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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]

This paper proposes a discrete-time model predictive control (MPC) scheme combined with an adaptive mechanism. To this end, first, an adaptive parameter estimation algorithm suitable for MPC is proposed, which uses the available input and output signals to estimate the unknown system parameters. It enables the prediction of a monotonically decreasing worst-case estimation error bound over the prediction horizon of MPC. These distinctive features allow for future model improvement to be explicitly considered in MPC. Thus, a less conservative adaptive-type MPC controller can be developed based on the proposed estimation method. Second, we show how the discrete-time adaptive-type state-feedback MPC controller is constructed by combining the on-line parameter estimation scheme with a modified robust MPC method based on the comparison model. The developed MPC controller guarantees feasibility and stability of the closed-loop system theoretically in the presence of input and state constraints. A numerical example is given to demonstrate its effectiveness. [ABSTRACT FROM AUTHOR]

This paper proposes a new model predictive control (MPC) method for linear parameter varying systems with bounded parameter variation subject to input constraints. The method adopts closed-loop prediction and constructs ellipsoidal sets to predict the future states with reasonable computational effort. Then the information on the parameter variation rate is exploited to improve the accuracy of the prediction. Furthermore, a relaxed terminal condition, which guarantees the stability for infinite horizon, is introduced to enlarge the stabilizable region. It is shown that the feasibility of the MPC problem at the initial step ensures the stability of the closed-loop system. Finally, a simulation result illustrates the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A wavelength channel data rewriter (WCDR) is a device that erases the data on an incoming signal by utilizing the saturation characteristic of a semiconductor optical amplifier (SOA) and then modulates it with new data to generate an upstream signal. This paper describes a theoretical and experimental investigation designed to improve the performance of the WCDR. Through numerical calculations, this paper shows that an SOA with a long waveguide with a large small-signal gain better suppresses optical bit patterns. This paper also uses calculated and experimental results to show that the amplified-spontaneous-emission noise in the SOA input signal degrades the bit-pattern suppression. This paper then describes the semiconductor optical saturator/modulator (SOSM), which this paper has developed for use in the WCDR based on the results of the author's theoretical investigations. This paper outlines the SOSM specifications and provides experimental results that confirm the improved WCDR performance obtained using the SOSM. [ABSTRACT FROM PUBLISHER]

This paper deals with a trajectory tracking problem for a class of bimodal piecewise affine systems, which is inherently difficult because of the discontinuous changes of their vector fields. First, we introduce an error variable and an error system as a generalization of the tracking error and its system. As an error variable, a function switched by the mode of a piecewise affine system is adopted to overcome the inherent difficulty in trajectory tracking control of piecewise affine systems. Next, we design a tracking controller which stabilizes the error system using a Lyapunov-like function, which can be applied to systems including state jumps. Furthermore, the feasibility condition of tracking for SISO piecewise linear systems is simplified. Finally, a numerical example is given to illustrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The concept of multiplexing thermography is applied to the design of the divertor thermography system for International Thermonuclear Experimental Reactor (ITER). The combination of the front mirror with multiellipticity and a Czerney–Turner spectrometer with a 0.2 mm pitched multichannel detector enables a spatial resolution of 3 mm and a time resolution of 20 μs above a target temperature of 300 °C to be achieved. This should be sufficient to measure ELM heat fluxes to the targets in ITER. To satisfy the measurement requirement, it is very important to keep an accurate alignment around the optical axis against movement of the vessel during the plasma discharges. Several key engineering problems, such as the survivability of components against mirror coating by redeposited divertor material, remain to be solved. Potential solutions have been identified. [ABSTRACT FROM AUTHOR]

This report summarizes the results of in situ measurements of noninductive voltages developed across prototype International Thermonuclear Experimental Reactor (ITER) magnetic coils performed at the Japan Materials Test Reactor. The voltages appear to be mainly thermoelectric in origin, with the thermal sensitivity developing gradually through irradiation and the thermal gradients supplied by nuclear heating. Possible mechanisms and circuits within the coils that can contribute to this radiation-induced thermoelectric sensitivity are described, and schemes to improve the ITER coil design are outlined. [ABSTRACT FROM AUTHOR]

ITER diagnostic equipment is integrated in six equatorial and 12 upper ports, five lower ports, and the 16 divertor cassettes directly in front of them, and at many locations in the vacuum vessel. The integration has to satisfy multiple requirements and constraints and at the same time must deliver the required diagnostic performance. Design work has been carried out in problematical and interfacing areas for most diagnostics. The main diagnostic support components, the port plugs and divertor port racks, comprise common structural elements with dedicated modules from several diagnostics. The scope of the engineering task is summarized and an overview of the integration of the diagnostic equipment is given. The engineering work to date represents the input to the port engineering tasks of the construction phase with common or repeated elements being assessed for feasibility, resolving issues, and identifying show stoppers. It has been dominated by allocation and spatial integration in the tokamak. The work that follows will be more oriented towards the acceptability for operation, suitability for function, and conformity for licensing. [ABSTRACT FROM AUTHOR]

This paper describes how coarse wavelength-division multiplexing can realize a multiplexed multichannel video and Internet protocol (IP) system. In the proposed configuration, each signal is optically amplified separately to extend the service area. The IP signals are boosted by cost-effective erbium-doped fiber amplifiers, which have a simple configuration optimized for single-channel use. Two multiplexer/demultiplexer configurations are described. The proposed configurations yield a contents distribution network that offers bidirectional IP service in addition to the multichannel video service, which is transmitted as an analog signal. This paper presents an experiment that confirms the feasibility of this proposed system. [ABSTRACT FROM PUBLISHER]

This paper describes a method for realizing the efficient utilization of wavelength resources in wavelength-division multiplexing networks with centralized light sources. Using a deeply saturated semiconductor optical amplifier (SOA) modulator located in a remote node (RN), we erase the data on a downstream signal with a low extinction ratio and modulate it with new data to generate an upstream signal. Thus, we use only one wavelength for bidirectional transmission between a center node and an RN, without placing lasers at the RN. In this paper, we analyze the data suppression characteristic of the SOA using a large signal model. We also estimate the bit error rate degradation in the presence of an unsuppressed downstream bit pattern in an upstream signal. We then report experimental results that confirm the basic characteristics of the wavelength channel data rewriter, which we constructed using a linear amplifier and an SOA. Finally, we provide the results of a data transmission experiment that we undertook using the data rewriter. [ABSTRACT FROM PUBLISHER]

Recent development of the JT-60U charge exchange recombination spectroscopy (CXRS) diagnostic system is reported. The measurements of the radial profiles of the ion temperatures, the toroidal and poloidal rotation velocities, and the impurity density are based on CXR spectra of fully stripped carbon ions induced by neutral beam injection. Measurements are made simultaneously at 59 spatial points (23 toroidal and 36 poloidal) with a time resolution of 1/60 s throughout the full discharge pulse of 15 s. Considerable effort has been expended to ensure the automatic provision of reliable profile data, where the mechanical components of the system must cope with both a baked tokamak vessel (∼300 °C) and an expected disruption-induced acceleration of up to 60 g, where g denotes the gravitational acceleration, i.e., 9.8 m2/s. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The current state of investigations of the problem of providing first mirrors (FMs) for diagnostic systems in a reactor-grade fusion device is summarized. Results obtained in simulation experiments that have been conducted during recent years in several laboratories are presented. Attention is concentrated on two processes that can have an opposite effect but both can lead to degradation of mirror optical properties, namely: sputtering by charge exchange atoms which leads to erosion, and deposition which leads to surface contamination. It is shown in the analysis that when sputtering dominates, mirrors of monocrystalline refractory metals (Mo, W) can have a sufficiently long lifetime even for FMs that have to be located close to the first wall. Similarly, films of low sputtering yield metals on high thermal conductivity substrates (e.g., Rh on Cu) can be used for FMs in locations where the charge exchange flux is reduced to about a tenth of that at the first wall. However, deposition poses a serious threat to the lifetime of FMs but more modeling and experimental investigations are necessary before quantitative conclusions can be reached. Some mitigation methods are possible and these are briefly discussed. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Describes the design of the divertor impurity monitoring system of the International Thermonuclear Experimental Reactor. Main functions of the system; Wavelength range; Three different types of spectrometer; Optimization of the optics by a ray trace analysis.

Describes the development of a vacuum sealing method on a V-shaped elastic ring for the International Thermonuclear Experimental Reactor (ITER) diagnostic windows. Compression of the ring by two valves; Examination of the performance of the seals to inner pressure rise resistance, heat cycle and acceleration at the level expected in the ITER environment.

Examines the feasibility of installing a vacuum ultraviolet spectrometer at the divertor level on the International Thermonuclear Experimental Reactor including the related engineering aspects. Design features and implementation constraints; Vacuum ultraviolet spectra in the divertor leg; Use of the narrow gap between divertor cassettes as access for lines of sight.

Low-cost plastic packaging of laser diodes and photodiodes mounted on planar lightwave circuit (PLC) platform are developed and its reliability is confirmed under various environmental and endurance tests. The high performance of the module is maintained under reliability tests, such as high-humidity high-temperature tests (85°C, 85%RH) and temperature cycling tests (-40°C/85°C). No laser diodes show any device characteristics change during environmental tests and their stability has very little dependence on current bias. Although the photodiodes show an increase in leakage current under high-temperature high-humidity tests and the rate of leakage current increase is proportional to the square root of bias voltage, the increase is negligible for system use. These plastic modules can be applied to actual access networks and other fiber-optic networks [ABSTRACT FROM PUBLISHER]