Romanian Reports in Physics, Vol. 65, No. 4, P. 1438–1442, 2013 STUDY OF OPTICAL FIBER AS NEW RADIATION DOSIMETER * E. BADITA 1,2 , E. STANCU 1,2 , F. SCARLAT 1 , C.VANCEA 1,2 , A.SCARISOREANU 1 1 National Institute for Laser, Plasma and Radiation Physics, 409 Atomistrilor str., Magurele, Ilfov, E-mail: a_m_mihalache@yahoo.com 2 National Bucharest University, Physics Faculty, 407 Atomistilor str, Magurele, Ilfov Received October 8, 2012 Abstract. New preliminary results obtained in the study of optical fiber properties, for the development of a new radiation dosimeter sensitive to high energy photon beams, are presented in this paper. Optical fiber has been exposed to high energy photon beam generated by ALIN 10 linear accelerator. The exposure of the optical fibers to the high energy photon beam has produced an increase in radiation induced attenuation (RIA), a physical quantity used to exposure dose quantification. Attenuation in the optical fibers was measured before, during and after irradiation, for two wavelength values. The experimental results show that the optical fiber has a good response to radiation exposure and, therefore, can be useful in achieving the purposes of this study. Key words: optical fiber, radiation dosimeter, RIA, high dose rate dosimeter. 1. INTRODUCTION Optical fibers are used in various fields, ranging from telecommunications to medicine. The exposure to ionizing radiation induces an increment in attenuation. The excess of the optical loses are due to the generation of point defects in the silica core. This effect will be used for the development of a new radiation dosimeter. The optical fiber radiation induced attenuation is proportional to exposure radiation dose (C.Yan 2007 [1], M.C.Paul 2007 [2]). Multimode optical fiber is characterized by the light wavelength transmitted simultaneously through the multi-mode wavelength guide. Modes appear due to light propagation only through the fiber core with different angles. The AFS50/125Y multimode optical fiber was chosen to be used in this study. This optical fiber is characterized by a core diameter of 50 µm, cladding diameter of 125 µm and coating diameter of 250 µm. This optical fiber is * Paper presented at the Annual Scientific Session of Faculty of Physics, University of Bucharest, June 22–23, 2012, Bucharest-Magurele, Romania.