Add taur
taur(rho=0.4) used as averaged proxy in B. Labit 2023 IBL paper Should add also volume averaged tau_R, as used in S. Van Mulders DEMO ramp-down paper
taur(rho=0.4) used as averaged proxy in B. Labit 2023 IBL paper Should add also volume averaged tau_R, as used in S. Van Mulders DEMO ramp-down paper