Proton beam therapy energy degraders using graphite and graphite/boron carbide composite with single-block and multi-slab geometries: SRIM simulation and economic analysis
One of the crucial parts of a cyclotron-based proton beam therapy is energy degrader, which is utilized to deliver the proper proton beam energy. This work focused on utilizing the Stopping and Range of Ions in Matter (SRIM) software in determining which energy degrader geometry (single-block and multi-slab) and material between graphite and graphite/boron carbide composite (BGC) with varying boron content would be more suitable in terms of effectiveness and economy. An incident 250 MeV proton beam was used with 70, 150, 225 MeV desired energy setting upon degradation while the gaps for the multi-slab geometry was set as dry air. From the results, graphite with single-block geometry produced accurate results in proton energy degradation while incurring less radiation damage and less cost compared to BGC and multi-slab geometry. However, BGC poses higher flexural strength than graphite. Consequently, deviating from the appropriate material thickness for each desired energy resulted in inaccurate proton energy degradation result. The SRIM results from this work can be used as a preliminary basis in determining the appropriate energy degrader design for cyclotron-based proton facilities.