Achievement and improvement of the JT-60U negative ion source for JT-60 Super Advanced (invited).
Developments of the large negative ion source have been progressed in the high-energy, high-power, and long-pulse neutral beam injector for JT-60 Super Advanced. Countermeasures have been studied and tested for critical issues of grid heat load and voltage holding capability. As for the heat load of the acceleration grids, direct interception of D- ions was reduced by adjusting the beamlet steering. As a result, the heat load was reduced below an allowable level for long-pulse injections. As for the voltage holding capability, local electric field was mitigated by tuning gap lengths between large-area acceleration grids in the accelerator. As a result, the voltage holding capability was improved up to the rated value of 500 kV. To investigate the voltage holding capability during beam acceleration, the beam acceleration test is ongoing with new extended gap.
Kojima
A
A
Japan Atomic Energy Agency, Naka, Ibaraki 311-0193, Japan. kojima.atsushi@jaea.go.jp
Hanada
M
M
Tanaka
Y
Y
Inoue
T
T
Watanabe
K
K
Taniguchi
M
M
Kashiwagi
M
M
Umeda
N
N
Tobari
H
H
Grisham
L R
LR