The gain of microchannel plates operated with low bias voltages in the analog mode has been measured forArq+ions(3⩽q⩽16)with energies in the range from 1.5 to 154 keV/q.The results show that the gain, most likely due to the varying number of secondary electrons emitted upon impact of the detected ions, depends substantially on the charge as well as the energy of the ions. The measured gain is shown as a function of the charge state for five different ion energies per charge to assist in the interpretation of the results from the ion sources. The measured gain is also shown as a function of ion impact velocity for all measured charge states, which indicates a rather complex dependence on the ion impact velocity. The interpolated gain is also shown as a function of charge states for four different ion impact velocities. For the lowest ion impact velocity, the gain seems to increase linearly with the ions’s potential energy with the gain measured forAr16+being roughly twice as large as the gain measured for low charge states. However, for higher ion velocities, the gain surprisingly decreases for the first few charge states before it increases for higher charges(q>8)forming a minimum for an intermediate charge state. For1.4×106m/s, the measured gain ofAr3+roughly matches the gain measured forAr16+,but is roughly 60&percent; larger than the gain measured forAr8+.©1997 American Institute of Physics.