Characterization on deuterium retention in tungsten target using spatially resolved laser induced desorption-quadrupole mass spectroscopy
Yan Lyu, Cong Li, Ding Wu, Zhonglin He, Dongye Zhao, Li Qiao, Peng Wang, Hongbin Ding
Abstract
Abstract It is still challenging to achieve the quantitative analysis with a spatially resolved measurement for a non-uniform fuel retention in Plasma Facing Materials (PFMs). In this work, a long-pulse ( τ p ≈ 750 μ s) Laser Induced Desorption-Quadrupole Mass Spectroscopy (LID-QMS) has been developed as a diagnostic approach for characterizing inhomogeneous deuterium (D) retention in tungsten (W) target exposed to D plasma for ∼1 h with the total ion flux of 4.0 × 10 21 D/(m 2 s) at the substrate temperature of 400 K. The behavior of desorption of trapped D during LID was analyzed. 2D-distribution features of D retention in the exposed and shadowed areas of the W-target were investigated with a lateral resolution of about 650 μ m and depth resolution of approximately 175 μ m. The results show that the D retention is almost uniform along lateral dimension in the D plasma exposure area with an average fluence of (2.51 ± 0.40) × 10 20 D m −2 , while the value in the shadow area is only (0.25 ± 0.04) × 10 20 D m −2 which is one order of magnitude smaller than that in the exposure region. In the depth dimension, about 86.5% of the retained D is desorbed by the first laser pulse, which indicates that the D-retention is mainly distributed in the region less than 6.6 μ m based on the diffusion length. The micro-structures of W target exposed to D plasma after the long-pulse laser irradiation present swelling, blistering as well as bubble-bursting, which might be attributed to the thermodynamic interaction due to the rapid release of D particles from bulk to surface of W target during LID.