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The calibrations and verifications that are performed in preparation of the ITER-Like antenna (ILA) reinstatement at JET are reviewed. A brief reminder of the ILA system layout is given. The different calibration methods and results are then discussed. They encompass the calibrations of the directional couplers present in the system, the determination of the relation between the capacitor position readings and the capacitance value, the voltage probes calibration inside the antenna housing, the RF cables characterization and the acquisition electronics circuit calibration. Earlier experience with the ILA has shown that accurate calibrations are essential for the control of the full ILA closepacked antenna array, its protection through the S-Matrix Arc Detection and the new second stage matching algorithm to be implemented. Finally the voltage stand-off of the capacitors is checked and the phase range achievable with the system is verified. The system layout is modified as to allow dipole operation over the whole operating frequency range when operating with the 3dB combiner-splitters. [ABSTRACT FROM AUTHOR]

The technology implications of potential FWCD systems have been assessed at two frequencies of relevance to DEMO as part of a wider study of heating and current drive systems for the EFDA Power Plant Physics and Technology (PPP&T), based upon two reference DEMO designs. Using the results of Van Eester et al [1], systems studies carried out for a 62MHz mid-harmonic system mounted on a 23MA 5.74T 8.5m major radius DEMO suggested that antenna voltages close to 50kV, and the handling of the resultant sheath power loadings, are likely to be required if all of the 12.9MA non-bootstrap current drive is to be provided by FWCD. The "wall plug" electrical efficiency of the midharmonic option of 0.18A/W.m², potentially rising to 0.23A/W.m² with the future development of solid state generators, however, looks very attractive, and the coupling is less sensitive to plasma edge parameters than for existing antennas, due to the low k// of 2.8m-1. The design could be based upon that presently under consideration for ITER, except for the replacement of insulating vacuum windows located relatively close to the plasma with all-metal designs [2]. A 352MHz high-harmonic option also looks technologically feasible, using a waveguide-based design and a port plug layout has been provided. This option might bring sheath effect and voltage hold-off benefits, but this is far from proven. In this case, systems studies were not feasible due to a lack of firm results from the physics studies. For both options: (a) the RF generators, power supplies and transmission line components required are either already available, or are under development for ITER, and (b) mechanical and material issues associated with the proposed FWCD antenna structures appear challenging, but will need solving on a wider basis across DEMO. [ABSTRACT FROM AUTHOR]

RF arc detection is a key operational and safety issue for the ICRF system on ITER. Indeed the high voltages inside the antenna put it at risk of arcing, which could cause substantial damage. This paper describes the various possibilities explored by circuit simulation and the strategy now considered to protect the ITER ICRF antenna from RF arcs. [ABSTRACT FROM AUTHOR]

The CYCLE consortium has been designing the ITER ICRF antenna since March 2010, supported by an F4E grant. Following a brief introduction to the consortium, this paper: describes the present status and layout of the design; highlights the key mechanical engineering features; shows the expected impact of cooling and radiation issues on the design and outlines the need for future R&D to support the design process. A key design requirement is the need for the mechanical design and analysis to be consistent with all requirements following from the RF physics and antenna layout optimisation. As such, this paper complements that of Durodie et al [1]. [ABSTRACT FROM AUTHOR]

The commissioning of the ITER-Like ICRF Antenna (ILA) [1] on JET plasmas from May 2008 to April 2009 in various conditions (33, 42 and 47 MHz, L- and H-mode, antenna strap-plasma separatrix distances of ∼9 to 17 cm) has provided relevant information for future antenna design and operation. The maximum power density achieved was 6.2 MW/m2 in L-mode with strap to plasma separatrix distance of ∼9–10 cm at 42 MHz on the lower half of the ILA extrapolating to 8 MW/m2 if the full generator power had been available. Efficient (trip-free operation) ELM tolerance was obtained both at 33 and 42 MHz on a large range of ELMs with strap voltages up to 42 kV and a maximum power density of 4.1 MW/m2. The paper reviews these achievements as well as remaining issues. [ABSTRACT FROM AUTHOR]

A set of simulation/interpretation tools based on transmission line theory and on the RF model developed by M. Vrancken [2] has been developed to study the ITER-like Antenna (ILA) at JET. For given tuning element settings, the unique solution of the equations governing the ILA circuit requires solving a system of coupled linear equations relating the voltages and currents at the antenna straps and other key locations. This computation allows cross-checking predicted values against measured experimental ones. Further more, a minimization procedure allows improving the correspondence with the quantities measured in the circuit during shots, thus coping with unavoidable errors arising from uncertainties in the measurements or from inaccuracies in the adopted RF model. Typical applications are e.g. fine-tuning of the second-stage of the ILA circuit for increased ELM-resilience, cross-checking the calibration of the measurements throughout the circuit and predicting the antenna performance and matching conditions in new plasma scenarios. [ABSTRACT FROM AUTHOR]

JET ICRH plant faults from 2008 - 2012 have been catalogued and a new assessment of the reliability of the plant by sub-system is given. Data from pulses where ICRH was used, excluding the ITER-Like Antenna (ILA) and its generators, has been collated. This is compared to fault data in order to investigate any correlation between faults and operations. The number of faults is shown to have decreased between 2011-2012 in comparison to 2008-2009 as the time between faults is shown to have increased. Future electronic fault logging requirements to enable easier analysis are discussed. Due to the changing configuration of the ICRH plant; the introduction of ELM tolerant systems, generator upgrade, changes to the settings of the VSWR protection et cetera, a method to expand the fault database to include more historical data [1] in a consistent way are discussed. [ABSTRACT FROM AUTHOR]