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JT-60SA is the satellite tokamak under construction in Naka, Japan, in the framework of the EU-JA -Broader Approach? Agreement. In JT-60SA, to attain steady-state high-beta plasmas, suppression of Resistive Wall Modes (RWM) is necessary. At this purpose, a passive stabilizing plate (SP) and an active control system based on 18 in-vessel sector coils (SC) are foreseen. In the past years, physics studies have been carried out to produce the inputs for the design of the RWM control system and the SC design evolved accordingly. In the present arrangement, the coils are placed on the plasma side of SP, to minimize the magnetic shielding effects of passive structures. Electromagnetic analyses on SC have been carried out in support to the evaluation of the different coil design solutions and to derive the requirements for the related power supply system (RWM-PS). To achieve the highest flexibility in RWM control, it has been devised to feed each SC independently, with currents following 18 real-time references. In 2012, the SC design has been further improved by increasing the number of turns from 2 to 8. This allowed reducing the rated current, thus the voltage drops on the feeders and the power required from RWM-PS. To keep the RWM under control with relatively low Ampere-turns (2.2 kAt), the RWM-PS has to guarantee very fast dynamics (current bandwidth: 3 kHz; maximum latency: 50 us), largely beyond that of standard industrial applications. This paper firstly reports the main requirements for the RWM control system. Then, the reference design of the RWM-PS is described. It includes an ac/dc conversion system, dc-link capacitor banks and a set of 18 fast inverters. The advantages of the proposed scheme are discussed and the main electrical parameters are shown in detail. The main requirements of the control section are given, with details on possible implementation and interfaces with JT-60SA central control.

In the present RF-driven plasma with a lot of high-energy electrons, there may be anisotropic plasma pressure, which makes the usual equilibrium analysis difficult, but the Cauchy condition surface method can reconstruct the plasma shape precisely regardless of the anisotropy. In addition, the plasma current effect in the open magnetic surfaces outside of the closed magnetic surfaces is considered in the RF-driven divertor plasma. In the reconstruction process, singular value (SV) decomposition is used and optimal criterion function for generalized cross validation is estimated concerning truncation or reduction of the small-SV components.

CCS (Cauchy Condition Surface) method is a numerical approach to reproduce plasma shape, which has good precision in conventional tokamaks. In order to apply it in plasma shape reproduction of ST (Spherical Tokamak), the calculation precision of the CCS method in a spherical tokamak CPD (Compact PWI experimental Device) (Bt = 0.25 T, R = 0.3 m, a = 0.2 m) has been analyzed. The precision was confirmed also in ST and decided to be applied to a spherical tokamak QUEST (Bt = 0.25 T, R = 0.68 m, a = 0.40 m).. In present stage from the magnetic measurement, it is known that the eddy current effect is large in QUEST experiment, and there are no special magnetic measurements for eddy current now, so some proper model should be selected to evaluate the eddy current effect. The eddy current density by not only CS (Center Solenoid) coil but also plasma current is calculated using EDDYCAL (JAEA). The eddy current magnitudes are taken as unknown variables and solved together with plasma shape reconstruction in ohmic discharge and ECCD (Electron Cyclotron Current Drive) discharge.

The design activity of JT-60SA (JT-60 Super Advanced) addresses the remodeling of JT-60 to a superconducting tokamak device under the JA-EU collaborative ITER–BA project. For the JT-60SA control system, the existing system should be reused as much as possible from the viewpoint of cost-effectiveness. Initial considerations of the configuration of the advanced supervisory control system (SVCS) including the following systems are: (1) an ultimate flexibility real-time control system, (2) a precision timing system able to diagnose a plasma event having a time range of ∼1 μs, and (3) a safety shutdown control system. In this report, we present the design study of the JT-60SA SVCS with the focus on the above systems.

The large tokamak fusion device JT-60 is expected to explore more advanced tokamak discharge scenarios toward the ITER and a future power reactor. Since various experimental issues are to be adequately discussed, and possibly to be solved in JT-60, the plasma real-time control system has been drastically improved with remodelling in hardware as well as in software. To satisfy the requirements, a “multiple networks” structure is employed as a basic principle of the remodelling. Distributed processors for diagnostics, actuators, and supervisory controllers are linked through a reflective memory (RM) network for fast, real-time communication. Similarly, advanced and complex calculations to reproduce plasma shape and profiles are performed by several processors connected to the same RM network. In this report, we discuss the developments to improve the JT-60 plasma control and data processing systems. In addition, a future plasma control system leading to a standard design for a power reactor is outlined, which is based on the 20-year plasma operation experience.

We have investigated the surface electronic structures of transition-metal diboride (0001) surfaces by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) and ab-initio calculations based on the slab model with 13 layers. In the spectra of NbB2 and TaB2, the peaks near -1 eV blow EF are derived from the π band of their surface graphitic boron layer. As compared with graphene, the dispersion curves of the π bonds are greatly modulated by the hybridization of B-π orbits with the metal d orbits. On the other hand, the similar peaks were not observed in spectra of ZrB2, of which the surface is terminated with Zr atoms. [DOI: 10.1380/ejssnt.2006.100]

We have successfully grown a uniform BC3 honeycomb sheet with high crystalline quality over the entire macroscopic area of the NbB2 (0001) surface by carbon-substituted technique in a boron honeycomb. This is the first macroscopic uniform sheet of single-crystal BC3 with a monolayer thickness. So far, only BC3 micro-crystals with radii of a few nanometres were produced. The properties of the sheet have been investigated by using XPS, AES, LEED, STM, ARUPS and HREELS. All the experimental data and the theoretical calculations, which are concerning with atomic structure, chemical concentration, and phonon structure, indicated that the uniform BC3 honeycomb sheet was grown in an epitaxial manner to the substrate lattice.

The JT-60U control system, composed of a UNIX-based workstation and a VME-bus system, has been successfully performing advanced plasma control for the JT-60U plasma discharges. Various hardware modifications and advanced plasma control algorithms have been continuously integrated into the JT-60U control system since its upgrade in 1991. The ZENKEI, the supervisory control system, has been entirely converted from its original 16-bit minicomputers and CAMAC system to the combination of a workstation and VME-bus system linked through an Ethernet network. The plasma equilibrium control system utilizes a full VME-bus system composed of three DEC alpha CPU modules that are currently running at control cycle times of 250 μs. The parameters for plasma equilibrium control are calculated by a newly developed real-time plasma shape calculation and reconstruction system. These parameters are fed to the plasma equilibrium control system synchronized by 250-μs clock pulses. To progress toward the advanced plasma control concept, which includes adoption of a global plasma parameter control algorithm and suppression of MHD instabilities, improvements were extensively consolidated into the plasma control system (PCS). Currently, additional modifications of the JT-60U control system have extended the pulse duration of the discharge without a major change in JT-60 equipment.

The real-time feedback control of the plasma stored energy has been developed for control of the plasma MHD stability in the JT-60U tokamak. The plasma stored energy can be detected with high accuracy in real-time by a function parameterization method for various plasmas available in JT-60U, such as Ohmic plasmas, the L-mode, the H-mode, the high poloidal beta mode and the reversed shear mode over a wide range of the plasma parameters. By manipulating the neutral beam injection power, the plasma stored energy has been successfully controlled along the preprogrammed reference waveform. Especially in the reversed shear mode, this feedback control scheme has improved the reproducibility of the formation of the internal transport barrier, and MHD activities could be suppressed keeping the normalized beta in a stable region. A DT equivalent fusion amplification gain of 0.5 was sustained for 0.8 s in a reversed shear plasma by employing this feedback control scheme.

The significance of real-time feedback control is emphasized in this paper as an indispensable method to improve and sustain the improved plasma characteristics in JT-60U high fusion performance discharges as well as to operate the fusion reactor under the optimal divertor conditions with respect to the heat load and exhaust pumping. In accordance, substantial improvement in the equivalent fusion amplification gain of over unity has been reproducibly achieved at the JT-60U tokamak in the reversed shear mode of operation with the robust feedback controls, where the value of target density was deliberately optimized for the reliable internal transport barrier formation, and the magneto-hydrodynamic stability control was performed with the stored energy feedback. The feedback control techniques also demonstrated the effectiveness to produce quasi-steady-state high-performance plasmas. In addition, three major parameters associated with the fusion reactor instrumentations, namely the neutron production rate, operating density, and divertor radiation power, were simultaneously feedback controlled in the ELMy H-mode plasmas. Here, the matrix response function was evaluated to identify the limitations involved with the linear combination of independent controls. Other advanced feedback schemes, such as the feedback suppression of the neoclassical tearing mode required to sustain high plasma pressure in a steady-state, are alsomore » described. Finally, the controversial issues for the future intelligent plasma control necessary for the advanced steady-stated tokamak reactor are addressed.« less

A pure yolk sac tumor (endodermal sinus tumor) of the dysgenetic gonad developed in a 23-year-old woman whose karyotype was mosaic 45X/46X + mar Turner's syndrome is reported. Molecular biological studies showed that the patient's DNA contained a fragment of Y chromosome. This case seems to be extremely rare case of developing a pure yolk sac tumor in a patient with mosaic Turner syndrome with a Y-chromosomal fragment.

The sustainment of radiative divertor plasma in JT-60U is performed by the feedback control of the gas puffing rate into the divertor region with an actuator of the divertor radiation power. The feedback control system switches the piezoelectric gas valve every 10 ms, so that the proper amount of gas flux is fed for divertor radiation power to follow the reference waveform. The divertor radiation of 6 MW, which is about 40% of the heating power, is sustained for about 3 s by the hydrogen gas puffing with feedback control. The present logic of the feedback system, however, is not sufficient to fully control the divertor radiation which is modified by the change in heatings and plasma parameters. In order to prevent the loss of control, multi actuators for the feedback control, for example, the involvement of the heating power, and the selection of observed bolometer channels may be required.

Fusion performance of reversed shear discharges with an {ital L}-mode edge has been significantly improved in a thermonuclear dominant regime with up to 2.8 MA of plasma current in the JT-60U tokamak. The core plasma energy is efficiently confined due to the existence of persistent internal transport barriers formed for both ions and electrons at a large minor radius of r/a{approximately}0.7 near the boundary of the reversed shear region. In an assumed deuterium-tritium fuel, the peak fusion amplification factor defined for transient conditions involving the dW/dt term would be in excess of unity. {copyright} {ital 1997} {ital The American Physical Society}

Recent lower hybrid current drive (LHCD), and heating (LHH) experiments on JT-60 are reported. The current drive product of neRpIRF approximately 12.5*1019 m-2 MA was achieved at the LH power of approximately 4.5 MW, and the CD efficiency, the energy confinement, the global power balance and the heat load on divertor plates were investigated in high power LHCD plasmas. Nearly steady state H-mode discharges were found during LHCD with two different frequency injections. Sawtooth suppression in NB heated plasmas by LHCD have shown an improvement in confinement near the plasma center. Parametric instabilities in LH heating experiments were significantly reduced by increasing the plasma current, and the stored energy increased linearly with heating power of up to approximately 9 MW at ne approximately 7*1019 m-3 and Ip=2.75 MA. Parametric instabilities near the plasma edge in the ion heating regime were also reduced in peaked density plasmas produced by pellet injection and LH waves increased the central plasma pressure at ne(0) > 1.4*1020 m-3.

Informed consent for patients becomes important clinics where the doctor explains diseases and treatments. But patients have difficulty understanding medical images, i.e. X-rays, CT or MRI because the patient is not expert in reading these medical images. In this paper, we tried to reconstruct the stereoscopic image of CT and MRI and display these using a simple and low cost auto-stereoscopic viewer.

Tokamak magnetic fusion research has progressed to an advanced project, i.e., ITER (International Thermonuclear Experimental Reactor). Therefore, existing tokamaks must explore operational scenarios necessary for a high-performance plasma while simultaneously suppressing any disruptive instabilities. To implement this investigation, various advanced real-time controls using processed profile data and all available actuators should be tested in the experiments. To satisfy these requirements at the large tokamak JT-60, we are upgrading its original real-time control system completely. Two criteria for the new system configuration have been adopted: (i) The distributed processors for the measurements, actuators, and supervisory controllers (SVCs) am linked through a "reflective memory (RM)" network for fast, real-time communication. The profile data in the RM modules are also updated in real time. (ii) For efficient parallel and pipeline processes performed by multiple controllers, synchronization is provided from two sources: external hardware clocks and software counters in the RMS, which are updated by the SVCs. For a control function, the following simple and flexible method has been employed to perform various experimental proposals: New test control methods are first registered in the supervisory controllers. In accordance with the preprogrammed waveforms that indicate which control method to use, the SVCs select the correct control method in real time. The upgraded configuration of the JT-60 plasma control system and its effectiveness in seeking advanced operational scenarios applicable to ITER are discussed in detail.

A new digital integrator based on the method using a voltage-to-frequency converter (VFC) and an up-down counter (UDC) has been developed for a precise long-time integration of magnetic signals in a tokamak. Three trial VFC boards have been made corresponding to the development steps: (a) to remove technical causes of drift by analyzing the old VPC-UDC system for JT-60, (b) to improve the precision of integral results, and (c) to suppress the drift speed to an allowably low amount. After various modifications, a precise VFC having a feature of low drift enough for ITER was successfully completed, where it is premised that the noise in the magnetic sensors and common ground at ITER is similar to that at JT-60. For a remaining problem of large integral error that related to plasma MHD activities, we present a design of a new system that can correct the integral result using two VFC's for one sensor in parallel.

A parallel processing system is designed for plasma position and shape control in the JT-60 upgrade tokamak. Fast digital signal processors (DSPs) which have inter-processor communication ports are applied to the system. The optimum number of the DSPs is estimated according to the degree of parallelism in the control processing and its allowable delay.

A tokamak plasma shape identification method based on boundary integral equations (BIE method) (ref. 1) using magnetic sensors is discussed in application to plasmas with low K to high K. This BIE method, the filament-current-plasma (FCP) method (ref. 2) and the Legendre-Fourier eigenfunction expansion (LFE) method (ref. 3) are applied to realtime visualization of plasma shape. The flux function value at a point × in the three methods is calculated in the same-type formula using poloidal field coil currents, magnetic sensor signals and coefficients depending on x. The design of a realtime visualization system is presented and the performance test results are reported.

Plasma shape reconstruction is important for plasma control of tokamak. Cauchy-Condition Surface (CCS) method is a numerical approach to reproduce plasma shape which has good precision in conventional tokamak. In order to apply it in the plasma shape reproduction of Compact PWI experimental Device (CPD) which is a new spherical tokamak in Kyushu University, the calculation precision of CCS method in CPD is analyzed in the paper.

This paper describes the central control system of the JT-60 tokamak. This control system not only has to organize plasma operation, but also has to utilize devices under isolated operation. Therefore the control system has been designed in a special way.

Dislocation loops of Burgers vectors (a/2) form in potassium chloride during examination at temperatures of --110 to 20 deg C in a 75-kV transmission electron microscope. In addition to these loops, dislocation loops whose character is not known well yet and dislocation loops of a Burgers vector of the type aSTAOO1! also form at a temperature higher than about --15 and --5 deg C, respectively. The third type of loops is transformed into cracks when they have developed. (auth)

Two different distributions of satellite reflections in electron diffractograms have been observed in HoBa 2 Cu 3 O 7−x after intense electron irradiation: diffuse elongated spots from orthorhombic materials, and sharp superlattice spots from material possibly transformed to tetragonal in the electron beam.- Two types of twin texture composed of sets of twin lamellae are observed, each involving four crystal orientations. The first type is assumed to originate in two genetic stages. In the second type, two adjacent crystal orientations occur which differ by about 1° in the more common configuration and by 2° in another configuration. In the junctions of the twin lamellae, the lattice planes are coherently connected and strongly bent.