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New real time tools have been developed for testing new 700kW/3.7GHz/CW klystrons and for the operations on very long plasma shots. After the commissioning of the 18 series tubes on the high power test bed facility, the installation of the first 8 klystrons in the Tore Supra transmitter and the adjustment tests on load, this upgrade work has been materialized during the last 2010 campaign by a successful operation on the Full Active Multijunction (FAM) C3 antenna, with new performances: 3.5MW/40s on plasma. The RF output power control in amplitude and phase has been improved for a better control of the wave spectrum launched into the plasma. The new klystrons have no modulating anode and the high cathode voltage must be adjusted with the RF input power in order to optimize the RF output power with a minimization of the thermal power losses in the collector. A new phase correction, depending on the 3 RF output power ranges used, has been introduced. The improvements made in 2009 and 2010 on the generic phase loop and the procedures used during the real time tests of the RF transfer functions in amplitude and phase are detailed below. All RF measurements systems, RF safety systems and the RF calibration procedures have been revised in order to have the best consistency, reproducibility and with a measurement error against the calorimetry measurement lower than 10%. [ABSTRACT FROM AUTHOR]

When testing the SHAD system on JET ICRF antennas, parasitic signals in the detection band (5-20MHz) were detected. We have identified emission from grid breakdown events in the Neutral Beam injectors, and Ion Cyclotron Emission from the plasma. Spurious signals in the band 4-10 MHz are also often observed at the onset of ELM events. Such parasitic signals could complicate the design and operation of SHAD in ICRF systems for fusion devices. [ABSTRACT FROM AUTHOR]

The aim of the Tore Supra tokamak is to address physics and technology issues of long pulse discharges. For this purpose, Tore Supra is equipped with two actively cooled Lower Hybrid Current Drive (LHCD) antennas (f = 3.7GHz), designed to operate in 1000s long pulses. One of these is the recently installed passive active multijunction (PAM) antenna, whose design is chosen for an LHCD system for ITER. The first experiments with the PAM antenna in Tore Supra have shown extremely encouraging results in terms of reflection coefficient behaviour and power handling. The maximum power and energy reached on the PAM, after ~500 pulses on plasma, was 2.7MW during 78s (exceeding 200MJ injected energy). In addition, 2.7MW has been coupled at a plasma-antenna distance of 10cm. The coupling behaviour on the PAM, characterised by the fraction of reflected power (RC), shows good agreement with the predictions from the ALOHA coupling code. Full non-inductive discharges lasting 50s have been sustained with the PAM alone, exhibiting a current drive efficiency comparable to that of the full active multijunction antennas in Tore Supra, in similar experimental conditions. [ABSTRACT FROM AUTHOR]

A Sub-Harmonic Arc Detection (SHAD) system has been installed on the transmission lines feeding the JET ICRF ITER-like-Antenna (ILA). Along with the commissioning of SHAD, extensive measurements of the RF field in the transmission lines were carried-out using fast sampling (125 Mb/s) oscilloscopes. The system is described, and the SHAD ability to detect arcs during ILA operation (in particular on ELMy H modes) is discussed. Overall, SHAD proved to be efficient, and in some conditions it can offer extra protection in complement to other arc detection systems. [ABSTRACT FROM AUTHOR]

A prototype of an ICRF antenna based on the load-resilient electrical layout foreseen for ITER has been built at CEA-Cadarache [1]. It consists of a two resonant double loop (RDL) based on the conjugate-T concept proposed for the ITER ICRF array arranged toroidally in a close package. The antenna conditioning and commissioning have been successfully performed to validate the load resilience and the heating capability at the end of 2007. On Tore Supra despite unexciting ELMs, the load resilience studies have been conducted in L-mode by mean of slow variations of the plasma position and fast transient variations with both pellet injection and Supersonic Molecular Beam Injection (SMBI). The capability to maintain the RF power on the ITER-like antenna has been done successfully contrary to the classical ICRF antenna during the SMBI shots, in which the corresponding transient coupling resistance increased by a factor 3–4. In term of coupled power, a maximum power density of 6.6 MW/m2 is reached. [ABSTRACT FROM AUTHOR]

The arc detection systems based on harmonics detection have been tested n USA (TFTR, DIII, Alcator C-mod) and Germany (Asdex). These systems have some advantages in comparison with traditonal securities which use a threshold on the Vr/Vf (Reflected to Forward voltage ratio) calculation and are ITER relevant. On Tore Supra (TS) 3 systems have been built using this principle with some improvements and new features to increase the protection of the 3 ICRH generators and antennae. On JET 2 arc safety systems based on the TS principle wil also be used to mprove the JET ITER-like antenna safety. In order to have the maximum security level on the TS ICRH system, the 3 antennae are used with these systems during all plasma shots n redundancy with the other systems. This TS RF principle and ts electronic interactions with the VME control of the generator are described. The results on the TS ICRH transmitter feeding the 3 antennae are summarized and some typical signals are given. [ABSTRACT FROM AUTHOR]

The recent experiments in Tore Supra has focused on the optimisation of the RF heating systems (ICRH and LHCD) in order to achieve high power levels simultaneously over long durations. This leads to njected power levels n the range of 10 MW, which is representative of ITER operation in terms of average power density and heat exhaust capability. Successful operation has been achieved up to 9–10 MW for 20–30 s, using real-time control of the antenna front face temperatures from nfrared measurements, and security on Cu and Fe brightness. The wave coupling was optimised for the two RF systems simultaneously, while at the same time minimising the hot spot formation due to RF sheath effects and interaction by fast particles (fast electrons accelerated n the near field of the LH wave and fast ions with large orbits created by ICRH). Local modification of the scrape-off layer density around an ICRH antenna impacts on magnetcally connected LHCD antennas. The LH coupling either improves or deteriorates locally, depending on the relative radial and poloidal positon of the LHCD waveguides and the ICRH antenna. The surface temperature related to the acceleration of electrons n the near-field of the LH wave evolves accordingly, i.e. it either increases or decreases as a response to the increase or decrease in scrape-off layer density. [ABSTRACT FROM AUTHOR]

On Tore Supra, the Lower Hybrid Current Drive (LHCD) 3.7 GHz system is being upgraded in the frame of the CIMES project. The paper describes the status of the development and manufacturing of the two main components of the project: the new klystron TH2103C and the PAM antenna. [ABSTRACT FROM AUTHOR]

In the framework of the ICRH development led at CEA Cadarache, a project of a prototype antenna based on the electrical layout foreseen for the ITER IC launcher has been initiated. First experiments have been performed on Tore Supra in 2004. Pulses of 500 kW lasting up to 6s have been achieved. The importance of the coupling effect between straps has been revealed during these experiments, and thus the need for an active control system of the current phasing between them. Despite the short experimental campaign terminated by the failure of the matching components due to undetected arcs, the load tolerant properties of such a circuit have been observed. Since, the prototype antenna has been repaired, reassembled and enhanced accordingly to the fruitful lessons harvested. The RF circuit was improved, corona rings were added on the capacitor poles and localized “sharp” edges were rounded to increase the voltage standoff capability. To reduce the toroidal coupling between adjacent straps, a thick poloidal septum was added on the Faraday screen, thus easing the tuning of the launcher. Another major improvement was the development and the integration of current probes on each of the four straps. This paper reports on: the launcher mechanical enhancements, the recent results obtained in 2007 and the experimental program planned on Tore Supra. [ABSTRACT FROM AUTHOR]