Neutron signal transfer analysis

A new method called neutron signal transfer analysis has been developed for quantitative determination of hydrogenous distributions from neutron radio graphic measurements. The technique is based on a model which describes the detector signal obtained in the measurement as a result of the action of t hree different mechanisms expressed by signal transfer functions. The expli cit forms of the signal transfer functions are determined by Monte Carlo co mputer simulations and contain only the distribution as a variable. Therefo re an unknown distribution can be determined from the detector signal by re cursive iteration. This technique provides a simple and efficient tool for analysis of this type while also taking into account complex effects due to the energy dependency of neutron interaction and single and multiple scatt ering. Therefore this method provides an efficient tool for precise quantit ative analysis using neutron radiography, as for example quantitative deter mination of moisture distributions in porous building materials. A comparis on between neutron signal transfer analysis and conventional methods has be en made by simulating an experiment with a sample containing a known moistu re distribution by Monte Carlo calculation. By using the neutron signal tra nsfer method the error is less than 3%. Whereas the calibration curve metho d overestimates the moisture content by a factor in the range around 10% an d the exponential attenuation method underestimates the moisture content by a factor in the range of 2. (C) 1999 Published by Elsevier Science B.V. Al l rights reserved.