"Portrait of the Artist as a Landscape" W.S. Taft, 1997

1. "Portrait of the Artist as a Landscape" W.S. Taft, 1997

2. X-rays Spectroscopies—XRF and PIXE sample Excitation beam: X-rays, electrons, ions, protons X-ray energy analyzer X-rays Radiography guts X-ray source spine film

3. What else can we probe with? • Recall NAA: irradiate sample with neutrons • Converts some nuclides into radioactive elements • Gamma rays—analysis of spectra gives nuclide, hence elemental composition—NAA • Normally small samples place in reactor core • Also possible—irradiation of full painting (if small) in beam outside reactor • Analogous to X-ray emission spectroscopies • Irradiating beam leaves sample in excited state • Returns to quiescent state by characteristic radiation

4. Same information from both? • Yes and no— • Both give us elemental analysis of materials of the painting • NAA —Sensitivity depends on accidents of the nuclear physics • X-ray emission good sensitivity but varies smoothly with atomic number: not useful for lightest elements

5. Neutron radiography???? • Try same setup as for X-rays—— neutron source painting film For some problems, yes O-ring example from Ward tour For paintings, NO too little absorption by thin paint layer

6. What about those beta rays? • Neutron induced typically gives both gamma andbeta activity • Betas (electrons) will expose photographic film • Let’s try “autoradiography”

7. Autoradiography Two step process neutron electron neutron source film gamma painting Nuclides activated by neutrons Film exposed by electrons How to know what you’re seeing?? count gammas at the same time some information about source of beta activity

8. Preferential nuclide selection activity long 1/2-life short 1/2-life irradiation time long short long 1/2-life activity short 1/2-life delay time long short

9. Four techniques Radiation Physics Element analysis Radiography X-rays atomic XRF, PIXE X-radiography Neutrons nuclear NAA autoradiography