International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators

4-8 May 2009, Vienna

New Developments in Pulsed Fast-Neutron Transmission Spectroscopy and Imaging

Ilan Mor¹, David Vartsky¹, Doron Bar¹, Gennady Feldman¹, Mark B. Goldberg¹, Volker Dangendorf², Kai Tittelmeier², Mathias Weierganz², Ronald Lauck², and Benjamin Bromberger²

¹Electro-Optics Division, Soreq Nuclear Research Cente Yavne, Israel
²Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany

Corresponding Author: ilmor@soreq.gov.il

Fast-Neutron Transmission Spectroscopy (PFNTS) is a radiographic imaging method that exploits the isotopespecific energy-dependence of total neutron cross sections to measure elemental distributions in inspected objects. Fast-neutron transmission, as opposed to X-ray transmission, depends only weakly on absorber Z and thus, neutrons readily penetrate high-Z materials. In particular, the method is well suited to quantitative measurements of the elemental distributions of light elements, such as C, N and O, even if these are embedded in complex matrices of high-Z materials. This is advantageous, since the latter would strongly attenuate low-E (sub-MeV) X-rays and γ-rays. Moreover, more penetrating electro-magnetic radiation, namely, high-E (few- MeV) X-rays and γ-rays, would fail to provide contrast for low Z-elements. On these grounds, PFNTS is considered to be a very promising method for fully-automatic detection and identification of explosives concealed in luggage and cargo.

In the late 1990s, Tensor Technology Inc. constructed an advanced PFNTS evaluation prototype. In a comprehensive series of blind tests, this system demonstrated the power of the method for detecting bulk explosives. However, its poor performance in detecting thin-sheet explosives and the relatively high false-alarm rates indicated that significant improvements on the detector side were called for, particularly with regard to spatial resolution, which was no better than several centimetres.

In this contribution we present the concept of a high-spatial-resolution fast-neutron imaging system with multiple-energy TOF-spectrometry capability. This is a further development of our Time-Resolved Integrative Optical Neutron detector (TRION), which, in its present version, is able to capture simultaneously up to 8 image frames at different neutron energies. A 4-energy TRION variant will be evaluated in the fast-neutron beam at the PTB accelerator facility in December 2008. Updated results on its position resolution, contrast sensitivity and elemental imaging capability will be presented.

[1] I. Mor, MSc Thesis, 2006, available: http://jinst.sissa.it/theses/2006_JINST_TH_002.jsp
[2] or: V. Dangendorf et al, Nucl. Instr. and Meth. A 535, p. 93, 2004