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A magnetically driven fast-ion loss detector (FILD) is being designed for ITER. Due to the high heat load expected, fast movements and several measurement cycles will be required during its operation. The measurement cycle characteristics (measuring and parking periods, as well as the probe insertion and retraction times) will be defined as a compromise between the thermal load acting on the probe head and the measuring requirements. In this article, dynamic simulations of the detector movement are presented and the thermal behavior of the probe head is analyzed during its operation within a complete plasma discharge. [ABSTRACT FROM AUTHOR]

A new scintillator based fast-ion loss detector (FILD) system has been designed for the Wendelstein 7-X (W7-X) stellarator. The mechanical design of the system is presented here along with engineering analyses of the system. This includes an assessment of the structural loads which also considers electromagnetic forces calculated for possible disruption scenarios as well as a mode frequency analysis of the system. Furthermore, an analysis of the thermal characteristics of the actively cooled probe head under prescribed steady state and transient heat loads is presented. Finally, the optical relay system is described and its properties used to forward model synthetic camera signals using the FILDSIM code and based on theoretical fast-ion losses incident on the probe head calculated using the ASCOT5 code. [ABSTRACT FROM AUTHOR]

Fast-α losses in future fusion power plants are expected to follow the co- and counter-current directions due to the isotropy of the fusion reaction. At the ASDEX Upgrade tokamak, the co-current direction (achieved with positive plasma current and negative toroidal magnetic field) has been extensively studied thanks to an array of five fast-ion loss detectors (FILD). A new fast-ion loss detector compatible with reversed I p /B t (negative plasma current and positive magnetic toroidal field, defining positive as counter-clockwise when the machine is viewed from the top), namely RFILD, has been designed and commissioned to study the behaviour of counter-current fast-ion losses and to expand our knowledge on QH-mode, I-mode, and the L-H transition. The detector is a modified version of the midplane manipulator fast-ion loss detector that features a new probe head orientation and collimator geometry, optimised using the FILDSIM code. A fast CMOS camera is used as a high spatial resolution acquisition system, while an array of photomultipliers (up to 1 MHz) serves as a fast channel. First measurements have been taken in I-mode, QH-mode, L-mode and H-mode with core densities ranging between 4·1019 and 9·1019 m−3, I P between -0.8 and -0.6 MA and B t of 2.5 T approximately. NBI fast-ion losses were observed for the first time in reversed I p /B t , producing high pitch (60 – 80°) losses. ICRH losses in H-minority heating configuration have also been observed in I-mode experiments. These losses correspond to the outer leg of banana particle trajectories. An upgraded double collimator detector design is also presented, that will increase the measurable particle range in future experimental campaigns (co- and counter-current particles simultaneously). Thus, we expand our understanding on the mechanisms behind fast-ion losses at the ASDEX Upgrade tokamak in the reversed I p /B t configuration. [ABSTRACT FROM AUTHOR]

The proton micro-beam of the CNA accelerator in Seville has been used to test two detectors based on single crystal diamond grown by chemical vapor deposition. The first diamond has a more traditional design, with dimensions 4.5 × 4.5 × 0.5 mm 3 , and features a large contact of the same size as the crystal. The second, with dimensions 2.0 × 2.0 × 0.3 mm 3 , features a small contact of 0.5 × 0.5 mm 2 . By using the micro-beam, the map of the charge collection efficiency for both the detectors have been measured. We show that the charge collection efficiency of the diamond with large contacts is generally uniform, while the diamond with smaller contacts needs further developments in this respect. A proof of principle test with a fast electronic chain has been performed to demonstrate that spatially resolved pulse shape analysis can be performed with this system. The micro-beam allowed also studying radiation-induced permanent damage and polarization, which are two irradiation effects of importance for the development of diamonds used in spectroscopy applications. [ABSTRACT FROM AUTHOR]

• Design proposal for the coils and power supplies for the SMART tokamak. • Dimensioning of coils by analytical thermal model in transitory scenarios. • Modular power supplies by the parallelization of H-bridges and supercapacitors banks. • Design of auxiliary circuit for central solenoid power supply for plasma breakdown. • Preliminary analysis of power supplies with MATLAB Simulink to prove feasibility. A new spherical tokamak, the SMall Aspect Ratio Tokamak (SMART), is currently being designed at the University of Seville. The goal of the machine is to achieve a toroidal field of 1 T, a plasma current of 500 kA and a pulse length of 500 ms for a plasma with a major radius of 0.4 m and minor radius of 0.25 m. This contribution presents the design of the coils and power supplies of the machine. The design foresees a central solenoid, 12 toroidal field coils and 8 poloidal field coils. Taking the current waveforms for these set of coils as starting point, each of them has been designed to withstand the Joule heating during the tokamak operation time. An analytical thermal model is employed to obtain the cross sections of each coil and, finally, their dimensions and parameters. The design of flexible and modular power supplies, based on IGBTs and supercapacitors, is presented. The topologies and control strategy of the power supplies are explained, together with a model in MATLAB Simulink to simulate the power supplies performance, proving their feasibility before the construction of the system. [ABSTRACT FROM AUTHOR]

The imaging heavy ion beam probe (i-HIBP) is a new diagnostic concept realized at the tokamak ASDEX Upgrade (AUG) in order to obtain two-dimensional information about the density, the magnetic field and the electrostatic potential at the plasma edge. Although the two main components of the i-HIBP, an alkali beam based injector and a scintillator based detector, involve well-developed technologies, further developments were necessary to realize the i-HIBP at AUG. In dedicated laboratory tests, a new type of cesium source was characterized and the neutralization efficiency and properties of the primary cesium beam were found to be similar to alkali beams made of lighter elements. The use of cesium had also impact on the choice of the scintillator material, which was experimentally investigated in terms of photon yield, energy dependence and degradation revealing significant differences under irradiation with cesium ions compared to irradiation with hydrogenic beams. Due to constrictions of the AUG experiment setup, the high voltage components, the in-vessel shutter technology and the maintenance capabilities of the i-HIBP required new developments for the commissioning of the diagnostic. [ABSTRACT FROM AUTHOR]

• Preliminary design of the JT-60SA FILD detector is described. • JT-60SA FILD motion is presented. • JT-60SA FILD thermal behaviour is presented. • JT-60SA FILD mechanical response during disruptions is presented. A fast-ion loss detector (FILD) is being designed for the JT-60SA tokamak. In this work, the preliminary mechanical design of this diagnostic is described. The expected motion needed to move the probe head between the parking and the measuring positions has been estimated by numerical simulations. A finite element thermal assessment of the detector is presented, to characterize its thermal response during the operation of the machine. Finally, the results of a preliminary electromagnetic analysis are reported to evaluate the impact of major disruptions on the structural components the system. [ABSTRACT FROM AUTHOR]

Abstract: This paper focuses on a study of the principal operation aspects of standard ICRF heating antennas in the ion cyclotron wall conditioning (ICWC) mode: (i) ability of the antenna to ignite the cleaning discharge safely and reliably in different gases including those most likely to be used in ITER – He, H2, D2 and their mixtures, (ii) the antenna capacity to couple a large fraction of the RF generator power (>50%) to low density (∼1016–1018 m−3) plasmas and (iii) the RF power absorption schemes aimed at improved RF plasma homogeneity and enhanced conditioning effect. The ICWC discharge optimization in terms of RF plasma wave excitation/absorption resulted in successful simulation of the conditioning scenarios for ITER operation at full field (JET) and half-field (TEXTOR, TORE SUPRA, ASDEX Upgrade). [Copyright &y& Elsevier]