Development of high-quality titanium--tritide targets for the rotating-target neutron source

The Rotating-Target Neutron Source II (RTNS II) at Lawrence Livermore Laboratory (LLL) is the most intense continuous source of 14-MeV D-T neutrons currently available and is a national center for the study of the effects of these neutrons on materials of interest to the fusion community. The 14-MeV neutrons are produced when a 400-keV deuteron beam strikes an approximately 10-μm-thick titanium--tritide layer that adheres to a dish-shaped water-cooled copper-alloy substrate, rotating at 5000 rpm. The lifetimes and average neutron source strengths of the targets used during routine operation on the older and less powerful RTNS I and during early operation on RTNS II have varied widely, and several targets have performed below minimum standards. A study at LLL for improving the reliability of each target and increasing the average neutron source strength and lifetime has been successfully completed. Four 20-cm-diam. targets were produced. The first was used on RTNS I for over 200 h, more than twice the previous average, and the neutron source strength was increased 6%. The three other targets were tested on RTNS II and were compared with three standard production targets. The greater average neutron source strength of the LLL targets was statistically significant. We attribute this success to the production of high-quality titanium--tritide layers. Materials characterization and the titanium evaporation and tritium reaction systems are described, as well as special production techniques