Physical Measurements with High-Energy Radioactive Beams

Physical measurements were made with high-energy radioactive beams (positron emitters) produced as secondary particles from a heavy-particle accelerator. Data are presented for waterequivalent thickness of a silicon diode, a comparison of Bragg peak ionization depth vs stopping depth, and differential stopping depths when a beam is intercepted by heterogeneous materials in the orthogonal direction. A special positron-emitting beam analyzing (PEBA) system was used to form images of the stopped radioactive beam. These measurements will have direct impact on charged-particle radiotherapy, since the precise range of beams of charged particles to targets within patients can be measured and used for treatment planning. Also, during the treatments the stopping point of the beam can be monitored to verify that the treatment is being delivered as planned.