The paper presents a study of anchor cell plasma buildup in the tandem mirror GAMMA 10 with the use of central cell ICRF antennas. For plasma buildup, it is demonstrated that an ion cyclotron resonance layer exists within the closed mod-B surface in the minimum-B anchor cell. The experimental plasma buildup rate in the anchor cell is compared with a one-dimensional Fokker-Planck simulation. A rapid increase in the anchor plasma density is observed and an associated reduction of the end-loss current when radiofrequency is applied.