Although the idea of proton Computed Tomography (pCT) is not new, it is currently not available. It is still unknown if the image quality of pCT is sufficient for localizing tumors and if the accuracy of proton range calculations surpass that of X-ray CT based range calculations without significantly increasing the patient exposure. The spatial resolution of pCT is limited mainly by multiple Coulomb scattering, while the contrast resolution is affected principally by the statistical nature of the proton energy loss mechanism. Both effects are more pronounced and thus easier to study at the low proton energies available at CV-28. An experimental setup for pCT at CV-28 was elaborated by our team. The first-generation CT scheme was assumed as the most adequate for the existing CV-28 proton "pencil" beam. All equipment, which includes the collimators for the initial and outgoing proton beam, the tomographic turntable, and the ORTEC L-035-025-5 proton detector, was assembled onto the support bar of the ORTEC vacuum chamber. A water-filled glass tube of 5 mm external diameter with a 1 mm diameter polyethylene rod on the central axis was chosen as the first sample to be studied. Later, the water will be substituted by tissue-equivalent solutions of different densities to study the contrast resolution. A Monte Carlo simulation of the experiment, assuming 25 MeV monochromatic proton beam, was made using the SRIM-2003.20 code. The simulation permitted to choose the critical parameters for the setup, such as the beam collimation, the steps of translation and rotation of the turntable, and the required statistics for an accurate measurement of proton energy.

The propagation of the struck proton through the nuclear medium is studied in the semi-classical multicolli-sional internuclear cascade approach. The probability of formation of various residual nucleus configurations and the corresponding excitation energies were obtained as a function of the energy omega transferred to the proton by the knockout.

We present the results of the polarization and intensity measurements versus photon energy Egamma = 5 - 35 MeV for the photon beam produced by the electron plane channeling with the energies 1.2 and 1.5 GeV in silicon crystals 500 mum and 290 mum thick along the (110) plane. The comparison with results of another research group and theoretical calculations indicate a qualitative agreement. The correlation between the shape of the radiation intensity spectrum and its polarization energy dependence is observed.