Nuclear reaction and heavy ion ERD analysis of wall materials from controlled fusion devices: Deuterium and nitrogen-15 studies

Abstract

Time-of-flight HIERDA (26 MeV 127I 7+) and micro-NRA (2.5 MeV 3He) were used to determine the composition of graphite and tungsten plasma-facing components (PFC) exposed at the TEXTOR and Tore Supra tokamaks. High sensitivity and resolution of HIERDA allowed, for the first time, for studies of nitrogen-15 showing that the gas injected during tokamak discharges is trapped on PFC, 3–7 × 10 15 N cm −2. Also helium retention in tungsten has been identified: up to 8 × 10 15 He cm −2. Deuterium distribution on the main limiters of Tore Supra is not uniform on tiles extracted from the erosion- and deposition-dominated areas. This is measured both on macro- (points 5 mm apart) and micro-scale (30 μm). The mapping with μ-NRA revealed the D content variation by a factor 40–50 in regions 1 × 2 mm 2: 1.2–40 × 10 17 D cm −2 and 4–230 × 10 18 D cm −2 in the erosion and deposition zones, respectively. In summary, the measurements of 15N contributed to material mixing studies and improved understanding of deuterium retention on PFC.