Beryllium-10 (10Be)

Beryllium-10 (10Be) is a rare long-lived radio-isotope of Beryllium. Beryllium-10 is called a cosmogenic nuclide, because it is created by energetic cosmic rays impacting matter in a fission reaction, called spallation.
half-life (λ) 1.36 +/- 0.07 My1
Protons 4
Neutrons 6
AMS Target Material beryllium oxide

1 Nishiizumi et al, NIMB B258 p.403, 2007.