The charged-particle dynamics in a 20-TW ion diode are determined from Stark-shift measurements of the accelerating electric field. The $\sim 10$-MV/cm peak field is an order of magnitude higher than any previous laboratory Stark-shift measurement. The data supply evidence for a field-limited ion source, a zero net-charge region near the anode, a positive net-charge region in the middle of the acceleration gap, and azimuthal asymmetries. Comparisons with quicksilver computer simulations provide new capabilities to evaluate the influence of charged-particle dynamics on ion-beam divergence and power.

• Received 3 October 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.1771