Mechanical experiments about pendulum support of vacuum vessel W7-X

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Abstract

At the Max-Planck-Institut für Plasmaphysik (IPP) the new stellarator fusion experiment WENDELSTEIN 7-X (W7-X) is under construction. Its ultimate goal is to verify that stellarator magnetic confinement concept is a viable option for a demonstration fusion power-plant.

Its toroidal plasma (major diameter of 11 m) is enclosed by a cryostat. The Outer Vessel (OV), ports and the vacuum vessel (VV) accumulate the cryostat together.

The main functions of the VV supports (VVS) are to withstand and transfer all vertical forces from the VV to the machine base and to allow horizontal movements simultaneously. Therefore, pendulum support system was introduced. The paper will describe their design and the destinations and results of a test campaigns (scale 1:1) at the University of Rostock.

Introduction

At the Max-Planck-Institut für Plasmaphysik (IPP) in Greifswald, the new stellarator Wendelstein 7-X (W7-X) is under construction. Its toroidal plasma (major diameter of 11 m) is directly enclosed by the vacuum vessel (VV). The vertical VV support system has to fulfil three functions:

  • 1.

    Withstand all the vertical loads

  • 2.

    Vertical adjustment (by hydraulic cylinders)

  • 3.

    Allow (passive) horizontal movement

Fig. 1 shows a schematic cut through the cryostat where are shown the main components (especially one inner vertical support) and the movements.

Section snippets

Values and design of the vertical support system

The VV of W7-X consists of five uniform modules (5× 72°). Each of them has to be supported and adjusted separately.

Therefore each VV module will be supported by three vertical supports which are of different lengths because of geometrical environment [1]. Two supports are located on the inner side and the third is placed at the outer side of the VV (Fig. 2).

The total number of VVS is accordingly 15.

The accepted total vertical load (dead weight) plus safety margin is 1300 kN. Conservatively

Experimental objectives

The goal was to find a convenient material and geometry of the hemisphere (ball/cup).

Therefore, analyses and tests had to be performed.

In order to prove that this pendulum support system has a low frictional resistance a series of experiments was developed, which were carried out at the University of Rostock.

At first the influence of the length of the pendulum support was examined. Secondly the required horizontal forces and respectively the equivalent friction factor were found.

The friction

Conclusions

The general feasibility of the pendulum support could be proved with the experiments. Different materials and geometries were tested.

The latest test (19) with cup material 1.4429 and ball material CC496K (lead–bronze) achieved the best results.

Therefore, this will be used for original VVS.

The observed smaller horizontal forces triggered by them will be used for following calculations of the whole cryostat.

References (4)

  • B. Missal, T.S. Test Pendelstütze für vertikale PG-Abstützung, IPP document Nr. 1-ABH00V-S0005.1, 22.12.2005, Max...
  • B. Missal, Zwischen-Auswertung der 1:1 Tests von Pendelstützen (Uni Rostock), IPP document Nr. 1-ABH00V-T0019.0,...
There are more references available in the full text version of this article.

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