This International Standard defines an empirical technique for the measurement of the effective collimation ratio

and effective L/D of thermal neutron radiography beams for values between 20 and 1 000. The technique is based

upon analysis of a neutron radiographic image and is independent of measurements and calculations based on

physical dimensions of the collimator system. The device described in this International Standard has been

developed and tested using Gd foil converters with a single emulsion, high resolution film in vacuum cassettes.