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The reflectometry diagnostic for demonstration fusion reactor (DEMO) is envisaged to provide the electron density profile and to be used as a control diagnostic for the real-time vertical position controller. An initial conceptual study has been performed defining the position of the antennas and the routing of the waveguides. In the present design, the integration has been driven by the remote handling and blanket interfaces. To progress with the system integration, neutronics simulations were performed to assess the cooling requirements. This paper presents a nuclear and thermal analysis for the initial design of the reflectometry diagnostic for DEMO. The neutronics simulations were performed using the Monte Carlo simulation program MCNP6 and FENDL 2.1 cross sections, while ANSYS mechanical v18 was used to perform the thermal analysis. Simulation results show that the nuclear heat loads reach 8 W/cm3 at the surface of the diagnostics section. Without an active cooling system, the operating temperatures of the components under such heat loads would be well above the acceptable from the thermomechanical point of view. The thermal analysis here presented provides the temperature distribution in the components when subjected to neutron/gamma irradiation and thermal radiation from the plasma, after the implementation of a preliminary design of the active cooling system. The operation temperatures of the plasma-facing antennas, as well as the performance of the diagnostics system from the neutron shielding point of view, are analyzed and discussed in this paper. [ABSTRACT FROM AUTHOR]

Forschungszentrum Jülich and partners are developing the ITER core charge exchange spectroscopy (cCXRS) hosted by upper port plug#3 (UPP). The system should withstand loading due to the plasma transients resulting in electromagnetic (EM) forces acting on the UPP and its onboard components. On the other hand, the eddy currents and shock dynamic EM loads occur in the vacuum vessel (VV) and make it vibrate. As a result, it excites the UPP and, consequently, its onboard components. The computational problem is a superposition of these solutions: 1) the deterministically calculated time-history UPP response to the applied EM forces and 2) the UPP response to the VV excitations that are specified as floor response spectra (FRS) at the port stub (attachment to the VV). On the top of this, the EM loads should be combined with the seismic ones which are also specified as an FRS. This paper considers a potential methodology for combining plasma transients with seismic events. A numerical modeling of the UPP hosting a specific cCXRS component is presented. This methodology gives a direct and transparent engineering way to estimate the mechanical strength of the UPP onboard components. The analysis uses port stub FRS input and does not depend on a spectra-to-spectra recalculation procedure (from VV to component attachment) that is well established for the seismic-type response spectra but is not validated for the FRS due to the plasma transients. [ABSTRACT FROM AUTHOR]

Most of ITER’s diagnostics will be provided with viewing lines (optical, microwave, and spectroscopic) for the monitoring of key characteristics of the plasma or for the achievement of physical measurements inside the vacuum vessel. The nature of the physical signal transmitted through the viewing lines requires the implementation of window assemblies incorporating nonmetallic window. Placed at the vacuum boundary, the window assembly shall also ensure the vacuum integrity required for the plasma. Moreover, the diagnostic window assemblies form part of the ITER primary confinement boundary, and thus, directly related to the nuclear safety. This paper gives an overview of their design and related on-going engineering assessments by analysis or tests in the final design phase. [ABSTRACT FROM AUTHOR]

The Hybrid Illinois Device for Research and Applications (HIDRA) is a toroidal fusion device at the University of Illinois at Urbana–Champaign, Urbana, IL, USA. HIDRA is the former WEGA stellarator that was operated at the Max Planck Institut für Plasmaphysik, Greifswald, Germany. The machine is a five-period, $l=2, m=5$ stellarator, with major radius $R_{0}=0.72$ m, and minor radius $a=0.19$ m. Initial heating is achieved with 2.45-GHz electron cyclotron resonance heating and an on-axis magnetic field of $B_{0}=0.087$ T that can go as high as $B_{0}=0.5$ T. HIDRA has the ability to operate as both a stellarator and a tokamak, initially operating in the stellarator mode. The focus of research on HIDRA will be doing dedicated studies on plasma-material interactions (PMIs) using the wealth of knowledge and experience at the Center for Plasma Material Interactions, Urbana, IL, USA. In early 2016, the first experiments were performed on HIDRA. This paper presents some of the first results obtained from the machine such as initial magnetic fields’ measurements and plasma discharges. It also shows the development of the control system being currently implemented and introduces HIDRA-materials analysis tool, the in situ PMI facility that will be mounted on HIDRA in the near future to further enhance the diagnostics and material testing experiments meant to be conducted on the machine. [ABSTRACT FROM AUTHOR]

ITER has many ports to install various diagnostics which view and measure various plasma parameters. One of the ports, the upper port #18 (UP18) is designed to integrate three tenant diagnostic systems: vacuum ultraviolet spectrometer, neutron activation system, and upper vertical neutron camera. The key design drivers for the port integration are requirements on neutron shielding and maintenance. In this paper, we discuss the neutron shielding design made following the as low as reasonable achievable principle in order to reduce the shut-down dose rate in the interspace and port cell which are human-accessible areas. The design choice for radiation shielding of electronics in the port cell is also discussed. The port maintenance in ITER consists of remote handling operation for the port plug and manual (or assisted-manual) operation for the interspace and port cell areas. The compatibility with the ITER maintenance strategy is investigated for UP18 and the associated issues are addressed. [ABSTRACT FROM AUTHOR]

Conventional direct current arc plasma spray torches generate highly unstable plasma jets. This leads to some difficulties with control of coating properties especially when injecting liquid feedstock for the elaboration of finely structured coatings. At constant applied current, a properly designed arc plasma torch can work in self-sustained pulsed mode that produces large amplitude oscillations of the arc, which are interrupted by very repeatable restrikes. This paper investigates the influence of the modulation of the applied current on the arc stability. Electrical and acoustic diagnostics permit to show that amplification of arc oscillation and a stabilizing mechanism occur when the arc current frequency approaches the torch resonance frequency. Time-resolved optical emission spectroscopy is used to determine temperature and enthalpy profiles close to the resonance and the enthalpy modulation. [ABSTRACT FROM PUBLISHER]

In this paper, we propose and use an experimental method permitting the measurement of optical depth of a self-absorbed spectral line emitted from laser-induced plasma on the surface of an aqueous solution. Using well-known equations describing the radiatif transfer and the evolution with the optical depth of the relative uncertainty on the measurement of line intensity and on the half width at half maximum, we have also deduced the uncertainty on the measurement of electron temperature and the electron density. An application to the diagnostics of this plasma has been realized, and we show the reliability of the spectroscopic measurements. [ABSTRACT FROM PUBLISHER]

The W -for tungsten- environment in steady-state tokamak (WEST) project consists in transforming the French tokamak Tore Supra into an X-point divertor one and aims at testing the ITER technology of actively cooled high heat flux tungsten components during ITER-relevant long pulses. In addition to the integration in the vacuum vessel of a lower divertor and an upper one, this metamorphosis has a strong impact on diagnostics initially present in Tore Supra. Indeed, the introduction of a divertor in the upper part of the machine leads to block the lines of sight (LOS) of diagnostics previously installed in the upper ports. Therefore, new diagnostics playing a paramount role for the safe tokamak operation need to be implemented, such as an infrared (IR) thermography diagnostic for the protection of plasma-facing components (PFCs) and heating antennas, and a visible spectroscopy system for the protection of tungsten PFCs. Besides, several existing diagnostics need to be modified to adapt their LOS to the new divertor targets and plasma shape. This paper presents the main issues linked to the integration of diagnostics deriving from the WEST project. First, the changes involved by the upgrade on the set of diagnostics currently implemented in Tore Supra are described. Then, a particular focus is put on the integration of the two new optical systems, namely the IR system and the visible spectroscopy one. These two systems being located within the vacuum vessel, a special care must be paid to their design, to allow them to withstand their harsh environmental conditions. Other new or updated fundamental diagnostics are also briefly presented. Finally, the resulting new implementation of diagnostics envisaged to reach the scientific and technological goals of the WEST project is described. [ABSTRACT FROM PUBLISHER]

An atmospheric-pressure plasma jet generated by a sinusoidal power input of tens of kilohertz and designed with a concentric wire-mesh cylinder electrode is characterized in this paper. Effects of gas flow rate on the length of plasma jet have been investigated, and the plasma jet is seen to have three different modes varied with the gas flow. The jet temperature is measured by fine-structure fitting of the emission bands of UV OH, \N2 molecules, and the Boltzmann plot method, and in comparison with the data obtained by an optical-fiber thermometer. In addition, the electron density in the generation region is diagnosed by stark broadening. Plasma bullet properties such as velocity, luminosity, their time of formation and extinguishment, and traveling distance are studied with variation of the applied voltage, gas flow rate, and operating frequency of power supply. Notably, the bullet velocity is found to have decreased with the applied voltage but increased with the operating frequency. Furthermore, the maximum velocity is reached earlier for lower gas flow rates and higher applied voltages, but its value is independent of the gas flow rate. [ABSTRACT FROM AUTHOR]

Diagnostics in International Thermonuclear Experimental Reactor (ITER) are supported by big structures called port plugs, the second main function of which is to ensure a sufficient shielding against neutrons and gammas. Regarding the integration of diagnostics in equatorial port plugs, a new approach is under study, which consists in installing the diagnostics in “drawers”. This paper describes the recent work which has been performed in Europe on the integration of diagnostics in drawers in the Equatorial Port Plug 1 (EPP1). First, the methodology which has been followed to progress on the integration of the diagnostics in this port plug is described, and the resulting arrangement of diagnostics is shown. Then, a special attention is paid to the integration of the two main diagnostics of EPP1, namely the visible/infrared wide angle viewing system and the radial neutron camera. Finally, the preliminary design of the drawers of EPP1, in particular the shielding modules around the diagnostics, is presented, and the preliminary results of the analyses performed to validate this design are provided. [ABSTRACT FROM PUBLISHER]

This paper describes the preliminary engineering investigation of the optical labyrinth and the first and second mirror mounts of the ITER core LIDAR diagnostics. The optical labyrinth is in a very sensitive location being close and open to the plasma. Therefore, it has been examined carefully to be able to provide different solutions satisfying the needs of the diagnostics. The present conceptual design considered the covering of the light path, the integration of the labyrinth into the port plug, as well as the shape, color, and material of the labyrinth inner surface. It was absolutely necessary, since the undesirable phenomena of scattered light and sputtered particles reaching the mirroring surface must be handled. Nevertheless, cooling/baking has also been considered, and appropriate solutions have been presented. Regarding the mirror mounts, concepts have been created. It has been identified that the mirrors must be conditioned at a certain temperature; therefore, cooling/baking options were developed. The cooling/baking and, particularly, the neutron absorption functions were detected to be essential for the extension tubes. The development basically focused on the different installation methods of the neutron-shielding plates, which also allow the tubes to be kept in the required temperature range. The result of the development was that a water-steel mixture varied through the length of the extension tubes could provide the maximum neutron shielding. This solution could satisfy the very strict six-orders-of-magnitude neutron absorption required to maintain the postoperation safety. The conceptual engineering design has been supported by the preliminary thermal analysis of the mirror extension tubes. [ABSTRACT FROM AUTHOR]

This paper surveys the present state of the art of diagnostics and removal techniques for particles suspended in plasma. Research on "dusty plasmas" is necessary for ITER and fusion reactors of the future. The aim is to transfer the knowledge acquired in complex (dusty) plasma research and low temperature plasma community to the broad fusion community, which is being mobilized to understand/quantify this phenomenon and find solutions. The introductory style makes it accessible also to safety personnel and other interested readers with only basic knowledge of plasma. In the transfer from research to technology, we have tried to assess the applicability of the methods proposed, and we have identified further much needed R&D. [ABSTRACT FROM AUTHOR]

In this paper, an inductively coupled pulsed plasma source with an operating frequency of 29 kHz is described. Using a series resonance circuit with a load capacitance of 12 µF and large diameter (approximately 20 cm) induction coils surrounding a spherical discharge vessel, a discharge plasma was produced and investigated in a pressure range of 0.1 to 100 Pa. Pulsed coil currents reached a maximum value of 9.6 kA with current rise times of 1.8 kA/µs while achieving an energy coupling efficiency of 80% between the driving circuit and the plasma. Pulsed-power peak values reached more than 800 kW. Moreover, the spectroscopic diagnostic revealed a high fraction of ionized particles and an emission spectrum in the near UV domain. Electron densities reached peak values of 1021 m-3. By using a fast camera system, the initiation of the discharge was investigated. The ignition of the discharge along an azimuthal path was documented, showing evidence of an entirely inductive plasma initiation without capacitive coupling. [ABSTRACT FROM AUTHOR]

In this paper, emission spectra of both positive column (PC) and negative glow (NG) regions of the dc glow discharge have been measured at different pressures and currents. The intensity of the lines in the NG is in the order of five times of that corresponding lines' intensity in the PC region. It is found that the line intensity increases linearly with the discharge current, while it increases as Pα with the gas pressure. The electron temperature Te has been estimated using the line-to-line- intensity-ratio technique. It is found that Te derived by this technique generally decreases with the pressure. Also, Te in NG region is about 3/2 of that in the PC. [ABSTRACT FROM AUTHOR]