A scalable electron cyclotron resonance (ECR) plasma source was investigated for plasma cathode applications. The rectangular source utilized permanent magnets to establish the ECR condition. The microwave applicator region was windowless, making the source applicable to sputtering environment applications. The source was characterized using primarily two diagnostics: (1) a near-field and far-field Langmuir probe and (2) a downstream electron extraction electrode. Source operation and plasma properties were characterized at low pressures ranging from 0.2 to 5 mTorr and power levels up to 250 W. Evidence of grad-B drift in the plane of the source was observed. Extracted currents. agreed well with predictions. (c) 2007 American Vacuum Society.