[Gate-users] Does anyone know the penelope package for gate?

[张辉]

Hi everyone:
            This paper(A microCT X-ray head model for spectra generation with Monte Carlo simulations;R. Taschereau, a, , P.L. Chowa, J.S. Choa and A.F. Chatziioannoua

) mentioned the penelope package for gate to implement more precisely the interaction of low-energy electrons, but I haven't found this package in gate source code.Does anyone know how to get this code? 
            Thanks a lot.