An electron cyclotron resonance (ECR)-plasma reactor has been built to do energetic ion deposition of refractory metals in vacuum. The system uses an E-beam gun to create refractory metal flux. The neutral metal flux feeds into a microwave resonator and forms pure metal plasma created by electron cyclotron resonance. The metal ions are extracted to a biased substrate for direct deposition. A retarding field energy analyzer is developed and used to measure the kinetic energy of metal ions at the substrate location. A high-quality niobium thin film is obtained through this deposition system. The niobium film exhibits an excellent superconducting transition. The niobium ion energy distribution has been measured. The niobium ion at the substrate location has a median kinetic energy of 64 eV with an energy spread of 20 eV under certain plasma conditions. (C) 2003 American Vacuum Society.