The conceptual design of NNBI electrostatic residual ion dump for fusion reactor

Abstract

BackgroundNegative ion source based on neutral beam injector is an important auxiliary heating and current driving system for the China Fusion Experimental Test Reactor (CFETR). Due to the high beam energy and large beam spot of negative ion based neutral beam injection system (NNBI), electrical deflection of residual ions has become the preferred scheme for residual ion dumping.PurposeThis study aims at the conceptual design of NNBI electrostatic residual ion dump system to deflect residual ions for neutralization of the beam.MethodsAccording to the development objectives of NNBI, three polar plates and two channels were adopted for the conceptual design of electrostatic residual ion dump (ERID). A negative voltage was applied to the intermediate plate to form a deflection electric field between the channels. When the mixed beam passed through the deflection channel, the residual ions were deflected to the panel due to the action of electric field force. Through theoretical calculation and beam deposition simulation, the structure of the ERID and more uniform heat load distribution on its surface were preliminarily determined.Results & ConclusionsThe simulation results show that the ERID can deflect the residual ions under the parameter design, providing a reference for future engineering design.

Keywords

• negative ion source
• neutral beam injector
• electrostatic residual ion dump