Comparison of damage effects in plastic scintillators due to irradiation with γ-rays, 190 MeV and 24 GeV protons

Plastic scintillation materials play a crucial role in the construction of large area detectors in high energy physics experiments. Future detector concepts for HEP experiments, particularly at collider facilities, will require an unique combination of the material features and of affordable price. Mandatory is a minimal level of radiation damage due to the electromagnetic part of ionizing radiation and energetic hadrons as well: tolerable deterioration of the optical transmission, negligible impact on the scintillation mechanism and small contribution of radio-luminescence due to secondary reaction products in the detector material. A systematic study of the radiation hardness of inorganic optical and scintillation materials has been performed by us since several years. It resulted in the understanding of the damage effects in particular in self activated, Ce3+-doped and cross-luminescent crystalline materials. Here we report on first results for the industrially produced plastic scintillation material EJ260 (ELJEN). This plastic is a bright, fast and green light emitting scintillator with properties similar to other materials such as BC428 and NE103, respectively. Samples of a thickness of 1.25 cm were tested before and after irradiation with γ-quanta (1.2 MeV, Giessen) and protons of 190 MeV (KVI, Groningen) and 24 GeV (CERN, PS), respectively. No damage of the material properties was observed after irradiation with γ-quanta up to an absorbed dose of 1 kGy consistent with similar studies. However, the exposure to 190 MeV protons with a fluence of 5×1013p/cm2 showed a large reduction of the optical transmission and a slowing down of the scintillation kinetics. In this study we also focused on the impact of high energetic protons. We obtained evidence that light fragments of the (p,12C) reactions play a significant role in the damage of the matrix and the luminescent organic dye centers.