Publications (19)19.85 Total impact
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Article: Polaribacter porphyrae sp. nov. isolated from the red alga Porphyra yezoensis and emended descriptions of the genus Polaribacter and two Polaribacter species.
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ABSTRACT: Three Gram-staining-negative, non-motile, strictly aerobic bacterial strains, designated LNM-20(T), LCM-1, and LAM-13, were isolated from thalli of the marine red alga Porphyra yezoensis. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the 3 isolates were associated with the genus Polaribacter in the family Flavobacteriaceae and were closely related to P. dokdonensis DSW-5(T) (96.2 % 16S rRNA gene sequence similarity) and P. gangjinensis K17-16(T) (95.0 %). The DNA G+C content of the 3 isolates was 28.6-29.2 mol%. DNA-DNA hybridization analysis showed that the 3 isolates belonged to a single species distinct from the 2 related species. The only isoprenoid quinone detected was menaquinone-6. The main polar lipids were phosphatidylethanolamine, 2 unidentified amino lipids, and 2 unidentified lipids. The major fatty acids were iso-C(15:0), iso-C(15:1)ω10c, and iso-C(15:0) 3-OH. The phenotypic features of strain LNM-20(T) differed from those of the 2 related species in several regards (colony color, growth with 1 % NaCl and on TSA plus 2.5 % NaCl, hydrolysis of Tweens 40 and 80, and oxidization of 5 carbon compounds). On the basis of the polyphasic analysis, the 3 isolates represent a novel species in the genus Polaribacter, for which the name Polaribacter porphyrae sp. nov. is proposed. The type strain is LNM-20(T) (LMG 26671(T) = NBRC 108759(T)). Emended descriptions of the genus Polaribacter, P. dokdonensis, and P. gangjinensis are also proposed.INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 08/2012; · 2.11 Impact Factor -
Article: Algimonas porphyrae gen. nov., sp. nov., a member of the family Hyphomonadaceae, isolated from a red alga Porphyra yezoensis.
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ABSTRACT: Three Gram-negative, stalked, motile bacteria, designated 0C-2-2(T), 0C-17, and LNM-3, were isolated from a red alga Porphyra yezoensis. 16S rRNA gene sequence analysis revealed that the three novel strains belonged in the family Hyphomonadaceae, and are closely related to Litorimonas taeanensis G5(T) (96.5 % 16S rRNA gene sequence similarity) and Hellea balneolensis 26III/A02/215(T) (94.3 % similarity). The DNA G+C contents of the new isolates (58.5-60.2 mol%) were clearly distinguished from L. taeanensis G5(T) (47.1 mol%) and H. balneolensis DSM 19091(T) (47.9 mol%). The G+C content of L. taeanensis G5(T) obtained in this study was distinct from a previous report (63.6 mol%). DNA-DNA hybridization experiments showed that the new strains constituted a single species. Eleven phenotypic features of the three isolates differed from those of both related genera. The predominant respiratory quinone was ubiquinone-10 and the major fatty acid was C(18:1)ω7c. On the basis of polyphasic taxonomic analysis, the novel strains represent a novel genus and species for which the name Algimonas porphyrae gen. nov., sp. nov. is proposed, with the type strain 0C-2-2(T) (= LMG 26424(T) = NBRC 108216(T)).INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 03/2012; · 2.11 Impact Factor -
Article: Determinants of the clinical outcome of patients with severe acute exacerbation of chronic hepatitis B virus infection.
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ABSTRACT: Severe acute exacerbation of chronic hepatitis B can sometimes occur and lead to hepatic failure and death. The objective of this study was to elucidate the predictors of progression to hepatic decompensation during severe acute exacerbation. We prospectively analyzed 37 consecutive patients with acute exacerbation of chronic hepatitis B (accompanied by jaundice and coagulopathy) for clinical outcome and factors that influenced the development of severe acute exacerbation, including viral kinetics. Fourteen (37.8%) patients progressed to severe acute exacerbation (accompanied by encephalopathy). Multivariate analysis identified serum bilirubin (>5 mg/dl, P = 0.002) as a significant determinant of progression to hepatic failure and prothrombin activity (<45%, P = 0.028) and as a determinant of liver-related death. The hepatitis B virus (HBV) DNA level before therapy was measured in 25 patients. HBV DNA levels increased or did not change from before commencement of treatment in all 11 patients who progressed to severe acute exacerbation. On the other hand, HBV DNA levels did not change or increased in 8 of 14 patients (57%) with acute exacerbation (P = 0.02). Serum bilirubin and prothrombin activities were significant predictors of clinical outcome in patients with severe acute exacerbation of chronic hepatitis B. Viral kinetics until commencement of therapy can predict the severity of acute exacerbation of chronic hepatitis B.Journal of Gastroenterology 02/2012; 47(9):1022-9. · 4.16 Impact Factor -
Article: Long-term efficacy of interferon therapy in patients with chronic hepatitis B virus infection in Japan.
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ABSTRACT: Few studies have investigated the long-term effects of interferon (IFN) therapy for chronic hepatitis B (CHB). In this retrospective study, we investigated the efficacy of and predictors of response to IFN therapy in CHB patients. We analyzed data for 615 Japanese CHB patients (hepatitis B e antigen [HBeAg]-positive 414, HBeAg-negative 201) treated with IFN, and conducted follow up for a median duration of 8.1 years (range 0.5-23.2). Responders were defined as patients who showed continuously normalized alanine transaminase (ALT) levels, HBeAg clearance, and low hepatitis B virus (HBV) DNA levels at 6 months post-treatment or for a span of more than 6 months until each test point at 1, 3, 5, and 10 years. The IFN response rates of all patients were 21, 18, 21, 23, and 25% at 6 months and 1, 3, 5, and 10 years, respectively. On multivariate analysis, significant determinants of the outcome of IFN therapy were as follows: at 6 months and 1 year, young age, low HBV DNA levels, and long duration of treatment; at 3 years, long duration of treatment, young age, and high level of albumin; at 5 years, high level of albumin, female, and pretreated with IFN; and at 10 years, HBeAg-negative. Sixty-nine of the 615 patients (11%) achieved seroclearance of hepatitis B surface antigen (HBsAg). On multivariate analysis, age ≥30 years, HBV genotype A, and male were all independent factors predicting the achievement of HBsAg seroclearance. HBeAg, HBV DNA level, age, sex, albumin, duration of treatment, pretreatment with IFN, and HBV genotype were important factors in determining long-term response to IFN therapy.Journal of Gastroenterology 02/2012; 47(7):814-22. · 4.16 Impact Factor -
Article: Prevalence and predictive factors of diabetes in hepatitis virus positive liver cirrhosis with fasting plasma glucose level of <126 mg/dL.
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ABSTRACT: Aim: The aim of this study was to evaluate the prevalence and predictive factors of diabetes in hepatitis virus positive liver cirrhotic patients with fasting plasma glucose (FPG) level of <126 mg/dL. Methods: A total of 263 patients with hepatitis C virus (HCV) or hepatitis B virus (HBV) positive liver cirrhosis, FPG level of <126 mg/dL, and had diabetes status evaluated by the use of 75-g oral glucose tolerance test (OGTT), were enrolled in this study. Plasma glucose and insulin levels were analyzed periodically for 3 h after oral glucose loading. Diabetes was defined as a 2-h post-load glucose on the OGTT of ≥200 mg/dL. The prevalence of diabetes by use of OGTT and predictive factors for diabetes were evaluated by the use of the Mann-Whitney U-test, Fisher's exact probability test or multivariate analysis by logistic regression. Hypoalbuminemia was defined as serum albumin level of <3.9 g/dL. Elevated indocyanine green retention rate at 15 min (ICG( R) 15) was regarded as ≥ 25%. Results: Out of 263 patients, 44 (16.7%) were diagnosed as having diabetes. Multivariate analysis showed that diabetes occurred when patients had hypoalbuminemia of <3.9 g/dL (odds ratio [OR] 2.33; 95% confidential interval [CI] = 1.04-5.24; P = 0.040) and ICG( R) 15 of <25% (OR 2.36; 95%CI = 1.01-5.58). Conclusions: Hypoalbuminemia and elevated ICG( R) 15 in hepatitis virus related cirrhotic patients with FPG level of <126 mg/day enhance diabetes pattern after OGTT with significant difference.Hepatology Research 01/2012; 42(6):558-63. · 2.20 Impact Factor -
Article: A study on plasma edge boundary in ergodic layer of LHD based on radial profile measurement of impurity line emissions
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ABSTRACT: Vertical profiles of edge impurity emissions have been measured in upper half region of elliptical plasmas at horizontally elongated plasma cross section in large helical device (LHD). The vertical profiles near upper O-point located just below helical coil are analyzed to study the plasma edge boundary of the ergodic layer consisting of stochastic magnetic field lines with connection lengths of 30 ≤ Lc ≤ 2000 m. As a result, C3+ ion emitting CIV spectrum is identified as the ion existing in the farthest edge of the ergodic layer. The peak position of CIV (312.4 Å: 1s23p 2P1/2,3/2-1s22s 2S1/2) vertical profile does not change at all in a wide temperature range of 150 ≤ Te(ρ = 1) ≤ 400 eV, whereas it moves inside the ergodic layer when Te(ρ = 1) is reduced below a threshold temperature, e.g., 130 eV at Rax = 3.75 m configuration. It is found that the C3+ ion exists at the boundary between ergodic layer and open magnetic filed layer at which the Lc distributes in lengths of 5 to 30 m. The result indicates that the edge boundary near the O-point in LHD is determined by a starting point of the open filed layer, where a tokamak-like steeper edge temperature gradient is formed, although the edge boundary is quite obscure at the X-point region. Any plasma does not exist between the edge boundary and the vacuum vessel. The CIV profile at the O-point is simulated using a three-dimensional edge transport code of EMC3-EIRENE in which the magnetic field structure in vacuum is used for the ergodic layer. A clear discrepancy of 8 mm is found in the peak positions of CIV between measurement and simulation for magnetic configurations with thick ergodic layer, i.e., Rax =3.90 m, while only a small discrepancy of 3 mm is observed for those with relatively thin ergodic layer, i.e., Rax = 3.75 m. It suggests that the discrepancy is caused by a modification of the magnetic filed due to the presence of plasma pressure.Physics of Plasmas 08/2011; 18(8):082511-082511-13. · 2.15 Impact Factor -
Article: Study on Radial Position of Impurity Ions in Core and Edge Plasma of LHD Using Space-Resolved EUV Spectrometer
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ABSTRACT: Radial profiles of impurity ions of carbon, neon and iron were measured for high-temperature plasmas in large helical device (LHD) using a space-resolved extreme ultraviolet (EUV) spectrometer in the wavelength range of 60 Å to 400 Å. The radial positions of the impurity ions obtained are compared with the local ionization energies, Ei of these impurity ions and the electron temperatures TeZ there. The impurity ions with 0.3 keV ≤ Ei ≤ 1.0 keV are always located in outer region of plasma, i.e., 0.7 ≤ ρ ≤ 1.0, and those with Ei ≤ 0.3 keV are located in the ergodic layer, i.e., 1.0 ≤ ρ ≤ 1.1, with a sharp peak edge, where ρ is the normalized radial position. It is newly found that TeZ is approximately equal to Ei for the impurity ions with Ei ≤ 0.3 keV, whereas roughly half the value of Ei for the impurity ions with 0.3 keV ≤ Ei ≤ 1.0 keV. It is known that TeZ is considerably lower than Ei in the plasma edge and approaches to Ei in the plasma core. Therefore, this result seems to originate from the difference in the transverse transport between the plasma edge at ρ ≤ 1.0 and the ergodic layer at ρ ≥ 1.0. The transverse transport is studied with an impurity transport simulation code. The result revealed that the difference appearing in the impurity radial positions can be qualitatively explained by the different values of diffusion coefficient, e.g., D= 0.2 m2/s and 1.0 m2/s, which can be taken as a typical index of the transverse transport.Plasma Science and Technology 04/2011; 13(2):140. · 0.41 Impact Factor -
Article: Edge and Core Impurity Transport Study with Spectroscopic Instruments in LHD
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ABSTRACT: Impurity transport was investigated at both edge and core regions in large helical device (LHD) with developed spectroscopic instruments which can measure one- and two-dimensional distributions of impurities. The edge impurity behavior was studied recently using four carbon resonant transitions in different ionization stages of CIII (977Å), CIV (1548Å), CV (40.3Å) and CVI (33.7Å). When the line-averaged electron density, ne, is increased from 1 to 6 × 1013 cm−3, the ratio of (CIII+CIV)/ne increases while the ratio of (CV+CVI)/ne decreases. Here, CIII+CIV (CV+CVI) expresses the sum of CIII (CV) and CIV (CVI) intensities. The CIII+CIV indicates the carbon influx and the CV+CVI indicates the emissions through the transport in the ergodic layer. The result thus gives experimental evidence on the impurity screening by the ergodic layer in LHD, which is also supported by a three-dimensional edge particle simulation. The core impurity behavior is also studied in high-density discharges (ne ≤ 1× 1015 cm−3) with multi H2-pellets injection. It is found that the ratio of V/D (V: convection velocity, D: diffusion coefficient) decreases after pellet injection and Zeff profile shows a flat one at values of 1.1–1.2. These results confirm no impurity accumulation occurs in high-density discharges. As a result, the iron density, nFe, is analyzed to be 6 × 10−7 ( = nFe/ne) of which the amount can be negligible as radiation source even in such high-density discharges. One- and two-dimensional impurity distributions from space-resolved VUV and EUV spectrometers newly developed for further impurity transport study are also presented with their preliminary results.Plasma Science and Technology 08/2009; 11(4):402. · 0.41 Impact Factor -
Article: Experimental study of impurity screening in edge ergodic layer of Large Helical Device using carbon emissions of CIII to CVI
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ABSTRACT: Four resonance transitions of CIII �977.03 Å:2s2 1S0-2s2p 1P1�, CIV �1550 Å:2s 2S-2p 2P�, CV 40.27 Å:1s2 1S0-1s2p 1P1�, and CVI �33.73 Å:1s 2S-2p 2P� have been observed in vacuum ultraviolet and extreme ultraviolet regions to study the edge carbon impurity transport in the Large Helical Device ergodic layer. Here, CIII and CIV indicate the carbon influx at the outside boundary of the ergodic layer and CV and CVI indicate the ions in higher ionization stages, which have already experienced the transport in the ergodic layer. The intensity ratio of CV+CVI to CIII+CIV, therefore, represents the degree of impurity screening, which has been analyzed with different edge plasma parameters and ergodic magnetic field structures. The ratio decreases by two orders of magnitude with an increase in electron density ne in the range of 1–8�1019 m−3. The CV and CVI emissions tend to decrease with ne, whereas the CIII and CIV emissions monotonically increase with ne. The result suggests an enhancement of the impurity screening in the higher ne range due to the increasing ion-impurity collision frequency ���i�1/�s=3.4�104 s−1 at ne=2�1019 m−3 and 1.0�105 s−1 at 6�1019 m−3 for CV�. The friction force parallel to the magnetic fields plays an important role in the edge impurity transport within the ergodic layer. When the ergodic layer structure is thicker, the ratio systematically decreases mainly due to a reduction in CV+CVI emissions. The ratio is also studied by changing the radial position of an externally supplied m/n=1/1 island. When the island is positioned in the ergodic layer, the ratio indicates a remarkable change, i.e., reduction in CV+CVI and increase in CIII+CIV. These experiments demonstrate that the modification of the ergodic magnetic field structure makes a clear change to the edge impurity transport. When the background ion species is changed from hydrogen to helium, the ratio is clearly reduced, at least at ne�4�1019 m−3, suggesting the enhancement of the impurity screening effect due to the increased collisionality. Finally, the experimental result is simulated using three-dimensional edge transport code of EMC3-EIRENE. The density dependence of the carbon ratio can be well reproduced with a simulation code suggesting that impurity screening is induced in the ergodic magnetic field layer.Physics of Plasmas 06/2009; 16:062502. · 2.15 Impact Factor -
Article: Density Regimes of Complete Detachment and Serpens Mode in LHD
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ABSTRACT: In the Large Helical Device (LHD), the hot plasma column shrinks at the high-density regime and complete detachment takes place. Hydrogen volume recombination is observed at complete detachment. This phase is self-sustained under specific experimental conditions and called the Serpens mode (self-regulated plasma edge ‘neath the last-closed-flux-surface). The Serpens mode is achieved after either rapid or slow density ramp up, and either by hydrogen or helium gas puffing. The threshold conditions for complete detachment and the Serpens mode are experimentally documented in the parameter space of heating power and density. The threshold density for the Serpens mode transition increases with ∼ 0.4 power of the heating power. The total radiation is shown to be not adequate to describe the threshold conditions, since it mainly includes the information of very edge region outside the hot plasma column. The operational density limit in LHD, which is sustainable in steady state, has been extended to 1.7 times as high as the Sudo density limit, by applying pellet injection to the Serpens plasmas. -
Article: Pellet Injection and Internal Diffusion Barrier Formation in Large Helical Device
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ABSTRACT: A high density internal diffusion barrier has been produced in the intrinsic helical divertor configuration in LHD by optimizing the pellet fueling scenario and magnetic configuration. The internal diffusion barrier easily appears in the outer shifted magnetic configuration in which magneto-hydrodynamic stability properties are considered to be favorable. The attainable central plasma density becomes higher as the magnetic axis shifts outward and the central density exceed 5 × 10^20m-3. Central pressure exceeds 130 kPa and, therefore, very large Shafranov shift is observed, even at high magnetic field (Bt > 2.54 T). -
Article: Abrupt Flushing of High-Density Core in Internal Diffusion Barrier Plasmas and its Suppression by Plasma Shape Control in LHD
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ABSTRACT: Abrupt flushing of central density occurs in internal diffusion barrier (IDB) plasmas in the Large Helical Device (LHD), where a super dense core (SDC) of the order of 1020 m-3 is formed inside; this event is called “core density collapse (CDC).” CDC must be suppressed as further increase of the central pressure is inhibited. Since CDC is always accompanied by a large Shafranov shift of the plasma center, it has been supposed that mitigation of the Shafranov shift might affect CDC. Vertical elongation of the plasma shape (κ > 1) is effective in mitigating the Shafranov shift, and κ can be controlled with the quadrupole magnetic field BQ. To examine the impact of plasma shape control on CDC, BQ scan experiment has been performed in the LHD. The large Shafranov shift in IDB plasmas is mitigated by increasing κ. As a result, CDC is suppressed and high central β values of approximately 7% have been achieved in vertically elongated plasmas. The optimum κ varies with the magnetic configuration. Beta gradients greater than those at CDC in the κ = 1 configuration are observed without CDC in vertically elongated plasmas. -
Article: Impurity Retention Effect in the Edge Ergodic Layer of the Large Helical Device
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ABSTRACT: The impurity transport characteristics in the ergodic layer of the Large Helical Device (LHD) are analyzed using the 3D edge transport code (EMC3-EIRENE), in comparison with the experimental data. The 3D modeling predicts the impurity retention (screening) in the ergodic layer at the high-density plasma. It is found that the edge surface layer plays an important role in impurity retention, where the friction force significantly dominates over the thermal force. The line intensity measurements of CIII to CVI show consistent behavior with the modeling, indicating impurity retention in the ergodic layer. The applicability of the model for high-Z impurity is also discussed, and it is found that the experimental data is consistent with the results of edge transport modeling. -
Article: Stability and Confinement Studies of High-Performance NBI Plasmas in the Large Helical Device Toward a Steady-State Helical Fusion Reactor
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ABSTRACT: Recent progress in plasma performance and the understanding of the related physics in the Large Helical Device is overviewed. The volume-averaged beta value is increased with an increase in the neutral beam injection (NBI) heating power, and it reached 5.0% of the reactor-relevant value. In high-β plasmas, the plasma aspect ratio should be controlled so that the Shafranov shift would be reduced, mainly to suppress transport degradation and the deterioration of the NBI heating efficiency. The operational regime of a high-density plasma with an internal diffusion barrier (IDB) has been extended, and the IDB, which was originally found using the local island divertor, has been realized in the helical divertor configuration. The central density was recorded as high as 1 × 1021 m-3, and the central pressure reached 130 kPa. Based on these high-density plasmas with the IDB, a new ignition scenario has been proposed. This should be a scenario specific to the helical fusion reactor, in which the helical ripple transport would be mitigated. A low-energy positive-NBI system was newly installed for an increase in the direct ion heating power. As a result, the ion temperature (Ti) exceeded 5.2 keV at a density of 1.2 × 1019 m-3 in a hydrogen plasma. Transport analysis shows improvement of ion transport, and the Ti-increase tends to be accompanied by a large toroidal rotation velocity of the order of 50 km/s in the core region. The plasma properties in the extended operational regime are discussed from the perspective of a steady-state helical fusion reactor. -
Article: Progress in Impurity-Related Physics Experiments in LHD
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ABSTRACT: A variety of density profiles observed in the Large Helical Device (LHD) have suggested an interesting core impurity transport. The edge impurity transport in the ergodic layer formed by stochastic magnetic field lines with long connection length (10-2000 m) can also exhibit interesting phenomena in the competition of perpendicular and parallel transport. The LHD discharge is highly robust against impurity buildup, and operation is possible essentially up to the global power balance limit because current-driven instability does not principally exist. The LHD plasma has therefore provided information on many interesting physics issues closely related to impurities. Recent results of impurity-related physics experiments in the LHD are briefly reviewed. The specific contents presented here are (1) core impurity behavior with perpendicular transport, (2) edge impurity behavior with parallel transport, (3) high-Z discharges with high ion temperature, (4) impurity pellet injection with improved plasma performance, (5) impurity pellet ablation in the presence of energetic ions with high heat flux and (6) observation of magnetic dipole forbidden transitions for high-Z elements. A result from the Compact Helical System (CHS) is used only in the impurity pellet ablation study, because detailed data have not yet been obtained from the LHD. Finally, the results are summarized and future directions in these topics are noted. -
Article: Study of a Closed Divertor Configuration for the Three-Dimensionally Complicated Magnetic Structure in the LHD Plasma Periphery
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ABSTRACT: The distribution of strike points in a closed divertor configuration with additional baffle plates installed in the toroidal ends of closed divertor components near lower/upper ports is calculated by tracing magnetic field lines from the last closed flux surface in various magnetic configurations (radial position of the magnetic axis, Rax = 3.50 ∼ 3.90 m). The calculation shows that the ratio of the number of strike points on additional plates is maximum for Rax = 3.60 m, showing that the plates are effective in this magnetic configuration. Neutral particle transport is investigated using a fully three-dimensional code EIRENE with one-dimensional plasma fluid analysis of divertor legs, where the plasma parameter profiles on the legs are obtained by an iterative calculation including interaction processes between the plasma and neutral particles. The plates raise the pressure of molecular hydrogen locally near the baffle plates to more than 0.2 Pa, which is enough for efficient particle control using vacuum pumping systems installed near the plates. The simulation proposes one possible candidate of optimized closed divertor configuration for the three-dimensionally complicated magnetic structure in the LHD plasma periphery. -
Article: Extension of Improved Particle and Energy Confinement Regime in the Core of LHD Plasma
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ABSTRACT: Recent two major topics of Large Helical Device (LHD) towards fusion relevant conditions, high-density operation and high-ion-temperature operation, are reported. Super dense core plasma was obtained by the combination of repetitive hydrogen ice pellet injection and high power neutral beam injection (NBI) heating. A very peaked density profile with the highest central density of 1.1 × 1021 m-3 was produced showing that the particle transport was suppressed very well in the plasma core. The spatial density profile varies as the position of magnetic axis (Rax), and the steepest profile is obtained at Rax = 3.95 m. The highest central ion temperature of 5.6 keV was obtained in hydrogen plasma at electron density of 1.6 × 1019 m-3 by NBI, where a peaked ion-temperature profile with internal ion energy transport barrier was observed. The profile of electron temperature did not change much and was broad even when the ion temperature had a peaked profile. The central ion temperature is higher than the electron temperature, which is a new operation regime of LHD. High central ion temperature accompanied strong toroidal rotation and an extreme hollow profile of carbon ions (impurity hole). These steep temperature profiles were obtained so far at around Rax = 3.6 m. The compatibility between particle and energy confinement is a new issue of LHD to explore a new operation regime for attractive fusion reactor. -
Article: A closed divertor configuration for reduction of the heat load and efficient particle control for helical fusion reactors
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ABSTRACT: An innovative closed helical divertor concept is proposed for reduction of a heat load on the divertor plates and efficient particle control/pumping. The closed divertor configuration is investigated by a neutral particle transport simulation code coupled with a one-dimensional plasma fluid analysis on the divertor legs for a helical fusion reactor in which the geometry of the plasma and the magnetic field line configuration is same as that in the large helical device (LHD). The closed divertor configuration practically utilizes intrinsic three-dimensional magnetic field line configurations in the plasma periphery (an ergodic layer and divertor legs). The divertor configuration is optimized to an inward shift magnetic configuration in which the best energy confinement time has been achieved, a highly ergodized magnetic field line structure is formed in the inboard side of the torus, and the neutral density there is higher than that in the other region in the LHD vacuum vessel. It means that the divertor configuration is compatible with good main plasma confinement, effective divertor heat load reduction and efficient particle control/pumping from the inboard side. The analysis in this closed helical divertor configuration shows many advantageous over that in the other divertor concepts. -
Article: Development of Imaging Bolometers for 3-D Tomography of Radiation from LHD
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ABSTRACT: Imaging bolometers are a powerful tool for diagnosing plasma radiation in a reactor relevant environment. In a tokamak, an imaging bolometer with a tangential view has demonstrated the ability to provide two-dimensional poloidal profiles of radiation through tomographic inversion under the assumption of toroidal symmetry. In helical devices the imaging bolometers have shown their usefulness in the interpretation of 3-dimensionl radiation structures. In the Large Helical Device, modeling of transport in the stochasitic edge region predicts a very three-dimensional structure in the flow velocities and in the associated accumulation of carbon impurity ions. In this paper we make a proposal for the diagnosis of these three-dimensional radiation structures. This is to be done through the measurement of the radiation using multiple imaging bolometers and the tomographic inversion of their signals to produce a three-dimensional image of the plasma radiation for comparison with the three-dimensional structure of the carbon radiation from the transport model. We present and discuss the recent results of this ongoing research including imaging bolometer development, possible symmetry assumptions and prospective research targets.
Top co-authors
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Institutions
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2011
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The Graduate University for Advanced Studies
Toki, Gifu-ken, Japan
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2009
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National Institute for Fusion Science
Toki, Gifu-ken, Japan
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