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Studies of energetic particle transport due to energetic-particle-driven Alfvénic instability have progressed using neutron and energetic particle diagnostics in Large Helical Device deuterium plasmas. Alfvénic instability excited by injecting an intensive neutral beam was observed by a magnetic probe and a far-infrared laser interferometer. The interferometer showed Alfvénic instability composed of three modes that existed from the core to the edge of the plasma. A comparison between the observed frequency and shear Alfvén spectra suggested that the mode activity was most likely classified as an Alfvénic avalanche. A neutron fluctuation detector and a fast ion loss detector indicated that Alfvénic instability induced transport and loss of co-going transit energetic ions. The dependence of the drop rate of the neutron signal on the Alfvénic instability amplitude showed that significant transport occurred. Significant transport might be induced by the large amplitude and radially extended multiple modes, as well as a large deviation of the energetic ion orbit from the flux surface. [ABSTRACT FROM AUTHOR]

A divertor simulation experimental module (D-module) in the tandem mirror GAMMA 10/PDX was used for the study of plasma detachment. In previous studies, it was difficult to measure far-upstream plasma parameters in the D-module, and only electrostatic probes on the target plate were used to perform electron temperature and density measurements. To study the detached plasma structure, a Thomson scattering (TS) system and a microwave interferometer system have been installed to measure the inside plasma parameters of the D-module, and a movable electrostatic probe has been placed at the inlet of the D-module to measure the inlet plasma density and temperature. The TS system in the central cell observed the electron temperature and density of the core plasma simultaneously. These measurements revealed the entire density and temperature structure from the core plasma to the divertor plate. The line average electron density measured by the microwave interferometer showed a rollover behavior during detachment. The results indicated that the ionization region was located around the center of the D-module, and it appears to move upstream along the axis. [ABSTRACT FROM AUTHOR]

A scalable system for real-time analysis of electron temperature and density based on signals from the Thomson scattering diagnostic, initially developed for and installed on the NSTX-U experiment, was recently adapted for the Large Helical Device and operated for the first time during plasma discharges. During its initial operation run, it routinely recorded and processed signals for four spatial points at the laser repetition rate of 30 Hz, well within the system's rated capability for 60 Hz. We present examples of data collected from this initial run and describe subsequent adaptations to the analysis code to improve the fidelity of the temperature calculations. [ABSTRACT FROM AUTHOR]

The multipass Thomson scattering (MPTS) technique is one of the most useful methods for measuring low-electron-density plasmas. The MPTS system increases Thomson scattering (TS) signal intensities by integrating all multipass (MP) signals and improving the TS time resolution by analyzing each pass signal. The fully coaxial MPTS system developed in GAMMA 10/potential-control and diverter–simulator experiments has a polarization-based configuration with image-relaying optics. The MPTS system can enhance Thomson scattered signals for improving the measurement accuracy and megahertz-order time resolution. In this study, we develop a new MPTS system comprising a laser amplification system to obtain continuous MP signals. The laser amplification system can improve degraded laser power and return an amplified laser to the MP system. We obtain continuous MP signals from the laser amplification system by improving the laser beam profile adjuster in gas scattering experiments. Moreover, we demonstrate that more MP signals and stronger amplified MP signals can be achieved via multiple laser injections to the laser amplification system in the developed MP system comprising a laser amplification system. [ABSTRACT FROM AUTHOR]

The authors have investigated the chemical states at the interface of metal/perovskite oxides both with and without bipolar resistive switching (RS) behavior using photoemission spectroscopy and x-ray absorption spectroscopy. Al/Pr0.7Ca0.3MnO3 (PCMO), Al/La0.7Ca0.3MnO3 (LCMO), and Al/La0.33Sr0.67FeO3 interfaces were chosen as typical examples of interfaces for the perovskite-based resistance random access memory (ReRAM), while Pt/PCMO and Ag/LCMO were chosen as references for the metal/perovskite interface without RS behavior. Detailed analyses of spectroscopic data revealed that transition layers were formed at the interfaces showing RS behavior as a result of interfacial redox reactions between the Al electrodes and the transition metal ions in the oxides. On the other hand, for the interfaces that did not exhibit RS behavior, no chemical reaction occurred at the interface. The formation of the interfacial transition layer is naturally explained by considering the redox potential between the electrode materials and transition metal ions. These results suggest that a suitable combination of electrodes and oxides could be designed based on their redox potentials. [ABSTRACT FROM AUTHOR]

We developed a Fe:ZnSe chirped pulse amplifier with a KTA-based optical parametric amplifier, achieving 0.6 mJ pulses at 4-micron wavelength. It should be inherently carrier envelope phase stable and applicable to strong field science.

This paper evaluates the accuracy of electron temperature measurements and relative transmissivities of double-pass Thomson scattering diagnostics. The electron temperature (Te) is obtained from the ratio of signals from a double-pass scattering system, then relative transmissivities are calculated from the measured Te and intensity of the signals. How accurate the values are depends on the electron temperature (Te) and scattering angle (θ), and therefore the accuracy of the values was evaluated experimentally using the Large Helical Device (LHD) and the Tokyo spherical tokamak-2 (TST-2). Analyzing the data from the TST-2 indicates that a high Te and a large scattering angle (θ) yield accurate values. Indeed, the errors for scattering angle θ = 135° are approximately half of those for θ = 115°. The method of determining the Te in a wide Te range spanning over two orders of magnitude (0.01-1.5 keV) was validated using the experimental results of the LHD and TST-2. A simple method to provide relative transmissivities, which include inputs from collection optics, vacuum window, optical fibers, and polychromators, is also presented. The relative errors were less than approximately 10%. Numerical simulations also indicate that the Te measurements are valid under harsh radiation conditions. This method to obtain Te can be considered for the design of Thomson scattering systems where there is high-performance plasma that generates harsh radiation environments. [ABSTRACT FROM AUTHOR]

This paper provides a software application of the sampling scope concept for fusion research. The time evolution of Thomson scattering data is reconstructed with a high temporal resolution during a modulated electron cyclotron resonance heating (MECH) phase. The amplitude profile and the delay time profile of the heat pulse propagation are obtained from the reconstructed signal for discharges having on-axis and off-axis MECH depositions. The results are found to be consistent with the MECH deposition. [ABSTRACT FROM AUTHOR]

Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO2 laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 x 1017 m-3 is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 x 1020 m-3 can be overcome by a sufficient sampling rate of about 100 kHz. [ABSTRACT FROM AUTHOR]

Comprehensive electrostatic gyrokinetic linear stability calculations for ion-scale microinstabilities in an LHD plasma with an ion-internal transport barrier (ITB) and carbon "impurity hole" are used to make quasilinear estimates of particle flux to explore whether microturbulence can explain the observed outward carbon fluxes that flow "up" the impurity density gradient. The ion temperature is not stationary in the ion-ITB phase of the simulated discharge, during which the core carbon density decreases continuously. To fully sample these varying conditions, the calculations are carried out at three radial locations and four times. The plasma parameter inputs are based on experimentally measured profiles of electron and ion temperature, as well as electron and carbon density. The spectroscopic line-average ratio of hydrogen and helium densities is used to set the density of these species. Three ion species (H,He,C) and the electrons are treated kinetically, including collisions. Electron instability drive does enhance the growth rate significantly, but the most unstable modes have characteristics of ion temperature gradient modes in all cases. As the carbon density gradient is scanned between the measured value and zero, the quasilinear carbon flux is invariably inward when the carbon density profile is hollow, so turbulent transport due to the instabilities considered here does not explain the observed outward flux of impurities in impurity hole plasmas. The stiffness of the quasilinear ion heat flux is found to be 1.7-2.3, which is lower than several estimates in tokamaks. [ABSTRACT FROM AUTHOR]

In the Large Helical Device (LHD), H-mode plasmas are produced, having large amplitude edge-localized modes (ELMs) which are induced by resistive interchange modes (RICs) at the ι/2π = 1 rational surface near the foot of the edge transport barrier (ETB). These large ELMs expel a large fraction of plasma stored energy, up to 20% of the stored energy (Wp). The ETB and the ι/2π = 1 surface are thought to be in the stochastic field region (SFR) generated intrinsically in three-dimensional magnetic configuration on LHD, because plasma shielding effects for such stochastic fields are not significant due to low electrical conductivity σ and moderate angular frequency of plasma rotation ω in the ETB and the field penetration depth is estimated to be comparable to the ETB width. Even if the ETB is in such intrinsic SFR where electron mean free path is much shorter than the connection length, large amplitude ELMs are excited. Such ELMs were mitigated by externally applied m = 1/n = 1 resonant magnetic perturbations (RMPs), for the first time, in a stellarator/helical plasma, where m and n are the poloidal and toroidal mode numbers, respectively. The RMPs reduce the amplitude, enhancing the repetition frequency significantly. The energy loss fraction ΔWp/Wp is reduced less than ∼5% by the mitigation. This mitigation is realized without terminating the H-mode and large penalty to global energy confinement. The RMPs preferentially decrease electron density in ETB indicating enhanced particle transport, while electron and ion temperature profiles are nearly unchanged. Plasma shielding effects for the applied RMPs is also not significant because of low σ and moderate ω in ETB. Noticeable decrease in the gradients of electron density and pressure in the ETB and also at the ι/2π = 1 surface is induced by the penetration of the applied RMPs. Enhanced ELM frequency indicates that MHD stability of ETB for RICs is degraded by RMPs. Potential mechanisms of ELM mitigation on LHD are discussed. [ABSTRACT FROM AUTHOR]

In the Large Helical Device experiments, a significant pressure gradient is observed in the edge region where the three-dimensional magnetohydrodynamics equilibrium analysis predicts the stochastization of magnetic field lines. Therefore, experimental investigation of this edge plasma behavior is attracting much interest to identify either the plasma response to stochastic magnetic fields or the topological change of magnetic fields due to the plasma. In this study, we have investigated the relation of the stochastization of magnetic field lines to the radial electric field, Er. When magnetic field lines become stochastic or open and connected to the vessel, electrons are lost along these field lines while ions are trapped. Then, a strong Er shear from negative to positive appears at the boundary. Two magnetic configurations with different widths of the stochastic layer in the vacuum are studied for low-β discharges. It has been found that the position of a strong Er shear appears outside of the last closed flux surface. When comparing the vacuum magnetic field, the positions of strong Er shear are observed in the edge of the stochastic layer. In the stochastic region, the scatter of stochastic field lines is studied. The position of a strong Er shear appears in the region where the outward scatter of the field lines increases. In that region, stochastic field lines intersect the regions with long and short connection lengths. Although the connection length is longer than the electron mean free path, the scatter of stochastic field lines with short connection lengths appear in the regions with positive Er. These results are compared with moderate-β discharges, where a large plasma response is expected. The prediction of the vacuum magnetic field qualitatively agree with the experimental observations but quantitative differences are found. [ABSTRACT FROM AUTHOR]

We have developed an analysis method to improve the accuracies of electron temperature measurement by employing a fitting technique for the raw Thomson scattering (TS) signals. Least square fitting of the raw TS signals enabled reduction of the error in the electron temperature measurement. We applied the analysis method to a multi-pass (MP) TS system. Because the interval between the MPTS signals is very short, it is difficult to separately analyze each Thomson scattering signal intensity by using the raw signals. We used the fitting method to obtain the original TS scattering signals from the measured raw MPTS signals to obtain the electron temperatures in each pass. Published by AIP Publishing. [ABSTRACT FROM AUTHOR]

The Thomson scattering diagnostic systems are widely used for the measurements of absolute local electron temperatures and densities of fusion plasmas. In order to obtain accurate and reliable temperature and density data, careful calibrations of the system are required. We have tried several calibration methods since the second LHD experiment campaign in 1998. We summarize the current status of the calibration methods for the electron temperature and density measurements by the LHD Thomson scattering diagnostic system. Future plans are briefly discussed. [ABSTRACT FROM AUTHOR]

Dental preparation sometimes causes transient congestion, edema, and necrosis of the pulp. We hypothesized that nitric oxide (NO) is involved in the pathophysiological changes in pulp after preparation. The mRNA and protein expression of the inducible isoform of NO synthase (iNOS) was examined in murine pulp after dental preparation. The effects of NO on the proliferation, mineralization, and apoptosis of pulp cells were also studied in vitro. We found that not only iNOS, but also mRNAs for alkaline phosphatase and plasma membrane glycoprotein-1, were expressed in the pulp after preparation. NOC-18, an NO donor, suppressed the proliferation of pulp cells without inducing cell death, whereas it promoted the mineralization of cells cultured in the presence of β-glycerophosphate, ascorbic acid, dexamethasone, and KH2PO4. Under these conditions, NOC-18 induced the apoptosis of pulp cells. These results suggest that NO regulates the growth, apoptosis, and mineralization of pulp cells. [ABSTRACT FROM AUTHOR]

Thomson scattering forms an important aspect of measuring the electron density and temperature profiles of plasmas. In this study, we demonstrate Thomson scattering measurements obtained over a short interval (<1 ms) by using an event triggering system with a multi-laser configuration. We attempt to use our system to obtain the electron temperature and density profiles before and immediately after pellet injection into the large helical device. The obtained profiles exhibit dramatic changes after pellet injection as per our shot-by-shot measurements. We believe that this measurement technique will contribute towards a better understanding of the physics of the pellet deposition. [ABSTRACT FROM AUTHOR]

A multi-pass Thomson scattering (TS) has the advantage of enhancing scattered signals. We constructed a multi-pass TS system for a polarisation-based system and an image relaying system modelled on the GAMMA 10 TS system. We undertook Raman scattering experiments both for the multi-pass setting and for checking the optical components. Moreover, we applied the system to the electron temperature measurements in the GAMMA 10 plasma for the first time. The integrated scattering signal was magnified by approximately three times by using the multi-pass TS system with four passes. The electron temperature measurement accuracy is improved by using this multi-pass system. [ABSTRACT FROM AUTHOR]

This paper provides a novel method for evaluating signal intensities in incoherent Thomson scattering diagnostics. A double-pass Thomson scattering system, where a laser passes through the plasma twice, generates two scattering pulses from the plasma. Evaluations of the signal intensities in the spectrometer are sometimes difficult due to noise and stray light. We apply the singular value decomposition method to Thomson scattering data with strong noise components. Results show that the average accuracy of the measured electron temperature (Te) is superior to that of temperature obtained using a low-pass filter (<20 MHz) or without any filters. [ABSTRACT FROM AUTHOR]

A new high speed Nd:YAG Thomson scattering AD Convertor (HYADC) that can directly convert the detected scattered light signal into a digital signal is under development. The HYADC is expected to improve a signal to noise ratio of the Nd:YAG Thomson scattering measurement. The data storage of the HYADC which is required for the direct conversion of whole plasma discharge is drastically reduced by a ring buffer memory and a stop trigger system. Data transfer of the HYADC is performed by the SiTCP. The HYADC is easily expandable to a multi-channel system by the distributed data processing, and is very compact and easy to implement as a built-in system of the polychromators. [ABSTRACT FROM AUTHOR]

In the KSTAR Tokamak, a "Tangential Thomson Scattering" (TTS) diagnostic system has been designed and installed to measure electron density and temperature profiles. In the edge system, TTS has 12 optical fiber bundles to measure the edge profiles with 10-15 mm spatial resolution. These 12 optical fibers and their spatial resolution are not enough to measure the pedestal width with a high accuracy but allow observations of L-H transition or H-L transitions at the edge. For these measurements, the prototype ITER edge Thomson Nd:YAG laser system manufactured by JAEA in Japan is installed. In this paper, the KSTAR TTS system is briefly described and some TTS edge profiles are presented and compared against the KSTAR Charge Exchange Spectroscopy and other diagnostics. The future upgrade plan of the system is also discussed in this paper. [ABSTRACT FROM AUTHOR]

We investigate, for the first time, the expansion of resistive random access memory (ReRAM) conductive filaments during pulse cycles, which may cause retention failure after cycling endurance. We find that filament size becomes larger gradually because of oxygen diffusion from the region surrounding a filament during reset operations. To achieve long-term use of ReRAM while avoiding filament expansion, it is the key to control both an electric power and a pulsewidth input at a switching operation. We successfully demonstrate good data retention even after endurance of 100-k cycles with an optimized reset pulse. [ABSTRACT FROM AUTHOR]

The relationship between interfacial chemical states and resistance-switching (RS) behaviors at the metal/Pr0.7Ca0.3MnO3 (PCMO) interfaces has been studied by photoemission spectroscopy and x-ray absorption spectroscopy. For Al/PCMO interfaces that exhibit RS behavior, redox reactions between Al and Mn ions occur at the interface. In sharp contrast, no chemical reactions occur at Pt/PCMO interfaces that do not exhibit RS behavior. These results strongly suggest that the interfacial transition layer due to the redox reactions is responsible for the RS behavior at metal/PCMO interfaces. [ABSTRACT FROM AUTHOR]

The spatial distribution of chemical states in resistance-switching devices with a planar-type Pt/CuO/Pt structure has been studied by photoemission electron microscopy. It has been found that the change in resistance that occurs with the application of the first voltage is caused by the formation of a reduction path through the CuO channel between the Pt electrodes. A detailed analysis suggests that Joule-heat-assisted reduction induced by the current flowing through the device may play an important role in the formation of the conductive reduction path. [ABSTRACT FROM AUTHOR]

The authors report on the crystallographic orientation dependence of the Schottky properties for heterojunctions between a half-metallic ferromagnet La0.6Sr0.4MnO3 (LSMO) and Nb-doped SrTiO3 semiconductor. The Schottky barrier height determined by in situ photoemission measurements is independent for the substrate orientations (001) and (110), while the magnetic properties of LSMO (110) films are more enhanced than for (001) films. These results suggest that the performance of magnetic devices based on ferromagnetic manganite is improved by using (110)-oriented substrates. [ABSTRACT FROM AUTHOR]

By using photoelectron emission microscopy, we systematically investigated the magnetic domain in the La0.6Sr0.4MnO3 patterned thin film with several microns, in which we can control the ratio of a shape anisotropy to a step-induced uniaxial anisotropy in magnitude. We demonstrate that a cooperative effect of a step-induced uniaxial anisotropy with a shape anisotropy causes the formation of a single domain, whereas the competitive effect makes a multimagnetic domain. [ABSTRACT FROM AUTHOR]

The authors have investigated ultrathin HfO2–Y2O3 composite films by photoemission spectroscopy and x-ray absorption spectroscopy (XAS) to elucidate the Y2O3 composition dependence of crystallization and band offsets. The authors have found that the crystal structure of ultrathin films can be predicted by the detailed spectral structure between 540 and 550 eV in XAS. Photoemission spectroscopy and XAS reveal that the films of x=0 and 0.05 are mainly in a monoclinic phase, while those of x=0.10 and 0.20 are in a cubic phase. Regardless of the crystal structure changes by adding Y2O3 to HfO2, the band gap and band offsets remain almost unchanged. [ABSTRACT FROM AUTHOR]

Electronic structures of (LaAlO3)1-x(Al2O3)x composite films (x=0, 0.2, 0.33, 0.5, and 1) for large scale integration (LSI) gate dielectrics deposited on p-type Si (100) substrates by a combinatorial pulsed laser deposition method have been analyzed using photoelectron spectroscopy and x-ray absorption spectroscopy. The systematic peak shifts due to chemical shifts were observed for core-level spectra. The conduction-band offset became smaller with increasing ratio of Al2O3, while the valence-band offset became larger. This precise determination of the band diagram revealed that LaAlO3 (x=0) had the optimum band offset for LSI gate dielectrics. [ABSTRACT FROM AUTHOR]

In LHD, real-time control of the incident EC wave polarization and quick response microwave bolometer for monitoring the stray radiations have been developed for efficient and safe operation of the high power and long pulse ECRH/ECCD. As a high power ECRH/ECCD application aiming for high density, ECRH has been demonstrated up to 85% of the cutoff density by the fundamental X-mode excitation in HFS with use of a horizontal port antenna located in LFS. As another application aiming for high temperature, the effect of the control of the rotational transform with use of the ECCD on the sustainment of the e-ITB is investigated. It has been suggested that higher local electron energy confinement time is obtained inside the e-ITB with placing the m/n = 2/1 magnetic island near the edge of the e-ITB compared to the case when the 2/1 island is vanished in the plasma.

In the GAMMA 10 tandem mirror, the typical electron density is comparable to that of the peripheral plasma of torus-type fusion devices. Therefore, an effective method to increase Thomson scattering (TS) signals is required in order to improve signal quality. In GAMMA 10, the yttrium-aluminum-garnet (YAG)-TS system comprises a laser, incident optics, light collection optics, signal detection electronics, and a data recording system. We have been developing a multi-pass TS method for a polarization-based system based on the GAMMA 10 YAG TS. To evaluate the effectiveness of the polarization-based configuration, the multi-pass system was installed in the GAMMA 10 YAG-TS system, which is capable of double-pass scattering. We carried out a Rayleigh scattering experiment and applied this double-pass scattering system to the GAMMA 10 plasma. The integrated scattering signal was made about twice as large by the double-pass system. [ABSTRACT FROM AUTHOR]

A novel configuration of the multi-pass Thomson scattering (TS) system is proposed to improve the time resolution and accuracy of electron temperature measurements by use of a polarization control technique. This configuration can realize a perfect coaxial multi-passing at each pass, and the number of round trips is not limited by the optical configuration. To confirm the feasibility of the new method, we installed this system in the GAMMA 10 plasma system. As a result, the integrated scattering signal of the double-pass configuration is about two times larger than that of the single-pass configuration. These results are in good agreement with the design. [ABSTRACT FROM AUTHOR]

The large helical device Thomson scattering system was designed for the target electron temperature (Te) range, Te = 50 eV-10 keV. Above 10 keV, the experimental error becomes rapidly worse. In order to obtain reliable Te data in the temperature range above 10 keV, we are planning to extend the measurable Te range by following two methods. First we have installed one more wavelength channel that observes shorter wavelength region in polychromators. Next applying forward scattering configuration is another candidate. We estimate the data quality when the two methods are used. Both of the two methods are expected to improve Te data quality at Te ≥ 10 keV. [ABSTRACT FROM AUTHOR]