Manufacturing technology development for an ‘angled’ accelerator grid segment for DNB Beam Source

Abstract The accelerator for the Diagnostics Neutral Beam (DNB) beam source is composed of a multi-aperture grid system with three water cooled grids made from Oxygen free Copper. To achieve the focusing requirements at the distance of > 20 m, the grid segments are designed with two stage angles (0.222° and 0.665°) from the centerline in the horizontal direction. The configuration of this kind of ‘angled segment’ includes the water cooling channels milled in the angular form, subsequently closed by copper electrodeposition, providing the angles on front and back surface and then drilling of apertures on the angular plane. The long beam path and low energy beam demands the tight tolerances on each of these mechanical features and therefore demands the high degree of manufacturing controls on each of the processes. To unveil the challenges those could appear during the production of such grid, a 1:1 prototype of the most complex type of grid has been manufactured. This paper shall present the technical data generated out of manufacturing of this prototype, summarizing the recommendations for real grid production on: optimization of the sequence of manufacturing, effect of each of the operations, post-manufacturing handling and identifying the measurement techniques. The experience gathered here provides a recipe for the best manufacturing practices for the accelerators of NB system for ITER and upcoming devices.