Open AccessDifference of co-extracted electron current and beam acceleration in a negative ion source with hydrogen-isotope ions
Author(s) -
K. Ikeda,
K. Tsumori,
H. Nakano,
K. Nagaoka,
Y. Takeiri,
S. Masaki,
E. Rattanawongnara,
M. Osakabe
Publication year - 2022
Publication title -
journal of physics. conference series
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 85
eISSN - 1742-6596
pISSN - 1742-6588
DOI - 10.1088/1742-6596/2244/1/012060
Subject(s) - deuterium , ion , atomic physics , hydrogen , chemistry , electron , neutral beam injection , plasma , materials science , physics , tokamak , nuclear physics , organic chemistry
Improvement of the performance on a hydrogen/deuterium negative ion source for a nuclear fusion device is reported. In particular, the suppression of the co-extracted electron current, I e , is an important issue to ensure the stable beam acceleration. Improvement of the I e has been confirmed by optimizing the magnetic field of the electron deflection magnet in the extraction grid. Two other new methods for reduction of the I e were validated. The first was an electron fence whose rods were set between the rows of apertures on a plasma grid. The electron and negative ion current ratio, approximately I e /I acc , was greatly improved from 0.7 to 0.25 in deuterium. The second was an outer iron yoke which enhanced the magnetic flux density 19% inside the arc discharge chamber. The I e /I acc using the outer yoke decreased by 0.1 compared with using a normal magnetic filter in a deuterium operation. These attempts have improved the total deuterium injection beam power of 8.4 MW by three negative ion based NBIs.