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The magnetic diagnostics foreseen for the Wendelstein 7-X (W7-X) stellarator are diamagnetic loops to measure the plasma energy, Rogowski coils to measure the toroidal plasma current, saddle coils to measure the Pfirsch–Schluter currents, segmented Rogowski coils (poloidal magnetic field probes) to add information on the distribution of the plasma current density, and Mirnov coils to observe magnetohydrodynamic modes. All these magnetic field sensors were designed as classical pick-up coils, after the time integration of induced signals for 1/2 hour had been successfully demonstrated. The long-pulse operation planned for W7-X causes nevertheless significant challenges to the design of these diagnostics, in particular for the components located inside the plasma vessel, which may be exposed to high levels of microwave (electron cyclotron resonance) stray radiation and thermal radiation. This article focuses on the tests and modelling performed during the development of the magnetic diagnostics and on the design solutions adopted to meet the conflicting requirements. All pick-up coils foreseen for the initial operation phase of W7-X and their signal cable sections inside the plasma vessel and the cryostat are now installed, and their electronics and data acquisition are under preparation.

The stellarator Wendelstein 7-X (W7-X) has a divertor consisting of 10 units installed inside the plasma vessel (PV). It was decided not to install the long pulse high-heat flux (HHF) divertor targets at the first two years stage of W7-X operation and to start with an adiabatically cooled test divertor unit (TDU) and shorter plasma pulses operation. This allows to accumulate operation experience with much simpler components, and as a result to adjust accurately the actively cooled HHF divertor which replaces the TDU for the stationary operation. Finite element (FE) analyses have been performed for better understanding of thermo-mechanical problems of divertor targets, and to guide the design of the TDU and HHF divertors. This paper presents the detailed results of the temperature response, the deformation and thermal stress of the divertor components.

For long-pulse plasma operation of the W7-X stellarator, one of the most serious challenges for the design of in-vessel diagnostic systems is the thermo-mechanical problem. Thermal load from convective losses and from plasma radiation can reach up to 500 kW/m 2 at some locations close to plasma. The typical thermal load from plasma radiation alone ranges from 10 kW/m 2 to 100 kW/m 2 as derived from 3D Monte-Carlo simulations. Most plasma facing diagnostic components require active cooling for the long-pulse plasma operation. Especially the design of optical components must be optimized to minimize thermal deformations. Finite element analyses (FEA) are performed for better understanding of thermo-mechanical problems on plasma facing components of diagnostics, and to guide the design of the diagnostic system. As examples the paper presents the FEA results of the Corner-Cube Retro-Reflectors for the CO 2 -laser interferometer and the movable pop-up probe arrays in the divertor.

The purpose of the Wendelstein 7-X cryostat is to thermally insulate the magnet system (operating at cryo-temperature) by high vacuum and super insulation, to provide and enclose the working space for the plasma, and to serve as a bearing structure for the system components that have to be placed in the immediate vicinity of the plasma, such as the first wall, the divertor and some of the diagnostic devices. Concerning structural components only, the cryostat is composed of the plasma vessel, the outer vessel and the ports that interconnect the vessels. The cryostat together with the machine base comprises the so called cryostat system, and this is the system that is under consideration in this paper. Due to both the geometrical complexity and the complexity of loading, individual subsystems of the cryostat system could not be analyzed separately. For that reason, a global finite element model of the whole cryostat system had to be created. The paper presents an overview of finite element modeling, simulations with ANSYS performed on this system, and the corresponding calculation results.

The Wendelstein 7-X (W7-X) modular stellarator is in the assembly phase at the Max-Planck-Institut fur Plasmaphysik (IPP) in Greifswald, Germany. The goal of the project is to demonstrate that this type of machine is a viable option for a fusion power-plant. The “pentagonal” magnet system of the machine encompasses 50 non-planar and 20 planar superconducting coils with sophisticated support structure. Structural reliability of components as well as resulting deformations and displacements during various modes of operation have to be considered not only for the magnet system but also throughout the whole cryostat whose main components are the plasma vessel, outer vessel, ports, and thermal insulation. A reliable prediction of the W7-X structural behaviour is only possible by employing complex finite element (FE) simulations with a hierarchical set of FE models. A special strategy has been developed and implemented for the task. The design is basically completed, main parameters are defined, and most of the W7-X components are manufactured. Therefore, the focus in the analysis is being shifted to the creation of parametric FE models which allow performing fast analyses of possible non-conformities, changes in the assembly procedure, and future exploration of operational limits. This paper gives an overview of the implemented analysis strategy, the applied safety margins, and focuses on the most remarkable results.

To observe the one-year neurologic prognostic outcome of newborns with moderate and severe hypoxic-ischemic encephalopathy (HIE) who received recombinant human erythropoietin (rhuEPO) combined with exogenous monosialotetrahexosylganglioside (GM1) treatment to provide new guidelines for clinical treatment.Seventy-six newborns with moderate and severe HIE were selected from February 2011 to February 2014 in our hospital. This study received the informed consent of our hospital's Ethics Committee and the newborns' guardians. The newborns were divided to an observation group (n = 34 cases) and a control group (n = 42 cases). All newborns underwent hypothermia and conventional treatment for their conditions. The control group received GMl treatment and observation group received rhuEPO combined with GMl treatment. The curative differences and neural behavior from these two groups were compared.The excellent, efficient proportion and total effective rate of the newborns from the observation group were higher than the control group. The death rate, cerebral palsy and the invalid ratio of the newborns from the observation group were lower than that of the control group. Awareness, muscle tension, primitive reflex and increased intracranial pressure recovery time of the newborns in the observation group were less than those of the control group. The Neonatal Behavior Neurological Assessment (NBNA) score of both groups after the treatment of 7, 14 and 28 days were significantly higher and increased with time (p0.05). The MDI, PDI and DQ score of newborns from the two groups all increased after treatment of 3, 6 and 12 months than those of before, which increased with time (p0.05).The rhuEPO + GMl treatment in newborns with HIE improves short-term clinical effects and long-term neurological symptoms.

Surface modification of polycrystal tungsten due to low-energy and high-flux helium plasma exposure was investigated. Micron-sized holes and bubbles were formed on the surface at a surface temperature of 2200 K even when the incident ion energy of helium was 10 eV. Hole formation was significantly reduced on the surface when the incident ion energy of helium was around 5 eV and no surface modification was seen at less than 5 eV. Coalescence of micron-sized helium bubbles was observed in the cross section of a W sample.

The stellarator experiment Wendelstein 7-X (W7-X) is designed for stationary plasma operation (30 min). Plasma facing components (PFCs) such as the divertor targets, baffles, heat shields and wall panels are being installed in the plasma vessel (PV) in order to protect it and other in-vessel components. The different PFCs will be exposed to different magnitude of heat loads in the range of 100 kW/m 2 –10 MW/m 2 during plasma operation. An important issue concerning the design of these PFCs is the thermo-mechanical analysis to verify their suitability for the specified operation phases. A series of finite element (FE) simulations has been performed to achieve this goal. Previous studies focused on the test divertor unit (TDU) and high heat flux (HHF) target elements. The paper presents detailed FE thermo-mechanical analyses of a prototype HHF target module, baffles, heat shields and wall panels, as well as benchmarking against tests.

The stellarator Wendelstein 7-X (W7-X) is presently under construction at the Max-Planck-Institut für Plasmaphysik in Greifswald, Germany. The plasma density profile will be measured by two-colour interferometry where for each line of sight through the plasma the phase shifts of two far-infrared laser beams are compared. Due to the 3D shape of the superconducting coils in W7-X, opposite ports are not available. Instead, corner cube retro-reflectors (CCR) will be incorporated in the plasma vessel heat shield that reflect the beams back to the entrance window and diagnostic. This requires high accuracy of the reflecting surfaces which will be subjected to thermal loads from plasma radiation and therefore be heated up, displaced and deformed during operation. ANSYS is used to perform coupled thermo-mechanical analyses of the CCR, including plasma radiation, thermal conduction, and radiation between all parts. The resulting displacements provide the inputs to MATLAB routines which then yield local deformations, curvature radii, and tilting of the reflecting surfaces. This information is used to optimize the design of the CCR and their fixations. © 2011 Elsevier B.V. All Rights Reserved.

With the aim of starting plasma operation in 2014 the Wendelstein 7-X (W7-X) project has developed a scenario with an intermediate operational phase in which a reduced number of in-vessel components are installed prior to going to the fully equipped, full performance phase. An important part of this scenario is the test divertor (TDU), an adiabatically cooled, reduced pulse length device that will allow machine operation over a comparable range of plasma configurations as the final long pulse high-heat flux (HHF) divertor, which will be installed after two years operation of the TDU. The design and development of the TDU has started by clearly defining the requirements of the TDU with regard to performance, material selection, geometry, interfaces to other components, diagnostic integration, installation requirements and tolerances and quality management. In fact, the whole TDU development will follow the procedures laid down for design and development of components within the W7-X project. This paper provides a description of the design and development of the TDU to date.

The steady state operation of Wendelstein 7-X stellarator presently under construction in Greifswald poses special challenges to the diagnostics development [1, 2]. A critical issue is the heat load on plasma facing components (∼500 kW/m2) over a long discharge time (up to 30 min), which leads to the necessity of active cooling. As result, the design of the 400 channel soft X-Ray Multi Camera Tomography System (XMCTS) [2, 3] has to cope with dark currents and amplifier drifts due to the heating of active components like photo diodes and in-vessel preamplifiers. In order to allow for a quantitative measurement of dynamic drifts and offsets, a shutter system and blind diodes are considered to compensate these effects. Another important issue is the large amount of data gathered by the XMCT system during long pulse discharges. A fast but less precise online reconstruction is planned, which will give information on the plasma shape and position on a human time scale. The two options under investigation are a ...

For long pulse plasma operation of the W7-X stellarator, the most serious challenge for the design of in-vessel diagnostic systems is the thermo-mechanical problem. Thermal load from convective losses and from plasma radiation can be as high as 500 kW/m2 at some locations close to plasma. The typical thermal load from plasma radiation alone ranges from several 10 to 100 kW/m2 as derived from 3-D Monte-Carlo simulations. A finite element analysis (FEA-ANSYS) is conducted for a better understanding of thermo-mechanical effects on in-vessel diagnostic components and to guide the design of the diagnostic system for steady state operation. All in-vessel diagnostic components require active cooling. Besides for long-pulse plasma operation optical components must be optimized to minimize thermal deformations. In this paper, we present the thermo-mechanical analyses of the CO2-laser interferometer retro-reflectors, the diamagnetic loops and the soft X-ray multi camera tomography system (XMCTS).