The plasma generated by a silicon filtered cathodic vacuum arc has been investigated using a Faraday cup and Langmuir probes. Ion energy distributions for arc currents ranging from 30 to 80 A were measured. Mean ion energies were found to range from 8 to 18 eV. The ion saturation current density varied from 0.1 to 1 mA/cm2depending on both the arc and filter coil currents. The energy distributions were fitted by a sum of Gaussians spaced according to the gas dynamic model for ion acceleration at the cathode spot. ©1996 American Institute of Physics.