Impact of helium implantation and ion-induced damage on reflectivity of molybdenum mirrors

• DOI: 10.1016/j.nimb.2016.02.065
• Publication Date: 2016-03-15T13:34:58Z
• Authors: A. Garcia-Carrasco; P. Petersson; A. Hallén; J. Grzonka; M.R. Gilbert; E. Fortuna-Zalesna; M. Rubel
• Keywords: 0103 physical sciences; 01 natural sciences

Abstract Molybdenum mirrors were irradiated with Mo and He ions to simulate the effect of neutron irradiation on diagnostic first mirrors in next-generation fusion devices. Up to 30 dpa were produced under molybdenum irradiation leading to a slight decrease of reflectivity in the near infrared range. After 3 × 10 17 cm −2 of helium irradiation, reflectivity decreased by up to 20%. Combined irradiation by helium and molybdenum led to similar effects on reflectivity as irradiation with helium alone. Ion beam analysis showed that only 7% of the implanted helium was retained in the first 40 nm layer of the mirror. The structure of the near-surface layer after irradiation was studied with scanning transmission electron microscopy and the extent and size distribution of helium bubbles was documented. The consequences of ion-induced damage on the performance of diagnostic components are discussed.