Calculational analysis of structural activation induced by 20–100 Mev proton beam loss in high-power linear accelerators

Abstract

For the new high-power accelerators currently being designed, activation of the accelerator structure has become an important issue. To quantify this activation, a methodology was developed and utilized that coupled transport and depletion codes to obtain dose rate estimates at several locations near the accelerator. To perform these calculations, simplified computer models were developed from detailed engineering drawings of a typical high-power accelerator design. This research focused on the 20 and 100 MeV sections of the bridge-coupled drift tube linear (BCDTL) accelerator. The peak dose rate was found to be approximately 6.5 mR/h in the 100 MeV section near the quadrupoles at a 25 cm radius, given an assumed beam loss of 1 nA/m. This peak occurs after the longest irradiation time (1 year) and the 1 hour decay time considered for this research. It was determined that the activation was caused mostly by proton interactions and subsequent spallation products, as opposed to absorption of the generated neutrons. The worst contributors were the spallation products created by proton bombardment of iron, and the worst component was the beam pipe, which consists mostly of iron.