Proceedings Article | 26 October 2004
KEYWORDS: Scattering, Absorption, Sensors, Spherical lenses, Phase shifts, Aluminum, Signal attenuation, Image resolution, Cadmium, Refraction
Two neutron microscope imaging experiments were performed at the Center for Neutron Research, at the National Institute for Standards and Technology (NIST) on the NG-7 30-Meter Small Angle Neutron Scattering Instrument. The NIST neutron source wavelength could be varied from 5 Å to 20 Å, and the neutron bandwidth could be varied. For both microscope experiments the image resolution was 5.0 mm, and was determined and limited by the NG-7 neutron detector’s 5.0 mm pixel size. The image acquisition times were set to 300 sec. In the first experiment the neutron source wavelength was set to 5 Å with an 11% bandwidth. A simple microscope with a 22.6x magnification, employing a compound refractive lens, composed of 201 aluminum (Al) biconcave lenses, was used to image a slit array in Cadmium (Cd) foil, located 139 cm downstream of the source. The Cd slit array consisted of 0.8 mm wide slits separated by 0.8 mm wide slats. The Al CRL had 1.98 mm radius of curvature, a 3.9 mm aperture, and a measured 1.2 cm field of view (FOV). An 85 lens version of this Al CRL had a measured 2.3 cm FOV and 9.4
x magnification, and was used to image at rat paw. The Cd slit array was placed upstream of the aluminum CRL at 74.5 cm object distance. In the second NIST experiment the neutron source wavelength was set to 8.5 Å with a 10% bandwidth. A simple microscope with a 22.5x magnification, employing a compound refractive lens, composed of 100 MgF2 biconcave lenses, was used to image materials and specimens containing hydrogen, whose main contrast mechanism for neutrons is incoherent scattering. The MgF2 CRL had a measured 2.4 cm FOV. The hydrogen-rich material imaged was a polypropylene (hydrogen-rich) grid, and the biological specimens were a scorpion, a rat paw, and a plant leaf, and they were situated 122 cm downstream of the source, and 78 cm upstream of the MgF2 CRL.
