Physics Design of the HNB Accelerator for ITER (Abstract/Comunicazione in atti di convegno)

Type
Label
  • Physics Design of the HNB Accelerator for ITER (Abstract/Comunicazione in atti di convegno) (literal)
Anno
  • 2012-01-01T00:00:00+01:00 (literal)
Alternative label
  • H. P. L. de Esch; M. Kashiwagi; T. Inoue; G. Serianni; P. Agostinetti; G. Chitarin; N. Marconato; E. Sartori; P. Sonato; P. Veltri; R. S. Hemsworth (2012)
    Physics Design of the HNB Accelerator for ITER
    in 3rd International Symposium on Negative Ions, Beams and Sources (NIBS 2012), Jyväskylä, Finland, 3-7 September 2012
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • H. P. L. de Esch; M. Kashiwagi; T. Inoue; G. Serianni; P. Agostinetti; G. Chitarin; N. Marconato; E. Sartori; P. Sonato; P. Veltri; R. S. Hemsworth (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#altreInformazioni
  • O - 501: Oral presentation (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#url
  • http://www.nibs2012.jyu.fi/NIBS2012_book_of_abstracts.pdf (literal)
Note
  • Comunicazione (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • 1 : CEA-Cadarache, IRFM, F-13108 Saint-Paul-lez-Durance, France; / 2,3 : Japan Atomic Energy Agency (JAEA), 801-1, Mukoyama, Naka 311-0193, Japan; / 4,5,6,7,8,9,10 : Consorzio RFX - Association EURATOM-ENEA, Corso Stati Uniti 4, 35127 Padova, Italy; / 11 : ITER Organization, Route de Vinon sur Verdon, F-13115 St Paul lez Durance, France. (literal)
Titolo
  • Physics Design of the HNB Accelerator for ITER (literal)
Abstract
  • Initially two neutral beam injectors, each delivering 16.5 MW D0 or H0, are foreseen to be installed on the ITER tokamak. A third injector may be added later. In this paper the physics design of the 5-stage 1 MeV, 40 A D? electrostatic accelerator for the ITER Heating Neutral Beams (HNB) is discussed. In the original design from 2001 the gaps between all the accelerator grids were different, the smallest being 50 mm. Concerns about the voltage holding forced larger, equal, gaps. To allow sufficient operating space (at least 1 mm clearance between beam and aperture wall on all grids) and still good beamlet optics (?3 mrad calculated), the gap spacing was chosen as 85 mm. The beam is extracted and accelerated from 1280 apertures covering a wide area (0.64 x 1.53 m2). The extractor contains 5.4x6.0 mm2 SmCo magnets that cause a ?2.8 mrad zigzag pattern on the beams. This is to be compensated for by either ?0.6 mm aperture offset on the downstream side of the extraction grid or by incorporating correction magnets in the grounded grid. Leakage of co-extracted electrons is calculated to be less than 2%. The produced beamlets have to be aimed through narrow parts in the beamline, meaning that some beamlets must be steered by 5.6 mrad. Also the beamlet-beamlet interaction (up to also 5.6 mrad) must be compensated for. Although conventional aperture offset steering does not work because the electric fields upstream and downstream of the acceleration grids are equal, it is possible to exploit the consequence of the finite thickness of the grids, i.e. the production of opposing polarity lenses at the entrance and exit of each aperture. By machining oblique or bi-axial apertures in all the four acceleration grids, a steering constant of 6.2 mrad/mm can be achieved. This steering is \"solid\" in that it does not depend on the beamlet position in the aperture. The current design of the (horizontal) magnetic filter field in the ion source produces a very uniform field inside the source, but a very small long-range field outside. However, some field is required to deflect stripped electrons out of the beam and prevent their acceleration to high energy. That is most efficiently achieved with a combination of this horizontal longrange field and local permanent magnets incorporated in the acceleration grids that produce a vertical field. The paper will summarise the current status of the design, the outstanding issues and the avenues considered for dealing with them. (literal)
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