NEURAL - a tracking detector for neutron-induced reactions of astrophysical importance

Observations from gamma ray telescopes indicate that most of the galactic 26Al originates in massive stars. Several sites have been discussed for its production, including proton burning in the winds of very massive stars, and the later, explosive burning stages of these stars. Observations from the RHESSI and INTEGRAL missions currently seem to point to the latter scenario. In the advanced burning stages of massive stars the presence of neutrons becomes an important factor in nuclear reaction networks, so in addition to the 26Al(p,γ)27Si reaction the neutron capture reactions 26Al(n,p)26Mg and 26Al(n,α)23Na can lead to the destruction of 26Al, and thus alter the observed 26Al abundance. NEURAL is a detector design to measure the excitation functions of these reactions over a wide range of energies. 26Al targets implanted at TRIUMF will be exposed to a pulsed neutron beam at the neutron time-of-flight facility at LANSCE (Los Alamos Neutron Science CEnter). NEURAL is designed to detect all charged reaction products, combining a time projection chamber for the heavy ions, and Si detectors for the light particles mounted around the target. A first prototype has been built and partially tested at TRIUMF and LANSCE in December 2009.