A Pulsed-Neutron Investigation of the Effect of Temperature on the Decay of a Thermal-Neutron Population in H₂O Ice

The pulsed-neutron method has been used with ice cylinders in the buckling range from 0.039 to 0.739 cm⁻² over temperatures between −5 and −85°C. The purpose was to determine whether there would be early establishment of an asymptotic neutron spectrum and, since this proved to be so, to measure the neutron diffusion parameters. The neutron decay data were analyzed by using a nonlinear least-squares fitting method with two exponential modes. The resulting diffusion parameters are compared with those found by other workers for H₂O at various temperatures, and the effect of the solid-liquid phase transition on the diffusion coefficient and diffusion cooling coefficient is discussed.