  The London penetration depth was measured in optimally doped Ba0.6K0.4Fe2As2
crystals, with and without columnar defects produced by 1.4 GeV 208Pb
irradiation. The low temperature behavior of unirradiated samples was
consistent with a fully gapped superconducting state with a minimum energy gap
delta_min/(k_B T_C) = 1. Similar gap values were observed for irradiation
levels corresponding to mean column-column separations of 32 nm and 22 nm. At
very high irradiation levels (column-column separation of 10 nm) a T^2 power
law was observed below Tc/3, most likely due to elevated scattering. Neither
the location nor the sharpness of the superconducting transition was affected
by irradiation. The data provides evidence for an s+/- pairing state.
