Penetrating heavy ion charge and velocity discrimination with a TimePix-based Si detector (for space radiation applications)

Abstract

Exposures were made with Medipix2 TimePix-based Si detectors at the HIMAC facility in Japan to explore the potential for discrimination between tracks with differing charges and energies, but with very similar d E/d x values. Data were taken at 15° increments for a number of different beams including 600 and 800 MeV/A Si, 180 MeV/A Ne and 100 MeV/A O. Data were also obtained for 400 MeV/A Si and 500 MeV/A Fe along with 290 and 180 MeV/A N. The TimePix chips have been calibrated to achieve the maximum resolution. Estimates for the angular resolution for these types of tracks are also possible from these data, which are essential in the development of a TimePix-based dosimetric device for use in a space radiation environment. One of the principal objectives of these data runs was to explore the resolution of TimePix-based Si detectors to discriminate between various ions with different energies and charges, but with similar d E/d x values in Si. Analysis of the images obtained shows the clear differences in the δ-ray halos for particles with similar d E/d x values but for differing charges and energies. These measurements are part of an ongoing program to explore the range of capabilities of the TimePix-based detector with respect to dosimetry uses in space.