Figure 2

Prototype X ray machine. An RS2400 self-shielded cabinet 150 kV X ray irradiator (Rad Source Technologies Inc, Alpharetta, Georgia, USA), with a working volume of about 18 L divided into 5 horizontal cylinders 176 mm diameter by 150 mm long (3.6 L each) with a dose uniformity ratio of 1.3. This unit requires a 10 kW, three phase electrical supply and is cooled by chilled water or a self contained water-to-air heat exchanger (seen in the background). High power X ray units have only recently become available and are not in general use yet.