Measurement of depth dose factors for various 60-Co and X-ray beams using ion chambers and thermoluminescent dosemeters

As the depth dose factors may vary with the type of 60Co unit (or X-ray generator) several determinations in this direction were done. The depth doses (mGy/s) for 60Co beam (SSD=80cm) for the depths 5,10,15 and 20 cm were 11.92, 8.25, 5.75 and resp. 4.10 for field size 10x10 cm and 12.70, 9.42, 6.63 and resp. 4.93 for field size 20x20 cm. In X-ray beam, the depth doses (mGy/s) for FSD=50 cm, open-end and field size 10 cm diam. were: 1.78, 0.66, 0.23 and 0.09 for 100 kV (0.143 mm HVL, in air) and depths 5, 10, 15 and resp. 20 cm; 2.61, 1.12, 0.46 and 0.19 for 135 kV and 4.13, 1.88, 0.88 and 0.40 for 180 kV. The quality of the radiation at different depths in the water phantom was determined using a tandem TLD within Cu sleeve and TLD without Cu sleeve. The values obtained ranged from 0.018 mm Cu for 100 kV to 0.170 for 180 kV at depth 5 cm. All determinations were done using an IAEA perspex water tank and Harshaw extruded LiF as detectors. An intercomparison using LiF powder capsules prepared and sent by the IAEA Dosimetry Laboratory was performed too, in order to check the consistency of thermoluminescent dosimetry systems