A series of upgrades have been undertaken at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, including the installation of a supercritical hydrogen moderator (T ' 20 K), which has boosted the flux of long-wavelength neutrons by over two orders of magnitude. In order to take advantage of the new capabilities, a 40 m-long small-angle neutron scattering (SANS) instrument has been constructed, which utilizes a mechanical velocity selector, pinhole collimation and a high-count-rate (>10 5 Hz) large-area (1 m 2 ) two-dimensional position-sensitive detector. The incident wavelength (), resolution (Á/), incident collimation and sample-to-detector distance are independently variable under computer control. The detector can be moved up to 45 cm off-axis to increase the overall Q range [<0.001 < Q = (4/)sin < 1 Å À1 , where 2 is the angle of scatter]. The design and characteristics of this instrument are described, along with examples of scattering data to illustrate the performance. research papers J. Appl. Cryst. (2012). 45, 990-998 George D. Wignall et al. Updates to GP SANS instrument at ORNL 997
The possibility of relatively fast neutron oscillations into a mirror neutron state is not excluded experimentally when a mirror magnetic field is considered. Direct searches for the disappearance of neutrons into mirror neutrons in a controlled magnetic field have previously been performed using ultracold neutrons, with some anomalous results reported. We describe a technique using cold neutrons to perform a disappearance and regeneration search, which would allow us to unambiguously identify a possible oscillation signal. An experiment using the existing General Purpose-Small Angle Neutron Scattering instrument at the High Flux Isotope Reactor at Oak Ridge National Laboratory will have the sensitivity to fully explore the parameter space of prior ultracold neutron searches and confirm or refute previous claims of observation. This instrument can also conclusively test the validity of recently suggested oscillation-based explanations for the neutron lifetime anomaly.
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