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You searched for subject:(Lithium foil). Showing records 1 – 2 of 2 total matches.

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Kansas State University

1. Nelson, Kyle. An investigation of aerogels, foams, and foils for multi-wire proportional counter neutron detectors.

Degree: PhD, Department of Mechanical and Nuclear Engineering, 2013, Kansas State University

The 3He gas shortage for neutron detection has caused an increase in research efforts to develop viable alternative technologies. 3He neutron detectors cover areas ranging from 10–1000 cm2 in cylindrical form factors and are ideal for many nuclear applications due to their high intrinsic thermal neutron detection efficiency (> 80%) and gamma-ray discrimination (GRR ≤ 1 x 10-6) capabilities. Neutron monitoring systems for nuclear security applications include Radiation Portal Monitors (RPM’s), backpack, briefcase, and hand-held sensors. A viable replacement technology is presented here and compares three neutron detectors, each with different neutron absorber materials, to current 3He standards. These materials include Li and/or B silica aerogels, LiF impregnated foams, and metallic Li foils. Additionally, other neutron absorbing materials were investigated in this work and include LiF coated Mylar, B foils, BN coated carbon foam, and BN coated plastic honeycomb. From theoretical calculations, the Li foil material showed the greatest promise as a viable 3He alternative, thus a majority of the research efforts were focused on this material. The new neutron detector was a multi-wire proportional counter (MWPC) constructed using alternating banks of anode wires and 95% enriched 6Li foils sheets spaced 1.63 cm apart. In total, six anode banks and five layers of foil were used, thus an anode wire bank was positioned on each side of a suspended foils. Reaction products from the 6Li(n,α)3H reaction were able to escape both side of a foil sheet simultaneously and be measured in the surrounding gas volume concurrently. This new concept of measuring both reaction products from a single neutron absorption in a solid-form absorber material increased the intrinsic thermal neutron detection efficiency and gamma-ray discrimination compared to coated gas-filled detectors. Three different sizes of Li foil MWPC neutron detectors were constructed ranging from 25–1250 cm2 and included detectors for RPM’s, backpacks, and hand-held systems. The measured intrinsic thermal neutron detection efficiency of these devices was approximately 54%, but it is possible to exceed 80% efficiency with additional foils. The gamma-ray discrimination abilities of the detector exceeded 3He tubes by almost three orders of magnitude (GRR = 7.6 x 10-9). Advisors/Committee Members: Douglas S. McGregor.

Subjects/Keywords: Neutron detector; Lithium foil; Foam; Multi-wire proportional counter; Aerogel

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Nelson, K. (2013). An investigation of aerogels, foams, and foils for multi-wire proportional counter neutron detectors. (Doctoral Dissertation). Kansas State University. Retrieved from http://hdl.handle.net/2097/35278

Chicago Manual of Style (16th Edition):

Nelson, Kyle. “An investigation of aerogels, foams, and foils for multi-wire proportional counter neutron detectors.” 2013. Doctoral Dissertation, Kansas State University. Accessed August 24, 2019. http://hdl.handle.net/2097/35278.

MLA Handbook (7th Edition):

Nelson, Kyle. “An investigation of aerogels, foams, and foils for multi-wire proportional counter neutron detectors.” 2013. Web. 24 Aug 2019.

Vancouver:

Nelson K. An investigation of aerogels, foams, and foils for multi-wire proportional counter neutron detectors. [Internet] [Doctoral dissertation]. Kansas State University; 2013. [cited 2019 Aug 24]. Available from: http://hdl.handle.net/2097/35278.

Council of Science Editors:

Nelson K. An investigation of aerogels, foams, and foils for multi-wire proportional counter neutron detectors. [Doctoral Dissertation]. Kansas State University; 2013. Available from: http://hdl.handle.net/2097/35278


Kansas State University

2. Edwards, Nathaniel Scott. ⁶Li-based suspended foil microstrip neutron detectors.

Degree: PhD, Department of Mechanical and Nuclear Engineering, 2018, Kansas State University

The low natural abundance and supply shortage of ³He has resulted in an increase in the cost of ³He. The increase in cost of ³He proportional counters has motived the development of low cost, high efficiency, low gamma-ray sensitivity alternative technologies. A recently developed alternative technology is the ⁶Li-based suspended foil microstrip neutron detector (SFMND) that combines the neutron-conversion and gamma-ray discrimination capabilities of ⁶Li foils with the mechanical robustness and electrical capabilities of microstrip electrodes. SFMNDs differ from Li-foil multi-wire proportional counters because the anode wires are replaced by a single microstrip electrode that improves the mechanical robustness, reduces the microphonic sensitivity, and allows for more ⁶Li foils to be incorporated within a smaller form factor. The first-ever SFMNDs containing one and five 96%-enriched, 75-µm thick ⁶Li foils were fabricated using a silicon microstrip electrode. Neutron-sensitivity testing was performed yielding measured intrinsic thermal-neutron detection efficiencies, εth, of 4.02 ± 0.04% and 14.58 ± 0.11%, respectively. High electrode capacitance and gain instability were exhibited by the silicon microstrip electrode during neutron-sensitivity testing that led to the search for an electrically-stable microstrip-electrode substrate. Schott Borofloat® 33 glass was identified as an electrically-stable substrate and microstrip electrodes were fabricated and characterized. The Schott Borofloat® 33 microstrip electrodes were electrically-stable for a minimum duration of time of approximately 23 hours and had capacitances over an order of magnitude less than the identically sized silicon microstrip electrodes. One- and five-foil SFMNDs were fabricated with a Schott Borofloat® 33 microstrip electrode. Using 96%-enriched, 75-µm thick ⁶Li foils, the one- and five-foil devices had maximum measured εth of 12.58 ± 0.15% and 29.75 ± 0.26%, respectively, with measured gamma-ray rejection ratios of 6.46 x 10⁻⁵ ± 4.32 x 10⁻⁷ and 7.96 x 10-5 ± 4.65 x 10-7 for a ¹³⁷Cs exposure rate of 50 mR hr⁻¹. Devices containing one, five, ten, and twenty 96%-enriched, 75-µm thick ⁶Li foils were simulated using MCNP6 and are theoretically capable of having εth of 18.36%, 54.08%, 65.43%, and 68.36%, respectively. The deviation between measured and simulated εth is suspected to occur due to the electric field strength distribution, electron attachment, microstrip-electrode capacitance, or any combination thereof and solutions for each of these suspected concerns are described. Advisors/Committee Members: Douglas S. McGregor.

Subjects/Keywords: Neutron detection; Radiation detection; Microstrip electrodes; Lithium foil; Device characterization; Gas-filled neutron detector

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Edwards, N. S. (2018). ⁶Li-based suspended foil microstrip neutron detectors. (Doctoral Dissertation). Kansas State University. Retrieved from http://hdl.handle.net/2097/39131

Chicago Manual of Style (16th Edition):

Edwards, Nathaniel Scott. “⁶Li-based suspended foil microstrip neutron detectors.” 2018. Doctoral Dissertation, Kansas State University. Accessed August 24, 2019. http://hdl.handle.net/2097/39131.

MLA Handbook (7th Edition):

Edwards, Nathaniel Scott. “⁶Li-based suspended foil microstrip neutron detectors.” 2018. Web. 24 Aug 2019.

Vancouver:

Edwards NS. ⁶Li-based suspended foil microstrip neutron detectors. [Internet] [Doctoral dissertation]. Kansas State University; 2018. [cited 2019 Aug 24]. Available from: http://hdl.handle.net/2097/39131.

Council of Science Editors:

Edwards NS. ⁶Li-based suspended foil microstrip neutron detectors. [Doctoral Dissertation]. Kansas State University; 2018. Available from: http://hdl.handle.net/2097/39131

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