Available online at www.sciencedirect.com Radiation Measurements 38 (2004) 311–315 www.elsevier.com/locate/radmeas A new ESR dosimeter based on bioglass material GamalM.Hassan a ; ∗ ,M.A.Sharaf a ,OmarS.Desouky b a Department of Ionizing Radiation Metrology, National Institute for Standards (NIS), Tersa Street, El-Haram El-Giza, P.O. Box 136 Giza, El-Giza, Cairo 136, Egypt b National Center for Radiation Research and Technology (NCRRT), Cairo, Egypt Received 30 June 2003; received in revised form 28 December 2003; accepted 8 January 2004 Abstract Bioglass (Bio-G) samples were irradiated with 60 Co -rays to study radicals for dosimetric materials with electron spin resonance (ESR). The ESR spectrum of Bio-G is characterized by two main signals. The rst signal at g ∼ =4:3 corresponds to Fe 3+ impurities and the second signal at g ∼ =2:0130 with line-width 10:85 G is ascribed as a hole center. The -ray dose response and thermal stability were studied to establish the suitability of bioglass as an ESR dosimeter. A radical formation eciency, G-value, of 0:53 ± 0:11 was obtained. The lifetime of radicals and the activation energy were estimated from Arrhenius plots to be approximately 255 ± 46 days and 0:71 eV, respectively. c 2003 Elsevier Ltd. All rights reserved. Keywords: ESR; Radiation; Dosimetry; Bio-G 1. Introduction Since the discovery of bioglass (Bio-G) by Hench et al. (1972), much research has focused on glasses and glass-based materials as biomedical materials, which can repair damaged living tissues and organs by interacting with biological systems. The Bio-G, which is based on some ox- ides such as Na2O, CaO, SiO2 and P2O5 shows high bioac- tivity. Bio-G forms a biologically active hydroxy-carbonate apatite layer, which provides bonding with bone and soft tissue without intervention of the brous tissue (Hench, 1994; Holand, 1997). Radiation induced defects in phosphate glasses of dier- ent composition are widely studied. The radiation induced PO 2- 4 hole centers in alkali phosphate glasses characterized by electron spin resonance (ESR) hyperne doublet from 31 P isotope (nuclear spin = 1 2 ) were studied by dierent au- thors (Nakai, 1965; Hasegawa and Miura, 1967; Weeks and Bray, 1968). Irradiated Bio-G of dierent compositions was previously investigated by Padlyak et al. (2000). They found that the eciency of electron and hole center gen- eration depends on basic Bio-G composition and is almost ∗ Corresponding author. Tel./fax: +20-274-169-36. E-mail address: gamalhassan65@hotmail.com (G.M. Hassan). independent of the type of ionizing radiation. The chemi- cal composition of Bio-G is similar to that of bones. Bone is composed of 1 3 of organic materials and 2 3 of inorganic materials and water (Padlyak et al., 2000). ESR dosimeters should ideally have a large G-value, a sharp line-width and thermal stability at room temperature. They should consist of light elements so that the response does not depend on radiation energy (tissue equivalent) (Ikeya, 1993). In the present study, Bio-G (45% SiO2, 24.5% CaO, 24.5% Na2O and 6% P2O5) was chosen as for an ESR dosimetry investigation. The calculated eective atomic number of Bio-G using Mayneord’s method (Johns, 1969) is 12.9 which is greater than that of tissue equiva- lent materials (∼ 7:5). This value needs further studies of photon energy dependence of Bio-G system. Some physical parameters such as dose response, thermal stability of the centers, the radiation eciency (number of free radicals per 100 eV of radiation, G-value), lifetime and activation energy were determined. 2. Materials and experimental technique 2.1. Materials and irradiation Bio-G (45S5) was prepared from reagent grade-l quartz; CaHPO4;CaCO3 andNa2CO3. Raw materials were weighed 1350-4487/$-see front matter c 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.radmeas.2004.01.020