Measurement of the long-lived Al26 production cross section in the Al27(n,2n) reaction

Experimental data for the Al27(n,2n)26Al cross section have never been reported in the neutron energy range above 15 MeV, since the detection of the long-lived Al26 (half-life of 7.2×105 yr) necessitates an intense high-energy neutron source and highly sensitive detection method. We have measured the Al27(n,2n)26Al cross section in the energy range of 1436 MeV by using a semimonoenergetic neutron beam from the Be(p,n) reaction. The activity of Al26 was measured by the accelerator mass spectrometry method and we found that the cross section has a maximum value of 95 mb in the neutron energy range of 2024 MeV.