SU‐GG‐T‐203: Measurements of Proton Pencil‐Beam Scanning Performance Characteristics

Purpose: Measurements and results related to the development of proton pencil‐beam scanning will be described. We will show the current performance and required tolerances on parameters, and expected results from future upgrades. Method and Materials: We devised measurement procedures to determine the values and uncertainty of parameters that effect the irradiation time and dose distribution. We compared the uncertainty of these parameters to clinical requirements. Results: Data will be presented for the stability of the beam current and the timing aspects that contribute to delivered dose. The latter includes quantities such as the time to turn off the beam, so‐called dark current, the drift time in Ionization Chambers (IC), and activation in the ICs. These values change as a function of nozzle current and irradiation time. Other factors include the settling time of the scanning magnets after changes in the beam position and the subsequent beam position and size stability. Conclusion: A pencil‐beam scanning system is being developed and progress toward achieving clinical requirements will be shown.