MULTIDISK NEUTRON VELOCITY SELECTORS

Helical multidisk velocity selectors used for neutron scattering applications have been analyzed and tested experimentally. Design and performance considerations are discussed along with simple "planation of the basic concept. A simple progression is used for the inter-disk spacing in the "Rosta" design. Ray tracing computer investigations are presented in order to assess the "coverage" (how many absorbing layers are stacked along the path of "wrong" wavelength neutrons) and the relative number of neutrons absorbed in each disk (and therefore the relative amount of gamma radiation emitted from each disk). We discuss whether a multidisk velocity selector can be operated in the "reverse" configuration (i.e. the selector is turned by 180-degrees around a vertical axis with the rotor spun in the reverse direction). Experimental tests and calibration of a multidisk selector are reported together with evidence that a multidisk selector can be operated in the "reverse" configuration.