1. Apparatus for measuring the uniformity of a beam of charged particles at an exposure location, comprising: a plurality of Faraday cups, each said cup including an electrometer for determining the current collected by said cup, a plurality of low current sensors, each sensor being coupled to an associated electrometer and configured to produce a sensor output based on the current collected, a processor electrically configured to receive the sensor outputs and produce a plurality of processor signals, computational analysis software executing on the processor for receiving the processor signals and calculating beam parameters, and display software executing on the processor for generating a graphical representation of the beam parameters calculated by said computational analysis software.