Electron emission radiography
An examination technique that uses electrons emitted from the surface of an object to form the image. Electron emiission radiography is conducted by placing a single layer radiographic or photographic film on top of and in close contact with the object. Air gaps will deteriorate the image quality. The object and film are then irradiated with high-energy X-rays (200 kV < HV < 450 kV), with a copper filter to absorb the low energy part of the primary X-ray spectrum. The X-rays pass through the film nearly without interacting with it. When the X-rays penetrate the object, they are absorbed and secondary electrons (photo-electrons and Compton electrons) are emitted. Those created in a thin upper surface of the examinated object (some 10 to some 100 micrometers) can reached the film and give an image with an excellent resolving power. Heavy elements have higher emission rates than lighter elements and thus the image relates to the elemental composition of the object's surface. Electron emission radiography is used for examination of drawings, illuminated manuscripts, postage stamps, banknotes, easel paintings on wood panels and radio-opaque supports, champlevé & cloisonné enamels, degraded stained glass, damasqued metal objects....
Synonyms and Related Terms
émissiographie (Fr.); radiographie par rééemission d'électrons (Fr.);
B.Knight "Imaging the Design on Corroded Mediaeval Window Glass by Beta-Backscatter Radiography" Studies in Conservation 34:207-211, 1989.