ARPANSA - Australian Radiation Protection and Nuclear Safety Agency

Fixed aperture collimators provide 10x10 cm² beams at 1 m from the ⁶⁰Co source (left) and 7 cm diameter beams at 1 m from the ¹³⁷Cs source (right). A square beam collimator is also available for the ¹³⁷Cs source. The collimators can be rotated through 90 degrees to provide both vertical and horizontal radiation beams.

Contact our Ionizing Radiation Standards Section for assistance.

The radiation sources are moved between the exposed and safe positions using electrically controlled linear compressed air systems. These systems can be operated either manually or under computer control. Timed exposures can be made for precise delivery of a prescribed radiation dose.

A computerised motion control system and a CCTV system are used in conjunction with micrometers, to ensure the precise positioning of test equipment in the radiation beams, and in the accurate adjustment of physical conditions, such as water depth in the case of absorbed dose to water measurements. Laser pencil beams are used to facilitate the reproducible positioning of equipment.

A current measurement system traceable to national measurement standards is used to calibrate radiotherapy ionization chambers and their associated electrometers. Calibration of therapy dosemeters can be made in terms of exposure / air kerma using the primary standard graphite cavity chamber, or in terms of absorbed dose to water using the primary standard graphite calorimeter.

Absorbed doses to arbitrary materials can be accurately delivered using an elegant theoretical protocol with only a few physical conversion factors, starting from absorbed dose to graphite as given by the primary standard graphite calorimeter.

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