J.J. Cordier

Preliminary results and lessons learned from upgrading the Tore Supra actively cooled plasma facing components (CIEL project)

Abstract The design and fabrication of large areas of actively cooled plasma facing components (PFCs) is a major issue for the next generation of tokamaks. Tore Supra is currently the only large fusion device which has implemented actively cooled PFCs from the beginning of operation in 1988, while maintaining continuous development activities to improve their performances and reliability. High heat flux PFCs based on copper alloy heat sink structures have been developed in order to enable a large increase of power extraction capacity. The result is an actively cooled high heat flux ‘finger’ element (capable of removing up to 10 MW/m2 in normal steady state operation). It has been used first for the RF antennas edge limiters (200 fingers) and then for the toroidal pump limiter (TPL), which is the main part of the Tore Supra upgrade of in-vessel components (CIEL project). The active part of the TPL structure is made of ≈600 actively cooled elements. Problems appeared during series manufacturing of such a large number of high heat flux elements that finally led to the development of a tile attachment repair process in order to allow the achievement of the manufacturing. The whole limiter was installed inside the Tore Supra inner vessel at the beginning of 2002. Very promising first results have been recently obtained (600 MJ of injected and removed power during 3 min 30 s discharge). Monitoring and technical lessons for future realisations from these more-than-10-year developments, in particular for ITER, are discussed.

New advanced launcher for lower hybrid current drive on Tore Supra

Abstract A new actively cooled advanced launcher is being built for Tore Supra LHCD to inject 4 MW during 1000 s at 3.7 GHz, at a power density of 25 MW/m 2 (a conservative value observed in Tore Supra experiments). It is made from an array of 6×48 active and 6×9 passive waveguides. The design uses technologies which are relevant for a next step machine such that it can: (i) withstand a plasma radiated flux of 0.15 MW/m 2 ; (ii) radiate power with spectra having peak N// values of 2.02±0.35; (iii) withstand a total torque of 8.6 10 4 N m during disruptions; (iv) allow an antenna 20 cm radial stroke adjustable in real time, (v) withstand a convected power flux of 10 MW/m 2 on its guard limiter made of CFC tiles. A prototype of each new component of this antenna has been tested successfully at the nominal power with a pulse length of 1000 s.

In-service experience feedback of the Tore Supra actively cooled inner first wall

Abstract Over 12 000 plasma shots (some of them with up to 8 MW of additional power and some as long as 60 s) have been achieved in Tore Supra, with a significant number of them limited by the inner first wall. This actively water-cooled wall is covered with brazed graphite tiles. High power, high energy experiments have shown that reliability of the graphite tile-heat sink joint and accurate alignment of the wall are needed. This paper summarizes the experience gained with this component, and the developments in progress to improve the performance of such an inner first wall.

Quality control of plasma facing components for Tore Supra

Abstract The high technology components used in fusion devices, especially high heat flux (HHF) plasma facing components, require high reliability. This can be only guaranteed by a very high level of quality control (QC) through rigorous acceptance inspection procedure. Qualification of the power exhaust capabilities of HHF components in normal operation requires control of their thermal and mechanical integrity. During the last 4 years, the Tore Supra QC team improved acceptance inspection procedures for HHF components, which have been 100% controlled before their installation in the Tokamak. Innovative investigations of non-destructive techniques, such as pressure drop test, helium leak testing procedure, infrared thermography, were performed and it was shown that these techniques are essential tools for QC of critical parts.

Effects of supra-thermal particle impacts on Tore Supra plasma facing components

Abstract Actively cooled plasma facing components (PFCs) for Tore Supra (TS) have been designed basically for heat exhaust of ‘normal’ (convected and radiated) plasma power. However, in some cases, fast particles have been observed, which locally increased the power flux density, leading to damage of these PFCs and other inner vessel components. Three different examples for irreversible component damage, such as component melting and water leaks, are described involving runaway and supra-thermal particle strikes. In view of the capability for TS to handle larger input powers and to control the particles over long pulse durations, inner vessel components have been completely redesigned. The improved design concepts retained for the CIEL upgrade and preliminary results in the new configuration are presented.

Ten years of maintenance on Tore Supra actively cooled components

Abstract Tore Supra, the only superconducting Tokamak equipped of actively water cooled plasma facing components, has now completed 10 years of operation (1988–1998). The associated primary pressurised water cooling loop (4 MPa at 150°C) is able to exhaust a 20 MW convected or radiated power during long pulses of 200 s. The first part of this paper is devoted to an inventory and analysis of the water leaks from the plasma facing and their consequences, such as the optimisation of the pressurised water loop emptying sequence. The experience gained during 10 years by maintenance operations has also led to an improvement of the water leak detection procedure, in order to identify as accurately as possible the location of the leak. The second part of the paper describes the improvements made on quality control of Plasma Facing Components during these last 10 years. Quality Control has been increased right through the technological developments and the manufacturing process of mock-up, prototypes and series production. A specific helium tightness procedure dedicated to water cooled components has been established, consists mainly of several validation tests under pressure and temperature operating conditions. Hence reliability of the components has been largely increased.

Design of the infrared monitoring system for CIEL project

The safety in long pulse operation is one of the main issues to guarantee the integrity of all materials. This is particularly true for the new Tore Supras toroidal pump limiter (TPL) built in the frame of CIEL project, and Tore Supras antennas, designed to operate in quasi-CW (up to 1000 s). A system made of infrared endoscopes equipped with infrared cameras will be devoted to such a task. Besides the safety task, it also allows the study of the physics of the power deposition on the TPL and on the antennas, as well as feedback control. This paper gives an overview of the design of the Infrared Monitoring System, the main technological choices and the thermal and mechanical calculations are presented.

High heat flux testing impact on the Tore Supra toroidal pumped limiter achievement

The toroidal pumped limiter of Tore Supra is made of 576 elementary high heat flux (HHF) cooled plasma-facing components (PFCs) and designed to sustain 10 MW/m/sup 2/ in steady state. One of the main technical difficulties is to ensure a high quality of the bond between the carbon fiber composite armor tile and the water-cooled heat sink due to the high thermal stresses that develop at the bond during operation. Consequently, a HHF facility able to reproduce in service operation of PFCs is required all along the development and manufacturing route. In Europe, the FE200 facility (electron beam, 200 kW, France) operating since 1991, was extensively used for such a development. A first testing campaign in 1995 was devoted to the qualification of this bond: AMC/spl reg/ technology from Plansee GmbH was selected. Afterwards, a second campaign on scale-one elements (1996) allowed an optimization of the element design and series production to be launched. During the mass production, a non-destructive control process - cheaper and faster than HHF testing - based on infrared characterization was routinely operated on 100% of the manufactured elements. Strong variability of the bond quality was observed and a repair process allowing the replacement of deficient tiles was developed. In 2000 and 2001, 2 campaigns of HHF testing were launched to correlate the non-destructive measurements and to optimize and validate the repair process. This was done, in two steps, with success. This yielded moreover interesting information for qualifying both tests across each other and also to analyze the fatigue evolution of the bond. The qualification and the achievement of the Tore Supra limiter has greatly been made possible by such HHF tests, which appears as essential before and during PFC manufacturing.

Design and manufacture of the Toroidal Pump Limiter-start up version for the CIEL project

After a one year shutdown devoted to the installation of Tore Supra new components (CIEL project) and the associated diagnostics, the first experimental campaign is mainly dedicated to the qualification of these high heat flux components and the general commissioning of the machine. Because of the delay of delivery of the high flux components (so-called fingers) and in order to enable the qualification of CIEL main components, a start version of the Tore Supra/CIEL Toroidal Pump Limiter (TPL) has been designed and manufactured.

Design integration of SINGAP accelerator and RF source in the ITER NB injector

The paper deals with the design integration of two alternative solutions for the negative ion source and accelerator of the ITER neutral beam (NB) injectors. The first alternative concerns the new 1 MV accelerator, named SINGAP, which has a single acceleration step instead of the five steps of the reference design. The second modification introduces a radio frequency (RF) negative ion source replacing the traditional filament solution. Design criteria, solutions and critical issues are presented in the paper