1 / 19

Novel Concept for a Directional Fast Neutron Detector

Novel Concept for a Directional Fast Neutron Detector. D. Stuenkel, Ph.D R. Wood, Ph.D, PE Trinity Engineering Associates, Inc. Abstract.

barr
Download Presentation

Novel Concept for a Directional Fast Neutron Detector

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Novel Concept for a Directional Fast Neutron Detector D. Stuenkel, Ph.D R. Wood, Ph.D, PE Trinity Engineering Associates, Inc.

  2. Abstract A directional fast neutron detector having alternating layers of a hydrogenous non-scintillating material for generating recoil protons, a non-hydrogenous scintillating material for generating scintillation photons, and a non-hydrogenous non-scintillating barrier material has been proposed. Neutrons are detected if the recoil protons they create deposit part of their energy in a layer of scintillating material, but are not detected if the recoil proton loses all its energy in the nonscintillating hydrogenous layer and/or barrier layer. The composition and thickness of the layered materials can be varied in order to reduce the probability that neutrons from large angles will be detected or to prevent their detection all together. Selecting layered materials that have similar indices of refraction and are transparent to the scintillation light produced facilitates light collection and minimizes the requirements for signal processing and data analysis. This concept, if proven feasible, could lead to the development of compact, relative easy to use, directional neutron detectors for use in locating and monitoring special nuclear materials and other sources of fast neutrons.

  3. Outline of Presentation • Introduction • Description and Theory • Preliminary Results • Applications • Summary and Conclusions

  4. Neutron-Proton Scattering • Neutrons elastically scatter off protons transferring a portion of their kinetic energy to the proton, resulting in a recoil proton. • The energy of the recoil proton depends on the energy of the incident neutron and the scattering angle.

  5. Proton Range

  6. Detector Description The detector is made from three different types of layers • Hydrogenous Non-Scintillating Material • Non-Hydrogenous Scintillating Material • Non-Hydrogenous Non-Scintillating Material Materials with the following properties should be selected • All materials should be transparent to scintillation light and have similar indices of refraction • Besides hydrogen, elements with high fast neutron cross sections should be avoided • Materials need to available as thin layers (10-100s of mm thick)

  7. Intrinsic Directionality

  8. Selecting the Layer Thicknesses • The total thickness of the hydrogenous layer and the second barrier layer is equal to the range of a 1 MeV proton in plastic. • The total thickness of the scintillating layer and the second barrier layer is equal to the range of a 1 MeV proton in glass. • The thickness of the second barrier is equal to the range of a 1 MeV proton in glass.

  9. Geometric Directionality The response of a detector to a monodirectional radiation field will usually depend somewhat on its shape and its orientation in the field. • Geometric directionality is greater for larger detectors • Geometric directionality is much greater when one dimension (i.e. diameter) is much larger than another (i.e. length)

  10. Geometric Directional Response

  11. Preliminary Results Results are shown in the following slides for a detector consisting of the following materials: • Barrier layers of alternating thickness with one layer 15 mm thick and the other between 1 and 12 mm thick, modeled as quartz (SiO2) • A hydrogenous layer between 8 and 19 mm thick, modeled as polystyrene (CH) • A scintillating layer between 3 and 14 mm thick, modeled as quartz (SiO2)

  12. Intrinsic Directionality (1 of 2)

  13. Intrinsic Directionality (2 of 2)

  14. Probabilities vs. Barrier Thickness

  15. Directional Resolution vs. Barrier Thickness

  16. Absolute Directionality

  17. Potential Advantages of Detector • Could be made small and rugged for field applications • Can be used with existing photomultiplier tubes and electronics • Lower background and greater sensitivities than homogenous detectors of similar size • The composition and thickness of the layered materials can be varied in order to reduce the probability that neutrons from large angles will be detected or to prevent their detection all together.

  18. Applications Directional fast neutrons have a number of potential applications, including • Locating sources of fast neutrons and monitoring sources of fast neutrons • Monitoring of SNM at nuclear facilities under safeguards regimes • Detecting sources of fast neutrons, including SNM, in containers and packages being scanned

  19. Questions or comments?

More Related