The time structure of the external beam can be varied but consists typically of a 200 micro second burst of protons every 5 milliseconds. Internal beam current is about 0.5 microamps. Beam diameter can be adjusted from less than 0.1 cm to a maximum of 30 cm. Most irradiations take place in air in the external beam. Due to the low beam current it is possible to have unusually quick access to the experimental areas for adjustment of apparatus and targets.
Irradiations can take place in the internal beam but are limited to small foil targets.
In this case the irradiations take place in vacuum and the proton energy is selected by the choice of target probe position. Selected Publications Clinical use of protons and ion beams from a worldwide perspective. J.M. Sisterson, Nucl. M. Austin-Seymour et al., Radiother. Relative survival rates after alternative therapies for uveal melanoma.