SURVEY MEASUREMENTS ON THE OPTIMALISATION OF THE SCATTERER SHAPE FOR A COLD NEUTRON SOURCE

摘要

The output of subthermal neutrons was measured for differently shaped lucite samples in a graphite stack which simulated a tangential beam hole of a reactor. The samples were cooled to liquid nitrogen temperature. The obtained values were normalized to the output of a circular slab by the introduction of a shape factor. The measurements show that an elliptical slab in the reflection position and a black body shaped scatterer have gain factors by 20 - 50 ％ higher than a circular scatterer of the same thickness. The usual gain factor, which is defined as the neutron output at high temperature to that at low temperature is for all shapes between 2.5 and 3.