[en] During last decades physicians' and physicist's experience and confidence in proton beam radiotherapy has grown significantly. Construction of a number of new proton therapy facilities is already underway, and several are in planning stages for the near future. Cost-effective shielding design of these facilities is important. We present comparative analysis of different shielding materials that are typically used at proton accelerators and in proton radiotherapy facilities. We have used Geant4 tool-kit for simulation of the passage of particles through matter. We have analyzed shielding properties of iron, borated concrete, a water tank with borated polyethylene walls, borated polyethylene, and borated fire retardant plywood. We have simulated 240 MeV protons incident on a thin copper target that generated radiation fields of primary protons as well as secondaries produced in the target incident on the shielding block. We found that iron is most effective per unit length. It may be the most cost-effective option if one considers using the so called SEG blocks in combination with 1 to 2 ft of concrete layer. The material of the SEG block consists primarily of iron from recycled government facility metals, and is slightly radioactive. The slight inherent radioactivity as well as low energy (< 847 keV) secondary neutrons from iron will be shielded by a thin concrete layer. We also find that borated fire retardant plywood can be a cost-effective alternative for borated polyethylene in many shielding applications where borated polyethylene sheets are used that are arguably not less fire hazardous. (authors)

[en] Purpose: The ProTom Radiance 330 proton radiotherapy system is a fully functional, compact proton radiotherapy system that provides advanced proton delivery capabilities. It supports three-dimensional beam scanning with energy and intensity modulation. A series of measurements have been conducted to characterize the beam performance of the first installation of the system at the McLaren Proton Therapy Center in Flint, Michigan. These measurements were part of the technical commissioning of the system. Select measurements and results are presented. Methods: The Radiance 330 proton beam energy range is 70–250 MeV for treatment, and up to 330 MeV for proton tomography and radiography. Its 3-D scanning capability, together with a small beam emittance and momentum spread, provides a highly efficient beam delivery. During the technical commissioning, treatment plans were created to deliver uniform maps at various energies to perform Gamma Index analysis. EBT3 Gafchromic films were irradiated using the Planned irradiation maps. Bragg Peak chamber was used to test the dynamic range during a scan in one layer for high (250 MeV) and Low (70 MeV) energies. The maximum and minimum range, range adjustment and modulation, distal dose falloff (80%–20%), pencil beam spot size, spot placement accuracy were also measured. The accuracy testing included acquiring images, image registration, receiving correction vectors and applying the corrections to the robotic patient positioner. Results: Gamma Index analysis of the Treatment Planning System (TPS) data vs. Measured data showed more than 90% of points within (3%, 3mm) for the maps created by the TPS. At Isocenter Beam Size (One sigma) < 3mm at highest energy (250 MeV) in air. Beam delivery was within 0.6 mm of the intended target at the entrance and the exit of the beam, through the phantom. Conclusion: The Radiance 330 Beam Performance Measurements have confirmed that the system operates as designed with excellent clinical performance specifications. Hovakim Nazaryan, Vahagn Nazaryan and Fuhua Wang are employees of ProTom International, Inc. who contributed to the development and completed the technical commissioning of the Radiance 330 proton therapy delivery system manufactured by ProTom International

[en] We report on a study of the longitudinal to transverse cross section ratio, R=σ_L/σ_T, at low values of x and Q², as determined from inclusive inelastic electron-hydrogen and electron-deuterium scattering data from Jefferson Laboratory Hall C spanning the four-momentum transfer range 0.06< Q²<2.8 GeV². Even at the lowest values of Q², R remains nearly constant and does not disappear with decreasing Q², as might be expected. We find a nearly identical behavior for hydrogen and deuterium