Wave-Function Amplitude Analysis of the ⁵He Resonance in the TT Neutron Spectrum

An understanding of the TT neutron spectrum is necessary for accurate modeling of neutron spectra as well as for analysis of experimental data from ICF implosions. The ⁵He resonance is an important component of the TT spectrum. Available OMEGA data suitable to study the ⁵He state include neutron time-of-flight spectra collected at three different ion temperatures. ¹ These data are used in a multi-step least-squares analysis that models the resonance line shape for the individual reaction branches involved in TT fusion including ⁵He (ground state) + n and ⁵He* (first excited state) + n. This analysis reveals a first excited state at ~2 MeV (Ref. 2) in ⁵He. The shape of the ⁵He resonance changes with ion temperature as expected and the width of each state is used to determine its lifetime.

¹ M. Gatu Johnson et al., “First Experimental Evidence of a Variant Neutron Spectrum from the T(T,2n)α Reaction at Center-of-Mass Energies in the Range of 16–50 keV,” submitted to Physical Review Letters.

² C. Wong, J. D. Anderson, and J. W. McClure, Nucl. Phys. 71, 106 (1965).