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The Tore Supra lower hybrid (LH) control system has been in operation for 10 years. Although its control system has given excellent service, it is an ageing system, and incompatible with many modern components and techniques. Hence, in order to improve the LH system's reliability, efficiency, compatibility and visibility, a new design of its control system was undertaken. A solution based on modern programmable logic controller coupled with a fast logic hardware ‘state machine’ has been selected as a replacement. This can handle the ‘state diagram’ and associated safety interlock functions for each klystron with the required time response. This paper presents the association of this state machine for fast control with the PLC for slow control, a PC based human interface, and all the control and process diagnostic functions which complete this Tore Supra LH control and security system.

A new LHCD launcher, designed to inject 4 MW during 1000 s, has been installed on Tore Supra and successfully tested. A power of 3 MW with 7% power reflection coefficient has been reached. The coupling has been studied for various plasma parameters and positions, in order to study the robustness of the mode converter used in the antenna to divide the power into three in the poloidal direction. Due to the reduced electric field and the very efficiently water-cooled guard limiter, the temperature increase induced by the acceleration of electrons in the near field has been drastically reduced.

The suprathermal electron cyclotron radiation is used to investigate fundamental phenomena governing electron tail formation during lower hybrid current drive (LHCD). To this end, an approximate analytical solution of the 2-D time-dependent Fokker-Planck equation is developed. Electron cyclotron emission (ECE) is analysed with this model. The pitch-angle scattering time, the characteristic time of the quasi-linear diffusion process, the perpendicular temperature and the quasi-linear diffusion coefficient are measured by fitting the temporal evolution of the ECE si,signal. (C) 2001 Elsevier Science B.V. All rights reserved.

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.

Strong toroidal asymmetries in power deposition during lower hybrid current drive experiments have been observed on TdeV and Tore Supra. These asymmetries are characterized by high heat loads on components magnetically connected to the LHCD antenna. The experimental results indicate that fast electrons generated by the rf fields in the scrape-off layer in front of the antenna are responsible for the localized heat loads. The rf power lost in the edge though this channel increases with both the edge density and the rf power level. In TdeV, the fraction of the injected power lost can exceed 10% at high power and high density, while it stays under 2% in Tore Supra. A simple model describing the trajectories of electrons in front of the antenna suggests that the high N| components of the near field spectrum are responsible for the acceleration of the scrape-off layer electrons.

The JET neutral beam injection system has proved to be both effective and reliable as a plasma heating device. The ion heating and plasma fuelling characteristics of the system are ideally suited to the production of high fusion performance plasmas while the flexibility in the choice of beam species (H, D, T, 3 He or 4 He) and the ability to inject into almost any JET plasma configuration allows a wide variety of related physics experiments to be carried out. The capability to inject (for the first time) tritium beams was essential to the successful execution of the first tritium experiments in which 1.7 MW of power from DT fusion reactions was generated.