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The in situ calibration method for the impurity influx monitor (divertor) is experimentally examined. The total reflectance of the optical path from the focal point of the Cassegrain telescope to the first mirror is derived using a micro retroreflector array. An optical fiber with angled physical contact (APC) connectors reduces the return edge reflection. APC fibers and a multimode coupler increase the signal-to-noise ratio by about one order compared to that of triple-branched fibers and enable measurement of the wavelength dependence of the total reflectance of the optical system even after potential deterioration of mirror surfaces reduces reflectance. [ABSTRACT FROM AUTHOR]

A new concept of a terrace retro-reflector array (TERRA) as part of the poloidal polarimeter for ITER is proposed in this paper. TERRA reflects a laser light even from a high incident angle in the direction of the incident-light path, while a conventional retro-reflector array cannot. Besides, TERRA can be installed in a smaller space than a corner-cube retro-reflector. In an optical sense, TERRA is equivalent to a Littrow grating, the blaze angle of which varies, depending on the incident angle. The reflected light generates a bright and dark fringe, and the bright fringe is required to travel along the incident-light path to achieve the objects of laser-aided diagnostics. In order to investigate the propagation properties of laser light reflected by TERRA, we have developed a new diffraction formula. Conditions for the propagation of the bright fringe in the direction of the incident light have been obtained using the Littrow grating model and have been confirmed in a simulation applying the new diffraction formula. Finally, we have designed laser transmission optics using TERRA for the ITER poloidal polarimeter and have calculated the light propagation of the system. The optical design obtains a high transmission efficiency, with 88.6% of the incident power returned. These results demonstrate the feasibility of applying TERRA to the ITER poloidal polarimeter. [ABSTRACT FROM AUTHOR]

The International Thermonuclear Experimental Reactor will have wide angle viewing systems and a divertor thermography diagnostic, which shall provide infrared coverage of the divertor and large parts of the first wall surfaces with spatial and temporal resolution adequate for operational purposes and higher resolved details of the divertor and other areas for physics investigations. We propose specifications for each system such that they jointly respond to the requirements. Risk analysis driven priorities for future work concern mirror degradation, interfaces with other diagnostics, radiation damage to refractive optics, reflections, and the development of calibration and measurement methods for varying optical and thermal target properties. [ABSTRACT FROM AUTHOR]

Neutron and gamma-ray irradiation complicates the design of the edge Thomson scattering (TS) system in ITER. The TS light is relayed through the relaying optics with labyrinth and fiber coupling optics. Electron density of 2×1019 m-3 is sufficient to measure Te and ne within a 10% and 5% margin of error, respectively, with a spatial resolution of 5 mm. This system can cover from 0.85 to 1 of the normalized minor radius. The time resolution is 10 ms, which is determined by the repetition rate of the laser device. A super-Gaussian is the ideal laser profile for the laser injection optics to avoid a breakdown of the filling gas used in density calibration through Raman scattering. [ABSTRACT FROM AUTHOR]

A convergence study of bispectral analysis on toroidal plasma turbulence is presented with a theoretical estimate of bicoherence for the system of the drift wave and zonal flow. Examples are chosen from the analysis of floating potential fluctuation in the edge region of the JFT-2M tokamak. The convergence properties of the bispectral functions are clarified for an oscillatory branch of zonal flow (or geodesic acoustic mode) and drift waves. The total squared bicoherence or the biphase converges inversely proportional to the realization number or to the square root of the realization number, respectively. The numbers of realizations to qualitatively converge and obtain a quantitatively significant value of bicoherence are discussed for the drift wave fluctuations and for the zonal flow. [ABSTRACT FROM AUTHOR]

Rapid frequency sweeping modes observed in reversed magnetic shear (RS) plasmas on the Japan Atomic Energy Research Institute Tokamak 60 Upgrade (JT-60U) [H. Ninomiya and the JT-60 Team, Phys. Fluids B 4, 2070 (1992)] have been identified as reversed-shear-induced Alfvén eigenmodes (RSAEs), which are ideal magnetohydrodynamic Alfvén eigenmodes (AEs) localized to the region of minimum safety factor, qmin, and are excited by negative-ion-based neutral beam injection. The chirping and subsequent saturation of the mode frequency are consistent with theoretical predictions for the transition from RSAEs to toroidal Alfvén eigenmodes (TAEs). The previously observed rapid frequency sweeping modes in ion cyclotron wave heated plasmas in JT-60U can also be similarly explained. The observed AE amplitude is largest during the transition from RSAEs to TAEs, and fast ion loss is observed when the AE amplitude is largest at this transition. It is preferable to operate outside the transition range of qmin, e.g., 2.4min<2.7 for the n=1 AE to avoid substantial fast ion loss in RS plasmas. [ABSTRACT FROM AUTHOR]

A ferritic steel wall, which might be employed in fusion demonstration reactors, has been installed in Japan Atomic Energy Research Institute Fusion Torus-2 Modified [Nucl. Fusion 41, 257 (2001)] to study the applicability of ferromagnetic walls to plasmas. The tearing mode equation is solved in presence of a ferromagnetic/resistive wall to study the effect of the ferromagnetism on the tearing mode stability in tokamaks. It is shown that a ferromagnetic wall has a weak effect on the surface tearing modes depending on the current profile. The destabilization effect due to the attraction of the perturbed magnetic field by permeability is shown to be very small compared to the stabilization effect of the conducting wall. [ABSTRACT FROM AUTHOR]

Fusion gamma rays were measured in D–[sup 3]He experiments using negative ion-based neutral beam injection (N-NBI) in reverse shear plasmas of the JT-60 tokamak. [sup 3]He gas was puffed at plasma initiation and just before N-NB injection. The D–[sup 3]He reaction produces 3.6 MeV alphas and 14.7 MeV protons, but there is also a small branch which provides [sup 5]Li and 16.7 MeV gamma rays. The total D–[sup 3]He reaction rate can be evaluated from measurement of gamma rays of the [sup 3]He (d,γ) [sup 5]Li reactions using a 3 in. diam by 3 in. long Bi[sub 4]Ge[sub 3]O[sub 12] scintillator. The gamma-ray detector was located 17 m below the plasma center and measured the gamma-rays in a vertical line of sight. The detector was mounted inside a heavy collimator with polyethylene and lead shielding. The floor penetration, a 4×8 cm[sup 2] hole, was used as a precollimator. Energy calibration of the detector was done with photopeaks for neutron capture gamma rays from the structural materials in D–D discharges. The detection efficiency was calculated with Monte Carlo code MCNP-4B for 16.7 MeV gammas. The pulse height analysis of the gamma rays resulted in the D–[sup 3]He fusion power of 110±30 kW in this experiment. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Reports on the high performance and steady-state experiments that have been conducted in the W-shaped divertor in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade. Equivalent deuterium-tritium fusion multiplication factor; Reduction in particle diffusivity in the internal transport barriers region of the reverses shear plasma.

Short duration (20 msec) neutral deuterium beams are injected into the TFTR tokamak [Plasma Physics and Controlled Nuclear Fusion Research 1986 (IAEA, Vienna, 1987), Vol. I, p. 51]. The subsequent confinement, thermalization, and diffusion of the beam ions are studied with multichannel neutron and charge exchange diagnostics. The central fast-ion diffusion (<0.05 m2/sec ) is an order of magnitude smaller than typical thermal transport coefficients. [ABSTRACT FROM AUTHOR]

Steady-state and perturbative transport analysis are complementary techniques for the study of transport in tokamaks. These techniques are applied to the investigation of auxiliary-heated Lmode and supershot plasmas in the tokamak fusion test reactor (TFTR) [R. J. Hawryluk et al., Plasma Physics and Controlled Nuclear Fusion Research, Proceedings of the 11 th International Conference, Kyoto, 1986 (IAEA, Vienna, 1987), Vol. 1, p. 51. ]. In the L mode, both steady-state and perturbative transport measurements reveal a strong temperature dependence that is consistent with electrostatic microinstability theory and the degradation of confinement with neutral beam power. Steady-state analysis of the ion heat and momentum balance in supershots indicates a reduction and a significant weakening of the power-law dependence on the transport in the center of the discharge. [ABSTRACT FROM AUTHOR]

In order to measure the ion temperature of the JT-60 tokamak, we have developed a Rutherford scattering system using a helium atom beam. A positive-ion beam generated by an ion source which has a capability of beam energy 200 keV and drain current 3.5 A is converted to a helium atom beam by collision with cold helium gas. The He atom beam, equivalent to 0.6 A, reaches the center of the vacuum chamber of the JT-60 tokamak. The scattering angle is 7.0°. Scattered helium atoms are analyzed by an EB-type neutral particle energy analyzer with a gas stripping cell. This scattering system has been applied to investigate additionally heated plasmas by the method of neutral beam injection (NBI), ion cyclotron wave (ICRH), lower hybrid wave (LHRH), and combined heating of NBI + LHRH or ICRH in a parameter range of B[sub t] = 4.0 to 4.5 T, I[sub p] = 1.0 to 3.2 MA, and ñ[sub e] ... 1 × 10[sup 20] m[sup -3]. The ion temperatures obtained by the system are consistent with those measured by Doppler broadenings of Ti XXI and Ti XXII resonance lines. To investigate the influence of ion temperature and density profiles and the beam component of NBI heating on the determination of ion temperature, we have evaluated an energy spectrum of scattered atoms by using a simulation code. The result shows that in JT-60 plasmas the beam component hardly exerts an important influence on the determination of ion temperature by this diagnostic system. [ABSTRACT FROM AUTHOR]

A high-repetition and high-energy transversely excited atmospheric carbon dioxide (CO2) laser for a collective Thomson scattering (CTS) diagnostic has been developed to establish a diagnostic method of confined α particles in burning plasmas. To excite a single-transverse and single-longitudinal mode, a continuous wave seed laser was injected to an unstable resonator with a cavity length of ∼4.4 m. Pulse energy of 10 J with a repetition rate of 10 Hz has been achieved in the single-mode operation. Pulse energies of 18 J with a repetition rate of 10 Hz and 36 J with single shot operation have also been achieved in the multimode operation. These results give a prospect for the CTS diagnostic on International Thermonuclear Experimental Reactor (ITER), which requires single-mode energy of 20 J with repetition rate of 40 Hz. [ABSTRACT FROM AUTHOR]

A natural diamond detector (NDD) has been installed on the JT-60U tokamak to measure the flux and the energy distribution of charge exchange (CX) fast neutral particles. A NDD has many important advantages to be used as a CX neutral particle analyzer, for example very compact size, high energy resolution, and high radiation hardness etc., while the neutrons and γ rays are a large noise source in the deuterium plasma. The shield was set up around the NDD to reduce those noises. Time-resolved energy distribution of CX neutral particles corresponding to injected beam energy have been successfully obtained under high intensity neutron yield Yn>1015 n/s. Further enhanced neutral particle fluxes during sawtooth oscillation and Alfvén eigenmodes were observed with the NDD. The performance of the NDD as CX neutral particle spectrometer under high intensity neutron yield was demonstrated for the first time on JT-60U in this work. [ABSTRACT FROM AUTHOR]

Develops a charge-exchange neutral particle beam analyzer for the measurement of the MeV energy range ions produced by nuclear fusion or radio frequency heating. Ionization of neutral particles entering the analyzer with a carbon foil thickness; Resolution of energy and mass of the stripped ions.

An E//B type neutral particle analyzer with an acceleration tube between a stripping cell and a deflection magnet has been developed to measure ion energy distributions in a wide energy range from thermal ions to fast ions up to several hundred kiloelectron volts simultaneously without making the analyzer size large. In the acceleration tube, ions are accelerated up to the detectable energy before coming into the deflection magnetic field. The acceleration method enables us to detect low-energy ions even for a strong deflection magnetic field to measure high-energy ions. Calibration experiments confirmed that ions were well accelerated according to expectation without degrading the abilities of the analyzer. The energy dynamic range E[sub max]/E[sub min] was improved up to 100 by the acceleration method. Using the analyzer, ion energy distributions have been measured in various heating experiments of JT-60. [ABSTRACT FROM AUTHOR]

In reactor-grade tokamaks, it is important to investigate confinement properties of alpha particles. A double charge-exchange method using a high-energy probing beam is considered to be the most reliable one in diagnostic methods proposed for the measurement. In JT-60U, an alpha particle production experiment by D-³He ICRF heating will be performed to study the behavior of fusion product alphas. The alpha particle measurement is planned using a helium diagnostic beam (200 keV) and a mass-resolved neutral panicle energy analyzer. The expected flux and spectral shape were evaluated by taking into account multistep ionization of helium beam atoms and neutralized alphas. The beam energy is lower than desirable for measuring fast confined alphas near the birth energy. However, by using the beam system, it has been found from the evaluation that we can investigate the confinement properties of fusion product alphas from the spectral shape. And also such a system using a present-day He beam is useful to diagnose behavior of confined alphas in reactor-grade tokamak such as ITER. [ABSTRACT FROM AUTHOR]

Focuses on the application of a two-dimensional measurement with an infrared television camera to toroidal field (TF) ripple loss study. Content of the study; Information concerning the thermal measurement of fast ion behaviors.

A prototype YAG laser system for the edge Thomson scattering system in ITER has been newly developed. Performance of the laser amplifier was improved by using flow tubes made of samarium-doped glass; the small signal gain reached 20 at its maximum. As a result, an output energy of 7.66 J at 100 Hz was successfully achieved, and the performance exceeded the target performance (5 J, 100 Hz). [ABSTRACT FROM AUTHOR]

A new type polychromator has been designed for the edge Thomson scattering system in ITER. Signal light is parallelly dispersed into two parts at the first interference filter. Spectral transmissivities for some spectral channels may enhance better than the conventional type polychromator. In the new type polychromator, the misalignment due to the machine accuracy is expected to be within the margin of APD area. In order to calibrate the spectral transmissivity using the dual-laser injection method during the plasma discharge, it is preferred that the spectral channels are separated at the geometric mean of the injected two wavelengths. [ABSTRACT FROM AUTHOR]

This study demonstrates the separation of the finite electron temperature on the plasma polarimetry in the magnetic confined fusion plasma for the first time. Approximate solutions of the transformed Stokes equation, including the relativistic effect, suggest that the orientation angle, θ, and ellipticity angle, ε, of polarization state have different dependency on the electron density, n(e), and the electron temperature, T(e), and that the separation of n(e) and T(e) from θ and ε is possible in principle. We carry out the equilibrium and kinetic reconstruction of tokamak plasma when the central electron density was 10(20) m(-3), and the central electron temperatures were 5, 10, 20, and 30 keV. For both cases when a total plasma current, I(p), is known and when I(p) is unknown, the profiles of plasma current density, j(φ), n(e), and T(e) are successfully reconstructed. The reconstruction of j(φ) without the information of I(p) indicates the new method of I(p) measurement applicable to steady state operation of tokamak.

Microfission chambers (MFCs) will measure the total neutron source strength in ITER. The MFCs will be installed behind blanket modules in the vacuum vessel (VV). Triaxial mineral insulated (MI) cables will carry signals from the MFCs. The joint connecting triaxial MI cables in the VV must be considered because the MFCs and the MI cables will be installed separately at different times. Vacuum tight triaxial connector of the MI cable has been designed and a prototype has been constructed. Performance tests indicate that the connector can be applied to the ITER environment. A small bending-radius test of the MI cable indicates no observed damage at a curvature radius of 100 mm.

In this study, we investigate designs for polychromators of the ITER edge Thomson scattering system by means of numerical calculations. For this purpose, we discuss the optimum transmission wavelength ranges of the optical filters and the optimum number of filters. Five different filter arrangements, including those with an optical notch filter to eliminate D(alpha) emission, are compared with each other. The measurement accuracy when using a polychromator is evaluated for midplane port configuration. It is found that the optimum filter number keeping in mind the cost performance cost is 5 or 6. Moreover, the use of an optical notch filter increases the measurement accuracy by approximately 5%.

Microfission chambers (MFCs) are one of the most important diagnostics for measuring neutron source strength in ITER. Using MFCs for high-power operations (fusion power of 100 kW-1 GW) and for low-power operations (<100 kW) in combination is one way to fulfill the target measurement requirements of ITER. The MFCs for high-power operations will be installed behind blanket modules in both the upper and lower outboard regions of the vacuum vessel so as to be insensitive to changes in the position of the plasma. For low-power operations, one possible location of MFCs is inside the equatorial (EQ) port. The effect of streaming neutrons and of changes in the position of the plasma on the responses of MFCs is estimated based on a neutron Monte Carlo calculation using the MCNP Version 5 code. Results suggest that the effect of streaming neutrons should be taken into account if the MFCs for high-power operations are installed closer than 20 cm to the gap between blanket modules. It has also been found for MFCs of low-power operations that the averaged output of the MFCs installed at the top and bottom of the EQ port is sensitive to horizontal plasma shifts but not to vertical shifts. This finding suggests that corrections based on the position of the plasma center will be needed for the absolute measurement of neutron source strength.