Focusing cold neutrons using capillary optics for analytical nuclear methods

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:191678

Chen, H; Sharov, V A; Mildner, D F.R. ^[1]

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1. National Inst. of Standards and Technology, Gaithersburg, MD (United States); and others

The authors demonstrate improved detection limits and lateral resolution for prompt gamma activation analysis (PGAA) by using a neutron focusing device to increase the neutron intensity. The neutron lens, made of glass fibers with hollow polycapillaries, was designed and constructed by X-Ray Optical Systems, Inc. It has been characterized and used for preliminary experiments at the PGAA station of the Cold Neutron Research Facility (CNRF) at NIST. The lens accepts a polychromatic cold neutron beam (wavelengths longer than 0.4 run) from a neutron guide 50 mm x 45 mm in cross section, and delivers a focused beam of 0.5 mm in diameter (full width at half maximum) at 52 mm from the exit of the capillaries. The average neutron current density at the focus within the FWHM is 80 times higher than that of the direct incident beam. Test samples of 2% gadolinium glass particles of size about 0.1 to 0.2 mm, and cylindrical glass samples of 0.5 mm and 1 mm in diameter containing 15 % boron have been scanned across the focal plane to determine the spatial response as well as the peak count rate. Results from both sets of measurements show promise for higher detection sensitivity on small samples, and for two-dimensional mapping of samples with lateral compositional variation. Problems associated with neutron background will be addressed.

• OSTI ID: 191678
• Report Number(s): CONF-941098--
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
COLD NEUTRONS
FOCUSING
GAMMA RADIATION
NEUTRON ACTIVATION ANALYSIS
NEUTRON BEAMS