Understanding Neutron Radiography

■ Neutron Induced Autoradiography
By exposing a painting to thermal or cold neutrons and later imaging the
radioactivity induced in the various paint components, a technique has been
developed sensitive to many elements including manganese, potassium,
copper, sodium, arsenic, phosphorus, gold, iron, mercury, antimony and
cobalt. The neutron exposures were originally performed in a moderator block
(thermal column), close to a reactor core. However, beams similar to those
used for transmission neutron radiography have been used for this neutron
induced autoradiography of paintings. Typically, a series of autoradiographs
is taken using a range of neutron exposure times and different decay times
before imaging. This, combined with a range of scintillator screen and film
sensitivities, can provide extensive information about successive layers of
each painting.
Charlie Chong/ Fion Zhang