The Energy Loss of Li and C Ions with MeV Energies in the Polycarbonate and Polypropylene

Stopping power and straggling of Li ions and C ions at mean energy 3.8-5.4 MeV and 5.6-6.9 MeV, respectively, in polycarbonate (PC) and at mean energy 3.7-5.2 MeV and 6.8-8.0 MeV in polypropylene (PP) foils have been measured using ion beams from a Tandetron 4130 MC accelerator. The ions scattered from a thin, primary gold target were registered by a surface barrier detector partially covered with a thin foil of the investigated polymer. The stopping power was determined from the energy difference between the signals from the ions directly backscattered from the Au layer and the ions backscattered and slowed down in the foil. The foil thickness was determined by the weighing procedure. The experimentally determined stopping powers were compared with those calculated with the SRIM 2010 code. The measured stopping powers are in good agreement for Li and C in PC, the differences being within 0.1-1.6% for Li and 0.2-2.1% for C. For Li and C in PP, the stopping powers are lower than the calculated ones, the differences being within 0.5-2.8% for Li and 3.6-6.1% for C. The energy straggling was determined from the width of the RBS signals. The experimentally determined energy straggling was found to fluctuate around the values calculated according to Bohr theory.