Abstract
Two thermoluminescent dosimeters (SiO2–GeO2 doped fibres and glass beads (GB)) were used to measure small photon field doses and compared against GAFCHROMIC film, a small ionisation chamber (RK-018) and a p-type silicon diode (SCANDITRONIX, F1356), as well as Monte Carlo simulations with FLUKA and BEAMnrc/DOSXYZnrc. Ge-doped SiO2 fibres have been shown by this group to offer a viable system for use as dosimeters. The fibres and GB offer good spatial resolution (~120μm and 2mm respectively), large dynamic dose range (with linearity from tens of mGy up to well in excess of many tens of Gy), are non-hygroscopic and are of low cost. Measurements of beam profiles for field sizes of 10mm×10mm, 20mm×20mm, 30mm×30mm, 40mm×40mm, and 100mm×100mm were carried out. Through the use of a customised solid water phantom, doped optical fibres and GBs were placed at defined positions along the x-and y-axes to allow accurate beam profile measurement. The maximum difference between FWHM measurements was 1.8mm. For penumbra measurements (measured between 80% and 20% isodoses), the maximum difference was<1mm. These measurements indicate good agreement, within measurement uncertainty, with Gafchromic film, data obtained from the use of two commonly used detectors and FLUKA and BEAMnrc/ DOSXYZnrc simulations.
•SiO2–GeO2 doped fibres and glass beads (GB) investigated as TLDs for their small field dosimetry.•The maximum inter-difference between FWHM measurements was 1.8mm.•The maximum difference for penumbra measurements (80% to 20% beam fall off points) was<1mm.