Identification of Uxo Using the Associated Particle Neutron Time-of-flight Technique, Final Report

The publisher by accepting the manuscript for publication acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or any third party's use or the results of such use of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof or its contractors or subcontractors. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. 4 He reaction is used to emit , almost back-to-back, a 14 MeV neutron and an alpha particle. The direction and time-of-flight of the neutron is deduced from measuring the associated alpha particle. The time delay between alpha-and gamma-detections determines the depth of neutron interaction (inelastic scattering) in the target (UXO)………..... 3 Figure 2.1-1. Schematics of the modular system………………………………………………. 4 Figure 2.1-2 (a) The 6.5 cm diameter alpha detector face plate of the neutron generator was mated with a (b) 5 cm diameter fast XP2020 PMT……………………………… 5 Figure 2.1-3. The 12.7 cm diameter gamma-ray detector in the shielded housing…………...... 5 Figure 2.1-4. Schematics of the laboratory electronics for acquiring time and gamma-ray energy spectra……………………………………………………………………. 6 Figure 2.1.2-1.(a) No overlapping clutter-The bottle of water was outside the defined neutron cone (diameter 23 cm), (b) Overlapping clutter (side view), (c) Overlapping clutter (top view)…………………………………………………………………. 7 Figure 3.1-1. Known nanosecond delays introduced in the alpha detector STOP channel produced shifts in the TAC output corresponding to changes in the time difference between START and STOP signals. The time resolution of the main time peak was found to be 2ns(FWHM)………………………………………….. 8 Figure 3.1-2. The linear relationship yielded a slope of 0.41 ns/channel……………………….. 8 Figure 3.2-1. Time distribution …