Determination of a neutron source position in an unknown homogeneous medium; the 2D case

The localisation of an unknown neutron source in various bulky homogeneous media was studied. For the planar case two ³He detectors on the opposite faces of a box were used. It is shown that the location of a single small neutron emitting source in a large box can be found to a better than 7% by using two neutron detectors positioned on parallel faces of the box, coplanar with the source. The localisation requires measurement of the count rate of both the unknown source (ratio of the count rates of the two detectors is R(x)) and an extra source positioned on one of the faces of the box (ratio of the count rates of the two detectors R(0)). The location of the neutron source is found according to the equation x = -a/2 · (1 - In[R(x)]/In[R(x)]) The localisation is based on the finding that the ratio of the count rates of the two detectors is an exponential function of the distance of the source from one of the detectors.