Hans-Stephan Bosch

Improved formulas for fusion cross-sections and thermal reactivities

For interpreting fusion rate measurements in present fusion experiments and predicting the fusion performance of future devices or of d-t experiments in present devices, it is important to know the fusion cross-sections as precisely as possible. Usually, it is not measured data that are used, but parametrizations of the cross-section as a function of the ion energy and parametrizations of the Maxwellian reactivity as a function of the ion-temperature. Since the publication of the parametrizations now in use, new measurements have been made and evaluations of the measured data have been improved by applying R-matrix theory. The authors show that the old parametrizations no longer adequately represent the experimental data and present new parametrizations based on R-matrix calculations for fusion cross-sections and Maxwellian reactivities for the reactions D(d,n)3He, D(d,p)T, T(d,n)4He and 3He(d,p)4He

Construction of Wendelstein 7-X - Engineering a steady state stellarator

The next step in the Wendelstein stellarator line is the large superconducting device Wendelstein 7-X, presently under construction in Greifswald. Steady-state operation is an intrinsic feature of stellarators, and one key element of the Wendelstein 7-X mission is to demonstrate steady-state operation at reactor relevant plasma conditions, as required for an economic fusion reactor. Such steady-state operation requires development of special technogies to be discussed in this paper.

Transition From Construction to Operation Phase of the Wendelstein 7-X Stellarator

Assembly of the superconducting stellarator Wendelstein 7-X is well advanced, and commissioning of the device is being prepared. A first draft of the commissioning tasks has been developed and will be discussed in this paper.

Progress, Challenges, and Lessons Learned in the Construction of Wendelstein 7-X

This paper reports on experiences gained during the construction of the large superconducting optimized stellarator device Wendelstein 7-X (W7-X). The goal of the project is to demonstrate the fusion reactor potential of optimized stellarators and to operate for the first time fusion-relevant plasmas under full steady-state conditions. In addition, the validity of the engineering concept is to be proven under operating conditions. The actual construction of the device is now running since more than ten years and will require about three further years of assembly and integration. The current technical status of W7-X is reviewed, the major construction challenges are highlighted, and conclusions are drawn from past experiences that may also be useful for other large-scale science projects.

Structural Analysis at the Transition From W7-X Construction to Operation

The Wendelstein 7-X modular advanced stellarator is in the commissioning phase at the Max Planck Institute for Plasma Physics in Greifswald, Germany. The focus of the numerical analysis has been shifted from support of the machine design and assembly toward preparation of the commissioning steps, assessment of possible field disturbances under operational loads, and exploration of operational limits. This paper emphasizes on the development, evolution, and realization of new analysis strategies, as well as on implemented numerical approaches for electromagnetic, thermal, and structural analyses. Remarkable results of the first comparisons with measurements from the extended mechanical instrumentation system are presented in detail and cover evacuation/flooding of the cryostat and plasma vessel, the first cooldown of the magnet system (MS), and both the superconducting coil groups and integral MS commissioning. Finally, some lessons learned during the transition phase are highlighted, which might be relevant for other large fusion machines.

Preparation of the Wendelstein 7-X commissioning

Assembly of the superconducting stellarator Wendelstein 7-X is well advanced, and commissioning of the device is being prepared. A first draft of the commissioning tasks has been developed and will be discussed in this paper.

Implementation of earned value management tools in the wendelstein 7-X project

The stellarator project W7-X, which is currently under construction, has recently implemented several earned value management tools to enable a tighter monitoring of internal processes such as the W7-X assembly process, the diagnostic engineering, and the manufacture of in-vessel components. Specification and implementation of these tools has posed several challenges characteristic of large-scale research projects that are subject to a number of changes during their life cycle. After putting these tools in operation, they have proven as early and transparent performance indicators for project control.

Wendelstein 7-X, Overview and Status of Construction

The line of the Wendelstein stellarators developed in IPP is being continued with a superconducting device, Wendelstein 7-X. This fully optimised stellarator which shall demonstrate the reactor potential of the Helias-type stellarator, is presently under construction in the Greifswald branch institute of IPP. Manufacturing of the W7-X components has progressed well over the last years, and assembly of the device has started early in 2005

Key results from the first plasma operation phase and outlook for future performance in Wendelstein 7-X

The first physics operation phase on the stellarator experiment Wendelstein 7-X was successfully completed in March 2016 after about 10 weeks of operation. Experiments in this phase were conducted with five graphite limiters as the primary plasma-facing components. Overall, the results were beyond the expectations published shortly before the start of operation [Sunn Pedersen et al., Nucl. Fusion 55, 126001 (2015)] both with respect to parameters reached and with respect to physics themes addressed. We report here on some of the most important plasma experiments that were conducted. The importance of electric fields on global confinement will be discussed, and the obtained results will be compared and contrasted with results from other devices, quantified in terms of the fusion triple product. Expected values for the triple product in future operation phases will also be described and put into a broader fusion perspective.

Do we need total quality management in fusion engineering? — Experience from construction of W7-X

The performance of all quality management (QM) and assurance (QA) activities in the project W7-X is a very complex task. If we understand QM as a request for continuous reflection on present tasks and on the best way to improve the processes with respect to the scientific and technical aims, it is a useful management tool. We can learn from industry but we have to adapt the system to our own requirements which differ and are more complex.