摘要： Negative ions are characterized in the helicon plasma source RAID (Resonant Antenna Ion Device) at the Swiss Plasma Center by means of Cavity Ring-Down Spectroscopy (CRDS) and Langmuir Probe (LP)-assisted laser photodetachment. A high density and axially homogeneous plasma column is produced via a RF antenna able to sustain the propagation of helicon waves in a steady state regime. An electron density ne ≈ 2.0 × 1018 m?3 in H2 plasma at 0.3 Pa and 3 kW of input power is measured in the center of the plasma column by LP and microwave interferometry. The electron temperature pro?le is peaked on axis reaching Te ≈ 5 eV and decreasing to 1.5 eV at r = 0.05 m. Thus, a hot core region forms where H2 molecules are rovibrationally excited (H2(ν)), and a cold edge, where low energy electrons can attach to H2(ν) and produce H? ions by dissociative attachment. In this work we use LP-assisted laser photodetachment and CRDS diagnostics to measure H? and D? radial density pro?les and how they depend on source parameters. We show that negative ions are distributed on a shell of 0.06 m radius with a peak value of ～ 2.0 × 1016 m?3 in H2 plasma. These results suggest that, although substantial technical development is needed, helicon plasmas could be considered as a possible candidate as sources of negative ions for future NBIs.