A compact ion source that produces hydrogen plasma with an electron cyclotron resonance (ECR) configuration combined with a 2-stage extraction system with a single aperture of 6 mm diameter has been designed and built to study the performance of different materials as the plasma electrode (PE) of a negative hydrogen ion source. The source has the capability to electrically bias the PE with respect to the ECR plasma. The first experiment with low ECR power input (less than 40 W) was carried out. The PE of the C12A7 electride showed the largest H− current among aluminum, molybdenum, and the C12A7 electride.

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