Fundamental study for analysis of CN-NDP spectrum

Neutron Depth Profiling (NDP) is a nondestructive near surface technique that is used to measure concentration versus absolute depth of several isotopes of light elements in various substrates. The NDP technique was originally developed by Ziegler et al. in 1972. In NDP, a thermal or cold neutron beam passes through a material and interacts with certain isotopes that are known to emit monoenergetic-charged particles upon neutron absorption and a recoil nucleus. The charged particle (p, α or T) and the recoil ion lose their energy while traveling through the sample to the surface. The residual energies of charged particles can be measured with charged particle detector. And the difference between the known initial energy of the particle and its measured residual energy can be used to determine the particle depth of emission in the sample. A Cold Neutron Activation Station (CONAS) is being constructed at Korea Atomic Energy Research Institute (KAERI). At the CONAS, a Cold Neutron Depth Profiling (CN-NDP) facility is being developed for various applications of NDP technique. A picture of the NDP vacuum chamber placed at the end of the CG1 neutron beam guide and the measurement electronics are shown in Figure 1. For the NDP applications, the process of conversion energy spectrum of charged particle to concentration profile is required. In this study, the principle of the relation between the energy spectrum and the concentration profile is presented for the ideal case. And the development of analysis code for NDP spectrum is started