Feasibility study of a compact heavy ion source for investigation of laboratory magnetospheric plasma

We are developing a laser ion source to provide a high brightness multi-charged heavy ion beam as a part of the heavy ion beam probe system, which will be used to diagnose plasma potential in the Ring Trap 1 device at the University of Tokyo. As a probe beam, Nb²⁺ was selected, and a detailed laser irradiation condition was explored. It was found that the laser power density of 1.2 × 10⁹ W/cm² gives the maximum particle number of Nb²⁺ per laser energy from a niobium foil target. Essential ablation plasma parameters to design the laser ion source were also obtained. The expected beam current was more than 12 mA/cm², with a pulse width of 3.1 µs at 200 mm away from the target.