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| THIN FILM SERVICES / APPLICATION AREA |
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Thin Film Boride Compounds
example: large-area neutron/gamma detectors
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MATERIALS / APPLICATION AREA: Helicon has a long history in sputtered and evaporated compounds across a range of specialized refractory and ionic compounds, some of which have unique properties that are only now being realized in commercial sectors. This includes unique boride, carbide, nitride, and fluoride phases that separately require unique sets of process approaches in energetic plasma environments, if practical applications are to be achieved. In particular, boron/boride compounds typically represent limitations with regard to deposition stability, morphology, and resultant environmental reliability that we have addressed through extended R&D programs.
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FIGURE 1: Boride neutron absorber stacks fabricated by Helicon TFS and integrated into detector packages at Rapiscan Laboratories. The neutron detection spectrum from the 6-layered ionization chamber is plotted against a background spectrum. (King, et al)2
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EXAMPLE APPLICATION: We've conducted multiple collaborative development programs with well-known manufacturers in airport and seaport security for development of high-rate deposition of the most promising neutron-absorber materials for next-generation neutron detectors, including various thin film forms of boron and boron compounds in modified plasma sputtering, as well as very-high-rate lithium and lithium compounds deposited in activated reactive evaporation processes.
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FIGURE 2: A boron parallel plate ionization chamber concept is based on two layers of boron that capture the thermal neutron.Upon capture, two charged particles are emitted and ionize the gas creating free ions and electrons. The applied voltage sweeps the charges creating a signal. (King, et al)1
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FIGURE 3: Conceptual drawing of prototype chamber with the electronics box attached to the base-plate of the chamber. The circular disks are the boroncoated substrates.(King, et al) 1,2 |
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The threat of rogue, un-monitored use of fissile / nuclear materials is one of the primary concerns for the sustainability of modern society. The detection and monitoring of fissile/nuclear materials that are transported through air, sea, and land, is one of the few critical means that we, as human society, have available for the curtailing of nuclear threats. Nuclear threat detection utilizes imaging and non-imaging detectors that are capable of detecting sub-atomic particle emissions from fissile materials. These nuclear threat detectors utilize materials having a high scattering cross-section for neutrons, gamma rays, and other particles of interest. Such detectors typically take the basic form of either, essentially, planar or tubular ionization chambers. A large-area imaging detector that Helicon contributed to in collaborative work with Rapiscan Technologies Corporation, one of the foremost providers of seaport and airport security detection, is shown in Fig.4, below.
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FIGURE 4: Concept for achieving large-area detection:(a)a 10 cm x 10 cm unit cell detector;(b)a 10 by 10 tiled array of unit cells for 1 m 2 coverage;(c)several 1 m x 1 m arrays attached together in a foldable geometry for larger area coverage and greater transportability. (King, et al)1 |
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Our work includes multiple studies in high-rate deposition of neutron-absorber isotopes, including various thin film forms of boron and boron compounds, as well as very-high-rate lithium and lithium compounds deposited in activated reactive evaporation processes. When it comes to materials containing these preferred isotopes, we have considerable "skin in the game" with regards to designing, building, and performing development work, with both reactive and non-reactive vapor sources strategies, for both of the preferred, lithium and boron, neutron-absorbing materials. Some of our work in this field has been published, below.
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King, M J, Gozani T, Benetti R, Hilliard D B, Benetti ; Development of a Portable B-Based He Replacement Neutron Detector; IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 60, NO. 2, APRIL 2013
Michael J. King, Tsahi Gozani and Donald B. Hilliard ; Development of 10B-Based 3He Replacement Neutron Detectors ; Rapiscan Laboratories, USA ,Helicon Thin Film Systems, USA Applications of Nuclear Techniques; AIP Conf. Proc. 1412, 216-223 (2011); doi: 10.1063/1.3665317;© 2011 American Institute of Physics 978-0-7654-0986-6
issued US Patent 8963094, Composite gamma-neutron detection system; Gozani, King, Hilliard, Bendahan
WO2013116241; Interntional Pat. applns (pending), PCT/US2013/023684; Gozani, King, Hilliard, Bendahan |
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