Search

A new temperature measurement method—the dual two-color method—was developed to accurately measure the temperature over an ultra-wide temperature range (200–3600 °C) for ITER divertor infrared thermography. This novel method introduces a third wavelength filter to the conventional two-color method by replacing the shorter single wavelength bandpass filter with a customized dual-bandpass filter having two transmission bands, without having to add a third infrared camera. The dominant wavelength band of the total radiance through the dual-band filter changes automatically as the temperature increases and, consequently, either the shorter or longer wavelength band of the dual-bandpass filter is used to establish the two-color combination at both low and high temperatures. The dual two-color method increased the acceptable measurement error of the two-color radiance ratio for the temperature measurement requirement of the ITER divertor infrared thermography to 9.45% from that of 4.3% when using the conventional two-color method.

Introduction of Lower Port 02 integration and its function and requirement for tenant diagnostic, Divertor Impurity Monitor. And Guide structure and Rack locking mechanism are described to achieve the tolerances requirement from tenant diagnostic. And Mock-up and plan for the structures are introduced., 41st Meeting of the ITPA Topical Group on Diagnostics

ITERダイバータ赤外サーモグラフィでは高い放射線環境下にミラー及びレンズを配置し光を伝送する。そのため、ITERでの全運転期間を通して顕著な光学特性の劣化がない光学材料の選定及び遮蔽設計が必要不可欠となる。本研究ではITERダイバータ赤外サーモグラフィで使用可能な光学素子の選定及びその遮蔽設計の指標の決定を目的とし、レンズ材料のガンマ線及び中性子照射を実施しその前後の光学特性の計測から中赤外領域における放射線耐性を評価した。今回はその中でもSi、ZnSe、ZnS、CaF2の主要材料に絞り各材料のガンマ線及び中性子照射特性の詳細を報告する。, 第38回プラズマ核融合学会・年会

本研究ではITERダイバータ領域用の紫外-近赤外域分光計測システム開発の一環として、タングステンダイバータ化したITERにおける燃料/壁材由来の中性粒子及びイオンの発光とそれに寄与する素過程について検討を行っている。現在設計中の分光システムで計測され得る各種発光強度分布に加え、これらを用いてイオン化フロント位置や粒子発生量等の物理量を評価するために重要な素過程であるイオン化/再結合の寄与等について、ITERのプラズマシミュレーションデータから計算した結果を報告した。, 第38回 プラズマ・核融合学会 年会

ITERではタングステン(W)ダイバータ板等で反射した光の混入によるプラズマ発光計測の精度悪化が問題視されており、この反射特性は壁面の表面状態に依存する。本研究では、様々な熱負荷を与えたITERダイバータ用Wモノブロックに対してゴニオフォトメーターを用いて双方向反射率分布関数(BRDF)を計測した。熱負荷を与える前のWモノブロックでは切削痕によって異方的な反射特性を示す一方、熱負荷を与えたWモノブロックでは再結晶化によって表面が粗くなり、拡散的な反射特性を示した。熱負荷による表面構造変化に応じたBRDFの変化について報告する。, 第38回 プラズマ・核融合学会 年会

ITERのダイバータは光の反射率の高いタングステン（W）で製造されるため、プラズマ分光計測器の測定光にダイバータ表面からの反射光が混入し、プラズマ発光量評価の精度が低下する恐れがある。反射光はダイバータ板表面の状態によって特性が変化するため、光の反射特性とダイバータ表面の状態の関係を把握することが重要となる。 本研究では、直線型プラズマ装置NAGDIS-IIで生成したアルゴンプラズマの照射によりスパッタリングしたW試料の双方向反射率分布関数（BRDF）をゴニオフォトメータを用いて調べた。プラズマ照射前のW試料表面には紙やすりで傷を作成し、ITERダイバータのWモノブロックの表面粗さ（Ra）を模擬している。W試料へのイオン入射エネルギーを変化させたときの、RaとBRDFの変化について報告した。, The 30th International Toki Conference on Plasma and Fusion Research

The in-vessel components for the edge Thomson scattering measurement system in ITER (ETS) will be exposed to high thermal and electromagnetic loads, however, their maintenance will be limited because the ITER radiological environment will not allow operators to align the optics near the vacuum vessel. This paper summarizes the development of components, in particular, the beam combiner so as to minimize neutron streaming through the port plug penetrations used for las er beam injection and the strengthening of the beam dump so it can withstand harsh thermal and mechanical loads. Furthermore, a method to align the collection optics field of view was proposed and verified by ray-tracing simulation. The resolution and accuracy of which were approximately 0.5 mm and 0.1 mm, respectively. These values were much finer than the expected characteristic length of electron temperature and density gradients in the edge plasma of ITER.

量研ITERプロジェクト部では、マイクロフィッションチェンバー(MFC)、ポロイダル偏光計(PoPola)、周辺トムソン散乱計測(ETS)、ダイバータ不純物モニター(DIM)、ダイバータ赤外線サーモグラフィー(IRTh)の５つのITER用計測装置の開発を進めている。ITERの計測装置の中で、高線量の真空容器内、真空境界と生体遮蔽の間のインタースペース(IS)と呼ばれる空間、生体遮蔽の外側のポートセル(PC)と呼ばれる部屋に設置する機器は、信頼性を担保するために、設計段階で放射線照射による動作試験等を実施し、その信頼性を示す必要がある。本研究では、2018年度より実験課題として、上記計測装置のうち放射線下で用いる光学部品等にガンマ線を照射し、その信頼性の評価を行っている。本報告では、これまでに行った実験結果、進捗状況及び今後の予定等に関して報告する。, QST高崎 サイエンスフェスタ 2020

The ITER Edge Thomson scattering system provides measurements of the electron temperature and density profiles at the periphery plasma of the ITER tokamak for physics studies and advanced plasma control. The front-end of the system contains a relatively large 23 cm × 25.8 cm metal first mirror (FM). Radio-frequency plasma is considered to remove contaminants from the FM. The new design approach for the power transmission circuit for plasma cleaning includes a pre-matching element next to the FM and a notch-filter. The FM is water-cooled and the water cooling pipe length is tuned as a notch filter for the driving frequency. The power dissipation in the circuit elements was analyzed in a series of simulations at frequencies 30, 40 and 50 MHz. New plasma impedance values used for the model were measured in argon and helium plasma at 1–10 Pa in a special mock-up of the front-end optics compartment. The results define inductance, capacitance and geometry of pre-matching elements and help to predict the performance of the plasma cleaning circuit.

Numerous plasma-near mirrors of optical diagnostics in ITER require protection from erosion and deposition caused by impinging particles. This is achieved by 63 Diagnostic Shutters, which shall operate in vacuum under high thermal and neutron fluxes over 20 years without maintenance, ruling out standard engineering solutions. In fact, these conditions are unprecedented even on fusion devices. Hence, qualification R&D efforts are extensive, because if a shutter fails, so does the respective diagnostic. Shutter design tasks are widespread among Domestic Agencies and their suppliers, because every shutter is part of the diagnostic it shall protect when not in use. However, as these highly resembling systems have obvious synergy potential, a coordination strategy for all ITER shutters was implemented at IO. An extensive shutter experience collection including failure reports from 14 fusion devices was performed. These are summarized in the present work. For the first time, the state-of-the-art of shutters is thereby defined and assessed as to its applicability to ITER. Furthermore, design-driving environmental effects due to the specific operating conditions are recalled and evaluated. The findings of both assessments are put into context with the current designs of all ITER shutters. In a next step, these are reviewed with emphasis on synergies between different shutter systems. Finally, recommendations on necessary prototyping and generic components are given.

Neutron shield for ITER Diagnostic Lower Port Integration in Vacuum Vessel consists of Diagnostic Rack that put tenant’s diagnostic on it and Backplates. This paper proposes a novel concept of Neutron shield that uses Boron carbide powder canned in a stainless-steel box. A prototype was made to demonstrate the novel concept of Neutron shield, and it confirmed the density of B4C for the prototyping reached 1915 kg/m3, 76 % of the actual density of 2520 kg/m3. Neutronics was performed by applying the density confirmed by the prototyping. As a result, 45 μSv/h of Shut Down Dose Rate (SDDR) was achieved and satisfied its target. And additionally, 9.35 ton of neutron shield weight satisfied its target.

This study developed a new correction method to reduce errors in temperature measurement caused by temperature-dependent emissivity for ITER divertor infrared (IR) thermography. In order to develop the method, we measured the spectral emissivity of tungsten from 200 °C to 1900 °C in the wavelength range of 1.5 μm to 4.5 μm and evaluated temperature measurement error of the two-color method. The results indicate that temperature-dependent emissivity is a major factor in temperature measurement errors, which suggests that accurately measuring temperature by using the conventional two-color method would prove difficult. The new correction method uses two emissivity inputs at different temperature points, in contrast to the conventional method, which uses emissivity measured at a single temperature point. Using this new correction method with a suitable wavelength combination for the two-color method, temperature measurement error was reduced to less than 5% at 1900 °C.

This study developed a new correction method to reduce errors in temperature measurement caused by temperature-dependent emissivity for ITER divertor infrared (IR) thermography. In order to develop the method, we measured the spectral emissivity of tungsten from 200 °C to 1900 °C in the wavelength range of 1.5 μm to 4.5 μm and evaluated temperature measurement error of the two-color method. The results indicate that temperature-dependent emissivity is a major factor in temperature measurement errors, which suggests that accurately measuring temperature by using the conventional two-color method would prove difficult. The new correction method uses two emissivity inputs at different temperature points, in contrast to the conventional method, which uses emissivity measured at a single temperature point. Using this new correction method with a suitable wavelength combination for the two-color method, temperature measurement error was reduced to less than 5% at 1900 °C.

真空容器内のITER下部ポート統合機器の中性子遮蔽体は、計測機器を搭載する計測機器構造体とバックプレートで構成されている。 この論文では、ステンレス製の缶に炭化ホウ素粉末を充填した新しい中性子遮蔽体のコンセプトを提案する。 このコンセプトを実証するためにプロトタイプが製作され、プロトタイプの炭化ホウ素の密度は1915 kg / m3に達し、実際の密度2520 kg / m3の76％に達することが確認された。 核解析には、プロトタイピングによって確認された密度を適用した。その結果、45 µSv / hの運転停止後線量率（SDDR）が達成され、ITERの要求値を満足した。

This paper reports the gamma-ray irradiation effects on optical coatings and polarizers to be used in the ITER edge Thomson scattering system (ETS). Outside a diagnostic port-plug, in the Interspace, a total dose of the order of 1 MGy is expected through 20 years of ITER operation. In this study, gamma-ray irradiation experiments were performed up to 10 MGy. A high peak power laser beam, i.e. a pulse energy of 5 J and a pulse duration of ∼4 ns, is needed for a Thomson scattering measurement in ITER. Laser-induced damage threshold (LIDT) of anti-reflection (AR) and high-reflection (HR) coatings at the laser wavelengths after gamma-ray irradiation were investigated. LIDT of AR coating for 0° injections was more likely higher for the irradiated samples at a wavelength of 1064 nm. Regarding HR coatings, LIDT was not noticeably degraded by gamma-ray irradiation. Regarding polarizers, no degradation of transmission and extinction ratio was observed at visible and near infrared wavelength ranges when a wire-grid polarizer substrate is made of fused silica. Since a signal of ETS is almost linearly polarized, a wire-grid polarizer enables to improve signal to noise ratio of electron temperature and density measurements by Thomson scattering in ITER.

An in situ spectral calibration method for Thomson scattering systems, which uses a double-pass scattering system, has been developed for burning plasma experiments, such as ITER and DEMO. In such ...

The laser beam dump of the Edge Thomson scattering (ETS) in ITER is being developed and a new type of beam dump called the chevron beam dump was proposed recently. The laser-induced damage on the surface is one of the most severe issues to be overcome. The key concept of the chevron beam dump is to reduce the laser energy absorption per unit area and to absorb the laser beam gradually. The laser irradiation tests onto flat-mirror-molybdenum sample were carried out. It was clarified that the absorbed (rather than incident) energy density of the laser pulses should be the correct figure of merit for the laser-induced damage. Therefore, the concept of the chevron beam dump design, that minimizes the absorbed laser energy density per unit area, was validated experimentally. The chevron beam dump enables us to extend its lifetime drastically relative to conventional beam dumps. Potential methods to improve the laser-induced damage threshold (LIDT) are also discussed in this paper.

This study developed a new heat flux reconstruction code based on the dual reciprocity boundary element method for the International Thermonuclear Experimental Reactor (ITER) divertor infrared (IR) thermography system. To use divertor heat flux reconstruction in ITER, we modeled the boundary condition between the coolant pipe inner wall and the coolant based on the temperature-dependent heat transfer coefficient and also considered the temperature dependence of tungsten thermal properties. Using this reconstruction code, we evaluated the sensitivity of the input data errors, divertor coolant temperature, and surface temperature errors on the accuracy of heat flux reconstruction by using simplified heat flux profiles, which are spatially uniform on the top surface of the monoblocks. This heat flux reconstruction method demonstrated that highly accurate heat flux reconstruction can be achieved for high heat flux cases in ITER; however, further studies are needed for low heat flux reconstruction.

This study developed a new heat flux reconstruction code based on the dual reciprocity boundary element method for the International Thermonuclear Experimental Reactor (ITER) divertor infrared (IR) thermography system. To use divertor heat flux reconstruction in ITER, we modeled the boundary condition between the coolant pipe inner wall and the coolant based on the temperature-dependent heat transfer coefficient and also considered the temperature dependence of tungsten thermal properties. Using this reconstruction code, we evaluated the sensitivity of the input data errors, divertor coolant temperature, and surface temperature errors on the accuracy of heat flux reconstruction by using simplified heat flux profiles, which are spatially uniform on the top surface of the monoblocks. This heat flux reconstruction method demonstrated that highly accurate heat flux reconstruction can be achieved for high heat flux cases in ITER; however, further studies are needed for low heat flux reconstruction.

The ITER poloidal polarimeter will install optical components, corner cube retro-reflectors, into the slot of the first wall (FW) panels. The issues of designing the retro-reflector were (i) to achieve good thermal contact between the retro-reflector assembly and the FW and (ii) to accommodate the different thermal expansion of the retro-reflector made of tungsten and the FW made of stainless steel. In order to solve the issues, the CuCrZr filler was employed. A coupled mechanical-thermal analysis was carried out to confirm that the required contact pressure of 60 MPa persists during plasma operation. The highest predicted temperature of the retro-reflector was 673 °C, which is acceptable for tungsten. Electromagnetic analysis was carried out to confirm that the retro-reflector assembly will not move during plasma disruption. A maximum force of 3.06 kN is predicted on the retro-reflector during disruption and is much less than the static friction of 136 kN. In addition, the manufacturability of the retro-reflector assembly was successfully demonstrated. The roughness (Ra) and the flatness (root mean square) achieved for the mirror surface were 0.43 nm and 0.068 μm, respectively. The angle between the assembled mirrors was 90 ± 0.03°, better than the requirement of 90 ± 0.05°.

This paper reports the gamma-ray irradiation effects on optical coatings and polarizers to be used in the ITERedge Thomson scattering system (ETS). Outside a diagnostic port-plug, in the Interspace, a total dose of the orderof 1 MGy is expected through 20 years of ITER operation. In this study, gamma-ray irradiation experiments wereperformed up to 10 MGy. A high peak power laser beam, i.e. a pulse energy of 5 J and a pulse duration of∼4 ns,is needed for a Thomson scattering measurement in ITER. Laser-induced damage threshold (LIDT) of anti-re-flection (AR) and high-reflection (HR) coatings at the laser wavelengths after gamma-ray irradiation were in-vestigated. LIDT of AR coating for 0° injections was more likely higher for the irradiated samples at a wavelengthof 1064 nm. Regarding HR coatings, LIDT was not noticeably degraded by gamma-ray irradiation. Regardingpolarizers, no degradation of transmission and extinction ratio was observed at visible and near infrared wa-velength ranges when a wire-grid polarizer substrate is made of fused silica. Since a signal of ETS is almostlinearly polarized, a wire-grid polarizer enables to improve signal to noise ratio of electron temperature anddensity measurements by Thomson scattering in ITER.

The ITER poloidal polarimeter will install optical components, corner cube retro-reflectors, into the slot of the first wall (FW) panels. The issues of designing the retro-reflector were (i) to achieve good thermal contact between the retro-reflector assembly and the FW and (ii) to accommodate the different thermal expansion of the retro-reflector made of tungsten and the FW made of stainless steel. In order to solve the issues, the CuCrZr filler was employed. A coupled mechanical-thermal analysis was carried out to confirm that the required contact pressure of 60 MPa persists during plasma operation. The highest predicted temperature of the retro-reflector was 673 °C, which is acceptable for tungsten. Electromagnetic analysis was carried out to confirm that the retro-reflector assembly will not move during plasma disruption. A maximum force of 3.06 kN is predicted on the retro-reflector during disruption and is much less than the static friction of 136 kN. In addition, the manufacturability of the retro-reflector assembly was successfully demonstrated. The roughness (Ra) and the flatness (root mean square) achieved for the mirror surface were 0.43 nm and 0.068 μm, respectively. The angle between the assembled mirrors was 90 ± 0.03°, better than the requirement of 90 ± 0.05°.

Japan Domestic Agency (JADA) is responsible for six diagnostic systems in the ITER project. We have successfully developed a prototype instrumentation and control (I&C) system for the ITER divertor thermocouples system. The prototype I&C system includes a supervisory function, a sequencing management function, and a data acquisition function. The supervisory function, which was implemented using EPICS (Experimental Physics and Industrial Control System), manages internal operations for measurement such as health check of sensors. We developed a conversion tool from flowcharts to EPICS record source codes. The EPICS records generated by the conversion tool are used to trigger each operation step and to indicate the progress of the sequence. We also developed the sequencing management function that coordinates the execution of operation steps. Both the flowchart conversion tool and sequencing management function were developed to reduce designers’ mistakes and to ensure rapid development. The prototype I&C system for the DTC was tested. We confirmed that the I&C system performed satisfying the requirements. This validated design will be applied to other ITER diagnostic systems procured by JADA.

Optical design for divertor Thomson scattering system in JT-60SA has been conducted. The measurement system will use a Nd:YAG laser at 1064 nm, and scattered photons are collected by a collection optical system. The collection optics consists of primary mirror, secondary mirror, relay optics, and fiber collection optics. The laser transmission mirror and collection optics were designed to be installed in a slender lower port of JT-60SA. The assessment of the measurement errors in temperature was conducted for the designed collection optical system. Because of spatial limitation, the solid angle from the measurement points would be small especially for the measurement points in high field side, and consequently, the temperature errors in the high field side would be considerably large. The effects of several improvements on the error are discussed. Moreover, an assessment for the in-vessel laser transmission metallic mirrors is conducted for the present design.

Distribution of carbon dust in the plasma discharges was measured, and sublimation of dust was dominant in the scrape-off layer (SOL). Dust collection in the vacuum vessel was performed after the e...

The effect of helium irradiation on in-vessel mirror materials, i.e. molybdenum and rhodium, are investigated experimentally. By the exposure to helium plasmas with low incident ion energy (∼50 eV) at different surface temperatures, the optical reflectivity of molybdenum and rhodium decreases significantly. From the surface analysis, it is shown that fiberlike nanostructure is formed on molybdenum surface when the surface temperature is high (at 1500 K), while rough surface is observed when the surface temperature is low (

The nuclear heating rates of the optical mirrors of the poloidal polarimeter installed in the equatorial port plug of ITER are calculated. Since the system cannot have a sufficiently labyrinthine structure and the second mirrors are located closer to the plasma than the first mirrors due to limited space, the nuclear heating rate of the second mirrors is as high as that of the first mirrors. However, it is possible to reduce the nuclear heating rates more than 1 order if the blanket shield module provides a sufficient degree of neutron shielding. The effect of the neutron shield on the peripheral region of the upper port plug, in which the optical system of the poloidal polarimeter is installed, is also evaluated. The gamma-ray dose rate 10 6 s after shutdown of operations in the back flange region has been estimated to be ∼60 μSv/h when the neutron shield is filled in the port plug, which is below the design threshold for the ITER maintenance phase. Further, the nuclear heating rate of the Poloidal field coil near the same upper port has been evaluated to be more than 2 orders lower than the allowable value of 1 mW/cc.

ITER plasma boundary and first-wall diagnostics are summarized in terms of their physical implementation and physics motivation. The challenge of extracting diagnostic signals while maintaining nuclear shielding is discussed, as well as the problems associated with high levels of erosion and redeposition.

In the ITER edge Thomson scattering measurement system, polychromators with optical band-pass filters and avalanche photodiodes are planned to be used. In this paper, we optimized the transmission wavelength ranges of the optical filters by a numerical method. Since measurements in a high electron temperature range are required for the measurement system, the Thomson spectrum could overlap a strong line emission of D α when the electron temperature is rather high. It is shown that a filter whose transmission wavelength range is shorter than D α becomes important to decrease the measurement error in the high temperature range. Moreover, it is found that a filter whose transmission wavelength range is above 1064 nm (laser wavelength) is useful to improve the measurement accuracy, in particular, when the number of filters is more than six.

A recent series of dimensionless pedestal identity experiments at JET and JT-60U failed to produce a match in the dimensional pedestal parameters and edge-localized mode (ELM) frequency despite a good match in the main dimensionless plasma parameters. This paper describes the progress made in understanding these experimental results. First, it is investigated whether differences in the magnetohydrodynamic stability of the pedestal, including those potentially arising from the 10% difference in the aspect ratio between the two tokamaks, can explain the results. The potential effects of differences in plasma rotation between the two machines are also examined. Given the result that these mechanisms fail to explain the experimental observations and the fact that JT-60U features considerably stronger toroidal magnetic field ripple than JET, the bulk of the paper, however, discusses the effects of ripple losses. The analysis shows that ripple losses of thermal ions can affect H-mode plasma performance very sensitively. Orbit-following simulations indicate that losses due to diffusive transport give rise to a wide radial distribution of enhanced ion thermal transport, whereas non-diffusive losses have a very edge-localized distribution. In predictive transport simulations with an energy sink term in the continuity equation for the ion pressure representing non-diffusive losses, reduced performance as well as an increase in the ELM

Recent R&D of an edge Thomson scattering system for ITER (International Thermonuclear Experimental Reactor) are reviewed. We have designed a diagnostic laser system (5 J, 100 Hz) based on JT-60U di...

In the KSTAR Tokamak, a “Tangential Thomson Scattering” (TTS) diagnostic system has been designed and installed to measure electron density and temperature profiles. In the edge system, TTS has 12 optical fiber bundles to measure the edge profiles with 10–15 mm spatial resolution. These 12 optical fibers and their spatial resolution are not enough to measure the pedestal width with a high accuracy but allow observations of L-H transition or H-L transitions at the edge. For these measurements, the prototype ITER edge Thomson Nd:YAG laser system manufactured by JAEA in Japan is installed. In this paper, the KSTAR TTS system is briefly described and some TTS edge profiles are presented and compared against the KSTAR Charge Exchange Spectroscopy and other diagnostics. The future upgrade plan of the system is also discussed in this paper.

This paper provides a novel method for evaluating signal intensities in incoherent Thomson scattering diagnostics. A double-pass Thomson scattering system, where a laser passes through the plasma twice, generates two scattering pulses from the plasma. Evaluations of the signal intensities in the spectrometer are sometimes difficult due to noise and stray light. We apply the singular value decomposition method to Thomson scattering data with strong noise components. Results show that the average accuracy of the measured electron temperature (Te) is superior to that of temperature obtained using a low-pass filter (

A new high speed Nd:YAG Thomson scattering AD Convertor (HYADC) that can directly convert the detected scattered light signal into a digital signal is under development. The HYADC is expected to improve a signal to noise ratio of the Nd:YAG Thomson scattering measurement. The data storage of the HYADC which is required for the direct conversion of whole plasma discharge is drastically reduced by a ring buffer memory and a stop trigger system. Data transfer of the HYADC is performed by the SiTCP. The HYADC is easily expandable to a multi-channel system by the distributed data processing, and is very compact and easy to implement as a built-in system of the polychromators.

The paper reviews recent theoretical and experimental results focussing on the identification of the key factors controlling ELM energy and particle losses both in natural ELMs and in the presence of external controlling mechanisms. Present experiment and theory pointed out the benefit of the high plasma shaping, high q(95) and high pedestal density in reducing the ELM affected area and conductive energy losses in Type I ELMs. Small benign ELMs regimes in present machines (EDA, HRS, Type II, Grassy, QH, Type III in impurity seeded discharges at high delta) and their relevance for ITER are reviewed. Recent studies of active control of ELMs using stochastic boundaries, small pellets and edge current generation are presented. (c) 2004 Elsevier B.V. All rights reserved.

The dependence of edge stability on plasma shape and local pressure gradients P' in the DIII-D and JT-60U tokamaks is studied. The stronger plasma shaping in DIII-D allows the edge region of DIII-D discharges with type I (giant) ELMs to have access to the second region of stability for ideal ballooning modes and a larger edge pedestal pressure gradient P' than JT-60U type I ELM discharges. These JT-60U discharges are near the ballooning mode first regime stability limit. The DIII-D results support an ideal stability based working model of type I ELMs as low to intermediate toroidal mode number, n, MHD modes. The results from a stability analysis of JT-60U type I ELM discharges indicate that the predictions of this model are also consistent with JT-60U edge stability observations.

Engineering analyses have been performed for the representative diagnostic upper port plug of ITER. Maintenance and integration design have been also carried out for the diagnostic components to be installed in the upper port plug. From the electromagnetic and structural analyses, it has come up an important problem to suppress the displacement of the upper port plug rather than to reduce the produced stress. Reducing the electro-magnetic (EM) force will help to decrease the severity of potential displacement. Maximum displacement of the port plug decreases with increase in the number of slits in a manner that the displacement would seem to be less than the design tolerance. A proposed low body roller and inner frame may enhance maintenance and integration. These studies and designs have established the design basis for the diagnostic upper port plug.

A compact and two dimensional detector has been developed for the JT-60U Thomson scattering system, that consists mainly of a proximity focused image intensifier, a 20×12 spatially and spectrally arrayed silicon photodiode, and a data processing unit enabling high repetitive measurement at 1 kHz. To secure a wide spectral bandwidth for an effective detection of the Thomson scattering spectrum, we have introduced a spectrometer and lens systems with enhanced transmission in a longer wavelength, which can compensate for the decreasing characteristic of quantum efficiency of a transmission-mode photocathode used in the image intensifier. The spectral divide of the photodiode array is designed to give its full performance in a wide electron temperature (Te) range of 0.2–15 keV with 12 spectral channels. The application of this newly developed detector to the JT-60U core plasma measurement is also presented.

The design and operation performance of the latest ruby Thomson scattering system for the JT-60U are described, which includes many novel approaches to attain the repetitive measurement of 60 spatial points with high resolution (8 mm), precision, and reliability especially for a high temperature and large size tokamak device. A beam combiner composed of a polarizer and a Faraday rotator for two ruby lasers has provided the transient measurement with the minimum time interval of 2 ms in burst operation and the multitime-slice measurement with the repetition rate of 0.5 Hz in normal operation. A newly developed photodiode array detector with high repetitive ability of 1 ms has been used for the high temperature core plasma measurement. A quantitative alignment of collection fiber object field has been utilized for the reliable ne profile measurement. By using Rayleigh scattering light, an in situ inferring method for a coated viewing window transmission has been found to have an effect on the precise correc...

A YAG laser Thomson scattering system has been developed to measure the time evolution of electron temperature (Te) and density (ne) profiles in the JT-60U. Presently this system provides Te and ne periodically every 100 ms (20 ms at the minimum) at 15 spatial channels. A six spectrum channel polychromator, which is a successive interference filter type, was designed to measure a wide Te range (20 eV–20 keV) by using five channels. The sixth channel is used for calibration by Rayleigh scattering. However, we also used the Rayleigh channel to measure Te and ne since the stray light level was very low. As a result, we were able to measure temperatures below 20 eV. The temperature of the silicon avalanche photodiode (APD) is stabilized by a Peltier element so that the gain is kept constant within ±0.5%. The stable performance of the APD enables accurate Te and ne measurement. During plasma operation, the electron temperature is measured over a wide range from the low temperature plasmas in the runaway plasma...

The design concept and operation performance of a novel alignment system for accurate electron density profile measurement is presented, which has been developed on the basis of the original method for adjusting quantitatively and actively an object field of collection fiber optics to a laser-beam axis. The quantitative expression needed for an appropriate alignment was able to be formulated using the beam width measured in situ by this alignment system and the four laser scattering intensity signals from special alignment fiber bundles. The effectiveness of this alignment system for precise and reliable measurement of electron density has been successfully demonstrated in the JT-60U Thomson scattering diagnostic through direct monitoring and quick restoration of alignment. The important and distinctive feature of this alignment system is to attain compatibility between a stable and accurate maintenance of alignment and an improvement of the signal-to-noise ratio of Thomson scattering to plasma light acco...

A new CO2 laser interferometer has been developed to measure the electron density of tokamak plasmas. Two different wavelength oscillators of 10.6 and 9.27 μm are utilized for simultaneous measurement of the density component and the optical path length change. A new technique using a common frequency shifter for two color lasers improves the stability of the system by a complete matching of both beat frequencies. The system provides advantages for practical problems of large tokmaks related to window darkening and large mechanical vibrations of reflection mirrors and offers improved laser beam monitoring and a simplified optical layout by using closer wavelengths. The electron density of JT‐60U is successfully measured for a plasma current of up to 3 MA. The density behavior during a fast major disruption is also diagnosed without a fringe loss. An effective density resolution is observed to be 2×1019 m−2, which corresponds to about 1/10 of a fringe. A very high resolution (1/104 fringe) phase comparator...

This paper focuses on a method for measuring the electron temperature (T(e)) without knowing the transmissivity using Thomson scattering diagnostic with a double-pass scattering system. Application of this method for measuring the anisotropic T(e), i.e., the T(e) in the directions parallel (T(eparallel)) and perpendicular (T(eperpendicular)) to the magnetic field, is proposed. Simulations based on the designed parameters for a JT-60SA indicate the feasibility of the measurements except in certain T(e) ranges, e.g., T(eparallel) ~ 3.5T(eperpendicular) at 120° of the scattering angle.

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).