Surficial Chemical States of Li₃N Synthesized on Lithium Target for Boron Neutron Capture Therapy

Abstract

To remove high level of contaminants by O and C from Li₃N surface for Boron Neutron Capture Therapy target, high temperature thermal desorption was conducted up to 1123 K in ultra high vacuum and the following results were derived; During thermal desorption up to 1023 K, typical three peaks of vacuum pressure disturbance due to vaporization of contaminants were observed in vacuum pressure-temperature curve. Over-layered contaminants with high melting temperature below 1023 K on Li₃N surface is completely removed by high temperature thermal desorption up to 1123 K in ultra high vacuum. From these desorption results, it is suggested that these contaminants corresponding to these vaporization peaks are H₂O and Li compounds with high melting temperature below 1023 K, of which LiOH and Li₂CO₃ were synthesized by decomposition process of Li₃N with residual H₂O and CO₂ in low temperature.