Table 2.

Reference irradiation conditions for low energy x-rays.

Influence quantity	Reference characteristics or value
Phantom material	Water-equivalent plastic or PMMA
Chamber type	Plane-parallel for low-energy x-rays
Reference point of chamber	At the centre of the outside surface of the chamber window (or additional foil, if this is used for beams above 50 kV)
Measurement depth	Phantom surface
SSD	30 cm
Field size at SSD	3 cm diameter or the closest field size to this that will be used clinically
Reference air pressure	1013.25 hPa
Reference air temperature	20 °C
Humidity	50%