model.

We present an effective method for transmitting electromagnetic waves as surface waves with a tape-based metasurface design. This design incorporates silver square patches periodically patterned on an adhesive tape substrate. Specifically, our study proposes a strategy to enhance the efficiency of power transfer in high-frequency bands by guiding signals as surface waves rather than free-space waves. Both the numerical and experimental results validate the markedly enhanced efficiency in power transfer of high-frequency signals compared to that achieved with conventional methods, such as wireless power transfer and microstrips. Importantly, our metasurface design can be readily manufactured and tailored for various environments. Thus, our study contributes to designing power-efficient next-generation communication systems such as 6G and 7G, which leverage high-frequency signals in the millimeter-wave and terahertz bands. [ABSTRACT FROM AUTHOR]

Silicone-based materials for outdoor insulators have the advantage that low molecular weight (LMW) components migrate through the material and coat the surface, thereby restoring hydrophobicity over a period of hours. By measuring the IR absorption of siloxane migrating to the silicone surface through a thin carbon coating, the time constant for migration was calculated. According to the time dependence of IR-absorbance, the time constant for migration ranged from 1.6 to 5.3 h depending on alumina trihydrate (ATH) filler concentration.

Heat-resistant in-vessel components, i.e., a heat sink, a front-end optics housing, and a diagnostic window have been designed in terms of heat-handling capability and thermal stress and mechanical stress by using a finite element method code. The heat sink, which is exposed to a plasma heat flux of up to 0.3 MW/m2, consists of carbon tiles, a carbon sheet, and a stainless steel heat sink with a water-cooling channel. Analysis shows that at a water flow rate of 0.9 kg/s with a water pressure of 0.5 MPa, an increase in the carbon tile temperature is mitigated below the limit related with detrimental red-hot (900°C). The front-end optics housing temperature and the diagnostic window of sapphire glass temperature are within the allowable temperature. The thermal stress and mechanical stress are less than the allowable value, respectively. [ABSTRACT FROM AUTHOR]

The design and fabrication of a magnetically controlled, 50-A persistent current switch (PCS) for use in a superconducting magnetic energy storage system is presented. The PCS consists of a CuNb wire and CuNi alloy matrix wound on a FRP bobbin and inserted into a control magnet rated at at 1.2 T. When integrated with a 5.5-T superconducting magnet, it operates in a persistent current mode at 50 A and has a switching-off time of less than 0.3 seconds.

The characteristics of SnO2 grazing-incidence antireflection thin films grown on Pd-coated quartz substrates for the monochromatization of synchroton radiation were investigatedusing off-resonance x-ray reflectivity and conversion electron Mossbauer spectroscopy. The results showed that the incident beam variation of layer thickness and surface roughness inhibited the performance of the material as monochromators. The incorporation of an amorphous buffer layer allowed a bettersurface morphology to be obtained.

An incoherent Thomson scattering diagnostic will be installed in the JT-60SA tokamak to measure electron temperature and electron density profiles. The target radial spatial resolution is 25 mm with 46 spatial channels. The accuracy in electron temperature and density is a few percent at ne = 7.5 × 1019 m−3, which is the expected value in the plasma core. This paper presents the designs of collection optics, fibers with their alignment system, and polychromators. The collection optics overcomes unique issues for superconducting fusion devices, i.e., limited design space, high-temperature measurements, and harsh radiation condition. When in several years the more performing plasma will generate intense nuclear radiation, the lens materials of the optics can be replaced by radiation resistant glasses without major changes in the lens holder. It will prevent transmission degradation and keep stable measurement accuracy. [ABSTRACT FROM AUTHOR]

Analysis using Gas Chromatography/Mass Spectroscopy (GC/MS) was performed for evaluation of surface degradation of silicone insulating materials. Silicones are used as coatings for porcelain insulators and shed material for high voltage composite insulators. A comparison between virgin silicone rubber and aged silicone rubber samples, which were aged either on actual power lines or during a field exposure test, was made by GC/MS analysis. The GC/MS spectrum of siloxane in silicone rubber has a series of peaks which corresponds to the number of dimethylsiloxane units in the molecule. We found that the aged samples had a larger concentration of low molecular weight siloxane species than the virgin samples. The top shed surfaces generated more low molecular weight siloxane species than the bottom shed surfaces. Since GC/MS analysis can determine the molecular weight distribution of polymer insulating materials, evaluation of the degree of surface degradation and estimation of the remaining life of insulators may be possible. Index Terms--silicone rubber, coating, composite insulator, GC/MS, degradation.

Anisotropic impedance surfaces have been used to control surface wave propagation, which has benefited applications across a variety of fields including radio-frequency (RF) and optical devices, sensing, electromagnetic compatibility, wireless power transfer, and communications. However, the responses of these surfaces are fixed once they are fabricated. Although tunable impedance surfaces have been introduced by utilizing power-dependent nonlinear components, such a tuning mechanism is generally limited to specific applications. Here we propose an additional mechanism to achieve tunable anisotropic impedance surfaces by embedding transient circuits that are controllable via the type of incident waveform. By switching between the open and short states of the circuits, it is possible to separately control the unit-cell impedances in two orthogonal directions, thereby changing from an isotropic impedance surface to an anisotropic impedance surface. Our simulation results show that a short pulse strongly propagates for both x and y directions at 3 GHz. However, when the waveform changes to a continuous wave, the transmittance for x direction is reduced to 26%, although still the transmittance for y direction achieves 77%. Therefore, the proposed metasurfaces are capable of guiding a surface wave in a specific direction based on the incident waveform even with the same power level and at the same frequency. Our study paves new avenues regarding the use of surface wave control in applications ranging from wireless communications to sensing and cloaking devices.

Pulsed dielectric barrier discharges are generated within bubbles of a gas-liquid two-phase flow that consists of argon bubbles and water. Discharge images were captured by using a high-speed video camera to understand the motion of discharge within bubbles, and an intensified charge-coupled device camera captured temporal discharge images at a nanosecond timescale. Index Terms--Gas bubbles, gas-liquid two-phase flow, pulsed barrier discharge.