Moedling Radiation Emitted from the CAMS S-15 Beamline

The Center for Accelerator Mass Spectrometry (CAMS) facility at the Lawrence Livermore National Laboratory (LLNL) applies isotope ratio measurement and ion beam analysis to meet a wide range of scientific needs. The S-15 high-energy ion implantation beamline is used to study radiation damage effects as well as experimental nuclear physics and radiochemistry. When the CAMS program first added the ion implantation beamline to the facility in 2008 an initial design review was completed to determine the shielding required for the Radiation Generating Device. As research interests expand there is a desire to run experiments that extend beyond the current design considerations. This research focuses on gaining a better understanding of the shielding attenuation factor and limitations.

The shielding attenuation factor was found by modeling the ion implantation target chamber and shielding layout using the LLNL Monte Carlo transport code, COG. An experiment consisting of a deuteron beam and iron target was modeled and dose measurements were taken before and after the shielding materials to determine a theoretical attenuation factor. Experimentally obtained dose measurements taken for this reaction were compared with the model to ensure accuracy of the results.

The COG model was also used to find the additional shielding needed for the high radiation generating reaction between a deuteron beam and tritium target (D,T). The theoretical neutron source for the reaction was found by simulating deuteron transport in COG. The neutron energies emitted from the D,T reaction were used as the source term in the shielding code and the material thicknesses were adjusted to find the optimal shielding needed to absorb the radiation.