Design of the stripping unit and the electromagnetic analysis unit for the E//B NPA on HL-2A/2M tokamak

AnE//B neutral particle analyzer is under development for fast ion diagnosis on HL-2A/2 M tokamak. The stripping unit is composed of a stripping room (equipped with two differential tubes and a gas supply bellows), a vacuum chamber and a vacuum pumping system. The stripping efficiency of the stripping room is calculated in the form of global efficiency R × f₊₁, where R is the non-scattered-away rate and f₊₁ is the fraction of charge state +1. The magnetic field of the E//B analyzer is produced with a permanent magnet. The yoke and the poles of the magnet are made of mild steel and the magnet plates are made of NdFeB. The magnetic poles are specially designed to focus the ion trajectories and to increase the use rate of the magnet. The shape of the magnet and the electric plates are carefully designed so that the ions are dispersed into two lines of H⁺ and D⁺ on the detector plane. For each line, the energy increases from 10 to 200 keV from one side to another.