An electrostatic potential well was produced by injecting positive zinc ions into a hollow cathode. The apparatus consisted of two concentric spherical electrodes with the inner wire‐mesh electrode being 91% transparent. Ion current pulses as high as 40 mA were injected by a vacuum‐arc source located between the spheres. The outer sphere was biased at 4 kV and the inner sphere from 0 to −1.5 kV so that the ions would circulate between the spheres and be drawn toward the inner sphere. Current pulses lasted up to 20 &mgr;s and during the current pulses, potential wells of up to 200 V were formed by the accumulation of ions within the inner electrode. The well profile was computed from the deflection of a 2‐nA swept electron beam. The deflection was measured with a many‐slotted circumferential detector which intercepted the beam after it traversed the space‐charge region. Each profile was calculated from data recorded during a single 2‐&mgr;s sweep of the probing beam.