Progress in conceptual design of a Heavy Ion Beam Probe diagnostic for the T-15MD tokamak

The Heavy Ion Beam Probe (HIBP) diagnostic is proposed for the T-15MD tokamak (R=1.48 m, a=0.67 m, A=2.2, B_t≤2 T, I_pl≤2 MA) located at NRC “Kurchatov Institute”, Moscow. Two similar HIBP systems will be installed in different poloidal cross-sections 90 degrees shifted around the torus. The arrangement will allow studying both poloidal and toroidal correlations of the plasma electric potential and electron density. The probing ions trajectories in the magnetic field of the tokamak are calculated with the 4th order Runge-Kutta method implemented in the HIBP-SOLVER code. Based on the calculations results, detector grids (plasma regions accessible for measurements) are obtained, and the probing beam attenuation in the plasma is estimated. The concept of a double secondary beamline is proposed to detect secondary ions from both peripheral and central regions of the plasma column. In starting T-15MD discharges with B_t=1 T, I_pl≤1 MA a Tl⁺ probing beam with the energy E_b<320 keV can provide measurements in a wide radial range (0.3<ρ<1) in the upper quarter (LFS) of the plasma cross-section. Additionally, the formation and focusing of the diagnostic beam in the injector is simulated, the values of focusing and extracting voltages are determined to obtain a quasi-parallel beam.