[en] The data acquisition for the infrared measurement system on Tore-Supra is a key element in ensuring the supervision of the new actively-cooled plasma facing components of the CIEL project. It will allow us to follow the thermal evolution of components of Tore-Supra, in particular the toroidal pumped limiter (LPT) (360 deg.-15 m long) and the five additional heating launchers. When fully installed, the infrared measurement system will be composed of 12 digital 16-bit infrared cameras. They cover a 100-1200 deg.C temperature range and each picture has a definition of 320x240 pixels with a 20 ms time resolution. The objectives of the data acquisition system is real-time recording and analysis of each view element for further post-pulse analysis in order to understand the physics phenomenon and ensure the supervision of the plasma facing components and also to be part of the global feedback control system of Tore Supra

[en] An imaging spectrometer using a sapphire prism as dispersing element has been conceived at Tore Supra for the spectral range of 1 - 4 μm. It measures simultaneously at various wavelengths the temperature on distributed high heat-flux elements under plasma impact with 36 optical fibres, 4 of which are ZrF₄ fibres. It employs an InSb focal plane array detector (256*320 pixels) behind a silicon filter and a ZnS window yielding a dynamic range of 200 to 1500 deg C with 20 ms temporal resolution. The fibre transmission and the spatial variation of gain and background of the camera are calibrated using a light source with integrating sphere. With a black body source one determines the non linearity of the average gain and controls its stability during operation. The spectral dispersion of about 30 nm/pixel is determined with interference filters and controlled with a spectral lamp. The measurements at various wavelengths allow to determine the temperature distribution in the held of view. (author)

[en] During operation of present fusion devices, the Plasma Facing Components (PFCs) are submitted to large heat fluxes within a range of 10-20 MW/m². Understanding and preventing overheating of these components during long pulse discharges is a crucial issue. The surface temperature of the PFCs in the vacuum chamber of a tokamak is measured by infrared (IR) digital cameras interfaced with complex optical systems. Due to the complexity of the observed IR scenes and the large amount of data produced, the real-time processing of IR images will be a key point for ITER, the next fusion device. As an illustration, the foreseen IR and visible diagnostic for ITER will consist in 12 IR equatorial views for the thermal monitoring of the vacuum chamber. The real-time processing will include all calibration factors related to the optical path and some corrections due to the variation of the emissivity of metallic objects. It will also include some intelligent processing to detect abnormal thermal events during plasma operation to avoid water leak, PFCs damages and to guarantee high performance plasmas. The use of high computational performance hardware is then mandatory to reach a real time processing of the IR images. At Tore Supra, we have recently made a major upgrade of our real-time IR image acquisition and processing board by the use of the new FPGA Xilinx Virtex 5 SX95T. This board is optimized for image processing and matrix calculations. It can be programmed using high-level languages like MatlabTM or SimulinkTM. We currently have implemented on the board all 1- and 2-dimensional calibration factors due to optics. This allows us to process in real-time IR images expressed in absolute temperature. This paper will describe briefly the old acquisition and processing system and will make emphasis on major progress obtained by the new FPGA board. Comparison between the old system and the new one will be presented. Some preliminary results will be given and a strategy will be proposed for the implementation of 'intelligent algorithms' based on video understanding approach. This document is composed of an abstract followed by the presentation transparencies. (authors)

[en] Full text: The new ITER-relevant Lower Hybrid Current Drive (LHCD) launcher, based on the Passive Active Multi-junction (PAM) concept, was brought into operation on the Tore Supra tokamak in October 2009. The PAM launcher concept was designed in view of ITER to allow efficient cooling of the waveguides due to plasma radiation, RF losses and neutron damping. In addition, it offers low power reflection close to the cut-off density, which is important in view of ITER, where the large distance between the plasma and the wall may bring the density in front of the launcher to low values. The complete system operated successfully on Tore Supra already on the second experimental day, coupling 0.4 MW into the plasma for 4.5 s. The maximum power and energy reached so far, after ∼ 400 pulses on plasma, is 2.7 MW during 77 s (exceeding 200 MJ injected energy). This corresponds to a power density of 25 MW/m² , i.e. its design value at f =3.7 GHz. The main goals of the initial experimental campaign were to: i) compare the coupling behaviour of the PAM launcher to the predictions from the ALOHA code, ii) demonstrate reliable power handling during edge perturbations mimicking ELMs and iii) achieve ITER-relevant power densities in pulse lengths exceeding several seconds. The power reflection coefficient (RC) behaviour on the PAM launcher shows good agreement with calculations, carried out with the ALOHA code. The average RC is < 2% when the electron density in front of the launcher is close to the cut-off density. When the density increases, RC increases, as predicted by modelling. Coupling experiments with edge perturbations, produced by supersonic molecular beam injection (SMBI) to simulate ELM-behaviour, were carried out at intermediate LHCD power (∼ 1.5 MW). During a SMBI, the electron density in front of the PAM launcher increases typically by a factor of four and the RC increases, in accordance with modelling. The applied power remained constant during the SMBI, demonstrating an ELM-resilient system. In standard coupling conditions, the maximum power and energy achieved on the PAM launcher so far is 2.7 MW during 77 s, corresponding to a power density of 25 MW/m². In addition, 2.7 MW was coupled at a plasma-launcher distance of 10 cm. The launcher front face security, based on infrared imaging and CuXIX-line emission, showed no arcing at the PAM launcher mouth during high LHCD power. (author)

[en] Highlights: • Active wall monitoring systems are an increasingly important asset for safe operation of metallic wall steady state magnetic fusion experiments. • Wall Infrared diagnostic connection to plasma control system enables wall monitoring. • WEST operates the C4 experimental campaign in 2019 with an ITER relevant wall monitoring system (soft control plus hard interlock). • The control activates on 63 occurrences, principally on an upper divertor pipe being heated by particles losses. • It facilitated WEST path to high power operation during C4 campaign, by effectively managing the technical risks to critical wall components. A real time Wall Monitoring System (WMS) is used on the WEST tokamak during the C4 experimental campaign. The WMS uses the wall surface temperatures from 6 fields of view of the Infrared viewing system. It extracts the raw digital data from selected areas, converts it to temperatures using the calibration and write it on the shared memory network being used by the Plasma Control System (PCS). The PCS feeds back to actuators, namely the injected power from 5 antennae's of the lower hybrid and ion cyclotron resonance radiofrequency (RF) heating systems. WMS activates feed back control 63 times during C4, which is 14 % of the plasma discharges. It activates mainly as the result of a direct RF loss to the upper divertor pipes. The feedback control maintains the wall temperature within the operation envelope during 97 % of the occurrences, while enabling plasma discharge continuation. The false positive rate establishes at 0.2 %. WMS significantly facilitated the operation path to high power operation during C4, by managing the technical risks to critical wall components.

[en] Tore-Supra was constructed with a steady-state magnetic field using superconducting magnets and water-cooled plasma facing components for high performance long pulse plasma discharges. The surface temperature from the main components are viewed with infrared cameras. In each camera's field of view, windows are set-up on zones of interest and temperature thresholds are defined within these zones. When any of the thresholds is crossed (with some integration time to avoid spurious warning), the main feedback control system switches down additional power for if limits are over-passed, a high risk of water leak appears. Because of the long pulse duration the infrared thermography system of Tore-Supra requires to be actively cooled and to be able to look at the entire surface of the toroidal pumped limiter (7.5 m², 15 meter long) and to the 5 additional heating antennas. We have developed a set of 7 actively cooled (steady-state) infrared endoscopes (which represents a total of 9 cameras) able to measure surface temperatures from 100 to 1500 Celsius degrees with an accuracy better than 8%

[en] A new Infrared diagnostic has been developed by CEA-IRFM and installed in the WEST tokamak to measure surface temperature of the actively cooled W-monoblocks components as foreseen for the ITER Divertor, with a very high spatial resolution of 100 μm. The goals are to investigate the effects of the shaping of these components on the heat load deposition pattern, the evolution of pre-damaged components specifically introduced in WEST, the behavior of the leading edges regarding the assembling tolerances between adjacent monoblocks, and finally to contribute to the specification assessment of the ITER divertor units. In WEST, each Plasma Facing Unit is composed of 35 W-monoblocks of individual surface of 28 × 12 mm. To analyze heat load pattern and phenomena on such tiny surfaces, the leading edges and in the narrow gaps between monoblocks (400–500 μm), a 100 μm spatial resolution is required. Then, a Very High spatial Resolution (VHR) infrared diagnostic has been specially developed at CEA-IRFM. The VHR operates at 1.7 μm wavelength to take advantage of the dynamic of the signal for the temperature range (400–3600 °C). The VHR infrared diagnostic is now operational above the divertor sector made of actively cooled W-monoblocks and graphite inertial components with W coating. This paper gives a description of the diagnostic.

[en] The WEST (Tungsten Environment for Steady State Tokamak) platform aims at testing ITER like divertor targets in an integrated tokamak environment, to minimize risks for procurement and operation. After 4 years of construction, WEST is now operational, with the first plasma breakdown achieved in December 2016. To operate long plasma discharge in WEST, infrared thermography is a key device, which enables a safe operation by means of a real time surface temperature monitoring, while providing essential data for various physics studies. For WEST, the IR thermography system has been deeply renewed, to match with the new tokamak configuration, and to fulfil the new measurement requirements. It consists of a set of 5 different diagnostics: 1) 7 endoscopes located in upper ports viewing the whole lower divertor and the 5 heating devices 2) a tangential endoscope located in a median port, providing a wide angle view of the vacuum vessel, and in particular of the upper divertor and first wall protections 3) a submillimetre resolution view on the divertor strike points from an upper port endoscope 4) 2 additional views of the divertor and of the heating devices. The paper describes the new IR diagnostics configuration (spatial covering, IR cameras, optics, data processing hardware and software), the main design options, manufacturing and installation issues, and some measurement performances.

[en] An imaging spectrometer using a sapphire prism as dispersing element has been conceived at Tore Supra for the spectral range of 1-4 μm. It measures simultaneously at various wavelengths the temperature on distributed high heat-flux elements under plasma impact with 36 optical fibers, four of which are ZrF₄ fibers. It employs an InSb focal plane array detector (256*320 pixels) behind a silicon filter and a ZnS window yielding a dynamic range of 200-1500 deg. C with 20 ms temporal resolution. The fiber transmission and the spatial variation of gain and background of the camera are calibrated using a light source with integrating sphere. With a blackbody source one determines the nonlinearity of the average gain and controls its stability during operation. The spectral dispersion of about 24 nm/pixel is determined with interference filters and controlled with a spectral lamp. The measurements at various wavelengths allow to determine the temperature distribution in the field of view

[en] Plasma Facing Components (PFCs) of modern fusion devices are submitted to large heat fluxes. Understanding and preventing overheating of these components during long pulse discharges is a crucial issue for next step tokamak ITER and future fusion reactors. Lower heat loads can be achieved by reducing the additional power resulting in a decrease of the plasma performance. So real time power optimisation is needed. Tore Supra, as a superconductor tokamak with water-cooled PFCs, is perfectly suited to tackle such a problem. A real time infrared thermography diagnostics [D. Guilhem et al. QIRT journal, 2 N^o 1 p. 77 to 96 (2005)] has been implemented in Tore Supra as part of the CIMES project [B. Beaumont et al. Fusion Engineering and Design, 56-57 667-672 (2001)] allowing real time temperature monitoring of the most sensitive components. While the toroidal pumped limiter has been designed to sustain heat fluxes of 10 MW/m² in steady state, the most critical points are ICRH heating antennae and LHCD launchers, where hot spots or overheating of large areas can be observed during high-injected power plasma discharges. The analysis of the heating processes identified the role of private power, cross interactions between antennas and launchers and formation of loose deposits. Using the thermography diagnostics, a new feedback control has been implemented to prevent PFCs overheating. Before a shot, sensitive areas and associated temperature threshold are selected on the PFCs and physical interaction process is associated to each area (private power or cross interaction with other RF heating systems). During the shot, the central plasma controller unit decides whether the power has to be reduced and which RF heating system the reduction is applied on. RF power reduction is thus limited to the minimum necessary to preserve PFCs integrity. Thermography feedback control has been successfully used to detect and extinguish electric arcs on LHCD launchers too. The infrared feedback control of PFCs temperature is a protection system, in the sense that it limits efficiently the PFCs temperature and a suitable tool for optimizing the RF plasma heating keeping the PFCs temperatures within their operational limits. (author)