15-20 October 2017
CERN
Europe/Zurich timezone

Achievement of 1 MeV Beam Accelerations for 60 s Toward High Power NBIs

16 Oct 2017, 09:40
30m
CERN

CERN

Centre international de Conférence Genève (CICG). http://www.cicg.ch/
Oral presentaion Ion sources for fusion 1st Session

Speaker

Dr Mieko Kashiwagi (National Institute for Quantum and Radiological Science and Technology)

Description

Long pulse beam accelerations with MeV-class hydrogen negative ions have been demonstrated by using Multi-Aperture and Multi-Grid (MAMuG) accelerators toward high power neutral beam injector (NBI) required in JT-60SA and ITER. This paper reports that pulse duration of the ITER-relevant current density of hydrogen negative ion beams at 1 MeV has been successfully extended from 0.4 s to 60 s by using a prototype five-stage MAMuG accelerator for ITER. The key for this achievement is to reduce the power loadings due to a direct interception of negative ions and secondary electrons on the acceleration grid. The extraction grid has been modified to optimize the beam optics and to control the beam directions. The acceleration grid has been modified to suppress the secondary electron generations. For these modifications, three-dimensional beam analyses including the collision process and the detail configuration of the accelerator have been improved step by step with the experimental validation. Finally, the total power loading on the acceleration grids has been successfully reduced to less than 10 % of the total beam acceleration power. As the result, 0.97 MeV, 190 A/m$^2$ negative ion beam was achieved for 60 s without breakdown, which was comparable to the ITER requirement of 1 MeV, 200 A/m$^2$. This long pulse beam acceleration with the ITER-relevant beam contributes to assure the 1 MeV accelerator for the ITER NBI.

Primary authors

Dr Mieko Kashiwagi (National Institute for Quantum and Radiological Science and Technology) Dr Atsushi Kojima (National Institute for Quantum and Radiological Science and Technology) Junichi HIRATSUKA (National Institute for Quantum and Radiological Science and Technology) Dr Naotaka Umeda (National Institute for Quantum and Radiological Science and Technology) Dr Masaya Hanada (National Institute for Quantum and Radiological Science and Technology) Mr Masayuki Dairaku (National Institute for Quantum and Radiological Science and Technology) Masahiro Ichikawa (National Insutitute for Quantum and Radiological Science and Technology) Mr Kazuhiko Mogaki (National Institute for Quantum and Radiological Science and Technology) Mr shunichi Sasaki (National Institute for Quantum and Radiological Science and Technology) Dr Hiroyuki Tobari (National Institute for Quantum and Radiological Science and Technology) Dr Kazuhiro Watanabe (National Institute for Quantum and Radiological Science and Technology) Mr Haruhiko Yamanaka (National Institute for Quantum and Radiological Science and Technology)

Presentation materials