A thermoluminescence system for the intercomparison of absorbed dose and radiation quality of X-rays with a HVL of 0-1 to 3-0 mm Cu.

A TLD system is described which permits the measurement of absorbed X-ray doses in a water phantom, together with the quality of the incident X-ray beam. The system has been developed for dose and energy intercomparison studies between centres with deep therapy X-ray machines. A distinction has been made between deep therapy treatments and treatments at or near the surface. For beam qualities with a HVL above 1-1 mm Cu, the deep therapy region, measurements have been performed at 5 cm depth in water using CaF2: Mn and LiF (TLD 700). For beam qualities with a HVL of 0-11-1-4 mm Cu, these qualities include the superficial therapy region, measurements with LiF dosemeters at 2 and 10 cm depth in water have been carried out. The uncertainty in the absorbed dose value for X-ray beams with a HVL of 0-11-3-0 mm Cu amounts to +/- 4%; the uncertainty in the determination of the effective energy of the incident beam is +/- 3 to +/- 7%.