Speakers
Dr
Christian Stieghorst
(Maier-Leibnitz Center, Technical University Munich)
Mr
Eschly Jan Kluge
(Institute of Nuclear Physics, University of Cologne)
Description
**Introduction**
Thanks to the increase of more diverse and research dedicated neutron sources as well as advancements in digital recording techniques, the range of available spectroscopy and imaging methods utilizing neutrons has significantly expanded in recent years. Especially the relatively new Prompt Gamma Neutron Activation Analysis Imaging and Neutron Tomography (PGAI-NT), a method to obtain and effectively visualize ever-higher resolving position-sensitive spectroscopy data sets, shows promising results for material research and archeometry.
**The PGAI-NT method**
PGAI-NT is the combination of a position-sensitive three-dimensional extension of the Prompt Gamma Neutron Activation Analysis (PGNAA) of a sample and the sample’s Neutron Tomography (NT) for the purpose of an easy assignment and clear representation of spectroscopy data. The via position-sensitive PGNAA obtained distribution of the various elements within a sample is visualized by differently colored voxels, hence the term PGA-Imaging. The relative abundance of a specific element itself is visualized by different intensities of the color assigned. The resulting voxel-matrix is finally embedded into the tomography-volume of the bulk sample. A PGAI sub-volume of a sample is established by the intersection of the collimated neutron beam and the collimated field of view (FOV) of one or more gamma detectors positioned in 90 degrees to the beam.
**The Current Instrument**
Because PGAI-NT is a method-combination with a strived application area, it should be as user friendly and cost effective as possible. For this reasons we opted for an all-in-one instrument approach by conducting the NT recoding at the same instrument site. To quicker parallelize the elliptically tapered beam of the facility for PGAI, a boron-lead collimator with a 2x2 cm2 profile is used. The pinhole-aperture used in combination with said collimator is a 3 mm thick boron-carbid plate with a 2 mm diameter. The resulting beam profile at sample position has a flux of 1.34×10^9 /cm2s and a PGAI-resolution determining diameter of 3.2 mm. The previously used gamma collimator was replaced by two 50 mm longer heavy-lead collimators with a conical 2x8 mm2 profile. In this way, the γ-energy dependent resolution in beam direction was improved by an average of 42%. The measuring time can be reduced significantly by using two collimated detectors simultaneously. The parallel-beam tomography flight-tube system was replaced by a cone-beam setup, realized by introducing a pinhole-aperture into the focal point of the even further elliptically tapered beam. The boron-carbide pinhole-aperture for this usage is of 3 mm diameter and thickness, resulting in a 47% greater L/D ratio of 247(2). The current 5.5 megapixel camera in combination with a 100 μm LiFZnS(Ag)P scintillator achieves a 130% improved object resolution of 175(4) μm. The reconstruction under cone-beam algorithms resolves now 140 μm details for negative and 40 μm details for positive contrast differences.
Primary author
Mr
Eschly Jan Kluge
(Institute of Nuclear Physics, University of Cologne)
Co-authors
Dr
Christian Stieghorst
(Maier-Leibnitz Center, Technical University Munich)
Prof.
Jan Jolie
(Institute of Nuclear Physics of the University of Cologne)
Dr
Zsolt Révay
(Maier-Leibnitz Center, Technical University of Munich)
