Development and optimization of STEP-A linear plasma device for plasma-material interaction studies

The linear plasma device Simulator for Tokamak Edge Plasma (STEP) has been constructed at Beihang University, Beijing, to study plasma-material interactions (PMIs) for fusion reactor applications. The device can produce versatile low-energy and high flux plasma in laboratory experiments and is highly cost-effective to replicate the fusion-relevant plasma environment to study PMI processes. The attractive feature of the device is its compact design with a main body dimension of 1.5 × 1.5 × 0.8 m³ including the plasma source, vacuum chamber, magnetic coils, and diagnostics. A longitudinal magnetic field of up to 0.26 T is used to confine the plasma onto the target in an ∼1-m-long vacuum tube. It can produce a steady-state plasma of low impinging ion energy of <100 eV, ion flux up to 10²² m^-2 · s^-1, and fluence of >10²⁶ m^-2 per exposure. Various plasma species such as hydrogen, deuterium, helium, and nitrogen can be produced to manipulate PMI processes for different target grades. The STEP device provides an experimental platform to improve the understanding of PMIs, validate computational simulation results, and build a database of fusion material performance and lifetime.