Results of the SINGAP neutral beam accelerator experiment at JAEA

摘要

IRFM (CEA Cadarache) and JAEA Naka have entered into a collaboration in order to test a Single Gap, Single Aperture (SINGAP) [H.P.L. de Esch, R.S. Hemsworth, P. Massmann, Updated physics design ITER-SINGAP accelerator, Fusion Eng. Des. 73 (2005) 329.] accelerator at the JAEA Megavolt Test Facility (MTF) at Naka, Japan. Whereas at the CEA testbed the acceleration current was limited to 0.1 A, at JAEA 0.5 A is available. This allows the acceleration of 15 H~- beamlets in SINGAP to be tested and a direct comparison between SINGAP and Multi Aperture, Multi Grid (MAMuG) [M. Taniguchi, T. Inoue, N. Umeda, M. Kashi-wagi, K. Watanabe, H. Tobari, M. Dairaku, K. Sakamoto, Acceleration of ampere class H~- ion beam by MeV accelerator, Rev. Sci. Instrum. 79 (2008) 02C110.] to be made.rnHigh voltage conditioning in the SINGAP configuration has been quite slow, with 581 kV in vacuum achieved after 140 h of conditioning. With 0.25 Pa of H_2 gas present in the accelerator 787 kV could be achieved. The conditioning curve for MAMuG is 200 kV higher.rnSINGAP beam optics appears in agreement with calculation results. A beamlet divergence better than 5 mrad was obtained.rnSINGAP accelerates electrons to a higher energy than MAMuG. Measurements of the power intercepted on one of the electron dumps have been compared with EAMCC code [G. Fubiani, H.P.L. de Esch, A. Simonin, R.S. Hemsworth, Modeling of secondary emission processes in the negative ion based electrostatic accelerator of the International Thermonuclear Experimental Reactor, Phys. Rev. ST Accel. Beams 11 (2008) 014202.] calculations.rnBased on the experiments described here, electron production by a SINGAP accelerator scaled up to ITER size was estimated to be too high for comfort.