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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. [ABSTRACT FROM PUBLISHER]

The commissioning of Wendelstein 7-X, the first numerically optimized stellarator, is a new phase in the project. The general planning and execution of the commissioning of the entire W7-X system follow its structure into appropriate components, subsystems and systems. The approach for taking these systems into operation will lead to so-called local commissioning which is usually executed for individual systems in connection with the necessary peripheral devices and auxiliary systems. The subsequent step-wise testing and commissioning of the systems in connection with the central device of W7-X, including the central safety control, and the central data acquisition system is performed in the second step, the so-called integrated commissioning. This leads directly to the preparation of first plasma operation. New organizational and quality management elements have been added to the running system, or existing, proven tools have been modified. The major new organizational structures and tasks and the quality planning and assurance tools are described in more detail. The experience during the first commissioning steps of the vacuum and cryogenic systems is outlined. [ABSTRACT FROM AUTHOR]

The stellarator device Wendelstein 7-X (W7-X) is now in the final stage of assembly. All the machine components have been built and in mid 2014 the commissioning activities should start. The first objective of W7-X is to prove the stellarator optimization principles, i.e., to reach at least the same confinement quality as a similar sized tokamak. The second objective is to demonstrate stable high-power steady-state operation. In the present paper, after a short description of the device, the ongoing activities to complete the construction will be summarized, focusing on the optimization of the layout of the torus hall and on the completion and assembly of the in-vessel components. The main lessons learned during the assembly will be presented as well as the application of the quality control, the handling of non-conformities and the design change procedures. The planning of the commissioning sequences to perform the integral tests of the major W7-X systems is discussed in order to prepare the W7-X device to start plasma operation. [ABSTRACT FROM AUTHOR]