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Proceedings Paper

Design, assembly, and testing of the neutron imaging lens for the National Ignition Facility
Author(s): Robert M. Malone; Brian C. Cox; Valerie E. Fatherley; Brent C. Frogget; Gary P. Grim; Morris I. Kaufman; Kevin D. McGillivray; John A. Oertel; Martin J. Palagi; William M. Skarda; Aric Tibbitts; Carl H. Wilde; Mark D. Wilke
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Paper Abstract

The National Ignition Facility will begin testing DT fuel capsules yielding greater than 1013 neutrons during 2010. Neutron imaging is an important diagnostic for understanding capsule behavior. Neutrons are imaged at a scintillator after passing through a pinhole. The pixelated, 160-mm square scintillator is made up of 1/4 mm diameter rods 50 mm long. Shielding and distance (28 m) are used to preserve the recording diagnostic hardware. Neutron imaging is light starved. We designed a large nine-element collecting lens to relay as much scintillator light as reasonable onto a 75 mm gated microchannel plate (MCP) intensifier. The image from the intensifier's phosphor passes through a fiber taper onto a CCD camera for digital storage. Alignment of the pinhole and tilting of the scintillator is performed before the relay lens and MCP can be aligned. Careful tilting of the scintillator is done so that each neutron only passes through one rod (no crosstalk allowed). The 3.2 ns decay time scintillator emits light in the deep blue, requiring special glass materials. The glass within the lens housing weighs 26 lbs, with the largest element being 7.7 inches in diameter. The distance between the scintillator and the MCP is only 27 inches. The scintillator emits light with 0.56 NA and the lens collects light at 0.15 NA. Thus, the MCP collects only 7% of the available light. Baffling the stray light is a major concern in the design of the optics. Glass cost considerations, tolerancing, and alignment of this lens system will be discussed.

Paper Details

Date Published: 3 September 2010
PDF: 15 pages
Proc. SPIE 7793, Optical System Alignment, Tolerancing, and Verification IV, 77930D (3 September 2010); doi: 10.1117/12.860756
Show Author Affiliations
Robert M. Malone, National Security Technologies, LLC (United States)
Brian C. Cox, National Security Technologies, LLC (United States)
Valerie E. Fatherley, Los Alamos National Lab. (United States)
Brent C. Frogget, National Security Technologies, LLC (United States)
Gary P. Grim, Los Alamos National Lab. (United States)
Morris I. Kaufman, National Security Technologies, LLC (United States)
Kevin D. McGillivray, National Security Technologies, LLC (United States)
John A. Oertel, Los Alamos National Lab. (United States)
Martin J. Palagi, National Security Technologies, LLC (United States)
William M. Skarda, National Security Technologies, LLC (United States)
Aric Tibbitts, National Security Technologies, LLC (United States)
Carl H. Wilde, Los Alamos National Lab. (United States)
Mark D. Wilke, Los Alamos National Lab. (United States)


Published in SPIE Proceedings Vol. 7793:
Optical System Alignment, Tolerancing, and Verification IV
José Sasián; Richard N. Youngworth, Editor(s)

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