atw International Journal for Nuclear Power | 04.2020

atw Vol. 65 (2020) | Issue 4 ı April
Radiation in Art and Cultural Heritage
Frank Meissner and Andrea Denker
225
1 Introduction Art objects like paintings or sculptures represent a considerable part of our history. Besides the
works of art that survived, further remnants are considered of major importance to understand the development of
mankind, like archaeological artefacts. All these objects – art and cultural heritage – give insight into the past and are
essential archives to understand our history. The objects themselves are conserved and studied by specialists, based on
classical knowledge and experience of art historians or archaeologists, but more and more supported by natural sciences
and technical investigation methods. The application of ionising radiation in art history, archaeology or palaeontology
is less known, but represents an important branch of the methods when it comes to the analysis of material composition
or imaging techniques of historically valuable objects. Nuclear methods and X-ray technologies are the most important
applications because of their quasi non-destructive features and their macroscopic to microscopic range of the
interactions with the object. Depending on the questions to be answered, one can imagine to introduce various
radiations from nuclear reactors, accelerators, spallation sources or X-ray generators. In this paper, a few selected
examples are presented to give brief insight into the use of reactor neutrons and X-rays in art and cultural heritage and
the results that can be obtained.
2 Methods and results
Nuclear methods and X-ray applications
have found entrance into the
investigation of art and cultural
heritage objects. Worldwide, several
institutes have launched research projects
or even founded working groups
in order to use reactor neutrons,
accelerator particle beams or X-rays in
the research of paintings or historical
artefacts. Many of these projects are
spin-offs from material testing and
material studies in solid state physics.
Results are presented at conferences
dedicated to the specific research
like the international “Synchrotron
Radiation and Neutrons in Art and
Archeology” Conference [1], connecting
nuclear physicists with e.g.
art historians, conservators, archaeologists
and paleontologists. Many of
the non-destructive testing methods
in material sciences are applicable to
art and cultural heritage, however,
two important constraints have to be
kept in mind.
First, it is evident that the use of
particles from accelerators or reactors
must be restricted to pure research or
very limited numbers of specific projects
since the technical effort for the
production of the radiation and the
facilities needed for their application
is very high. Besides nuclear reactors,
this is also valid for synchrotron facilities
which are well suited to produce
high quality X-rays for such investigations
and usually operate dedicated
beamlines.
Second, important samples in art
and cultural heritage are unique and
irreplaceable. Owners and conservators
might therefore be reluctant to
offer them to research institutes for
such studies, unless there is close
cooperation and trust. Even if an
object leaves a museum or conservatory
site, considerable efforts and
costs for appropriate transportation
and insurance have to be taken into
account and the correct handling of
the objects within the conservatory
parameters always requires specialist
knowledge.
These constraints are usually not
limiting in the case of X-ray investigations
which take place on-site using
designated equipment like X-ray
generator tubes operated by museums
or mobile X-ray devices from external
service providers. Such X-ray studies,
in particular with the up-to-date hardware
and software, cover a large
fraction of the issues questioned by
the experts and are therefore the
first choice when it comes to imaging
or elemental analysis with X-ray
fluorescence.
Imaging methods with neutrons
are usually complementary to X-ray
imaging techniques, so each method
adds specific results because of the
different interaction mechanisms of
neutrons and X-rays in matter. Therefore,
the neutron results can be well
compared with those obtained by
X-rays [2,3,4,5,6].
Neutrons have no charge and
therefore exhibit a higher penetration
depth in matter as compared to other
particles and as compared to X-rays. In
particular, they can pass easily many
centimeters of dense materials like
iron, copper or lead, while their interaction
with light nuclei is larger and
thus scattering and attenuation is
higher in typical organic matrices of
elements like hydrogen, carbon, nitrogen
and oxygen. Besides, neutrons
may also interact with nuclei of the
elements in materials allowing activation
reactions. In this case, the specific
cross sections have to be taken into
account, which will depend on the
energy of the neutrons and the specific
nuclei they interact with. Reactor
neutrons offer the option to use fast
neutrons as well as thermal neutrons
with their different behaviour in
matter [3]. Neutrons have been used
in material sciences since many
decades and the use in art and cultural
heritage, as a later development, is
based on the experience therefrom.
Three methods are widely used, these
are:
p Neutron radiography/tomography,
which produces a twodimensional
or even threedimensional
image by detecting
the images revealed by absorbed
and scattered neutrons,
p Neutron activation analysis (NAA),
which is a method very sensitive to
the elemental composition of the
sample, and
p Neutron activation radiography
(NAR), which reveals images of the
distribution of activation products
by autoradiography.
For such studies, it is sometimes
possible to use accelerators for the
required neutron production, but
many specialists rely on nuclear
fission sources, which are represented
by reactors with dedicated beamlines
and defined neutron properties. In
Germany, the neutron source FRM-II
in Munich, the research reactor TRIGA
in Mainz and the (now shutdown)
research reactor BER-II in Berlin are
known for their neutron studies in art
and archaeology, some examples can
be found in [3,5,6,7].
For instance, the neutron activation
radiography (NAR) of a painting
is capable of analysing different paint
layers and the painting support. In
RESEARCH AND INNOVATION
Research and Innovation
Radiation in Art and Cultural Heritage ı Frank Meissner and Andrea Denker