Micro-PIXE analysis of doped SiO 2 fibres intended as TL dosimeters for radiation measurements S. F. Abdul Sani, a * G. W. Grime, b V. Palitsin, b G. A. Mahdiraji, c H. A. Abdul Rashid, d M. J. Maah e and D. A. Bradley a,f Sample elemental concentrations can be determined using the microbeam proton-induced X-ray emission (PIXE) technique, providing non-destructive simultaneous low-background multi-element analysis. Present interest concerns analysis of Ge- doped SiO 2 fibres intended as high spatial-resolution thermoluminescence (TL) dosimeters for radiation measurements in place of their more typical applications in telecommunications. During fibres fabrication, defined amounts of the Ge dopant are added, the dopant more usually having a determining role in the transmission properties of the fibre. Characteristic X- rays produced in PIXE analysis provide information on the relative distribution of elements within a sample, as in for in- stance Ge and Si concentrations, the Ge acting as point defect centres that promote TL. With the dopant tending to diffuse in and away from the fibre core, it is essential to define the sample matrix composition in order to accurately evaluate the X- ray yield. This is determined in part using simultaneous Rutherford Back Scattering analysis. In present work, PIXE/Rutherford Back Scattering measurements have been employed to ascertain dopant concentrations of fibres that have been fabricated at the University of Malaya with a view to improving TL yield. Present results concern cylindrical fibres, nominally with 4%, 6% and 8% weight peak Ge concentrations and flat fibres of nominal 6% weight Ge concentration. For the cylindrical fibres, Ge dopant concentration has been found to be in the range of 2.41–4.56%, 6.44–8.29% and 10.27–12.25% weight, respec- tively, while for the flat fibres, the Ge concentration range is broader, at 0.07–6.55% weight. Copyright © 2014 John Wiley & Sons, Ltd. Introduction Over the past decade and more, optical telecommunication fibres have been widely investigated for application as thermolumines- cence dosimeters (TLD), offering relatively high TL yield as a result of extrinsic doping of the fibre core. [1,2] As a result of irradiation, electrons are excited into the point defect traps that have been cre- ated by the doping process so that in principle, the concentration and storage capacity of these traps can provide a medium suitable for dosimetric applications. To date, the main dosimetric attributes that have been associated with such small diameter optical fibres (typically ~100 μm) have included the following: the possibility of producing a dosimeter with excellent spatial resolution; a wide dy- namic range of dose sensitivity, from a fraction of a grey to many tens of grey and beyond, providing for applications in radiotherapy and high dose industrial dosimetry; water and corrosion resistance; reusability; and modest cost. Ultimately, we are seeking to fabricate in-house, enhanced TL yield fibres that would extend applications to diagnostic and environmental radiation doses (milligray down to fractions of a microgray, respectively). As such, one is looking to offer radiation sensitivity approaching or exceeding that of more well-established TL dosimeters such as the LiF phosphor-based commercial product TLD-100. The TL response of commercial doped SiO 2 optical fibres has been investigated by a number of workers, demonstrating promis- ing TL properties with respect to ionising radiation, including for photons, [3–7] electrons, [4,8] protons, [9] alpha particles, [10] fast neutrons [11] and synchrotron radiations. [12] Optical fibre is typically made from a preform of silica, comprising two essential components, the doped silica core and the outer silica cladding, such that for telecommunication purposes, a difference in refractive index is produced between the core and the cladding. This refractive index profile is controlled and manipulated through the addition of the dopant. As an example, a particularly popular process is to flow and deposit a gaseous mixture of GeCl 4 and SiCl 4 within an initially pure silica hollow tube. Simultaneously, the tube is collapsed down to produce what is referred to as a preform, using a high-temperature drawing and fusion process [13] producing an in- ner core of Ge 2 O 3 in amorphous SiO 2 . * Correspondence to: Siti Fairus Abdul Sani, Centre for Nuclear and Radiation Physics, Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK. E-mail: s.abdulsani@surrey.ac.uk a Centre for Nuclear and Radiation Physics, Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK b Surrey Ion Beam Centre, Nodus Laboratory, University of Surrey, Guildford, Surrey, GU2 7XH, UK c Integrated Lightwave Research Group, Department of Electrical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, 50603, Malaysia d Faculty of Engineering, Multimedia University, 2010 Cyberjaya, Selangor, Malaysia e Department of Chemistry, University of Malaya, Kuala Lumpur, 50603, Malaysia f Department of Physics, University of Malaya, Kuala Lumpur, 50603, Malaysia X-Ray Spectrom. (2014) Copyright © 2014 John Wiley & Sons, Ltd. Research article Received: 9 September 2014 Revised: 28 November 2014 Accepted: 30 November 2014 Published online in Wiley Online Library (wileyonlinelibrary.com) DOI 10.1002/xrs.2575