Plasma-Facing Material Erosion Products Formed Under ITER-Like Transient Loads at QSPA-T Plasma Gun Facility

Edge-localized mode (ELM) simulation experiments were held on the quasi-stationary plasma accelerator QSPA-T to study the formation of plasma-facing material (PFM) erosion products. Parameters of the deuterium plasma heat loads in QSPA-T were close to those expected during transient events in ITER. A diagnostic system for measuring the deposition rate of the erosion products with resolution time of 0.02 ms (pulse duration 0.5 ms) was designed. It allowed defining the deposition rate dependence on time and property changes of the deposited film during the pulse. The average deposition rate in QSPA-T under exposures to ultra-short D plasmas was in the range of (0.1 to 100)×10¹⁹ at·cm²·s⁻¹, which was much higher than that for stationary processes. It has been found that deuterium concentration in the deposited W films depends on substrate temperature and deposition rate approximately in the same way as for stationary processes. As the substrate temperature and deposition rate increased, the D/W atomic ratio in the W films decreased. For describing the evolution of the D/W ratio with the substrate temperature and the tungsten deposition rate, an empirical equation proposed by De Temmerman and Doerner (J. Nucl. Mater., 2009), but with alternative parameters, has been used.