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The electron density was measured at various bias voltages to understand how the plasma grid bias affects the electron near the plasma grid in large-scaled negative ion sources. It was found that the response of the electron to the bias voltage changes depending on negative ion production processes. The electron density remarkably decreases with increasing the bias voltage in the pure-volume plasma. On the other hand, the electron density depends on the bias voltage weakly in the Cs-seeded plasma. In addition, it was observed that the response of the co-extracted electron current to the bias voltage has similar trend to that of the electron density.

A comparative study of electromagnetic acceleration in rail-type accelerators with two kinds of rail geometry was carried out. The accelerators were energized by 200 kJ capacitor bank and the weight of loaded projectiles was about 1.3 grams, with a 10 mm*10 mm square bore. The velocity attained was 4.3 km/s in the augmented accelerator, while it was 3.8 km/s in the classical device. These differences in attained velocity are briefly discussed. A theoretical understanding of the rail erosion is also described. >

An 88-year-old Japanese woman with splenomegaly, but without lymphadenopathy, was admitted because of epigastric distress. Laboratory data disclosed an RBC of 310 x 10(4)/microliter, Hb of 10.1 g/dl, Ht of 30.6%, Plt count of 9.8 x 10(4)/microliter, and WBC of 4,470/microliter with 38% abnormal lymphocytes. Peripheral blood films revealed lymphocytes with thin, short cytoplasmic villi, condensed nuclear chromatin, and small nucleoli. The lymphocytes stained negative for tartrate-resistant acid phosphatase. Also, immunophenotyping was positive for expression of the cell surface markers CD19, CD20, IgG, kappa and HLA-DR, but not for CD5, CD10, CD11c, CD23, CD25, CD38, or CD103 antigens. Chromosomal analysis of peripheral blood cells disclosed the 46, XX, del(7), (q32) aberration. A splenectomy was performed simultaneously with partial colon resection because of a mucinous carcinoma found in the transverse colon. Histologic examination of resected spleen tissues revealed a distinctive pattern of white pulp infiltration by lymphoma cells. The histologic findings and clinical data were consistent with the features of splenic lymphoma with circulating villous lymphocytes. Our patient exhibited a relatively benign clinical course, and was being followed on an outpatient basis with no additional therapy.

IL-18 is a multifunctional cytokine playing various regulatory roles in the immune system including induced cytokine production. As a part of our ongoing studies on the molecular mechanisms of IL-18-induced IFN-gamma production, we have examined the transcriptional regulation of the IFN-gamma gene by IL-18 in a human myelomonocytic cell line, KG-1. On the basis of DNA/protein binding, we have determined an IL-18-inducible NF-kappa B binding site located at -786 to -776 of the IFN-gamma gene regulatory region (designated KBBsite). Transient transfection of promoter-reporter gene constructs revealed that the KBBsite is required for full IL-18-induced activation of the IFN-gamma gene transcription induced by IL-18. In addition, stable transformants of a dominant-negative form of the I kappa B alpha showed an inhibition of IL-18-dependent I kappa B alpha degradation, NF-kappa B activation, and expression of IFN-gamma. These results are the first to show the actual significance of the NF-kappa B pathway in the regulation of IFN-gamma gene expression by IL-18.

To determine the source of circulating inhibin and estradiol-17beta during the estrous cycle in mares, the cellular localization of the inhibin alpha, betaA, and betaB subunits and aromatase in the ovary was determined by immunohistochemistry. Concentrations of immunoreactive (ir-) inhibin, estradiol-17beta, progesterone, LH, and FSH in peripheral blood were also measured during the estrous cycle in mares. Immunohistochemically, inhibin alpha subunits were localized in the granulosa cells of small and large follicles and in the theca interna cells of large follicles, whereas inhibin betaA and betaB subunits were localized in the granulosa cells and in the theca interna cells of large follicles. On the other hand, aromatase was restricted to only the granulosa cells of large follicles. Plasma ir-inhibin concentrations began to increase 9 days before ovulation; they remained high until 2 days before ovulation, after which they decreased when the LH surge was initiated. Thereafter, a further sharp rise in circulating ir-inhibin concentrations occurred during the process of ovulation, followed by a second abrupt decline. After the decline, plasma concentrations of ir-inhibin remained low during the luteal phase. Plasma estradiol-17beta concentrations followed a profile similar to that of ir-inhibin, except during ovulation, and these two hormones were positively correlated throughout the estrous cycle. Plasma FSH concentrations were inversely related to ir-inhibin and estradiol-17beta. These findings suggest that the dimeric inhibin is mainly secreted by the granulosa cells and the theca cells of large follicles; granulosa cells of small follicles may secrete inhibin alpha subunit, and estradiol-17beta is secreted by the granulosa cells of only large follicles in mares.

The progress of physical understanding as well as parameter improvement of net-current-free helical plasma is reported for the Large Helical Device since the last Fusion Energy Conference in Daejeon in 2010. The second low-energy neutral beam line was installed, and the central ion temperature has exceeded 7 keV, which was obtained by carbon pellet injection. Transport analysis of the high-T-i plasmas shows that the ion-thermal conductivity and viscosity decreased after the pellet injection although the improvement does not last long. The effort has been focused on the optimization of plasma edge conditions to extend the operation regime towards higher ion temperature and more stable high density and high beta. For this purpose a portion of the open helical divertors are being modified to the baffle-structured closed ones aimed at active control of the edge plasma. It is compared with the open case that the neutral pressure in the closed helical divertor increased by ten times as predicted by modelling. Studies of physics in a three-dimensional geometry are highlighted in the topics related to the response to a resonant magnetic perturbation at the plasma periphery such as edge-localized-mode mitigation and divertor detachment. Novel approaches of non-local and non-diffusive transport have also been advanced.

A reversal of intrinsic torque is observed during the formation of an internal transport barrier (ITB) in the Large Helical Device. The intrinsic torque evaluated from the disparity of rotation between coinjection and counterinjection changes sign from counter to codirection inside the ITB after the ITB formation. Both the internal transport barrier and the reversal of the intrinsic torque propagate inwards. This experiment demonstrates that the sign of the nondiffusive term of momentum transport is sensitive to the confinement mode of heat transport.

Alfven eigenmode (AE) activity driven by NBI-produced fast ions is observed in TJ-II plasmas. A two-step response of the measured AEs to electron cyclotron heating (ECH) power is seen. In a first step, the continuous character of the unstable AEs changes to a chirping character of the marginally unstable AEs when moderate values of ECH power are applied to the NBI-only-heated plasma. In a second step, a significant reduction of the AE amplitude is observed when the ECH power is doubled. This stabilizing effect has been experimentally confirmed both on a shot-by-shot basis and along a single discharge by means of ECH modulation. The observed stabilizing effect is stronger with on-axis ECH than with off-axis ECH power injection.

A central ion temperature of 7 keV in a neutral beam injection (NBI)-heated plasma and a central-electron temperature of 20 keV in an electron cyclotron resonance heating plasma were achieved in the Large Helical Device (LHD) using an upgraded heating system with a newly installed perpendicular-NB injector and gyrotrons. The values of Ti and Te significantly exceeded 5.6 and 15 keV, obtained in previous experiments, respectively. High-Ti plasma was obtained using a carbon pellet injection and the kinetic-energy confinement improved by a factor of 1.5. Transport analysis of the high-Ti plasmas showed that the ion-thermal diffusivity and the viscosity were reduced after the pellet injection. Dynamic-transport analysis is applied and the transition to the ion-internal-transport barrier and back transition are discussed.

Three-dimensional effects on plasma flows have been experimentally studied in the large helical device with 3D configurations. Spontaneous toroidal flow without net driving force using the combination of perpendicular neutral beam injection (NBI) heating and balanced tangential NBI heating has been investigated with two magnetic configurations. Co- and counter-directed spontaneous flows have been observed depending on the collisionality. Toroidal flow shear changes the sign at 0.4

Dynamic transport study taking account of the slowing-down effect on the neutral beam injection heating is applied to a high ion temperature plasma with an ion internal transport barrier (ITB) obtained by carbon pellet injection, which records the highest ion temperature of around ~7 keV in the Large Helical Device. The transient increase in ion heating is clarified during the density decay phase just after the carbon pellet injection by considering the slowing-down effect. The dynamic transport analysis also includes the change in heat flux due to the change in kinetic energy inside the plasma with the time scale of the global energy confinement time, which is required to investigate the heat and momentum transport during the transient phase more exactly. The characteristics of the ion heat and momentum transport improvement during the ion ITB formation phase are clarified by the dynamic transport study.

A questionnaire written in Portuguese was administered from December 1993 to February 1994 to study the frequency of allergic symptoms among Brazilians of Japanese descent in Japan. The results obtained were as follows. 1) The frequencies of allergy histories were 18% for allergic rhinitis, 14% for atopic dermatitis, 12% for alimentary allergy, 10% for allergic conjunctivitis, 9% for allergy to metals, 8% for drug allergy, 7% each for urticaria and pollinosis, and 5% for asthma. 2) The frequencies of allergic rhinitis, allergic conjunctivitis, pollinosis, urticaria and drug allergy were higher among those who came from metropolitan districts in Brazil with severe environmental pollution compared to those who came from rural districts. 3) The characteristics of persons who had subjective symptoms of pollinosis in early spring during their stay in Japan were as follows: The districts they resided in while in Japan were in the Kanto area where the frequencies of Japanese-cedar pollen-specific IgE antibodies positives were high and also where the frequencies of Japanese cedar pollinosis were high among Japanese living in Japan. The districts they originally came from were the metropolitan areas in Brazil, and they were resident in Japan for more than one year.

Alfvén eigenmodes (AEs) were studied in neutral beam injection (NBI) heated plasmas in the TJ-II stellarator using a heavy ion beam probe (HIBP) in the core, and by Langmuir (LP) and Mirnov probes (MP) at the edge. AEs were detected over the whole plasma radius by the HIBP with a spatial resolution of about 1 cm. AE-induced oscillations were detected in the plasma density n e, electric potential φ and poloidal magnetic field B pol with frequencies 50 kHz f AE k θ , mode numbers m(m V θ ∼ 30 km s−1 were detected for various branches of AEs, having different radial locations. When the density rose due to NBI fuelling, the AE frequency decreased as predicted by the Alfvén law . During the AE frequency decay the following new AE features were observed: (i) the poloidal wave-vector k θ and mode number m remained constant, (ii) the cross-phases between the oscillations in B pol, n e and electric potential remained constant, having an individual value for each AE branch, (iii) V θ decreased proportional to the AE frequency. The interaction of the AEs with the bulk (thermal) plasma resulted in clearly pronounced quasi-coherent peaks in the electrostatic turbulent particle flux spectra. Various AE branches exhibited different contributions to the particle flux: outward, inward and also zero, depending on the phase relations between the oscillations in E pol and n e, which are specific for each branch. A comparison with MHD mode modelling indicated that some of the more prominent frequency branches can be identified as radially extended helical AEs.

Electron density measurements of a large-scaled negative ion source were carried out with a surface wave probe. By comparison of the electron densities determined with the surface wave probe and a Langmuir probe, it was confirmed that the surface wave probe is highly available for diagnostic of the electron density in H(-) ion sources. In addition, it was found that the ratio of the electron density to the H(-) ion density dramatically decreases with increase of a bias voltage and the H(-) ions become dominant negative particles at the bias voltage of more than 6 V.

We report on the characteristics of the electronegative plasma in a large-scale hydrogen negative ion (H(-)) source. The measurement has been made with a time-resolved Langmuir probe installed in the beam extraction region. The H(-) density is monitored with a cavity ring-down system to identify the electrons in the negative charges. The electron-saturation current decreases rapidly after starting to seed Cs, and ion-ion plasma is observed in the extraction region. The H(-) density steps down during the beam extraction and the electron density jumps up correspondingly. The time integral of the decreasing H(-) charge density agrees well with the electron charge collected with the probe. The agreement of the charges is interpreted to indicate that the H(-) density decreasing at the beam extraction is compensated by the electrons diffusing from the driver region. In the plasmas with very low electron density, the pre-sheath of the extraction field penetrates deeply inside the plasmas. That is because the shielding length in those plasmas is longer than that in the usual electron-ion plasmas, and furthermore the electrons are suppressed to diffuse to the extraction region due to the strong magnetic field.

A seroepidemiologic study of house dust allergy and pollinosis was performed among a general population aged 17 to 69 in Aichi Prefecture, Japan. The prevalence of blood containing IgE antibodies to four perennial antigens and three seasonal antigens was examined among 198 persons whose serum total IgE antibodies were above 40 IU/ml. The prevalence of blood containing IgE antibodies was from 9 to 18 percent among perennial antigens and from 6 to 30 percent among seasonal antigens. These results show that Dermatophagoides farinae, Cryptomeria japonica pollen and Anthoxanthumodoratum pollen are important antigens in this population.

The peaked ion-temperature profile with steep gradient, the so-called ion internal transport barrier (ion ITB), was formed in the neutral beam heated plasmas on the Large Helical Device and the high-ion-temperature regime of helical plasmas has been significantly extended. The ion thermal diffusivity in the ion ITB plasma decreases down to the neoclassical transport level. The heavy ion beam probe observed the smooth potential profile with negative radial electric field (ion root) in the core region where the ion thermal diffusivity decreases significantly. The large toroidal rotation was also observed in the ion ITB core and the transport of toroidal momentum was analysed qualitatively. The decrease in momentum diffusivity with ion temperature increase was observed in the ion ITB core. The toroidal rotation driven by ion-temperature gradient, the so-called intrinsic rotation, is also identified.

A heavy ion beam probe was installed on the Large Helical Device (LHD) to investigate the roles of radial electric fields (Er) in magnetically confined high-temperature plasmas. Two new observations are presented. One is the observation of electrostatic potential profiles during the formation of extremely hollow density profiles of impurities, called the impurity hole (Ida K et al 2009 Phys. Plasmas 16 056111), in the LHD plasmas. The measured Er is negative, and the Er determined by the ambipolarity condition of neoclassical particle fluxes is consistent with this observation. However, the transport analysis indicates that the formation of the extremely hollow profile is not attributable to the impurity fluxes driven by Er and the density and temperature gradients of the impurity. The other new observation is on the geodesic acoustic mode (GAM). The electrostatic potential fluctuation associated with the GAM, which is probably induced by energetic particles, in plasmas with the reversed or weak magnetic shear is identified. The GAM is localized in the core region of the plasma.

Energetic ion driven Alfvén eigenmodes (AEs) are believed to be an important element disturbing the transport in a future fusion reactor. The studies of the AE properties in modern toroidal devices have made crucial contributions to the reactor relevant physics. AEs are conventionally studied by magnetic probes (MPs), which provide the poloidal m and toroidal n mode numbers and their spectral characteristics. Heavy ion beam probing (HIBP) has become a new tool to study AEs with high spatial and frequency resolution. HIBP in the TJ-II heliac observes locally (∼1 cm) resolved AEs over the whole radial interval. The set of low-m (m < 8) modes, detected with the high-frequency resolution (f AE < 300 kHz. Various AE modes are visible in the neutral beam injector (NBI)-heated plasma for co-NBI (, and the cross-phase between the plasma density, poloidal magnetic field and potential remains constant. The amplitude of the AE potential oscillations δφAE ∼ 10 V was estimated. Poloidally resolved density and potential measurements may provide information about the AE poloidal wavelength and the AE contribution to the poloidal electric field E pol and the turbulent particle flux 𝚪 E × B . The typical range of E pol oscillations for AEs is . Depending on the δn e and δE pol amplitudes and cross-phase, AEs may make a small or a significant contribution to the turbulent particle flux 𝚪 E × B for the observed wavenumbers k θ < 3 cm−1.

Characteristics of multibeamlets are investigated by means of beamlet monitoring technique. The beamlets are extracted from an accelerator with multislot grounded grid and the profiles are observed as infrared images of temperature distributions on a cold isostatic pressed graphite plate exposed by H-beamlets. The optimal horizontal and vertical divergence angles of single beamlet are estimated at 4.1 and 6.1 mrad, respectively.

Remarkable progress in the physical parameters of net-current free plasmas has been made in the Large Helical Device (LHD) since the last Fusion Energy Conference in Chengdu, 2006 (Motojima et al 2007 Nucl. Fusion 47 S668). The beta value reached 5% and a high-beta state beyond 4.5% from the diamagnetic measurement has been maintained for longer than 100 times the energy confinement time. The density and temperature regimes have also been extended. The central density has exceeded 1 × 1021 m−3 due to the formation of an internal diffusion barrier. The ion temperature has reached 5.2 keV at the density of 1.6 × 1019 m−3, which is associated with the suppression of ion heat conduction loss. Although these parameters have been obtained in separated discharges, each fusion-reactor relevant parameter has elucidated the potential of net-current free heliotron plasmas. Diversified studies in recent LHD experiments are reviewed in this paper.

Dynamics of ion internal transport barrier (ITB) formation and impurity transport both in the Large Helical Device (LHD) heliotron and in the JT-60U tokamak are described. Significant differences between heliotron and tokamak plasmas are observed. The location of the ITB moves outwards during the ITB formation regardless of the sign of magnetic shear in JT-60U, and the ITB becomes more localized in plasmas with negative magnetic shear. In LHD, a low T e/T i ratio (

Stable toroidicity-induced Alfvén eigenmodes (TAEs) with low toroidal mode number (n = 1 and n = 2) were excited by application of alternating magnetic field perturbations generated with a set of electrodes inserted into the edge region of neutral beam injection heated plasmas on the Compact Helical System [ K. Nishimura, K. Matsuoka, M. Fujiwara et al., Fusion Technol. 17, 86 (1990) ]. The gap locations of TAEs excited by the electrodes are in the plasma peripheral region of ρ>0.7 (ρ is the normalized minor radius) where energetic ion drive is negligibly small, while some AEs are excited by energetic ions in the plasma core region of ρ

Spontaneous toroidal flows driven by radial electric fields and ion temperature gradients are studied in the Large Helical Device (LHD). The positive radial electric field drives spontaneous flow in the counter-direction at the plasma edge and in the co-direction near the magnetic axis. The difference in the direction of the spontaneous flow between the core and the edge is considered to be due to the difference in the ratio of the helical ripple to the toroidal ripple. It is clearly observed that the ion temperature gradient causes a spontaneous toroidal flow and is expected to be one of the dominant components of the toroidal flows in the high ion temperature discharges in the LHD.

An extremely hollow profile of carbon impurity (denoted as an ‘impurity hole’) is observed associated with an increase in the ion temperature gradient after an impurity injection in the Large Helical Device. The central carbon density drops to 0.3% of the plasma density due to a strong outward convection driven by the ion temperature gradient, while an inward convection is predicted by neoclassical theory. Transport analysis gives a low diffusion coefficient of 0.4 m2 s−1 and an outward convection velocity of 3 m s−1 at half of the minor radius.

Extremely hollow profiles of impurities (denoted as “impurity hole”) are observed in the plasma with a steep gradient of the ion temperature after the formation of an internal transport barrier (ITB) in the ion temperature transport in the Large Helical Device [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)]. The radial profile of carbon becomes hollow during the ITB phase and the central carbon density keeps dropping and reaches 0.1%?0.3% of plasma density at the end of the ion ITB phase. The diffusion coefficient and the convective velocity of impurities are evaluated from the time evolution of carbon profiles assuming the diffusion and the convection velocity are constant in time after the formation of the ITB. The transport analysis gives a low diffusion of 0.1?0.2 m2/s and the outward convection velocity of ~1 m/s at half of the minor radius, which is in contrast to the tendency in tokamak plasmas for the impurity density to increase due to an inward convection and low diffusion in the ITB region. The outward convection is considered to be driven by turbulence because the sign of the convection velocity contradicts the neoclassical theory where a negative electric field and an inward convection are predicted.

Edge transport barrier (ETB) formation and a reheat mode have been simultaneously realized on the Compact Helical System (CHS). The new mode is induced by neutral particle reduction in the edge region, which is caused by shutting off fueling after a strong gas-puffing. When both the reheat mode and the ETB are simultaneously realized, the density reduction is suppressed by the ETB in the peripheral region, and the temperature continues to increase by the reheat mode. This mode provides an enhanced confinement in the high density region (e ~ 1.2 × 1020mr-3) compared to the ETB formation without the reheat mode, because of a large suppression of an anomalous transport, which is confirmed with fluctuation measurements in the edge region.

The formation of an edge transport barrier (ETB) has been observed in the high-density region (ne ~ 1.0 × 1020 m-3) of the Compact Helical System (CHS). The high-density ETB is observed in so-called 'reheat mode' discharge, an improved confinement mode in which the temperature increases due to the change of density profile by controlling gas-puff fueling. In the present study, we investigated the behaviour of the density profile and the density fluctuations in the edge region accompanied by the formation of the high-density ETB using beam emission spectroscopy (BES), and we compared the behaviour with that of the normal ETB transition of CHS. BES has been implemented in CHS to simultaneously measure both local density fluctuations and gradients. It revealed that the density, density gradient, and inverse value of the density scale length increase in the edge region at both the normal ETB transition and the high-density ETB transition. The turbulence of the frequency at less than 20 kHz is suppressed at the formation of the high-density ETB.

High-ion-temperature (exceeding 5 keV) hydrogen plasmas have been successfully produced in the Large Helical Device [Iiyoshi et al., Nucl. Fusion 39, 1245 (1999); Motojima et al., Nucl. Fusion 47, S668 (2007)] with the ion heat confinement improvement in the core region. The experimental ion heat diffusivity at the core region is found to be almost independent of the ion temperature, T_i (even decreasing as T_i increases). The neoclassical (NC) ripple transport is suppressed by the ambipolar radial electric field, E_r (

The experimental studies on zonal flows and turbulence have been carried out in Compact Helical System [K. Matsuoka, S. Kubo, M. Hosokawa, in Plasma Physics and Controlled Nuclear Fusion Research, Proc. 12th Int. Conf., Nice, 1988 (International Atomic Energy Agency, Vienna, 1989, Vol. 2, p. 411] using twin heavy ion beam probes. The paper presents the experimental observations of stationary zonal flow, nonlinear couplings between zonal flow and turbulence, and the role of zonal flow in the improved confinement, together with the recent discovery of zonal magnetic field. The presented experimental results strongly support the new paradigm that the plasma transport should be considered as a system of drift wave and zonal flows, and provides the first direct evidence for turbulence dynamo that the structured magnetic field can be really generated by turbulence. © 2008 American Institute of Physics.

The beam profiles, port-through, rates and injection powers obtained with an improved accelerator with the multislot grounded grid are described. The accelerator has a combination of a steering grid with racetrack shaped aperture and multislot grounded grid to improve the beam optics. The optimal beam optics is obtained at the voltage ratio of 16.5-16.8, and the profiles are well fit by superposing multibeamlets with the divergent angles of 5.0 and 7.2 mrad along the direction parallel to the long and short axes of the slots of grounded grid. By adopting the racetrack shaped steering grid, the port-through rate increases from 34% to 38%, and the maximum injection power reaches 6 MW/187 keV.

A case of Reiter's syndrome with severe keratoderma being successfully treated with oral Etretinate is reported. A 38 year-old man was referred to our hospital in December, 1985 for treatment of refractory skin eruptions and polyarthralgia. He previously experienced urethritis in December, 1983 with subsequent development of high fever, balanitis, skin eruptions and polyarthritis. Treatments with antibiotics, anti-inflammatory drugs and glucocorticoids were ineffective at that time. The patient was diagnosed as Reiter's syndrome based on his clinical symptoms and the presence of HLA-B27. He was treated in our clinic with oral administration of Etretinate, aromatic retinoids, at the initial doses of 40 mg/day with subsequent increase up to 75 mg/day in 2 weeks. This maintenance dose was continued for two months, resulted in improvements of joint pain, skin eruptions and the laboratory abnormalities. The doses of Etretinate was gradually decreased and then was discontinued after 4 months, when approximately 90% of the skin lesion disappeared. No noticeable side-effect was observed except slight stomatitis. The remission continued for about 2 and half years after cessation of Etretinate without any medication. However, evidence of relapse with the same skin lesions and arthralgia was observed in March, 1989. A repeated treatment with oral Etretinate was attempted with similar but slightly delayed effects.

One of the three C-P bond formation steps, defined as step 5 in the bialaphos (BA) biosynthetic pathway, was analyzed using a new BA non-producing mutant NP71. The mutant was derived from a BA producer by gene replacement of an unidentified region next to the gene responsible for the step 5 deficiency of the mutant NP213, obtained by conventional mutation procedures. Biochemical analysis of these two mutants indicated that NP71 was defective in the formation of carboxyphosphonoenolpyruvate (CPEP), while NP213 lacked the enzyme CPEP phosphonomutase, which catalyzed the intramolecular rearrangement of CPEP.

The main purpose of this work was to investigate the possibility of solid state amorphization of Ni-B crystal powder. A Ni-B alloy powder was obtained by mechanical alloying of Ni and B powder using a conventional ball milling machine. X-ray diffraction and EXAFS measurements were made for the mechanically alloyed samples as a function of milling time. An amorphization reaction was observed in Ni64B36 at 400 h of milling time. The long range order of the crystalline Ni phase diminished with an increase of solution of B into the Ni matrix. This suggests that the solution of B atoms into the Ni crystalline phase, forced by mechanical alloying, plays an important role in the crystalamorphous transformation.

The 3-D spatial structure - radial locality and poloidal /toroidal mode numbers - of the magnetohydrodynamic fluctuation called “edge harmonic oscillation (EHO)” in the compact helical system (CHS) was investigated using beam emission spectroscopy (BES) as the diagnostic method of the local density fluctuations and the magnetic probe array. We found two groups of harmonic oscillations in CHS, one with a frequency of 4.0 kHz and a harmonic located in the edge region of the normalized minor radius ρ = 0.95 near the rotational transform ι = 1 surface, and the other with a frequency of 3.5 kHz and a harmonic located in the core region ρ = 0.53 near the ι = 0. 5s urface. The magnetic probe signals showed that the poloidal/toroidal mode numbers of the edge mode and the core mode were −1/ 1a nd−2/1, respectively. They were consistent with the rotational transform of the magnetic field at the locations of those modes. c

In reduced recycling discharges using a local island divertor in the Large Helical Device [O. Motojima, H. Yamada, A. Komori et al., Phys. Plasmas 6, 1843 (1999)], a stable high-density plasma develops in the core region when a series of pellets is injected. A core region with ~5×10^20 m^?3 and temperature of 0.85 keV is maintained by an internal diffusion barrier (IDB). The density gradient at the IDB (r/a~0.6) is very high, and the particle confinement time in the core region is ~0.4 s. Because of the increase in the central pressure, a large Shafranov shift up to ~0.3 m is observed. The critical ingredients for IDB formation are a strongly pumped divertor to reduce edge recycling, and multiple pellet injection to ensure efficient central fueling. No serious magnetohydrodynamics activity and impurity accumulation have been observed so far in this improved discharge.

The ergodization of the magnetic field lines imposed by the dynamic ergodic diverter (DED) in TEXTOR can lead both to confinement improvement and to confinement deterioration. The cases of substantial improvement are in resonant ways related to particular conditions in which magnetic flux tubes starting at the X points of induced islands are connected with the wall. This opening process is connected with a characteristic modification of the heat deposition pattern at the divertor target plate and leads to a substantial increase and steepening of the core plasma density and pressure. The improvement is tentatively attributed to a modification of the electric potential in the plasma carried by the open field lines. The confinement improvement bases on a spontaneous density built up due to the application of the DED and is primarily a particle confinement improvement.

Electric field fluctuations are directly measured using twin heavy-ion-beam probes in Compact Helical System. The spectrum of the electric field fluctuation reveals the existence of a zonal flow at a frequency of less than 1 kHz, coherent modes with a long correlation length (conjectured as geodesic acoustic modes), and background turbulence. Analyses using a wavelet elucidate nonlinear interactions between these fluctuation components in disparate scales. The highlighted findings are that the turbulent fluctuations should be modulated in response to the direction of zonal flow, and should be suppressed, on average, by the zonal flow. This is the first observation that demonstrates the causal linkage between zonal flow and turbulence in toroidal plasmas at a high temperature.

Polarimeters based on the Cotton-Mouton effect hold promise for electron density measurements. We have designed and installed a Cotton-Mouton polarimeter on the Compact Helical System. The Cotton-Mouton effect is measured as the phase difference between probe and reference beams. In this system, an interferometric measurement can be performed simultaneously with the same probe chord. The light source is a HCN laser (wavelength of 337 ?m). Digital complex demodulation is adopted for small phase analysis. The line averaged density evaluated from the polarimeter along a plasma center chord is almost consistent with that from the interferometer.

The purpose of this work is to measure lost fast ions as an ion current so as to make quantitative argument on flux of fast-ion loss possible. We have designed and constructed a lost fast-ion probe based on combination of thin Faraday films and small rectangular apertures, called FLIP, for the Compact Helical System. The current generated by escaping fast ions has been successfully measured with the FLIP in neutral-beam-heated plasmas. The FLIP detected increased flux of escaping fast ions while fast-ion-driven magnetohydrodynamics instabilities appear.

In the present study, a coherent density fluctuation similar to the edge harmonic oscillation (EHO) in tokamaks was observed in the edge transport barrier discharge in the Compact Helical System (CHS) [K. Matsuoka et al., Plasma Physics and Controlled Nuclear Fusion Research, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 2, pp. 441] using beam emission spectroscopy (BES). The fluctuation had both fundamental (f=4.5 kHz) and second-harmonic (2f=9 kHz) frequencies. EHO in CHS had a peak amplitude at approximately ρ=0.95. The mode has a continuous phase shift in the radial direction. If this is interpreted as the radial propagation, the mode propagates in the outer radial direction at an apparent phase velocity of several hundreds of meters per second, which is a characteristic similar to the radial phase shift of EHO in tokamaks.