(Dr. Nolan Hertel, advisor)
"148Gd Production Cross Section Measurements for Accelerator Target Facilities"
At the LANSCE accelerator complex, protons are accelerated to 800 MeV and directed to two tungsten targets, Target 4 at the WNR facility and the 1L target at the Lujan Center. DOE requires hazard classification analyses to be performed on these targets and places limits on certain radionuclide inventories in the targets to avoid characterizing the facilities as “nuclear facilities.” 148Gd is a radionuclide created from the spallation of tungsten. Allowed isotopic inventories are particularly low for this isotope because it is an alpha-particle emitter with a 75-year half-life. The activity level of 148Gd is low, but it encompasses almost two-thirds of the total dose burden for the two tungsten targets at LANSCE based on present yield estimates. From a hazard classification standpoint, this severely limits the lifetime of these tungsten targets. The cross section is not well-measured and thus is the motivation for measuring the W(p,x)148Gd production cross section. A series of experiments have been planned to measure the 148Gd production cross section with 600- and 800-MeV protons on tungsten, tantalum, and gold.