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Volumes / Journal / 21 - 2010 / Schulze R., Szentmiklósi L., Kis Z.

The Ancient Charm Project: new neutron based imaging methods for cultural heritage studies

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Fig. 1 – Visualisation of an active measurement volume for the scanning based approach. (a) 3D setup with gamma collimator (double collimated geometry). (b) 2D setup without gamma collimator (chord geometry). The blue line represents the path of the neutron beam. The yellow line shows the collimated view of the gamma detector. The intersection of the two lines gives the currently measured sample volume for (a) while for (b) the whole volume irradiated by the neutron beam is measured.

Fig. 1 – Visualisation of an active measurement volume for the scanning based ap...

Fig. 2 – Reconstruction process with the Fourier-slice theorem. The parallel projection taken at an angle delivers via 1D Fourier transform a slice in the frequency domain. The combination of multiple Fourier transformed projections at different angles fills up the frequency domain. The 2D Fourier transform back in space domain yields the wanted 2D distribution.

Fig. 2 – Reconstruction process with the Fourier-slice theorem. The parallel pro...

Fig. 3 – The filtered backprojection algorithm yields slices of the measured object. These slices are finally stacked with the help of a visualisation software, to deliver the 3D image of the object.

Fig. 3 – The filtered backprojection algorithm yields slices of the measured obj...

Fig. 4 – Some of the samples investigated during the Ancient Charm Project. (a) Fibula found at the Kölked-Feketekapu site, Hungary. Dated to the end of 6th century. (b) Replica of the fibula. (c) Belt mount found in Környe, Hungary. Dated to the middle of 7th century. (d) Belt replica (original objects provided by the Hungarian National Museum; replicas provided by the Mineralogisch-Petrologisches Institut, Universität Bonn).

Fig. 4 – Some of the samples investigated during the Ancient Charm Project. (a) ...

Fig. 5 – Steps in the tomography process. (a) Fibula replica in sample holder used for the measurements. (b) Radiography of the fibula replica at 0°. (c) Reconstructed slice obtained with the filtered backprojection algorithm. (d) Visualisation of the complete tomography.

Fig. 5 – Steps in the tomography process. (a) Fibula replica in sample holder us...

Fig. 6 – Illustration of a combined PGAI/NT setup. For PGAI measurements the neutron collimator is put into the beam, while for NT an open neutron beam is needed.

Fig. 6 – Illustration of a combined PGAI/NT setup. For PGAI measurements the neu...

Fig. 7 – PGAI measurement on: (a) Fibula replica with chord geometry. (b) Replica taken apart after analysis; left: top of replica, right: back-plate with filling material. Measurement positions can be seen in (c) for frontal orientation and in (d) for lateral orientation. In combination with the earlier performed NT a 3D elemental distribution can be deduced: (e) Boron in the pearl of the fibula; (f) Calcium in the filling material; (g) Iron mainly in the outer ring of the fibula.

Fig. 7 – PGAI measurement on: (a) Fibula replica with chord geometry. (b) Replic...

Fig. 8 – Principle of NRT. The sample is rotated in front of a position sensitive neutron detector and turned. For each angle time-of-flight absorption spectra are recorded.

Fig. 8 – Principle of NRT. The sample is rotated in front of a position sensitiv...

Fig. 9 – NRT on the replica of a belt point shown in (a) measured at the ISIS spallation source. (b) Silver intensities measured with the pixelated neutron detector. The picture is a combination of 3×3 different distinct NRT exposures to cover the whole sample. (c) Bilinear interpolation provides subjective better resolution and a “clearer” image but cannot improve the real resolution (Intensities in arbitrary units).

Fig. 9 – NRT on the replica of a belt point shown in (a) measured at the ISIS sp...

Fig. 10 – Picture of the NRCI measurement chamber at the ISIS facility. The arrow labeled with “n” indicates the direction of the incoming neutrons.

Fig. 10 – Picture of the NRCI measurement chamber at the ISIS facility. The arro...

Fig. 11 – Use of reference markers for sample positioning. (a) Fibula sample in holder with reference markers. (b) NT of fibula. The references markers are clearly visible in the reconstruction. (c) and (d) Slices of the NT reconstruction. The slice number gives the z-coordinate. (c) A slice in the middle of the two upper reference markers. The known distance in mm of the reference markers and the distance in pixels in the reconstruction slice give the conversion factor for the transfer of positional information from reconstruction to laboratory system. For the y-axis the lower front reference marker can be used. (d) Slice in the middle of the fibula.

Fig. 11 – Use of reference markers for sample positioning. (a) Fibula sample in ...

Schulze R., Szentmiklósi L., Kis Z. 2010, The Ancient Charm Project: new neutron based imaging methods for cultural heritage studies, Archeologia e Calcolatori 21