Neutronics analyses for Li/V-alloy and Flibe/V-alloy liquid blankets with and without external beryllium were performed for the FFHR2 design in order to assess the tritium breeding ratios (TBRs) and neutron shielding performances. Beryllium multiplier significantly improved the TBRs for both the Li/V-alloy and Flibe/V-alloy blankets. The shielding performance of the Li/V-alloy blanket with Be was greatly improved because the adequate TBRs can be obtained with the thinner breeding region than in the Li/V-alloy blanket without Be and the thickness of the shielding region was increased. On the other hard, the shielding performance of the Flibe/V-alloy blankets with and without external Be was comparable. It was shown that the Li/V-alloy and Flibe/V-alloy liquid blankets with and without solid Be satisfied the requirement for TBRs and shielding for the superconductor magnet of FFHR2. The activation of MHD coating of Er₂O₃ for the Li/V-alloy blankets and activation performance of the Flibe/V-alloy blankets were also investigated for the cases with and without external Be. The MHD coating of Er₂O₃ in the Li/V-alloy blankets introduced long-lived activation products. The activation of the Flibe/V-alloy blanket with external Be was comparable to that without external Be.

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Advances in potential formation have led to remarkable discoveries on the effects of radial electric field distribution on turbulence suppression and transverse loss reduction. In order to study the improvement in plasma confinement because of the formation of plasma confinement potential, we constructed a multi-channel microwave interferometer system that can measure the density and density fluctuation radial profiles in a single plasma shot. We obtained clear density fluctuation suppression by the formation of the plasma confinement potential. Therefore, we have a powerful diagnostic tool with which to study the improvement in plasma confinement.

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Recent advances of magnetic resonance imaging have been described, especially stressed on the diffusion sequences. We have recently applied the diffusion sequence to functional brain imaging, and found the appropriate results. In addition to the neurosciences fields, diffusion weighted images have improved the accuracies of clinical diagnosis depending upon magnetic resonance images in stroke as well as inflammations.

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Two dimensional (2-D) images of electron temperature fluctuations with high temporal and spatial resolution have been employed to study the sawtooth oscillation (m/n = 1/1 mode) in Toroidal EXperiment for Technology Oriented Research (TEXTOR) tokamak plasmas. 2-D imaging data revealed new physics which were not available in previous studies based on the 1-D electron temperature measurement and X-ray tomography. Review of the physics of the sawtooth oscillation is given by comparative studies with prominent theoretical models suggest that a new physics paradigm is needed to describe the reconnection physics of the sawtooth oscillation. The new insights are: A pressure driven instability (not a ballooning mode) leads to the “X-point” reconnection process. The reconnection process is identified as a random 3-D local reconnection process with a helical structure. The reconnection time scale is similar for different types of sawtooth oscillation (“kink” and “tearing” type) and is significantly faster than the resistive time scale. Heat flow from the core to the outside of the inversion radius during the reconnection process is highly collective rather than stochastic.

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We discuss aspects of imaging of plasma turbulence, taking the standpoint that the imaging is a path for induction of law from complex signals. An example of induction of symbol from signals is illustrated. Then the image of plasma turbulence is extended, putting an emphasis on the identification of the nonlinear interaction in turbulence. By employing the bipspectral method, magnitudes of interactions among excited modes are estimated. Interactions between microscopic turbulence and large-scale structures are demonstrated, providing our understanding of structure formation in turbulent plasmas.

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The recent magnetic resonance imaging (MRI) technology and techniques used in human brain mapping are remarkable. They are getting, faster, stronger and better. The advanced MRI technologies and techniques include, but not to limited to, the magnetic resonance imaging at higher magnetic field strengths, diffusion tensor imaging, multimodal neuroimaging, and monkey functional MRI. In this article, these advanced MRI techniques are briefly overviewed.

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This paper briefly reviews recent developments regarding the brain mechanisms of visual self-recognition. A special cognitive mechanism for visual self-recognition has been postulated based on behavioral and neuropsychological evidence, but its neural substrate remains controversial. Recent functional imaging studies suggest that multiple cortical mechanisms play self-specific roles during visual self-recognition, reconciling the existing controversy. Respective roles for the left occipitotemporal, right parietal, and frontal cortices in symbolic, visuospatial, and conceptual aspects of self-representation have been proposed.

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The amygdala plays a critical role in the neural system involved in emotional responses and conditioned fear. The dysfunction of this system is thought to be a cause of several neuropsychiatric disorders. A neuroimaging study provides a unique opportunity for noninvasive investigation of the human amygdala. We studied the activity of this structure in normal subjects and patients with schizophrenia by using the face recognition task. Our results showed that the amygdala was activated by presentation of face stimuli, and negative face activated the amygdala to a greater extent than a neutral face. Under the happy face condition, the activation of the amygdala was higher in the schizophrenic patients than in control subjects. A single nucleotide polymorphism in the regulatory region of the serotonin type 3 receptor gene had modulatory effects on the amygdaloid activity. The emotion regulation had a significant impact on neural interaction between the amygdala and prefrontal cortices. Thus, studies on the human amygdala would greatly contribute to the elucidation of the neural system that determines emotional and stress responses. To clarify the relevance of the neural dysfunction and neuropsychiatric disorders, further studies using physiological, genetic, and hormonal approaches are essential.

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HDC-TEM has opened a way to visualize the ultrastructure of ice embedded whole cells. The extraordinary advantage of this technique is that it exhibits structures close to the living state while retaining all the in vivo molecular constituents undisturbed. We attempted to identify in vivo DNA by incorporation of BrdU, which conferred electron density to newly synthesized DNA in ice embedded cyanobacterial cells. Localization of Br in the electron dense area in the identical cell was investigated by electron spectroscopic imaging (ESI). Br was also appeared to be associated with polyphosphate bodies, which would indicate a close relationship between newly synthesized DNA and polyphosphate bodies. While ESI indicates the DNA localization, high resolution HDC-TEM reveals the fine fibrous structures in situ. The combination of ESI with HDC-TEM will be extremely useful to study the in vivo dynamics of DNA synthesis, and its structural and conformational changes close to the living state at high resolution.

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The third Japanese solar observing satellite, SOLAR-B, was launched on 2006 Sep 23 from the Uchinoura Space Center of JAXA and it was named “Hinode” (sunrise). Hinode carries three major telescopes: Solar Optical Telescope (SOT), X-Ray Telescope (XRT), and Extreme-ultraviolet Imaging Spectrometer (EIS). These telescopes have been built in an international collaboration of Japan, US, and UK for understanding the formation mechanism of the solar corona, mechanism of dynamic events such as solar flares and coronal mass ejection, and general magnetic activities on the sun. All telescopes have started their commissioning activities after the successful launch of the spacecraft. The performance of the spacecraft that supports the diffraction-limited SOT observations and the first-light observation of each telescope are briefly introduced.

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The Solar Optical Telescope (SOT) onboard Hinode is a 50 cm aperture telescope to observe the sun in visible lights (388-668 nm) for the first time with high and extremely stable spatial resolution from space. The focal plane package of SOT consists of Broad-band Filter Imager which provides the highest spatial resolution images of the solar photosphere, the Narrow-band Filter Imager which takes 2-dimentional Dopplergram and Magnetogram of photosphere and chromosphere in high cadence and with wide field of view, and the Spectro-Polarimeter which takes full Stokes line profiles to provide the highest precision magnetic field maps of the photosphere. The most outstanding characteristics of SOT is its continuous and uniform data quality with the unprecedentedly high precision and high spatial resolution of 0.2-0.3 arcsec. The door of the telescope was deployed on 25th Oct. followed by a successful SOT first light. Initial check-outs of the instrument were conducted and superior performance of SOT was confirmed. SOT is starting the regular observation of the daily target region on the sun and producing excellent scientific data. Overview of the SOT instrument is summarized and initial results are demonstrated.

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The Soft X-ray Telescope (XRT) aboard the Hinode satellite is a grazing incidence X-ray telescope equipped with 2 k × 2 k CCD. XRT has 1 arcsec resolution with wide field-of-view of 34 × 34 arcmin. It is sensitive to < 1 MK to 30 MK, allowing us to obtain TRACE-like low temperature images as well. Co-alignment with SOT and EIS is realized through the XRT visible light telescope and with temperature overlap with EIS. Spacecraft mission data processor (MDP) controls XRT through the sequence tables with versatile autonomous functions such as exposure control, region-of-interest tracking, flare detection and flare location identification. Data is compressed either with DPCM or JPEG, depending on the purpose. This results in higher cadence and/or wider field-of-view for given telemetry bandwidth. With focus adjust mechanism, higher resolution of Gaussian focus may be available on-axis.

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The Extreme Ultraviolet Imaging Spectrometer on board the Japanese Sun Observing Satellite “Hinode” realizes the highest sensitivity ever achieved in the two EUV wavelengths of 17-21 nm and 25-29 nm. EIS will be able to provide the detailed diagnostic information on solar corona and transition region. A new tool of timedependent collisonal-radiative model will be developed to analyze the data taken by this EIS instrument, and to diagnose temperatures and densities of those plasmas in the outer atmospheres of the Sun.

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Solar atmosphere is filled with plasma and magnetic field. Activities in the atmosphere are due to plasma instabilities in the magnetic field. To understand the physical mechanisms of activities / instabilities, it is necessary to know the physical conditions of magnetized plasma, such as temperature, density, magnetic field, and their spatial structures and temporal developments. Multi-wavelength imaging is essential for this purpose. Imaging observations of the Sun at microwave, X-ray, EUV and optical ranges are routinely going on. Due to free exchange of original data among solar physics and related field communities, we can easily combine images covering wide range of spectrum. Even under such circumstances, we still do not understand the cause of activities in the solar atmosphere well. The current standard model of solar activities is based on magnetic reconnection: release of stored magnetic energy by reconnection is the cause of solar activities on the Sun such as solar flares. However, recent X-ray, EUV and microwave observations with high spatial and temporal resolution show that dense plasma is involved in activities from the beginning. Based on these observations, I propose a high-beta model of solar activities, which is very similar to high-beta disruptions in magnetically confined fusion experiments.

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In order to obtain a better understanding of impurity transport in magnetically confined plasmas, a Tracer-Encapsulated Soild PELlet (TESPEL) has been developed. The essential points of the TESPEL are as follows: the TESPEL has a double-layered structure, and a tracer impurity, the amount of which can be known precisely, is embedded as an inner core. This structure enables us to deposit the tracer impurity locally inside the plasma. From experiences of developing the TESPEL production technique and its injection experiments, it became clear that various plasma properties can be studied by the TESPEL injection. There are not only impurity transport in the plasma but also transport both outside and inside of the magnetic island O-point, heat transport and high-energy neutral particle flux. Therefore, the TESPEL injection has a favorable multi-functional diagnostic capability. Furthermore a Tracer-Encapsulated Cryogenic PELlet (TECPEL) has been also developed. The TECPEL has an advantage over the TESPEL in terms of no existence of carbons in the outer layer. The TECPEL injector was installed at LHD in December 2005, and the preliminary injection experiments have been carried out.

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The interpretation of Doppler broadened spectral line shapes for extended radiating media, such as flames and discharges, is complicated by the spatial inhomogeneity of the source. In this paper, we consider the conditions under which the Doppler tomography problem is invertible. For media in drifting thermal equilibrium, it is found that the visibility of fringes produced by modulated or fixed-delay quadrature interferometers deliver the Radon transform of a quantity related to the inhomogeneous temperature distribution. In view of this, we introduce novel imaging polarization interferometers suitable for high spectral and temporal resolution plasma Doppler tomography. One such system has been used to obtain images of ion spectral-line brightness and temperature for low-field rf-heated argon discharges in the H-1NF heliac. Tomographic reconstructions for a number of different plasma régimes are presented.

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We describe a neural network collocation method (NNCM) for tomographic image reconstruction with small amount of projection data, which has been successfully applied to the three-dimensional ionospheric tomography based on the dataset of signal delays from the GPS satellites. In NNCM the neural network is trained by minimizing an object function composed of squared residuals of the governing equations evaluated at the collocation points and some constraining conditions imposed usually by observation data. This method is applied not only to the computerized tomography but also to the analyses of various inverse problems such as the data assimilation, the parameter estimation, the time series prediction, and so on.

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When the ratio of the plasma pressure to the magnetic pressure increases, Various kinds of instabilities evolve. Among them, magnetohydrodynamic instabilities, by which the plasma is deformed macroscopically, are in concern. Non-linear evolution of them is fairly complicated and two-dimensional structure of them is the key to understanding the phenomena. Tangentially viewing SX camera is promising diagnostics for 2D visualization, because most of the perturbations tend to have the equal phase along the field lines, the tangential view, which is almost parallel to the field lines, give a good opportunity to resolve the structure. Issues in this kind of camera are discussed. Improved system using multi-layer mirror is also described.

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A novel x-ray imaging method, providing spatial resolution of 10 μm, temporal resolution 10 ps, and spectral resolution of E/ΔE = 200 (E: photon energy), is suggested to diagnose laser driven fusion plasma. This scheme consists of a monochromatic x-ray imager with the use of two-dimensional (2D) curved crystals and an imagesampling streak camera. Feasibility of the method was studied using GEKKO XII laser and chlorinated plastic shell targets. Early appearance of Cl-Heα line emission during the implosion stage was found for the present conditions, which made image reconstruction difficult.

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An overview of the research and development of imaging bolometers giving a perspective on the applicability of this diagnostic to a fusion reactor is presented. Traditionally the total power lost from a high temperature, magnetically confined plasma through radiation and neutral particles has been measured using one dimensional arrays of resistive bolometers. The large number of signal wires associated with these resistive bolometers poses hazards not only at the vacuum interface, but also in the loss of electrical contacts that has been observed in the presence of fusion reactor levels of neutron flux. Imaging bolometers, on the other hand, use the infrared radiation from the absorbing metal foil to transfer the signal through the vacuum interface and out from behind a neutron shield. Recently a prototype imaging bolometer known as the InfraRed imaging Video Bolometer has been deployed on the JT-60U tokamak which demonstrates the ability of this diagnostic to operate in a reactor environment. The application of computed tomography demonstrates the ability of one imaging bolometer with a semi-tangential view to produce images of the plasma emissivity. In addition, new detector foil development promises to strengthen the foil and increase the sensitivity by an order of magnitude.

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Millimeter wave technology advances have made possible active and passive millimeter wave imaging for a variety of applications including advanced plasma diagnostics, radio astronomy, atmospheric radiometry, concealed weapon detection, all-weather aircraft landing, contraband goods detection, harbor navigation/surveillance in fog, highway traffic monitoring in fog, helicopter and automotive collision avoidance in fog, and environmental remote sensing data associated with weather, pollution, soil moisture, oil spill detection, and monitoring of forest fires, to name but a few. The primary focus of this paper is on technology advances which have made possible advanced imaging and visualization of magnetohydrodynamic (MHD) fluctuations and microturbulence in fusion plasmas. Topics of particular emphasis include frequency selective surfaces, planar Schottky diode mixer arrays, electronically controlled beam shaping/steering arrays, and high power millimeter wave local oscillator and probe sources.

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Recently, the technology of generating and detecting terahertz (THz) waves by using ultrashort pulse lasers has made great progress. In this paper, we describe THz spectroscopies and imaging with the intention of applying them to diagnostics of plasmas in the future. After a brief description of the method of generating and detecting THz pulses with a femtosecond laser, the principle of THz time-domain spectroscopy is described. The THz magneto-optical effect measurement system up to the magnetic field of 10 T and down to 5 K is also shown. These systems are used to characterize solid state plasmas in semiconductors. The transmission- and reflection-type imaging systems are described and some examples of measurements are shown. Finally, the application of the THz technology to fusion plasma diagnostics is proposed.

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This paper reviews the high-speed video cameras developed by the authors. A video camera operating at 4,500 frames per second (fps) was developed in 1991. The partial and parallel readout scheme combined with fully digital memory with overwriting function enabled the world fastest imaging at the time. The basic configuration of the camera later became a de facto standard of high-speed video cameras. A video camera mounting an innovative image sensor achieved 1,000,000 fps in 2001. In-situ storage with more than 100 CCD memory elements is installed in each pixel of the sensor, which is capable of recording image signals in all pixels in parallel. Therefore, the sensor was named ISIS, the in-situ storage image sensor. The ultimate parallel recording operation promises the theoretical maximum frame rate. A sequence of more than one hundred consecutive images reproduces a smoothly moving image at 10 fps for more than 10 seconds. Currently, an image sensor with ultrahigh sensitivity is being developed in addition to the ultra-high frame rate, named PC-ISIS, the photon-counting ISIS, for microscopic biological observation. Some other technologies supporting the ultra-high-speed imaging developed are also presented.

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The full-wave Maxwell simulations on electromagnetic wave propagation based on a finite difference time domain method are performed to study the shift in cutoff density due to relativistic electron mass modification. The simulations on one-dimensional ultrashort-pulse reflectometry are also performed and the density-profile reconstruction is shown to have an underestimated density profile by the relativistic effect, and an idea of electron temperature estimation by means of reflectometry is discussed. Its related technology such as metallic wire-made discrete waveguide and beam former is also briefly discussed.

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Magnetically confined fusion plasmas are mostly heated by small populations of energetic ions. In current devices these fast ions are mainly generated by auxiliary heating, while in ITER fusion generated alpha particles will dominate. A multitude of MHD phenomena, some of them driven by the fast ions, can redistribute or eject the energetic ions prematurely, affecting fusion performance and potentially damaging walls. Theory and modeling of fast ion dynamics in fluctuating or turbulent plasmas is challenging and needs guidance from - and bench marking against - measurements of the fast ion dynamics. Collective Thomson Scattering (CTS) can provide such measurements of the confined fast ions. Here we present CTS measurements of the TEXTOR tokamak plasma which show fast ions responding to sawteeth and display slowdown evolution of the fast ion velocity distribution after switch off of neutral beam heating. The toroidal rotation velocity of the bulk ions is inferred from the measurements. Plans for an ITER fast ion CTS are also briefly discussed.

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Present status of the analysis of HIBP data on zonal flows, streamers and drift-wave turbulence of the JIPPT-IIU tokamak plasmas, is reviewed. Limiting factors and improvements of heavy ion beam probe towards better understanding of tokamak turbulence, beam attenuation, beam quality of the probing beam, multiple energy analyzers for simultaneous measurement at various cross-sections of the plasmas, proposal for 2-dimensional measurement of the plasma turbulence, are discussed.

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Beam Emission Spectroscopy (BES), a high-sensitivity, good spatial resolution imaging diagnostic system, has been deployed and recently upgraded and expanded at the DIII-D tokamak to better understand density fluctuations arising from plasma turbulence. The currently deployed system images density fluctuations over an approximately 5 × 7 cm region at the plasma mid-plane (radially scannable over 0.2 < r/a ≤ 1) with a 5 × 6 (radial × poloidal) grid of rectangular detection channels, with one microsecond time resolution. BES observes collisionally-induced, Doppler-shifted D_α fluorescence (λ = 652-655 nm) of injected deuterium neutral beam atoms. The diagnostic wavenumber sensitivity is approximately k_⊥ < 2.5 cm^-1, allowing measurement of longwavelength (k_⊥ρ_I < 1) density fluctuations. The recent upgrade includes expanded fiber optics bundles, customdesigned high-transmission, sharp-edge interference filters, ultra fast collection optics, and enlarged photodiode detectors that together provide nearly an order of magnitude increase in sensitivity relative to an earlier generation BES system. The high sensitivity allows visualization of turbulence at normalized density fluctuation amplitudes of ‾n/n < 1%, typical of fluctuation levels in the core region. The imaging array allows for sampling over 2-3 turbulent eddy scale lengths, which captures the essential dynamics of eddy evolution, interaction and shearing.

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A high-throughput polarization interferometer is being developed to demonstrate for the first time the utility of Fourier transform spectroscopy for Thomson scattering diagnostics of high temperature plasma. Target T_e and n_e ranges for the prototype polarization interferometer are < 1 keV and > 5 × 10¹⁸ m^-3 , respectively. This paper describes the design of the polarization interferometer and the results of initial tests.

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This paper describes innovative laser diagnostics under development at the National Institute for Fusion Science, aiming for the establishment of reliable density measurement techniques in the next step magnetically confined fusion devices. There are two approaches, interferometry and polarimetry. A new type of two color laser (47.6/57.2-μm CH₃OD) interferometer has been developed and its original function, vibration subtraction, was confirmed in a test stand. The line integrated density measurement at Compact Helical System by using the polarimeter based on Cotton-Mouton effect was demonstrated by the use of a 337-μm HCN laser source.

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We discovered the 3-dimensional twist motion of sperm flagella of the stag beetle Prosopocoilus inclinates. The morphological features are discussed with experimental data obtained through various ‘imaging techniques’ including those developed in thermo-nuclear fusion research. The helical deformation length observed in the optical micrograph agreed statistically with those of transmission electron micrographs (TEM) on both ultra-thin section and negatively stained samples. This indicated that the helical twist mechanism of flagellar axoneme could be safely discussed from TEM. In order to elucidate this, we applied the newly developed Constrained Electron Beam Tomography (CEBT) technique adapted from our unique fusion plasma diagnosis. This requires basic assumptions of “the optimum deformation” and “the coherent length” as mathematical constraints. The results are the key parameters of the flagellum deformation, e.g. the helical pitch (HP) of both axoneme and mitochondrial derivatives as well as the phase slip (PS) between them. They allow the quantitative discussion on this motion.

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Using the extended Trubnikov's expression for the fully relativistic Maxwellian in the case of oblique propagation to the magnetic field (B_t), electron cyclotron emission (ECE) spectra are calculated in a high temperature (T_e) tokamak plasma. We investigate the ECE by changing the angles between the sight line and the equatorial plane or B_t direction. Feature of ECE spectra can be interpreted from the viewpoints of relativistic, Doppler and absorption effects. The downshift frequency variation due to the relativistic effect in the high field side (HFS) observation is bigger than that in the low field side observation. Absorption at the HFS plasma results in the deep dip at the HFS of fundamental, second and third harmonics in the ECE spectra. For the vertical observation, in the case of optically thin case, ECE spectra are similar to the emissivity profile, and when electron density (n_e) is higher, ECE spectra are modified due to the absorption in plasma. Since the B_t, n_e, T_e increase in the case of the SlimCS DEMO reactor, the ECE spectra expands to high frequency emission (∼2000 GHz). So, ECE detector in the case of Fourier transform spectrometer system should be modified from present liquid He cooled InSb detector because of the detection of high frequency emission.

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For plasma diagnostic imaging systems such as the electron cyclotron emission imaging (ECEI) system, spurious rf heating power may saturate or even damage the mixer arrays. Without protection, the sensitivity of the mixers can significantly decrease or in the extreme case, the diodes can even be burnt. A metallic dichroic plate is usually used to rejection the spurious rf heating power. However, as a high pass filter, the dichroic plate can not be used when the frequency of the heating power is in the middle of the frequency range of interest. Consequently, a frequency selective surface (FSS) has been introduced as a planar filter in ECEI systems. FSSs can work as low pass, high pass, and band stop filters according to the various system requirements. Also, as a thin, light, planar filter, it is very easy to mount in imaging systems. This paper will focus on the design and fabrication of the FSS notch filter applied in TEXTOR, which is used to protect the imaging array from stray 140 GHz ECRH power. The filter is used in TEXTOR due to its deep rejection, and excellent angle insensitivity. The design procedure will be presented. More FSS applications will be talked in this paper. The new fabrication technique Electro Fine Forming (EF2) technology will also be introduced. FSS filters in the millimeter wave range also have possible applications in imaging systems in other fusion machines such as KSTAR, DIIID, and LHD.

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The detection and control of instabilities in a tokamak is one of the exciting challenges in fusion research on the way to a reactor. Thanks to a combination of an innovative 2D temperature imaging technique (ECEI), a versatile ECRH/ECCD system and a unique possibility to externally induce tearing modes in the plasma, TEXTOR is able to make pioneering contributions in this field. This paper focuses on two meso-scale phenomena in tokamaks: m = 2 tearing modes and magnetic structures in the stochastic boundary. In these cases the 2D-ECEI diagnostic can resolve features not attainable before. In addition the possibility to use the diagnostic for fluctuation measurements is addressed.

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Electron cyclotron emission (ECE) imaging has been an important tool to investigate behaviors of temperature perturbations in the specific spatial area. So far, we have applied ECE detection system to a LHD plasma to measure electron temperature fluctuations in core region, however, it was difficult to distinguish perturbed temperature signals to a noise, which is naturally consisted in radiometry features and so on. Recently, we have optimized an ECE detector array especially in sensitivity to increase signal to noise ratio. An intermediate frequency(IF) system composed of commercial components have been replaced by an integrated system utilizing millimeter(microwave) integrated circuit technology(MIC) to fabricate a compact system maintaining the performance of the commercial system. As a result of application to the LHD plasma, we have successfully obtained ECE signal even in comparably low temperature operation sequence.

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After installation of CO₂ laser (wavelength 10.6 μm) heterodyne imaging interferometer (CO₂ HI) in 2001, continuous developments have been carried out to improve the measurements capability and stability of operation. The CO₂ HI works almost without phase jumping at high electron density (> 1 × 10²⁰ m^-3), where the existing far infrared laser (wavelength 118.9 μm) interferometer suffers from fringe jump due to the reduction of signal intensity caused by refraction. However a second interferometer is required to compensate mechanical vibration. A YAG laser (wavelength 1.06 μm) heterodyne imaging interferometer (YAG HI) is presently used for the vibration compensation. In the 10th LHD experimental campaign (2006∼2007), sixty four channels of CO₂ HI to measure electron density profile and ten channels of YAG HI to measure mechanical vibration are working. A measurement example of a pellet fuelled high-density discharge is reported.

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Two dimensional (2D) phase contrast imaging (PCI) is an excellent method to measure core and edge turbulence with good spatial resolution (Δρ ∼ 0.1). General analytical consideration is given to the signal interpretation of the line-integrated signals, with specific application to images from 2D PCI. It is shown that the Fourier components of fluctuations having any non-zero component propagating along the line of sight are not detected. The ramifications of this constraint are discussed, including consideration of the angle between the sight line and flux surface normal. In the experimental geometry, at the point where the flux surfaces are tangent to the sight line, it is shown that it may be possible to detect large poloidally extended (though with small radial wavelength) structures, such as GAMS. The spatial localization technique of this diagnostic is illustrated with experimental data.

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A novel phase contrast imaging is employed for diagnostics of plasma density fluctuations on LHD. With the use of two dimensional 48 ch (6×8) detector array and CO₂ laser probe beam this technique permits observation of radial profiles of density fluctuation during a single discharge either within the entire plasma diameter in overview mode or within some fraction of the diameter in zoom mode. The velocity of density fluctuations in laboratory frame can be determined simultaneously with fluctuations of velocities. Analysis of system performance was made with the use of numerical calculations. The targets for the analysis include wave number and spatial resolution of the method, contrast of instrumental function, which is determined by low k signal leakage into the high k spectral region, and focal depth of the optical system for different fluctuation wave numbers. The role of shortcomings of optical system like distortion of the optical front by diffraction is studied. Suggestions for future upgrade of the diagnostics are advanced.

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Fluctuation in the plasma is important to be measured for studying the improvement of the plasma confinement by the formation of the plasma confinement potential. Density fluctuation is observed using microwaves, such as interferometer, reflectometry and Fraunhofer diffraction method. We have constructed a new multi-channel microwave interferometer for measuring the plasma density and fluctuation radial profiles in a single plasma shot. In order to study higher density plasma operation, we have started sub-millimeter hydrogen ice pellet injection experiments into the potential confined plasma. We successfully measured the time dependent density and line-integrated density fluctuation radial profiles in the pellet injection experiments using the multi-channel microwave interferometer.

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A reflectometer in Ka-band was designed, constructed and applied to the TST-2 spherical tokamak in order to detect density fluctuations induced by the radio frequency (RF) heating wave, and to measure the density profile. The optics of the reflectometer consists of two concave mirrors to make a small microwave beam spot inside the plasma. Using Kirchhoff integration, the parameters of the optics were optimized to achieve a high throughput (i.e. the ratio of the received to the launched powers) in various measurement conditions. Using the reflectometer, the density fluctuations in the frequency range of RF were detected and the electric field excited by RF (21 MHz/260 kW) was estimated to be about 1.3 kV/m.

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Microwave Imaging Reflectometry (MIR) is under development for 2-D/3-D measurement of the electron density fluctuations in Large Helical Device (LHD). A rotatable ellipsoidal mirror has been installed inside the vacuum chamber of LHD in order to optimize the illumination beam angle vertically and horizontally. The illumination and reflected beam paths near the reflection surface are calculated by using the ray-tracing code. The illumination angles are optimized in the plasma experiment.

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We have evaluated a Fermi antenna newly designed in X band for use in a multichannel reflectometer. The advantages of the Fermi antenna are that it can be adopted as an array antenna owing to its planer shape and fabricated with a low cost due to its compactness and a light-weighted structure. The radiation-beam widths in the E- and H-plane are almost equal to each other and the side-lobe levels are low. Plasma behaviors in the HITOP device are measured by reflectometry using two Fermi antenna receivers. Time evolution of the cutoff layer and plasma rotation velocity measured by the reflectometer are in good agreement with an electrostatic probe measurement.

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Polarimetry diagnostic for International Thermonuclear Experimental Reactor (ITER) considered among the tools to measure and, thus, to provide ability to control the thermonuclear plasma in the next generation fusion device. The shortage of the reliable sources in the short wavelength far infrared (FIR) region suggests to use common CH₃OH oscillation line. Recently new laser sources became available at 50 μm FIR region. Proposed system unveil the alternative possibilities apart from 118.8 μm poloidal polarimeter for ITER. This system, which introduces 47.6 and 57.2 oscillation lines of CO₂-laser pumped CH₃OD laser inherits all well documented features from it 118.8 μm predecessor will shows the clear advantages to utilize shorter wavelength radiation for plasma probing.

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We report an oversized K-band backward wave oscillator (BWO) operating above 20 GHz in the weakly relativistic region less than 100 kV. It is very important to prevent microwave from going into the beam diode, since intense microwaves will harmfully affect beam generation. A weakly relativistic oversized BWO is demonstrated using a Bragg reflector at the beam entrance of slow wave structure (SWS). The effect of the Bragg reflector on the BWO operation is examined, by changing the boundary condition at the beam entrance. The Bragg reflector improves the performance of the oversized BWO.

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As the importance of plasma imaging diagnostics increases, the fabrication of high performance millimeterwave planar components becomes essential. This paper describes the development of high performance millimeter-wave planar components such as antennas and filters using a low-loss fluorine substrate. The problems to be solved are the low degree of adhesion between copper foil and the fluorine substrate and the shape of the antenna pattern. In order to solve the problems, surface treatment of fluorine films and a fabrication method using Electro Fine Forming (EF2) are utilized.

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The gyrotron FU-VI, which can oscillate in the terahertz region has been developed. Tera-hertz operations with the second harmonic operation have been detected by a hot electron detector after a high-pass filter and/or a band-pass filter. The main magnetic field coil of the FU-VI is a pulse magnet coil protected by ice with alumina powder, and can generate the magnetic field 20 T or higher in the resonant cavity. One of the second harmonic operations has been confirmed experimentally at 1.010 THz due to TE_4,12 cavity mode at the magnetic field 19.1 T in the resonator.

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The density resolution of a measurement system using laser absorption spectroscopy is evaluated in order to diagnose a fraction of metastable helium atoms (2 ³S₁) in a neutral helium beam. Experiments performed in a hollow cathode device show that the density resolution of the present system is about 5 × 10¹³ m^-3 for a 1 m absorption length. Optimization of absorption scheme and improvements of signal detection are suggested, which shows that laser absorption spectroscopy is a promising diagnostic method for a neutral helium beam.

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The Fulcher-α ro-vibronic band spectra in mixed hydrogen isotope plasmas were investigated. The spectra were measured in H₂ and D₂ mixed plasmas as well as calculated for D₂ and T₂ mixed plasmas. In both the measured and calculated spectra, several overlaps were observed. In order to avoid an error in the ro-vibrational temperature estimation, detailed assignment of the spectral line shapes are reguired. The coronal model combined with a fitting procedure which is not largely disturbed by the decrease in the number of available lines was adopted to evaluate the ro-vibrational temperatures. The estimated vibrational temperatures of H₂, D₂, and HD isotopes were not fully equilibrated, and may be explained by a combination of the electron-impact and Eley-Rideal surface recombination processes. The rotational temperatures, on the other hand, were basically in equilibrium, and suggest a correlation with the surface temperature.

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Magnetic field produced by helical and poloidal coils in LHD forms a complicated structure of the magnetic field lines in the plasma periphery (ergodic layer and divertor legs), which can change the radial position of the magnetic axis, the shape and size of magnetic surfaces and the location of the strike points, etc. CCD cameras have observed complicated structure of the visible emission depending on the magnetic configurations. The dependence of the images of visible emission on three magnetic parameters which specify magnetic configurations (the position of the magnetic axis, coil pitch parameter, quadruple magnetic components) is investigated by tracing magnetic field lines. The images of the three-dimensional plots of the magnetic field lines quite agree with the observations in various magnetic configurations. Safe operational range of the three magnetic parameters from the viewpoint of minimizing the direct heat load onto the vacuum vessel is found by calculating the distributions of strike points.

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Effective production of hydrogen negative ions (H^-) is one of the important issues in high power neutral beam injection (NBI) for fusion experimental devices. Cesium (Cs) vapor is seeded in the H^- sources to enhance the H^- production rate, which depends strongly on the amount of Cs inside the source. On the other hand, oxygen and water attenuate the production rate. In order to investigate the states of those species inside ion source, we have installed two multi-channel spectrometer systems with different spectral resolution. Hydrogen emissions, Cs emissions and oxygen emission are clearly observed with the time resolution of several handled milliseconds. Most of evaporated Cs atoms ionize in arc discharge plasma, and the emission increases strongly due to the ion back streaming with beam extraction. Oxygen neutral emission increases at the beginning of the beam conditioning, and its evaporation depends on the condition of the grid system.

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In order to measure a high density plasma more than 10²⁰ m^-3 in the vicinity of a magneto-plasma-dynamic arcjet (MPDA), a visible-laser interferometer is fabricated using a He-Ne laser (λ = 632.8 nm). As it doesn't have enough phase shift when the light passes through the MPDA plasma once, we adopt a multi-reflection optical system in this interferometer to improve the phase sensitivity. We measured a plasma density by the interferometer and estimated the maximum value of line-integrated density of 4 × 10¹⁹ m^-2 . These experimental results are consistent with that of electrostatic probe measurement in the downstream region.

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