Speaker
Jaydeepkumar Joshi
(Diagnostic Neutral Beam (DNB))
Description
The acceleration system of Beam Source(BS) of Neutral Beam(NB) system is composed of water cooled Oxygen-Free Copper multi-aperture grid systems which is designed for focusing of beamlets to a focal point located at distance>20m from the Grounded Grid. For present application in the accelerator for DNB, this focusing is obtained using a combination of segment bending and aperture offsets. In vertical direction, segments(1&3) and(2&4) are bent by 0.549° and 1.647° respectively. In horizontal direction, segment is shaped in horizontal direction(over length of ~825mm) to have two stage angles(i.e.0.222°,0.665°) on each side of centerline and to be fixed on a frame with flat plane, which therefore forms a ‘six-planed’ grid.
Manufacturing of such ‘Bend Segment’ with stringent functional demands of tolerances on positioning(50µm), flatness(40µm) and angle(+/-0.002°) has been undertaken for the first time to the best of authors’ knowledge. Further, geometrically complex aperture shape is to be machined perpendicular to its own plane with very thin material left(1mm) after milling of water cooling channels and scooping of material for current distribution(for Plasma Grid(PG)). Therefore, need arose to establish a manufacturing methodology along with the impact and interdependence of various operations(i.e.milling of water cooling channel, aperture drilling, copper electro-deposition, material scooping, angled machining to achieve desired angle, and intermediate stress relieving).
To address above issues, a full scale prototype of PG has been manufactured and significant data is now available on manufacturing tolerances and handling of ‘angled grid’. The 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 accelerator of NB system for ITER and upcoming devices.
Co-authors
Aron Metz
(Research Instruments GmbH, Friedrich-Ebert Str. 1, 51429 Bergisch Gladbach, Germany)
Arunkumar Chakraborty
(Diagnostic Neutral Beam (DNB), ITER-India (Institute for Plasma Research), Gandhinagar, India)
Chandramouli Rotti
(Diagnostic Neutral Beam (DNB), ITER-India (Institute for Plasma Research), Gandhinagar, India)
Christian Eckardt
(PVA Industrial Vacuum Systems GmbH, Im Westpark 10-12, 35435 Wettenberg, Germany)
Dusan Stupar
(Research Instruments GmbH, Friedrich-Ebert Str. 1, 51429 Bergisch Gladbach, Germany)
Eberhard Pfaff
(PVA Industrial Vacuum Systems GmbH, Im Westpark 10-12, 35435 Wettenberg, Germany)
Jaydeepkumar Joshi
(Diagnostic Neutral Beam (DNB), ITER-India (Institute for Plasma Research), Gandhinagar, India)
Jorg Schafer
(PVA Industrial Vacuum Systems GmbH, Im Westpark 10-12, 35435 Wettenberg, Germany)
Mainak Bandyopadhyay
(Diagnostic Neutral Beam (DNB), ITER-India (Institute for Plasma Research), Gandhinagar, India)
Wischet Yannic
(Research Instruments GmbH, Friedrich-Ebert Str. 1, 51429 Bergisch Gladbach, Germany)
