Ion irradiation of polymethylmetacrylate (PMMA)

Radiation damage of polymethylmetacrylate (PMMA) is investigated irradiatin g thin films with 100-300 keV helium beams. The damage is deduced by measur ing in situ the molecular ejection from the irradiated polymer with a quadr upole mass spectrometer. The main ejected molecular masses are 2, 15, 16, 1 8, 26, 28 and 44, corresponding to H-2, CH3, CH4, H2O, C2H2 and CO2, respec tively. The heavier ejected masses are 60 and 70, corresponding to C2O2H4 a nd C3O2H2 groups, respectively. The molecular ejected yields, in terms of removed molecules per incident io n, and the chemical yields, in terms of ejected molecules per 100 eV deposi ted energy, are given. The damage induced by ion beams in PMMA is discussed and correlated to the effects produced in plastic scintillators for charged particles detection.