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Doppler-backscattering (DBS) has been used in several fusion plasma devices because it can measure the perpendicular velocity of electron density perturbation v⊥, the radial electric field E r, and the perpendicular wavenumber spectrum S( k⊥) with high wavenumber and spatial resolution. In particular, recently constructed frequency comb DBS systems enable observation of turbulent phenomena at multiple observation points in the radial direction. A dual-comb microwave DBS system has been developed for the large helical device plasma measurement. Since it is desirable to control the gain of each frequency-comb separately, a frequency-comb DBS system was developed with a function to adjust the gain of the scattered signal intensity of each channel separately. A correction processing method was also developed to correct the amplitude ratio and the phase difference between the in-phase and quadrature-phase signals of the scattered signals. As a result, the error in Doppler-shift estimation required to observe vertical velocity and the radial electric field was reduced, which enables more precise measurements.

The analysis method of the Motional Stark Effect (MSE) diagnostic to measure the rotational transform and current profiles in the Large Helical Device has been improved. This was done by using the Variational Moments Equilibrium Code to calculate an equilibrium database for various pressure profiles and current profiles. This method looks for the radial profile of the rotational transform in the equilibrium database that gives the best fit to the polarization angle profiles measured with the MSE diagnostic. This analysis improves the measurements of rotational transform, especially near the magnetic axis, where the sensitivity of the polarization angle measurements becomes low and the uncertainty due to error in the estimation of the Pfirsch-Schlüter current becomes large. The radial profiles of the rotational transform and current profiles for Electron Cyclotron Current Drive and Neutral Beam Current Drive are obtained in the new analysis method with a sufficiently high accuracy to discuss the discrepancy of the current density profiles between the measurements and the calculations.

Retraction: Emoto, M., Emoto, Y., Yoshizawa, I., Kita, E., Shimizu, T., Hurwitz, R., Brinkmann, V. and Kaufmann, S.H.E. (2010), α-GalCer ameliorates listeriosis by accelerating infiltration of Gr-1

This paper presents an overview of the current status of the Virtual Atomic and Molecular Data Centre (VAMDC) e-infrastructure, including the current status of the VAMDC-connected (or to be connected) databases, updates on the latest technological development within the infrastructure and a presentation of some application tools that make use of the VAMDC e-infrastructure. We analyse the past 10 years of VAMDC development and operation, and assess their impact both on the field of atomic and molecular (A&amp, M) physics itself and on heterogeneous data management in international cooperation. The highly sophisticated VAMDC infrastructure and the related databases developed over this long term make them a perfect resource of sustainable data for future applications in many fields of research. However, we also discuss the current limitations that prevent VAMDC from becoming the main publishing platform and the main source of A&amp, M data for user communities, and present possible solutions under investigation by the consortium. Several user application examples are presented, illustrating the benefits of VAMDC in current research applications, which often need the A&amp, M data from more than one database. Finally, we present our vision for the future of VAMDC.

The National Institute for Fusion Science (NIFS) has compiled and developed atomic and molecular numerical databases for various collision processes and makes it accessible from the internet to the public. The database contains numerical data of cross sections and rate coefficients for electron collision or ion collisions with atoms and molecules, attached with bibliographic information on their data sources. The database system provides query forms to search data, and numerical data are retrievable. The graphical output is helpful to understand energy dependence of cross sections and temperature dependence of rate coefficients obtained by various studies. All data are compiled mainly from published literature, and data sources can be tracked by the bibliographic information. We also have data of sputtering yields and back-scattering coefficients for solid surfaces collided by ions in the database. All data in the database are applicable to understand atomic and molecular processes in various plasmas, such as fusion plasma, astrophysical plasma and applied plasma, as well as for understanding plasma&ndash, surface interaction in plasmas.

Density control is crucial for maintaining stable confined plasma. Divertor pumping, where neutral particles are compressed and exhausted in the divertor region, was developed for this task for the Large Helical Device. In this study, neutral particle pressure, which is related to recycling, was systematically scanned in the magnetic configuration by changing the magnetic axis position. High neutral particle pressure and compression were obtained in the divertor for a high plasma electron density and the inner magnetic axis configuration. Density control using divertor pumping with gas puffing was applied to electron cyclotron heated plasma in the inner magnetic axis configuration, which provides high neutral particle compression and exhaust in the divertor. Stable plasma density and electron temperature were maintained with divertor pumping. A heat analysis shows that divertor pumping did not affect edge electron heat conductivity, but it led to low electron heat conductivity in the core caused by electron-internal-transport-barrier-like formation.

The Large Helical Device (LHD) successfully started the deuterium experiment in March 2017, in which further plasma performance improvement is envisaged to provide a firm basis for the helical reactor design. Some major upgrades of facilities have been made for safe and productive deuterium experiments. For radiation safety, the tritium removal system, the integrated radiation monitoring system, and the access control system have been newly installed. Each system has new interlock signals that will prevent any unsafe plasma operation or plant condition. Major interlock extensions have been implemented as a part of the integrated radiation monitoring system, which also has an inter-connection to the LHD central operation and control system. The radiation monitoring system RMSAFE (Radiation Monitoring System Applicable to Fusion Experiments) is already operating for monitoring γ(X)-rays in LHD. Some neutron measurements have been additionally applied for the deuterium experiments. The LHD data acquisition system LABCOM can acquire and process 24 h every day continuous data streams. Since γ(X)-ray and neutron measurements require higher availability, the sensors, controllers, data acquisition computers, network connections, and visualization servers have been designed to be duplicated or multiplexed for redundancy. The radiation monitoring displays in the LHD control room have been carefully designed to have excellent visual recognition, and to make users immediately aware of several alerts regarding the dose limits. The radiation safety web pages have been also upgraded to always show both dose rates of γ(X)-rays and neutrons in real time.

The physical data of the Large Helical Device (LHD) project have been serviced by the Analyzed Data Server system, and approximately 600 kinds of physical data are served. In order to execute simulation programs for the LHD experiment, one must gather sets of physical data. Because the Automatic Analyzed Server (AutoAna) calculates the physical data automatically, it eases the scientist’s task of collecting these physical data. The AutoAna has provided better computing environments for the scientists. Thus, the scientists, having recognized its benefits, make various requests as issues arise. In this paper, the authors introduce the current status of the AutoAna system.

The tongue-shaped deformation (TSD), a possible trigger for the evolution of quasi-stable magneto hydrodynamic (MHD) modes into MHD bursts, was first experimentally identified in the large helical device (LHD) (Ida et al 2016 Sci. Rep. 6 36217). Further analysis has been based on the experimental data in low density (

The isotope effect on impurities and bulk ion particle transport is investigated by using the deuterium, hydrogen, and isotope mixture plasma in the Large Helical Device (LHD). A clear isotope effect is observed in the impurity transport but not the bulk ion transport. The isotope effects on impurity transport and ion heat transport are observed as a primary and a secondary effect, respectively, in the plasma with an internal transport barrier (ITB). In the LHD, an ion ITB is always transient because the impurity hole triggered by the increase of ion temperature gradient causes the enhancement of ion heat transport and gradually terminates the ion ITB. The formation of an impurity hole becomes slower in the deuterium (D) plasma than the hydrogen (H) plasma. This primary isotope effect on impurity transport contributes the longer sustainment of the ion ITB state because the low ion thermal diffusivity can be sustained as long as the normalized carbon impurity gradient R/L n,c, where L c =-(∇n c/n c) -1 is above the critical value (∼-5). Therefore, the longer sustainment of the ITB state in the deuterium plasma is considered to be a secondary isotope effect due to the mitigation of the impurity hole. The radial profile of H and D ion density is measured using bulk charge exchange spectroscopy inside the isotope mixture plasma. The decay time of H ion density after the H-pellet injection and the decay time of D ion density after D-pellet injection are almost identical, which demonstrates that there is no significant isotope effect on ion particle transport.

A 90 GHz W-band millimeter-wave back-scattering system is designed and installed for measuring electron scale turbulence (k⊥ρs ∼ 40). A metal lens relay antenna is used for in-vessel beam focusing, and a beam diameter of less than 40 mm is achieved in the plasma core region. This antenna can be steered at an angle of 159° ± 6°, which almost covers the plasma radius. The estimated size of the scattering volume is ∼105 mm at the edge and 135 mm at the core, respectively. A 60 m corrugated waveguide is used to achieve a low transmission loss of ∼8 dB. A heterodyne detection system for millimeter-wave circuits with probing power modulation can distinguish the scattered signal from background noise.

The Remote Experimentation Centre (REC) in Japan has been preparing to replicate the full dataset of ITER over 10 000 km distance. In such a multi-site data repository environment, the data location informing service will be essential to find and retrieve the data efficiently. Considering the long latency time and the self sustainability of remote sites, the data location database should be running at each repository site. Multi-master asynchronous replication between cooperating databases will be essential to realize the remote experimental collaborations in fusion research. This study has investigated the functional differences of some relational databases and found that Postgres BDR has the expected database replication capabilities. Bi-directional replication (BDR) tests by using the LHD database and SNET revealed that the throughputs are sufficient for remote collaborations in fusion experiments.

During the Large Helical Device (LHD) experiments, many scientists and technical staff are working in the central control room to operate the experiment. They must manage the diagnostics and controlling devices referring to the results of the last plasma shot. Also, the experiment coordinator must decide the conditions for the subsequent experiments using the results. Furthermore, many scientists are participating in the experiment from remote sites. Therefore, it is important to share the information in the control room quickly, such as the results of the last plasma discharge, with the remote user as well as with the staff in the room. In this paper, the data monitoring environment in the LHD central control room is introduced.

The deuterium (D) operation was initiated in the LHD in 2017. In the first campaign of the D experiments, we successfully extended the high temperature regime in the LHD. The new record of the ion temperature (Ti) of 10 keV associated with the ion internal transport barrier (ITB) was achieved due to several operational optimization. The thermal confinement characteristics of ITB plasmas were compared between hydrogen and D discharges. The effective ion thermal diffusivity of the ion-ITB plasmas was found to be smaller in the D discharges than that in the H discharges. The profiles of the Ti, the electron density, and the impurity of the high Ti plasmas strongly depended on the magnetic configuration and these profiles tended to peaked in the inward-shifted configuration. It was also found that the electron thermal confinement of the electron-ITB plasmas was clearly improved in the deuterium case. The GKV simulation showed the linear growth rate of TEM/ITG reduced in the plasmas with D both for the ion ITB and the electron ITB plasmas and qualitatively agreed with the tendency of the change in the thermal diffusivity obtained from the power balance analysis.

A new method for measuring density fluctuation profiles near the edge of plasmas in the Large Helical Device (LHD) has been developed utilizing reflectometry combined with pellet-induced fast density scans. Reflectometer cutoff location was calculated by proportionally scaling the cutoff location calculated with fast far infrared laser interferometer (FIR) density profiles to match the slower time resolution results of the ray-tracing code LHD-GAUSS. Plasma velocity profile peaks generated with this reflectometer mapping were checked against velocity measurements made with charge exchange spectroscopy (CXS) and were found to agree within experimental uncertainty once diagnostic differences were accounted for. Measured density fluctuation profiles were found to peak strongly near the edge of the plasma, as is the case in most tokamaks. These measurements can be used in the future to inform inversion methods of phase contrast imaging (PCI) measurements. This result was confirmed with both a fixed frequency reflectometer and calibrated data from a multi-frequency comb reflectometer, and this method was applied successfully to a series of discharges. The full width at half maximum of the turbulence layer near the edge of the plasma was found to be only 1.5–3 cm on a series of LHD discharges, less than 5% of the normalized minor radius.

Aims The renin–angiotensin system (RAS) plays an important role in the pathogenesis of diabetic nephropathy. The aim of the present study was to investigate intrarenal RAS activity in patients with type 2 diabetes (T2DM). Methods We measured urinary angiotensinogen, a reliable biomarker of intrarenal RAS activity, in 14 controls without T2DM, 25 T2DM patients without nephropathy, 11 chronic kidney disease (CKD) patients without T2DM and 46 CKD patients with T2DM. Associations between urinary angiotensinogen and clinical parameters were examined. Results Compared with the controls, urinary [angiotensinogen:creatinine] were significantly higher in T2DM patients without nephropathy (4.70±2.22 vs. 8.31±5.27μg/g, p =0.037). Age, hemoglobin A1c (HbA1c) and fasting plasma glucose correlated significantly and positively with the log{urinary [angiotensinogen:creatinine]} ( r =0.632, p =0.007; r =0.405, p =0.027; r =0.583, p =0.003, respectively) in T2DM patients without nephropathy. In contrast, the urinary [angiotensinogen:creatinine] were not significantly different between CKD patients with and without T2DM (22.7±27.8 vs. 33.5±40.8μg/g, p =0.740); although they were significantly higher when compared with non-CKD patients. In the CKD patients with T2DM systolic blood pressure, serum creatinine, estimated glomerular filtration rate and urinary [albumin:creatinine] correlated significantly with the log{urinary [angiotensinogen:creatinine]} ( r =0.412, p =0.004; r =0.308, p =0.037; r =−0.382, p =0.001; r =0.648, p Conclusions Our findings indicate that poor glycemic control is significantly associated with intrarenal RAS activity in T2DM patients without nephropathy, and that decreased renal function is significantly associated with intrarenal RAS activity in CKD patients with T2DM.

Aims To examine whether glomerular hemodynamic parameters in humans are associated with glycemic control indices, by simultaneously measuring clearance of inulin (Cin) and para-aminohippuric acid (CPHA). Methods Thirty-one subjects (age 55.4 ± 14.7 years; 15 men and 16 women; 21 diabetics and 10 non-diabetics) were enrolled. Cin and CPAH were measured simultaneously. Afferent arteriolar resistance (Ra), efferent arteriolar resistance (Re), glomerular hydrostatic pressure (Pglo) and glomerular filtration fraction (FF) were calculated according to Gomez’ formula. Results FF correlated significantly and positively with fasting plasma glucose (FPG), hemoglobin A1c (HbA1c) and glycated albumin (GA) (r = 0.396, p = 0.0303; r = 0.587, p = 0.0007; r = 0.525, p = 0.0070, respectively). Pglo correlated significantly and positively with FPG, HbA1c and GA (r = 0.572, p = 0.0008; r = 0.535, p = 0.0019; r = 0.540, p = 0.0053, respectively). Although there was no significant correlation between Ra and glycemic control indices, Re correlated significantly and positively with HbA1c and GA (r = 0.499, p = 0.0043; r = 0.592, p = 0.0018, respectively). FF, Pglo and Re were associated significantly with HbA1c and GA after adjustment for age. Conclusions These results demonstrate, in humans, that poor glycemic control is associated with increased Re, but not Ra. It is suggested that increased Re causes increased Pglo, leading to increased FF. Thus, hemodynamic abnormalities with poor glycemic control may be related to glomerular hypertension in humans.

The use of bright and wide field-of-view (FOV) displays in future TV systems will enable us to enjoy TV programs with a rich sense of presence, i.e., a sense of “being there.” However, such displays can strongly stimulate human peripheral vision, which is sensitive to flicker. The recent widespread adoption of hold-type displays such as liquid crystal displays might circumvent the flicker problem in current TV systems. For temporal specification of future TV systems with bright and wide FOV displays, we measured the critical fusion frequency (CFF) in 26 participants, using varying luminance, duty ratios, and FOVs. We showed that CFF depended on the duty ratio and the FOV, and that more than 90 Hz was required to avoid flicker perception with wide FOV displays. Moreover, we demonstrated that flicker was regularly perceived in viewing wide FOV natural images presented at 60 Hz with a 50% duty ratio.

For superconducting direct current applications, heat leak reduction at the terminal is a key issue for high performance systems and especially for small ones such as the distribution in internet data centers. We propose a double Peltier current lead (PCL), where the suitable combination of two Peltier modules can enhance the performance of PCL. Using the model parameters of actual thermoelectric materials, we estimated the heat leak on PCL using a thermal balance equation. At the double PCL, the large temperature difference on the current lead can be split to two thermoelectric materials and then the performance of PCL can be enhanced. As each of the thermoelectric materials has better working temperature range, an optimized combination of shape factors can be used for the high performance current lead at the terminals for superconducting application systems.

Physical data produced by large helical device (LHD) experiments is supplied by the Kaiseki server, and registers more than 200 types of diagnostic data. Dependencies exist amongst the data; i.e., in many cases, the calculation of one data requires other data. Therefore, to obtain unregistered data, one needs to calculate not only the diagnostic data itself but also the dependent data; however, because the data is registered by different scientists, each scientist must separately calculate and register their respective data. To simplify this complicated procedure, we have developed an automatic calculation system called AutoAna. The calculation programs of AutoAna are distributed on a network, and the number of such programs can be easily increased dynamically. Our system is therefore scalable and ready for substantial increases in the size of the target data.

We succeeded in increasing the radial observation points of the microwave frequency comb Doppler reflectometer system from 8 to 20 (or especially up to 45) using the high sampling rate of 40 GS/s digital signal processing. For a new acquisition system, the estimation scheme of the Doppler shifted frequency is constructed and compared with the conventional technique. Also, the fine radial profile of perpendicular velocity is obtained, and it is found that the perpendicular velocity profile is consistent with the E × B drift velocity one.

The Large Helical Device (LHD) is the world’s largest heliotron-type device with l = 2, m = 10 continuous superconducting helical coils and three pairs of superconducting poloidal coils. The major ...

This paper presents a proposal of the remote participation system for the international thermonuclear experimental reactor (ITER). The object of this paper is to clarify technical issues to analyze the ITER data safely and conveniently. The Japanese case is considered as an example, but technologies presented here can be used worldwide. Major technical issues are as follows: (1) the long distance data transfer; (2) the massive data server; (3) the secure network; (4) the convenient and fast data analysis system. Raw data of ITER can be transferred from France to Japan in a short time by optimizing TCP/IP parameters. The virtual private network (VPN) technology provides a secure environment of the data mirroring and the distributed computation. The analysis server with the WEB user interface enables physicists to analyze the ITER data from the Internet. Streaming data, such as plasma parameters in the steady state, video and sound of the ITER plasma and the status of experiment, which provides feeling of reality, are delivered by using the multi-cast technology. These technologies are being developed in SNET, which is a virtual laboratory for Japanese fusion community. International collaboration is required to develop a global distributed file system and a data analysis system further.

This paper presents the control, data acquisition, data analysis and remote participation facilities of the Large Helical Device (LHD), which is designed to confine the plasma in steady state. In LHD the plasma duration exceeds 3000 s by controlling the plasma position, the density and the ICRF heating. The “LABCOM” data acquisition system takes both the short-pulse and the steady-state data. A two-layer Mass Storage System with RAIDs and Blu-ray Disk jukeboxes in a storage area network has been developed to increase capacity of storage. The steady-state data can be monitored with a Web browser in real time. A high-level data analysis system with Web interfaces is being developed in order to provide easier usage of LHD data and large FORTRAN codes in a supercomputer. A virtual laboratory system for the Japanese fusion community has been developed with Multi-protocol Label Switching Virtual Private Network Technology. Collaborators at remote sites can join the LHD experiment or use the NIFS supercomputer system as if they were working in the LHD control room.

Distributions of the velocity, the temperature and the pressure of a liquid nitrogen (LN2) flow are analyzed at hydraulic cross-sections on two types of superconducting power transmission lines (SC PT). One is on a DC-SC PT, the other is on a three phase AC-SC PT. Inflow heat from the pipe wall and the cables to LN2 are evaluated, however the heat flux from the DC cable is zero. The channels are straight, and hydraulic cross-sections are 3.77 times 10-3 m2 and 4.27 times 10-3 m2 on the DC and AC-SC PT lines, respectively. The increased temperature and the pressure drops on the DC-SC PT lines are lower than those of the AC-SC PT. The fluid velocity dependence on the distance between two cooling stations and on the pump power are estimated. When cooling stations are installed every 10 km, the flow velocity of the DC and AC system are 0.10 and 0.25 m/s, respectively. The pump power of the DC system is dramatically lower compared with the AC system. Therefore, minimizing the SC PT by using DC systems is much more practical.

A higher body mass index (BMI) is a predictor of better survival in hemodialysis patients, although the relative importance of body fat and lean mass has not been examined in the dialysis population. We performed an observational cohort study in 808 patients with end-stage renal disease on maintenance hemodialysis. At baseline, fat mass was measured by dual-energy X-ray absorptiometry and expressed as fat mass index (FMI; kg/m2). Lean mass index (LMI) was defined as BMI minus FMI. During the mean follow-up period of 53 months, 147 deaths, including 62 cardiovascular (CV) and 85 non-CV fatal events, were recorded. In univariate analysis, LMI was not significantly associated with CV or non-CV death, whereas a higher FMI was predictive of lower risk for non-CV death. Analyses with multivariate Cox models, which took other confounding variables as covariates, indicated the independent associations between a higher LMI and a lower risk of CV death, as well as between a higher FMI and a lower risk of non-CV death. These results indicate that increased fat mass and lean mass were both conditions associated with better outcomes in the dialysis population.

To support the steady-state plasma experiments in LHD, new functions have been developed for the LABCOM data acquisition system. Using new WE7000 and PXI digitizers for continuous ultra-wideband data acquisition at 80 MB/s, the system is now able to perform data acquisition, storage, and server-to-client transfer fully in real-time. To manage the high amount of data for long-pulse experiments, the system has been modified to use 64-bit integer values for the number of samples, to segment the compressed data into multiple blocks by using the “titz” library, and to use the JPEG-LS algorithm for compressing image data. Its merit as complete solution for the next generation of fusion experiments has been demonstrated by faultlessly recording an 84 GB shot.

To accomplish a large-scale experiment, such as large helical device (LHD) experiment, effective cooperation among institutes is necessary. In order to establish such cooperation, the NIFS provides the following remote participation facilities for the LHD experiments. (1) Remote access: The user can use a virtual private network (VPN) to connect to the LAN. This is the most flexible technique to participate in the experiments. The users who are not familiar with the experiments can log into the remote server running MetaFrame and Linux. In these computers, the required software is already installed. Therefore, the user need not be concerned with installing software. (2) Remote data reference: A mirror server exists to provide physical data to remote users. Moreover, the users can retrieve summarized data via a web server, which provides summarized information of each discharge experiment and graphs of the principal physical data. These graphs are useful for finding the required data quickly. (3) Remote communication and monitoring: For effective remote cooperation, communication between researchers is very important. For this purpose, a video conferencing system and a video streaming service are available. In addition to these facilities, the NIFS introduced Super SINET in 2002. This is an optical-fiber-based network. The backbone speed of this network is 10 Gbps, and the speed is 1 Gbps for direct connections.

In order to unify various types of data, the Kaiseki Server was developed. This server provides physical experimental data of large helical device (LHD) experiments. Many types of data acquisition systems currently exist in operation, and they produce files of various formats. Therefore, it has been difficult to analyze different types of acquisition data at the same time because the data of each system should be read in a particular manner. To facilitate the usage of this data by researchers, the authors have developed a new server system, which provides a unified data format and a unique data retrieval interface. Although the Kaiseki Server satisfied the initial demand, new requests arose from researchers, one of which was the remote usage of the server. The current system cannot be used remotely because of security issues. Another request was group ownership, i.e., users belonging to the same group should have equal access to data. To satisfy these demands, the authors modified the server. However, since other requests may arise in the future, the new system must be flexible so that it can satisfy future demands. Therefore, the authors decided to develop a new server using a three-tier structure.

To evaluate visual fatigue when viewing stereoscopic TV, a technology expected to become the broadcasting display system of the future. Wide public acceptance of stereoscopic TV awaits resolution of many issues, including visual fatigue on viewing TV images. Visual fatigue was induced using a visual function simulator, consisting of prism and lens optical systems, while viewing stereoscopic TV. We assessed subject visual fatigue through subjective reports of symptoms and by the changes in visual functions. These functions included: viewer B [Js fusional break point, recovery point, accommodation step response, and visual evoked cortical potentials (VECP)]. Significant changes of some visual functions were found after watching simulated stereoscopic TV when the vergence load was heavy or when it changed over time; relative vergence limits decreased and the latency of VECP increased after watching, reflecting visual fatigue. After subjects rested, relative vergence limits recovered to pre-viewing levels. Our findings lead us to conclude that, aside from excessive horizontal binocular parallax, discontinuous changes in parallax is also a major factor that contributes to visual fatigue in the viewing of stereoscopic images. It also causes a decreased range of relative vergence, accommodation response, and a delay in the P100 latency of VECP.

The Large Helical Device is a heliotron device with L = 2 and M = 10 continuous helical coils with a major radius of 3.5–4.1 m, a minor radius of 0.6 m and a toroidal field of 0.5–3 T, which is a candidate among toroidal magnetic confinement systems for a steady state thermonuclear fusion reactor. There has been significant progress in extending the plasma operational regime in various plasma parameters by neutral beam injection with a power of 13 MW and electron cyclotron heating (ECH) with a power of 2 MW. The electron and ion temperatures have reached up to 10 keV in the collisionless regime, and the maximum electron density, the volume averaged beta value and stored energy are 2.4 × 1020 m−3, 4.1% and 1.3 MJ, respectively. In the last two years, intensive studies of the magnetohydrodynamics stability providing access to the high beta regime and of healing of the magnetic island in comparison with the neoclassical tearing mode in tokamaks have been conducted. Local island divertor experiments have also been performed to control the edge plasma aimed at confinement improvement. As for transport study, transient transport analysis was executed for a plasma with an internal transport barrier and a magnetic island. The high ion temperature plasma was obtained by adding impurities to the plasma to keep the power deposition to the ions reasonably high even at a very low density. By injecting 72 kW of ECH power, the plasma was sustained for 756 s without serious problems of impurities or recycling.

One of the main objectives of the LHD is to extend the plasma confinement database for helical systems and to demonstrate such extended plasma confinement properties to be sustained in steady state. Among the various plasma parameter regimes, the study of confinement properties in the collisionless regime is of particular importance. Electron cyclotron resonance heating (ECRH) has been extensively used for these confinement studies of the LHD plasma from the initial operation. The system optimizations including the modification of the transmission and antenna system are performed with the special emphasis on the local heating properties. As the result, central electron temperature of more than 10 keV with the electron density of 0.6 x 10$^{19}$ m$^{-3}$ is achieved near the magnetic axis. The electron temperature profile is characterized by a steep gradient similar to those of an internal transport barrier observed in tokamaks and stellarators. 168 GHz ECRH system demonstrated efficient heating at over the density more than 1.0 x 10$^{20}$ m$^{-3}$. CW ECRH system is successfully operated to sustain 756 s discharge.

A local island divertor (LID) experiment has begun on LHD, with the aims of controlling edge recycling and improving the plasma confinement. The fundamental divertor functions of the LID have been demonstrated in the recent experiments. From the particle flux profile measurements on the LID head it was found that the particles diffusing out from the core region are well guided along the island separatrix to the LID head. Owing to the closed configuration around the LID head, evidence of the high efficient pumping was observed, together with a strong capacity to screen impurities. The first results of edge modeling using the EMC3-EIRENE code are also presented.

Several kinds of computer systems are used to perform large helical device (LHD) experiments, and each produces its own data format. Therefore, it has been difficult to deal with these data simultaneously. In order to solve this problem, the Kaiseki server was developed; it has been facilitating the unified retrieval of LHD data. The data acquired or analyzed by various computer systems are converted into the unified ASCII format, or Kaiseki format, and transferred to the Kaiseki server. With this method, the researchers can visualize and analyze the data produced by various kinds of computers in the same way. Because validations are needed before registering on the Kaiseki server, it takes time to make the validated data available. However, some researchers need data as soon as it is gathered in order to adjust their instruments during the experiments. To satisfy this requirement, a new visualization system has been under development. The new system has two ways to visualize the data as physical values from the raw data. If the conversion task is not complex, the NIFSscope, a visualization tool, converts the raw data into physics data by itself. If the task is too complex to handle, it asks the ANACalc server to make physics data. When the ANACalc server receives a request, it delegates calculation programs to convert the acquired data into physics data. Because the interfaces between the server and the calculation processes are independent of programming languages and operating systems, the calculation processes can be placed on different computers and the server load can be reduced. Therefore, the system can respond to changes in requirements by replacing the calculation programs, and can easily be expanded by increasing the number of calculation servers.

The large helical device (LHD) is the world largest helical system having all superconducting coils. After completion of LHD in 1998, six experimental campaigns have been carried out successfully. The maximum stored energy, central electron temperature, and volume averaged beta value are 1.16 MJ, 10 keV, and 3.2%, respectively. The confinement time of the LHD plasma appears to be equivalent to that of tokamaks. One of the most important missions for LHD is to prove steady-state operation, which is also significant to international thermonuclear experimental reactor (ITER) and to future fusion reactors. LHD is quite appropriate for this purpose based upon the beneficial feature of a helical system, that is, no necessity of the plasma current. So far, the plasma discharge duration was achieved up to 150 s. The plasma density was kept constant by feedback control of gas puffing with real time information of the line density. The issue for demonstrating steady-state operation is whether divertor function to control particle and heat flux is effective enough. Relevant to this, LHD diagnostics should be consistent with the following: 1) continuous operation of main diagnostics during long-pulse operation for feedback control and physics understanding; 2) measurement of fraction of H, He, and impurities in the plasma; 3) heat removal and measure against possible damage or surface erosion of diagnostic components inside of the vacuum chamber; 4) data acquisition system for handling real time data display and a huge amount of data. Although there are already some achievements on the above subjects, there remain still several issues to be resolved. On the other hand, the long-pulse operation of the plasma gives benefits to the diagnostics. For example, the polarizing angle of ECE emission can be changed during the discharge, and the intensity dependence on the polarizing angle has been obtained. The spatial scanning of the neutral particle analyzer and the spectrometer can supply the spatial profiles of the fast neutral particle flux and the specific impurity lines. In this paper, the present status of these issues and future plans are described.

Characteristics of MHD instabilities and their impacts on plasma confinement are studied in current free plasmas of the Large Helical Device. Spontaneous L?H transition is often observed in high beta plasmas close to 2% at low toroidal fields (Bt ? 0.75?T). The stored energy starts to rise rapidly just after the transition accompanying the clear rise in the electron density but quickly saturates due to the growth of the m = 2/n = 3 mode (m and n: poloidal and toroidal mode numbers), the rational surface of which is located in the edge barrier region, and edge localized mode (ELM) like activities having fairly small amplitude but high repetition frequency. Even in low beta plasmas without L?H transitions, ELM-like activities are sometimes induced in high performance plasmas with a steep edge pressure gradient and transiently reduce the stored energy up to 10%. Energetic ion driven MHD modes such as Alfv?n eigenmodes (AEs) are studied in a very wide range of characteristic parameters (the averaged beta of energetic ions, ?b?, and the ratio of energetic ion velocity to the Alfv?n velocity, Vb?/VA), of which range includes all tokamak data. In addition to the observation of toroidicity induced AEs (TAEs), coherent magnetic fluctuations of helicity induced AEs (HAEs) have been detected for the first time in NBI heated plasmas. The transition of a core-localized TAE to a global AE (GAE) is also observed in a discharge with temporal evolution of the rotational transform profile, having a similarity to the phenomenon observed in a reversed shear tokamak. At low magnetic fields, bursting TAEs transiently induce a significant loss of energetic ions, up to 40% of injected beams, but on the other hand play an important role in triggering the formation of transport barriers in the core and edge regions.

Standard diagnostics for fundamental plasma parameters and for plasma physics are routinely utilized for daily operation and physics studies in the large helical device (LHD) with high reliability. Diagnostics for steady-state plasma are under intensive development, especially for Te, ne (yttrium–aluminium garnet (YAG) laser Thomson, CO2 laser polarimeter), data acquisition in steady-state and heat-resistant probes. To clarify the plasma properties of the helical structure, two- or three-dimensional diagnostics are being aggressively developed: tangential cameras (fast SX TV, photon counting CCD, Hα TV); tomography (tangential SX CCD, bolometer); imaging (bolometer, ECE, reflectometer). Divertor and edge physics are important key issues for steady-state operation. Diagnostics for neutral flux (Hα array, Zeeman spectroscopy) and ne (fast scanning probe, Li beam probe, pulsed radar reflectometer) are also in advanced stages of development. In addition to these, advanced diagnostics are being intensively developed in LHD through domestic and international collaborations.

Significant progress has been made with ion cyclotron range of frequencies (ICRF) heating in the Large Helical Device. This is mainly due to better confinement of the helically trapped particles and less accumulation of impurities in the region of the plasma core. During the past two years, ICRF heating power has been increased from 1.35 to 2.7 MW. Various wave-mode tests were carried out using minority-ion heating, second-harmonic heating, slow-wave heating and high-density fast-wave heating at the fundamental cyclotron frequency. This fundamental heating mode extended the plasma density range of effective ICRF heating to a value of 1×1020 m−3. This use of the heating mode was its first successful application in large fusion devices. Using the minority-ion mode gave the best performance, and the stored energy reached 240 kJ using ICRF alone. This was obtained for the inward-shifted magnetic axis configuration. The improvement associated with the axis-shift was common for both bulk plasma and highly accelerated particles. For the minority-ion mode, high-energy ions up to 500 keV were observed by concentrating the heating power near the plasma axis. The confinement properties of high-energy particles were studied for different magnetic axis configurations, using the power-modulation technique. It confirmed that with the inward-shifted configuration the confinement of high-energy particles was better than with the normal configuration. By increasing the distance of the plasma to the vessel wall to about 2 cm, the impurity influx was sufficiently reduced to allow sustainment of the plasma with ICRF heating alone for more than 2 min.

Internal transport barriers with respect to electron thermal transport (eITB) were observed in the large helical device, when the electron cyclotron resonance heating (ECH) power was highly localized on the centre of a plasma sustained by neutral beam injection. The eITB is characterized by a high central electron temperature of 6–8 keV with an extremely steep gradient, as high as 55 keV m−1 and a low electron thermal diffusivity within a normalized average radius ρ≈0.3 as well as by the existence of clear thresholds for the ECH power and plasma collisionality.

The behaviour of high-energy ions accelerated by an ion cyclotron range of frequency (ICRF) electric field in the large helical device (LHD) is discussed. A better confinement performance of high-energy ions in the inward-shifted magnetic axis configuration was experimentally verified by measuring their energy spectrum and comparing it with the effective temperature determined by an electron slowing down process. In the standard magnetic axis configuration a saturation of the measured tail temperature was observed as the effective temperature was increased. The ratio between these two quantities is a measure of the quality of transfer efficiency from high-energy ions to a bulk plasma; when this efficiency was compared with Monte Carlo simulations the results agreed fairly well. The ratio of the stored energy of the high-energy ions to that of the bulk plasma was measured using an ICRF heating power modulation method; it was deduced from phase differences between total and bulk plasma stored energies and the modulated ICRF heating power. The measured high energy fraction agreed with that calculated using the injected ICRF heating power, the transfer efficiency determined in the experiment and the confinement scaling of the LHD plasma.

The present study was undertaken to assess the effect of hyperthyroidism on stiffness in the common carotid artery (CCA) in patients with Graves' disease (GD) and elucidate the mechanism by which arterial stiffness is increased in hyperthyroidism. The arterial stiffness index beta (stiffness beta) was evaluated in the CCA using an ultrasonic phase-locked echo-tracking system. Stiffness beta was defined as the logarithm of the ratio of systolic to diastolic blood pressure divided by the fractional diameter increase during the cardiac cycle and thus established as a measure of arterial stiffness uninfluenced by the change in blood pressure. Seventy euthyroid GD patients were measured for CCA stiffness beta to determine its relationship to retinal blood flow and plasma levels of vascular injury markers. To investigate the effect of hyperthyroidism, 27 GD patients were measured for changes during antithyroid drug (ATD) therapy in stiffness beta and in hemodynamic parameters, retinal blood flow and plasma vascular injury markers. In euthyroid GD patients, stiffness beta in the CCA showed a significant and positive correlation with systolic blood pressure and pulse pressure, but not with peripheral blood flow in the central retinal artery. ATD therapy significantly reduced stiffness beta from 5.23 +/- 2.10 to 4.36 +/- 1.48. The fractional reduction of stiffness beta during ATD therapy correlated significantly with reductions in pulse pressure and retinal blood flow, but not with the reductions in systolic and mean blood pressure, or any of the plasma injury markers. In summary, the significant increase in stiffness beta in the hyperthyroid state may reflect the harmful effect of hyperthyroidism on the arterial wall, which may in turn result from increased stroke volume.

User-friendly visualization tools are indispensable for quick recognition of experimental data. One such tool, the dwscope component of the MDS-Plus system, is widely used to visualize the data that MDS-Plus acquires. However, the National Institute for Fusion Science does not use MDS-Plus, so our researchers on the Large Helical Device (LHD) project cannot use dwscope without modification. Therefore, we developed a new visualization tool, NIFScope. The user interface of NIFScope is based on JavaScope, which is a Java version of dwscope, but NIFScope has its own unique characteristics, including the following: (1) the GUI toolkit is GTK+; (2) Ruby is the equation evaluator; and (3) data loaders are provided as Ruby modules. With these features, NIFScope becomes a multi-purpose and flexible visualization tool. For example, because GTK+ is a multi-platform open source GUI toolkit, NIFScope can run on both MS-Windows and UNIX, and it can be delivered freely. The second characteristic enables users to plot various equations besides experimental data. Furthermore, Ruby is an object-oriented script language and is widely used on the Internet, allowing it to serve not only as an equation evaluator but also as an ordinal programming language. This means users can easily add new data loaders for their own data formats.

The experimentally optimized magnetic field configuration of the Large Helical Device [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)], where the magnetic axis is shifted inward by 15 cm from the early theoretical prediction, reveals 50% better global energy confinement than the prediction of the scaling law. This configuration has been investigated further from the viewpoints of high energy particle confinement and magnetohydrodynamic (MHD) stability. The confinement of high energy ions is improved as expected. The minority heating of ion cyclotron range of frequency was successful and the heating efficiency was improved by the inward shift. The confinement of passing particles by neutral beam injection was also improved under low magnetic field strength, and there could be obtained an almost steady high beta discharge up to 3% in volume average. This was a surprising result because the observed pressure gradient exceeded the Mercier unstable limit. The observed MHD activities became as high as beta but they did not grow enough to deteriorate the confinement of high energy ions or the performance of the bulk plasma, which was still 50% better than the scaling. According to these favorable results, better performance would be expected by increasing the heating power because the neoclassical transport can also be improved there.