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

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.