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In the framework of the development of a neutral beam injection system for the international thermonuclear experimental reactor (ITER), the electrostatic acceleration of negative ion H(-)/D(-) beams up to an energy of 1 MeV has been studied. With the support of 3-dimensional beam trajectory calculations, the limitations of the multi-aperture multi-grid acceleration concept, the ITER reference concept, are shown and the relevance of a new concept, called SINGAP, is demonstrated. In a SINGAP accelerator, beamlets are pre-accelerated with a classical triode multi-apertures system up to approximately 50 keV. The pre-accelerated beamlets are then merged into a single beam and post-accelerated at high energy through a large aperture lens using a single gap. The optics of one pre-accelerated beamlet has been studied on the INCA triode accelerator at the École Polytechnique. A diagnostic has been developed to measure the emittance of the pre-accelerated beamlet. Besides, the effects of co-extracted electrons and pressure in the transport region on the beam optics are shown and experiment is compared to beam numerical simulation. On the Cadarache 1 MeV, 100 mA, D(-) SINGAP accelerator, SINGAP optics has been investigated using an infrared calorimetric beam profile diagnostic and a neutral beam profile diagnostic. 3-dimensional simulations and experiment are in good agreement.

Additional information

Authors: BUCALOSSI J, L'Université Paris (FR)
Bibliographic Reference: Report: EUR-CEA-FC-1631 FR (1998) 156pp.
Availability: Available from Association Euratom-CEA, CEN Cadarache, 13108 Saint-Paul-lez-Durance (FR)
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