Production management and quality assurance for the fabrication of the In-Vessel Components of the stellarator Wendelstein 7-X

The In-Vessel Components (IVC) of the stellarator Wendelstein 7-X consist of the divertor components and the first wall (FW) with their internal water cooling supply and a set of diagnostics. Due to the significant amount of different components, including many variants, a tool called Production Managing System (PMS) has been developed to organize the fabrication and the associated quality assurance. The PMS works by building a database containing the basic parts and assembly data, manufacturing and quality control plans, and available machine capacity. The creation of this database is based mainly on the parts lists, the manufacturing drawings, and details of the working flow organization. As a consequence of the learning process and technical adjustments during the design and manufacturing phase, the database needed to be permanently updated. Therefore an interface tool to optimize the data preparation has been developed. PMS has been demonstrated to be an efficient tool to support the IVC production activities providing reliable planning estimates, easily adaptable to problems encountered during the fabrication and provided a basis for the integration of quality assurance requirements.     

Magnetic configuration effects on the edge heat flux in the limiter plasma on W7-X measured using the infrared camera and the combined probe

Controlling the heat and particle fluxes in the plasma edge and on the plasma facing components is important for the safe and effective operation of every magnetically confined fusion device. This was attempted on Wendelstein 7-X in the first operational campaign, with the modification of the magnetic configuration by use of the trim coils and tuning the field coil currents,commonly named iota scan. Ideally, the heat loads on the five limiters are equal. However, they differ between each limiter and are non-uniform, due to the (relatively small) error fields caused by the misalignment of components. It is therefore necessary to study the influence of the configuration changes on the transport of heat and particles in the plasma edge caused by the application of error fields and the change of the magnetic configuration. In this paper the upstream measurements conducted with the combined probe are compared to the downstream measurements with the DIAS infrared camera on the limiter.     

Service oriented architecture for scientific analysis at W7-X. An example of a field line tracer

Service oriented architecture based on web-services is a universal method of combining software components. SOAP web-services chosen for W7-X are characterized by strong standards and readily available tools. In this paper the SOAP technology is explained and is illustrated with a new service for field line tracing.The field line tracing package consists of a C++ library and a web-service interface. It features a flexible structure and can handle a realistic machine geometry. The following problems can be solved: getting a field line; making Poincaré maps; calculating flux surface characteristics; calculating heat fluxes to the wall; constructing magnetic coordinates, etc. The service is applied to estimate W7-X divertor loads with an 1/1 error field.     

CLAM钢、EUROFER97钢与钨在HT-7托卡马克中辐照后的表面分析

两种低活化马氏体钢(CLAM、EUROFER97)以及钨被放入HT-7托卡马克的刮削层中,以研究托卡马克装置中高温等离子体与低活化马氏体钢和钨表面的相互作用。通过SEM装置观察,发现某些样品的表面形貌发生了很大变化。低活化马氏体钢的表面起泡比较密集,钨的表面起泡比较稀少,且直径较大。在一些样品的表面,还观察到了等离子体灰尘以及明显的被等离子体冲击后的痕迹。另外,XPS分析发现样品表面的某些元素成分也发生了变化,而且处在托卡马克装置中不同位置处的样品,其表面硅的含量呈现出明显的规律性。     

Thermal analysis and tests of W/Cu brazing for primary collimator scraper in CSNS/RCS

To the transverse beam collimation system in a rapid cycling synchrotron,an important component is the primary collimator,which improves emittance of the beam halo particles such that the particles outside the predefined trajectory can be absorbed by the secondary collimators.Given the material properties and power deposition distribution,the beam scraper of the primary collimator is a0.17 mm tungsten foil on a double face-wedged copper block of 121.5 mm x 20 mm.The heat is transferred to the outside by a φ34 mm copper rod.In this paper,for minimizing brazing thermal stress,we report our theoretical analysis and tests on brazing the tungsten and copper materials which differ greatly in size.We show that the thermal stress effect can be controlled effectively by creating stress relief grooves on the copper block and inserting a tungsten transition layer into the copper block.This innovation contributes to the successful RD of the primary collimator.And this study may be of help for working out a brazing plan of similar structures.     

AC operation of large titanium sublimation pumps in a magnetic field: Results of the test stand for the W7-X neutral beam injectors

A neutral beam injection (NBI) system is being built for the Stellarator experiment Wendelstein 7-X (W7-X) currently under construction at IPP Greifswald. The NBI system consists of two injectors which are essentially a replica of the system present in the Tokamak experiment ASDEX-Upgrade at IPP Garching. A vacuum system with high pumping speed and large capacity is required to ensure proper vacuum conditions in the neutral beam line. For this purpose, large titanium sublimation pumps (TSP) are installed inside the NBI boxes, consisting of 4 m long hanging wires containing Ti and the surrounding condensation walls. The wires are DC ohmically heated up with 142 A to Ti sublimation temperature. A TSP system has been operated since many years in the AUG-NBI system, sublimating Ti in the pauses between the plasma discharges, when no magnetic field is present. However, at W7-X the superconducting coils generate a magnetic field permanently during experimental campaigns, whose stray B field with a maximum of 30 mT, affects the TSPs. Operated with DC, the wires would be deflected against the surrounding panels due to the Lorentz force. A simple possible solution is heating with AC, which reduces the wire deflection amplitude, inducing a risky wire oscillation. The feasibility of the AC operation in an equivalently strong B field such as the stray B field around W7-X has been demonstrated in a test stand for different AC waveforms and frequencies. Several test campaigns have shown no qualitative difference in the pumping properties between AC and DC operation of the TSP and no critical dynamic behaviour of the wires.