Micro-XRF: Principles, Methodology and Applications in CH Studies. Birgit Kanngießer

Transcription

1 Micro-XRF: Principles, Methodology and Applications in CH Studies

2 Outline 1. Basics 2. X-ray optics 3. Application Examples 4. Discussion

3 Modern X-ray optics

4 Polycapillary optics Energy dependency of spot size s( E) = dcap + 2θcrit ( E) f T. Wolff et al., submitted

5 Polycapillary optics Energy dependency of transmission T = e µ air ρ air L I I optic air T. Wolff et al., submitted

6 Micro XRF Spectrometer Tabletop Spectrometers and Portable Spectrometers Conventional Tubes Microfocus Tubes Monocapillaries Polycapillaries Crystals, Multilayer CCD camera + laserpointer for allignment µ-focus X-ray tube polycapillary lens SDD Si(Li)- and HPGe-Detectors Drift chambers Synchrotron Spectrometers Synchrotron Radiation + Compound Refractive Lenses + Cryodetectors

7 Application Example

8 Investigation of historical manuscripts and compositions written with iron gall ink. Assignment of single sheets, corrections, amendments, to authors or to certain periods of genesis by Nondestructive analysis of minor constituents in iron gall inks with Micro-XRF. B. Kanngießer, W. Malzer, O. Hahn

9 Experimental set-up: A portable spectrometer is important to measure on site in the archives and museums! Portable technique: drift chamber detector, capillary lens helium flooding for light elements spot size ~ 100 µm Flexible, non-destructive investigations!

10 Considerable variance of the count rate due to the fibrous structure and inhomogeneity of the paper An area of at least 10 x 100x100 µm2 is measured relative standard deviation [%] as function of the number of measurements Reihe1 K Reihe2 Ca Reihe3 Mn Reihe4 Fe Reihe5 Zn

11 ink paper f.103v: black browish iron gall ink on rag paper. I /counts Parameter: Spot size ca. 100 µm 30 W Mo-tube 45 kv, 600 µa Accumulation: 100 s (lt) E /kev Investigation with Micro X-Ray Fluorescence Analysis

12 0,4 [Zn]/[Fe] 0,3 0,2 0,1 0,0 f.15 schwarz f.15 braun f.20 braun f.22 braun f.24 braun f.28v braun f.34 schwarz f.34 braun f.38 schwarz f.38 braun 0,0 0,2 0,4 0,6 0,8 [Cu]/[Fe] Ratio of the Cu to Zn intensities, without taking the fluorescence of the paper into account. Linear relationship?

13 Blatt 224 Zn [Counts] WZ99 übrige Cu [Counts] Ratio of the Cu to Zn intensities: The linear relationship is due to brass tools ( Holländer ) for the paper manufacturing!

14 [Zn]/[Fe] 1,2 1,0 0,8 0,6 0,4 Ratio of the Cu to Zn intensities The paper background is just subtracted from the ink. 0,2 0,0-0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 [Cu]/[Fe] No simple additive relation for the fluorescence from the ink and the paper! 0,5 0,4 Re. Häufigkeit 0,3 0,2 0,1 Additive assumption: ca. 35% of the samples have Cu-intensities 0. 0,0 0,0 0,2 0,4 0,6 0,8 1,0 1,2 [Cu]/[Fe]

15 Ink main component: Fe minor components: Cu, Zn, K,... w 1 ink Model paper Q II Q pm, Q Im Q pp 0 z d I d m d p Paper contamination: Fe, Cu, Zn, K,... Fibers of approx µm diam. Linear decrease of the ink density in the paper ρ Im = ρ I (1- z/d m )

16 The fingerprint value W takes into account the paper background the thickness of the ink layer the diffusion of the ink into the paper

17 Visual inspection: three types of ink have been used Investigation with µ-xrf: 0.06 light brown brown W = K i w i /K Fe w Fe Cu Mn Zn Two types of ink can be identified dark brown Folio 38 of Mozart s Zauberflöte Mass depositon in mg/cm 2 : light brown: 0.6 (may be diluted brown) brown: 3 dark brown: 0.7

18 original Investigation of manuscripts of J.W. Goethe Fragment of Faust II 0,0 1,0 (a) Faust I (a) Faust I, amendments (b) Faust I Faust II 0,2 0,8 [Zn]/[Fe] 0,6 0,4 0,6 [Cu]/[Fe] 0,4 Goethe ( ) 0,8 0,2 1,0 0,0 0,0 0,2 0,4 0,6 0,8 1,0 [Mn]/[Fe] amendment Fragment of Faust I original Goethe- und Schiller-Archiv, Weimar Fragment of Faust II Further development : improvement of reliability and error analysis

19 Absolute quantification is not necessary! A fingerprint which characterises the content of minor constituents is sufficient CCD camera + laserpointer for allignment µ-focus X-ray tube polycapillary lens SDD To distinguish two specimen a quantitative fingerprint is necessary a knowledge of the uncertainty is desirable

20 Literature: B. Beckhoff, B. Kanngießer, N. Langhoff, R.Wedell, H. Wolff (eds.), Handbook of Practical X-Ray Fluorescence Analysis, Springer-Verlag ISBN , (2006) B. Kanngießer, Quantification Procedures in Micro X-ray Fluorescence Analysis, Spectrochimica Acta B 54 /4, , (2003). W. Malzer, O. Hahn, B. Kanngießer, A fingerprint model for inhomogeneous ink paper layer systems investigated with micro x-ray fluorescence analysis, X-Ray Spectrom. 33, (2004). O. Hahn, W. Malzer, B. Kanngießer, B. Beckhoff, Characterization of iron gall inks in historical manuscripts and music compositions using x-ray fluorescence spectrometry, X-Ray Spectrom. 33, (2004).