This talk addresses the use of neutron probe as a tool for Cultural Heritage (CH) research. Thanks to non-destructive nature of the probe this is a

Size: px

Start display at page:

Download "This talk addresses the use of neutron probe as a tool for Cultural Heritage (CH) research. Thanks to non-destructive nature of the probe this is a"

Claud Gibson
5 years ago
Views:

1 This talk addresses the use of neutron probe as a tool for Cultural Heritage (CH) research. Thanks to non-destructive nature of the probe this is a rapidly growing area of research which complements other techniques. 1

Neutron tool provides important piece of information on the science of ancient materials, i.e. in preservation and restoration of artifacts of different composition.

2 Neutron tool provides important piece of information on the science of ancient materials, i.e. in preservation and restoration of artifacts of different composition. Several examples will be addresses: these exploit the penetrating abilities of neutrons to study and visualize the interior properties of objects in totally non destructive and non invasive mode of analysis. 2

$In this context neutron diffraction help to establish and monitor the condition of an artifact.$

3 For example in conservation, to preserve artifacts and objects, it is important to assess their condition in order to develop tailored procedures to prevent deterioration. In this context neutron diffraction help to establish and monitor the condition of an artifact. Concerning making techniques, it has to be stressed that the material characterisation via neutron diffraction of an artifact is important to have insight about the materials and technologies that craftsmen used in ancient times. 3

4 Properties of neutron probe. The application of neutron-based imaging and analysis techniques overcame the limited penetrating power common to other probes. Neutrons can penetrate thick layers of dense materials without substantial scattering or loss of energy. 5

5 Neutrons visualize the interior properties of objects in totally non destructive and non invasive mode of analysis.

6 Neutron Fan showing the development of neutron scattering over the past four decades -- inner ring to outer ring, reading anticlockwise: 1960s Antiferromagnetism - basic physics 7

7 8

8 9

9 10

10 11

11 At X-ray and neutron facilities are available a number of nondestructive analytical techniques that are used in the CH field. In recent years the application of nuclear-based techniques to CH research has also expanded following the installation of laboratories with small ion accelerators close to museums which has facilitated the study of CH objects. 12

12 The history of neutron facilities 13

13 Intense neutron beam can be generated either in a reactor, from a neutron emitting isotope, or from a target in a proton accelerator.

14 Neutron beams

15 16

16 At ISIS neutron beams are generated from a target in a proton accelerator. 17

17 A ion source gun produces proton in the synchrotron. These are then accelerated and sent on a target that produces neutron beam can through a process know as Spallation, literally breaking the nucleus of the target. 18

18 Instrument suite 19

19 The Budapest Nuclear Reactor

20 The FRMII Neutron Reactor

21 Neutron Fluxes 22

22 A comparison of X-ray and neutron cross sections 23

23 Examples of Neutron Based Techniques 24

24 Neutron in Archeometry

25 26

26 27

$Typical diffraction spectra as normalised number of counts as a function of$

27 Typical diffraction spectra as normalised number of counts as a function of d-spacing: best fit of data are shown, with the peak position of the different components.

$Effects on the diffraction patterns: diffraction peak$

28 Effects on the diffraction patterns: diffraction peak position, peak width and intensities as a function of d-spacing. 29

$Determination of the provenance of the raw materials via neutron diffraction provides information on the identification of$

30 Determination of the provenance of the raw materials via neutron diffraction provides information on the identification of the manufacturing processes and the reconstruction of the trade paths of bronze artefacts of various provenance and times 31

31 Texture analysis measures the grain orientation distributions of crystallites in a material. Preferred orientations are visualized in pole figures that display characteristic pole density maxima and minima. This analysis provides information on making technique and whether the material is genuine or fake. The distribution of pole density maxima in the pole figures depends characteristically on the deformation history (e.g. plastic deformation during working; tectonic deformation of geological specimens). 32

32 These texture analysis provideed information on making technique of the coins and to asses whether the material was genuine or fake.

34 (Neutron diffraction experiment on INES)

35 The texture and microstucture analysis shows indications of successive hardening-annealinghardening processes.

In the ancient period funerary dowry is considered a distinctive characteristic of aristocrats, who also detained military and ritual power.

36 In the ancient period funerary dowry is considered a distinctive characteristic of aristocrats, who also detained military and ritual power. The artefacts objects of this study were found not only in male tombs, suggesting that also women played a primary role in such ritual activities. 40

37 The samples analysed, 14 fragments, were part of a collection that comes from the ancient tombs. 41

$Typical diffraction spectra as normalised number of counts as a function of d-spacing: best fit of data are shown, with the peak position of the different components; residue is reported in violet.$

38 Typical diffraction spectra as normalised number of counts as a function of d-spacing: best fit of data are shown, with the peak position of the different components; residue is reported in violet. The corrosion products and patinas revealed by the study, like Azurite, Nantokite, etc. depend on chemicalphysical conservation conditions of the particular object (for instance presence of water or absence of air). 42

39 Sample composed of two distinct parts (not coming from the same casting) Covellite is present in objects buried in non oxygenated conditions 43

Patina is a smooth and continuous layer that preserves detail and shape. Whereas corrosion describes discontinuous deposits of other environmental materials that determine a chemical attack.

40 Patina is a smooth and continuous layer that preserves detail and shape. Whereas corrosion describes discontinuous deposits of other environmental materials that determine a chemical attack. Different events such as burial, exposure to the atmosphere, marine conditions, laboratory environment (protection covering or pigments), lead to different corrosion products and patinas. Sequence of optical microscopy to characterise samples 44

41 45

45 The PGAI/NT set up at FRM II. 49

46 The Neutron Resonance Capture Analysis (NRCA) is used to determine the elemental composition of materials and artefacts. In NRCA neutron with energies corresponding to energy levels of the nucleus to be formed after capture are captured preferentially. Interaction of neutrons with nuclei as a function of neutron energy shows sharp peaks, known as resonances, at energies specific for each isotope. Resonances are the fingerprints of elements. They can be visualized in the neutron capture spectrum as a function of neutron energy. 50

Each capture event is followed by a number of prompt gamma rays. The energy of a neutron is determined by measuring the time it needs to travel a known distance (L in m).

47 Each capture event is followed by a number of prompt gamma rays. The energy of a neutron is determined by measuring the time it needs to travel a known distance (L in m). With a pulsed neutron source the time-of-flight (T in μs) can be determined from the start pulse of the source and a stop pulse generated by detection of the prompt capture gamma rays. 51

48 Example of NRCA experiment on brass object at GELINA, Belgium. The energies reveal the isotopes present and the areas the amount of the isotopes.

The principle of neutron thomography is based on the attenuation, through both diffusion and absorption, of a directional neutron beam by the matter through which it passes.

50 The principle of neutron thomography is based on the attenuation, through both diffusion and absorption, of a directional neutron beam by the matter through which it passes. Since different materials vary in their ability to attenuate neutrons, then both composition and structure can be probed. Principle: when beam pass trough a sample, part of the radiation is attenuated by the material related with the absorption coefficient 54

51 Roman sword. The neutron radiograhy is complimentary to X-ray radiography. 55

52 Roman dagger. Whereas X-rays are scattered and absorbed by the electrons, and as such atoms with greater electron shells interact more strongly, neutrons on the other hand interact with the atomic nuclei. 56

53 Neutron tomography: The basic principle behind tomography is that the interior structure of a 3-dimensional (3D) sample can be calculated based on a set of 2-dimensional (2D) projections (also called radiographies) of this sample, taken under different angles. 57

54 Cold neutron Tomography 58

Neutron Tomography/Imaging has wide industrial and scientific significance and can provide detailed information concerning the inner structure and composition of objects.

55 Neutron Tomography/Imaging has wide industrial and scientific significance and can provide detailed information concerning the inner structure and composition of objects. The principle of neutron imaging is based on the attenuation, through both diffusion and absorption, of a directional neutron beam by the matter through which it passes. Since different materials vary in their ability to attenuate neutrons, then both composition and structure can be probed. 59

56 An example of combined used of 3 neutron techniques 60

57 61

58 Example of neutron analysis from marble objects from Villa Adriana Tivo Composition resulted from the studies: calcite (CaCO 3 ), dolomite (CaMg(CO 3 ) 2 ), silica (quarzo, plagioclasio, mica), oxides (rutite, magnetite) 63

59 Components: Plagioclasio (Ca 0.85 Na 0.14 Al 1.86 Si 2.14 O 8 ) = % 83.0 in weight Orthoclasio (KSi 3 AlO 8 ) = % 15.5 in weight Quarzo (SiO 2 ) = % 1.5 in in weight 64

60 An Aryballos Greek vase from Etruscan tumb dated VII-VI century A.C. 66

61 The project ANCIENT CHARM exploits the idea of developing an analysis technique based on neutron absorption. This idea is quite innovative in the field of archaeology, with a number of scientific and technical challenges. The project has been established to tap into some of Europe's leading research on neutron-based imaging and to apply it to artefact analysis. Neutrons with energies similar to chemical bonds are used to produce quantitative measures and even 3D images of the elemental composition and physical structure of artefacts. The multidisciplinary ANCIENT CHARM team includes neutron beam facilities, detector manufacturers, software engi-neers, physicists and representatives fromthe fields of archeology and cultural heritage. The aim of ANCIENT CHARM is to develop innovative neutron-imaging techniques and the associated equipment, and help establish neutron imaging as a mainstream archaeological analytical technique. In particular, the aim is to develop a neutron resonant capture imaging combined with neutron resonance transmission (NRCI/NRT). Both gamma-emission and neutron transmission measurements will be used to determine the elemental composition of an object in 3D. One of the key developments in the project has been the construction of a new equipment for 3D analysis of small objects, to be used at the ISIS spallation neutron sources. The equipment is now available at the ISIS spallation source and is used for experiments on test objects and on selected archaeological samples. 67

62 Neutrons that are either scattered or absorbed in the sample are removed from the incident beam. Bulk element concentrations can be determined by neutron resonance transmission (NRT) by placing an entire object in a neutron beam without any sample preparation. Transmitted neutrons are registered in the NRT detector while the gamma-rays emitted after neutron capture are recorded by the NRCA detector array. 69

63 Example

64 73

65 Black boxes are manifactured by archeaologists and then given to researcher. The archeaologists are the only one to know the material inside and how they are arranged. Combined use or radiography, tomography and diffraction allow to reconstruct what is inside.

66 75

67 76

69 The Baptistery, San Giovanni in Florence 78

70 79

1. The advanced deterioration state of the mercury-amalgam gilded sculptures suggested specific strategies for urgent restoration, especially addressing suitable cleaning treatments. 2.

71 1. The advanced deterioration state of the mercury-amalgam gilded sculptures suggested specific strategies for urgent restoration, especially addressing suitable cleaning treatments. 2. The gilding is also covered by encrustations due to a mixture of corrosion products and deposits (gypsum, quarts, feldspars, carbon, etc.) as a result of the interaction with the outdoor environment. 3. As a consequence oxide and salt layers constitute the current bed of the gold layer, requiring special attention from a restoration point of view. 80

72 81

73 82

74 83

75 84

76 85

77 86

78 Results of the analysis did not show any chlorine in the areas treated with chemical agents. Chlorine was instead detected in area treated with laser ablation. Copper Chlorine is a dangerous compound for the gilding since it forms excrescences. 87

79 Radiography with cold neutron showed the presence of an hole or of a material with less neutron absorption material. 88

80 89

81 90

$Ghiberti Heads mounted on the ENGIN-X diffractometer at the ISIS neutron$

82 Laser-scan of the samples and definition of the measurement points for the Ghiberti Heads mounted on the ENGIN-X diffractometer at the ISIS neutron source. 91

83 92

84 93

85 94

86 The different shapes of the peaks observed in the measurements are due to working processes: this is the proof that Ghiberti made a rifusion of one of the head. 95

87 96

88 97

89 98

90 99

91 101

92 Results from a Neutron Resonance Imaging experiment 103

93 Results from a Neutron Resonance Imaging experiment 104

94 105

95 107

Progetto per l'applicazione dei Neutroni Alla Ricerca in Elettronica e Archeometria is financed by CNR within the Agreement concerning collaboration in scientific research at the spallation neutron

96 Progetto per l'applicazione dei Neutroni Alla Ricerca in Elettronica e Archeometria is financed by CNR within the Agreement concerning collaboration in scientific research at the spallation neutron source ISIS signed between CNR and the STFC (Science Technology Facility Council). The project team, an Italian-British collaboration, aims, by 2014, to deliver at ISIS two instruments : IMAT, a Neutron Imaging diffractometer and CHIPIR, an instrument for Chip Irradiation. 108

98 110

99 Criteria for Research Infrastructure within FP7 111

100 112

101 113

102 114

103 115

Neutron Imaging at Spallation Neutron Sources

Neutron Imaging at Spallation Neutron Sources E.H. LEHMANN, A. KAESTNER Paul Scherrer Institut, Deptm. Spallation Neutron Source, Switzerland OUTLINE 1. Introduction: Motivation for Neutron Imaging 2.