High heat flux testing is a vital part of engineering component validation for fusion technology. The Heat by Induction to Verify Extremes (HIVE) facility is designed to provide a practical avenue for this aspect of cornponent testing. It provides fast turnaround for smaller concepts and a cost-effective approach by utilising induction heating within a small vacuum vessel. Due to the potential complexity of induced current paths in an induction heating system, the extent and homogeneity of power coupled to a component is difficult to model. This uncertainty increases where components have geometrical features such as the grid pattern castellations that are often present on plasma facing components in fusion reactors. This project investigates the influence of various castellation patterns on the coupling characteristics of HIVE. It shows for example that as the grid density of castellations is increased, the applied heat flux increases from 4.5 MW/m2 to 6.93 MW/m2 for an input power of 30kW over 2 s, due to an improvement in the efficiency of the inductive coupling from 13.4% to 20.8%. Additional experimental factors affecting efficiency and homogeneity of heating are also discussed.

It is clear that fusion demonstration devices offer unique challenges due to the myriad, interacting material degradation effects and the numerous, conflicting requirements that must be addressed in order for in-vessel components to deliver satisfactory performance over the required lifetime. The link between mechanical engineering and materials science is pivotal to assure the timely realisation and exploitation of successful fusion power. A key aspect of this link is the verification of structural integrity, achieved at the design stage via structural design criteria against which designs are judged to be sufficiently resilient (or not) to failure, for a given set of loading conditions and desired lifetime. As various demonstration power plant designs progress through their current conceptual design phases, this paper seeks to highlight key shortfalls in this vital link between engineering needs and materials science, offering a perspective on where future attention can be prioritised to maximise impact.Firstly, issues in applying existing structural design criteria to demonstration power plant designs are identified. Whilst fusion offers particular challenges, there are significant insights to be gained from attempts to address such issues for high performance, high integrity applications in other demanding environments. Therefore case studies from beyond fusion are discussed. These offer examples where similar shortfalls have been successfully addressed, via approaches at the design stage and through service lifetime in order to deliver significant insight for structural materials and improved design solutions for first-of-a-kind engineering endeavours where the consequences of failure were of similar concern.Finally, drawing inspiration from these case studies, the current state-of-the-art is explored to propose how both materials science and engineering should be aligned in order to address the issues we face in realizing effective fusion demonstration power plants. (C) 2016 EURATOM/CCFE Fusion Association. Published by Elsevier B.V. All rights reserved.

The paper reports on latest developments for the ITER Ion Cyclotron Heating and Current Drive system: imminent acceptance tests of a prototype power supply at full power; successful factory acceptance of candidate RF amplifier tubes which will be tested on dedicated facilities; further design integration and experimental validation of transmission line components under 6MW hour-long pulses. The antenna Faraday shield thermal design has been validated above requirements by cyclic high heat flux tests. R&D on ceramic brazing is under way for the RF vacuum windows. The antenna port plug RF design is stable but major evolution of the mechanical design is in preparation to achieve compliance with the load specification, warrant manufacturability and incorporate late interface change requests. The antenna power coupling capability predictions have been strengthened by showing that, if the plasma scrape-off layer turns out to be steep and the edge density low, the reference burning plasma can realistically be displaced to improve the coupling.

In the framework of the Ion Cyclotron (IC) antenna design, ITER Organization requested qualification tests on sliding Radio-Frequency (RF) contacts, to verify that these contacts (quality class 1) are designed appropriately to guarantee a sufficient operational life time. These RF contacts will be integrated into the antenna structure at different locations to facilitate the assembly and decouple the different mechanical parts. This design will in addition lower the thermo-mechanical constraints and allow radial shimming of the antenna front face. As commercial contacts were not suitable for the ITER ICRH antenna operation, substantial efforts have been made on mechanical design of the new RF contact. Two prototypes have been manufactured and delivered to CEA for testing. In parallel a test stand facility (TITAN) has been refurbished to provide a way to test these RF contacts in relevant conditions (2.25kA @ 62.5MHz, vacuum pressure <10−3Pa, 1000s). This paper reports on main results we get during the com...

ITER's Ion Cyclotron Range of Frequencies (ICRF) system [1] comprises two antenna launchers designed by CYCLE (a consortium of European associations listed in the author affiliations above) on behalf F4E for the ITER Organisation (IO), each inserted as a Port Plug (PP) into one of ITER's Vacuum Vessel (VV) ports. Each launcher is an array of 4 toroidal by 6 poloidal RF current straps specified to couple up to 20 MW in total to the plasma in the frequency range of 40 to 55 MHz but limited to a maximum system voltage of 45 kV and limits on RF electric fields depending on their location and direction with respect to respectively the torus vacuum and the toroidal magnetic field. A crucial aspect of coupling ICRF power to plasmas is the knowledge of the plasma density profiles in the Scrape-Off Layer (SOL) and the location of the RF current straps with respect to the SOL. The launcher layout and details were optimized and its performance estimated for a worst case SOL provided by the IO. The paper summarizes the estimated performance obtained within the operational parameter space specified by IO. Aspects of the RF grounding of the whole antenna PP to the VV port and the effect of the voids between the PP and the Blanket Shielding Modules (BSM) surrounding the antenna front are discussed.

ITER's Ion Cyclotron Range of Frequencies (ICRF) system [Lamalle et al., Fusion Eng. Des. 88, 517–520 (2013)] comprises two antenna launchers designed by CYCLE (a consortium of European associations listed in the author affiliations above) on behalf of ITER Organisation (IO), each inserted as a Port Plug (PP) into one of ITER's Vacuum Vessel (VV) ports. Each launcher is an array of 4 toroidal by 6 poloidal RF current straps specified to couple up to 20 MW in total to the plasma in the frequency range of 40 to 55 MHz but limited to a maximum system voltage of 45 kV and limits on RF electric fields depending on their location and direction with respect to, respectively, the torus vacuum and the toroidal magnetic field. A crucial aspect of coupling ICRF power to plasmas is the knowledge of the plasma density profiles in the Scrape-Off Layer (SOL) and the location of the RF current straps with respect to the SOL. The launcher layout and details were optimized and its performance estimated for a worst case SOL provided by the IO. The paper summarizes the estimated performance obtained within the operational parameter space specified by IO. Aspects of the RF grounding of the whole antenna PP to the VV port and the effect of the voids between the PP and the Blanket Shielding Modules (BSM) surrounding the antenna front are discussed. These blanket modules, whose dimensions are of the order of the ICRF wavelengths, together with the clearance gaps between them will constitute a corrugated structure which will interact with the electromagnetic waves launched by ICRF antennas. The conditions in which the grooves constituted by the clearance gaps between the blanket modules can become resonant are studied. Simple analytical models and numerical simulations show that mushroom type structures (with larger gaps at the back than at the front) can bring down the resonance frequencies, which could lead to large voltages in the gaps between the blanket modules and perturb the RF properties of the antenna if they are in the ICRF operating range. The effect on the wave propagation along the wall structure, which is acting as a spatially periodic (toroidally and poloidally) corrugated structure, and hence constitutes a slow wave structure modifying the wall boundary condition, is examined.

The ongoing design of the ITER Ion Cyclotron Heating and Current Drive system (20 MW, 40-55 MHz) is rendered challenging by the wide spectrum of requirements and interface constraints to which it is subject, several of which are conflicting and/or still in a high state of flux. These requirements include operation over a broad range of plasma scenarios and magnetic fields (which prompts usage of wide-band phased antenna arrays), high radio-frequency (RF) power density at the first wall (and associated operation close to voltage and current limits), resilience to ELM-induced load variations, intense thermal and mechanical loads, long pulse operation, high system availability, efficient nuclear shielding, high density of antenna services, remote-handling ability, tight installation tolerances, and nuclear safety function as tritium confinement barrier. R&D activities are ongoing or in preparation to validate critical antenna components (plasma-facing Faraday screen, RF sliding contacts, RF vacuum windows), as well as to qualify the RF power sources and the transmission and matching components. Intensive numerical modeling and experimental studies on antenna mock-ups have been conducted to validate and optimize the RF design. The paper highlights progress and outstanding issues for the various system components. (C) 2013 ITER Organization. Published by Elsevier B.V. All rights reserved.

This paper deals with a first analysis of the Remote Handling (RH) maintenance procedure for the replacement of Removable Vacuum Transmission Lines (RVTL) of the ICRH antenna Port Plug (PP). In the framework of the grant F4E-2009-GRT-026, CEA IRFM studied the maintenance in parallel with the design of the antenna provided by CCFE.The RVTL are 8 components of the ICRH antenna which form the interface between the matching system and the four port junction integrating the straps. A folded stub is attached to the principal line to ensure water cooling of the interspace. At the front and the rear of the RVTL are installed double RF windows that provide the first tritium barrier. In case of failure of the first window, all the RVTL have to be replaced. Due to the contamination and activation, the replacement must take place in the hot cell. The complete maintenance sequence is studied. It starts when the PP is in place in the Tokamak equatorial port, it continues with: the preparation in the port cell, transfer to the HC, cleaning, RVTL replacement, returns to the port cell. It finishes with reconnection to the port.The ITER requirements [1] and the hot cell constraints [2] are used to extract specifications for the RH tooling (for handling, cutting, welding, etc.). Each step is studied and suitable tools identified. For specific steps, mechanical concepts for dedicated tools are proposed.Furthermore, the critical steps identified are simulated to check the feasibility. (C) 2013 Elsevier B.V. All rights reserved.

After the installation and commissioning of the TITAN [1] , [2] , test facility, a key element – the T resonator – was assembled in order to facilitate testing components at high RF voltages and currents. This work is within the CEA roadmap for testing ITER ICRH components in a relevant environment. Several components of the future ITER ICRH antenna have been targeted. The embedded RF contact within the ITER ICRH antenna appeared as a critical component for antenna performance, requiring extensive R&D. Therefore, CEA has proposed and subsequently prepared a platform to test and validate the anticipated RF contact. A steady state resonator with active water cooling has been manufactured and assembled within the TITAN facility, including a hot pressurized water loop. The program consists of testing the contact at 2.25 kA and 62 MHz in steady state conditions. Sliding tests are also performed at high temperature and vacuum to understand component aging, including wear. The equipment installed is consistent with that required to test an ITER ICRH extensively.

The ITER Ion Cyclotron Range of Frequencies (ICRF) antenna's capacity to couple power to plasma is determined by the plasma Scrape-Off Layer (SOL) profile, shaping of the front strap array, layout of the Port Plug (PP) and detailed design of its RF components. The first two factors are taken into account by the Torino Polytechnic Ion Cyclotron Antenna (TOPICA) calculated strap array Scattering/Impedance 24-port (S24×24−/Z24×24−) matrices, while this paper deals with the optimisation of the PP layout and components. The RF modeling techniques are explained and used to maximise the coupled power under a set of constraints on RF quantities inside the PP. The total PP RF surface conductive and volumetric dielectric losses are calculated. The resulting S-parameters at the rear RF PP flanges are evaluated as input for the design of the pre-match, decoupling and matching network outside the PP. A discussion of the effect of errors on the PP excitation on the coupled power is also included.

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].