Neutron Flux Unfolding through Foils

Xenon 135 currently has the largest known neutron capture cross sectional area. Because of this, it has a significant role it can play in nuclear physics. An important part in finding the neutron capture cross sectional area is the neutron flux. The neutron flux describes how many neutrons flow through some area in a certain period of time. This shows how many of the neutrons are fast and how many are thermal. Although there is an estimate of what neutron flux was used on the xenon, this was not completely accurate. In order to get the most accurate flux possible, neutron spectrum unfolding had to be performed on the flux. The first step in this process was to expose foils to the neutron beam along with the xenon. These “foils” were samples of elements that have known half lives, branching ratios, and energy peaks. In addition, the internal conversion coefficient, represented by alpha, was taken from the ENSDF data sheets. Mo-99, Zr-95, and Fe-59 were used as the foils in this experiment. After neutron irradiation, spectrums were counted, and Interspec graphs were produced. The known energy values were used to find the relevant peaks in these graphs, which provided the relevant peak areas. In addition to this, lifetime and realtime were taken from Interspec. This data was used to calculate the activity at the beginning of counting and then the end of irradiation. The end of irradiation will eventually be put into a code, which will unfold the spectrum; however, this step has not yet been completed.