JYFL-ACCLAB-ISG007 Parametric study of the ambipolar plasma potential dip in an ECRIS

Results of an experimental campaign to measure the magnitude of the potential dip in the ambipolar plasma potential of an ECR ion source with varied ion source operating parameters. The study was performed with the JYFL 14 GHz ECR ion source operated with argon plasma in a microwave-pulsed mode. The temporal behavior of the extracted Ar9+ ion current and the shape of the Ar9+ visible light emission line profile from the plasma were measured. The Ar9+ ion temperature was determined from the Doppler broadening of the emission line profile. The potential dip magnitude, determined from the previous quantities, was measured with varied plasma heating microwave power, plasma confining magnetic field, plasma chamber gas pressure and bias disc voltage. The parametric sweeps were performed for two different ion source baseline tunes: CW tune, where the steady-state ion current of Ar9+ was maximized, and afterglow tune, where the peak afterglow current was maximized.