a geometric surface, perpendicular to the beam axis, through which radiation passes; its boundary is determined by the shape, size, and location of the source of radiation and of the beam-limiting devices such as cones and diaphragms Found on http://www.electropedia.org/iev/iev.nsf/display?openform&ievref=881-16-05
a geometric surface, perpendicular to the beam axis, through which radiation passes; its boundary is determined by the shape, size, and location of the source of radiation and of the beam-limiting devices such as cones and diaphragms