T-261.2 Determination of Source Size. When manufacturer’s
or supplier’s publications are not available,
source size may be determined as follows:
(a) X-Ray Machines. For X-ray machines operating at
500 kV and less, the focal spot size may be determined
by the pinhole method,1 or in accordance with SE-1165,
Standard Test Method for Measurement of Focal Spots of
Industrial X-Ray Tubes by Pinhole Imaging.
(b) Iridium-192 Sources. For Iridium-192, the source
size may be determined in accordance with SE-1114,
Standard Test Method for Determining the Focal Size
of Iridium-192 Industrial Radiographic Sources.