Cr plasma-material-interaction in PISCES-RF: D thermal release, retention, and erosion

Pure chromium (Cr) targets were exposed to high-flux deuterium (D) plasmas in the Pisces-RF linear plasma device, and measurements of D retention, release, and erosion were subsequently performed. Post-exposure D retention was quantified using temperature-programmed desorption on Cr targets irradiated by 50 eV ions over a broad range of exposure temperatures (423–873 K) and ion fluences ( 3 × 1 0 24 – 3 × 1 0 26 m −2 ). The retained D inventory was observed to decrease rapidly with increased exposure temperature, from approximately ∼ 7 × 1 0 20 m −2 at ∼ 420 K, to then saturate near ∼ 10 20 m −2 for exposure temperatures above ∼ 550 K. Separately, at fixed exposure temperature ( ∼ 450 K), D retention was found to have only a weak dependence on increasing ion fluence. Lastly, the erosion of Cr in D plasma was investigated for ion impact energies in the range 40 ≤ E i ≤ 250 eV. Erosion was inferred using optical emission spectroscopy (OES) from the ratio of emission lines (Cr I (425.4 nm)/D I (656.1 nm)) measured close to the target. Conversion of the OES yield data to net erosion yield was made with singular ion energy target mass-loss measurements. These net erosion yield data were then further corrected to obtain gross erosion yield by accounting for a re-deposition factor, computed using a simple model. The gross erosion yield is found to be 2–4 times lower than predicted by SDTrimSP, consistent with that typically observed for light-ion sputtering under high-flux plasma conditions. • Cr targets are exposed to high-flux D plasma in the Pisces-RF linear device to assess fuel retention and erosion behavior. • D retention in Cr decreases sharply for plasma exposure above 550 K and shows a weak fluence dependence. • The gross erosion yield (re-deposition taken into account) is a factor of 2–4 lower than that predicted by SDTrimSP, which is typical in light-ion high-flux plasmas.