Investigation of objects d'art by PIXE with 68 MeV protons

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Vol. 161; pp. 704 - 708
• Main Authors: Denker, A., Maier, K.H.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-03-2000
• Subjects: High-energy PIXE; Ion beam analysis; Non-destructive analysis; 82.80Ej; High-energy PIXE; Ion beam analysis; Non-destructive analysis
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/S0168-583X(99)00704-1

PIXE with 68 MeV protons has been developed to investigate the elementary composition of samples, that are up to several millimeters thick, in particular for objects d'art. The small energy loss of the beam allows to handle and position large and delicate objects conveniently in air. The cross-section for producing K and L X-rays is around 100 times higher for 68 than for 3 MeV protons, while the specific energy loss and therefore radiation damage is 10 times less; the radiation damage per emitted characteristic X-ray is consequently 1/1000. The beam can be focussed to 0.5 mm diameter, the typical measuring time is 200 s at 1 pA beam current. Nuclear reactions cause a background of γ-rays but do not noticeably activate the samples. The present set-up is sensitive to all elements heavier than sulfur, it is unrivalled for detecting all heavy elements in a depth of millimeters. The different absorption of the various K and L lines indicates the depth of the element in the sample. Systematic studies on realistic test samples, that simulate ancient paintings, and on glasses, ceramics and metallic objects have demonstrated the possibilities of the method.