title SIMILARITIES BETWEEN ION-IMPACT AND PHOTO-DOUBLE IONISATION OF HELIUM AT SMALL MOMENTUM TRANSFERS authors B. Bapat, R. Moshammer, S. Keller, W. Schmitt, A. Cassimi, L. Adoui, H. Kollmus, R. D\"orner, Th. Weber, K. Khayyat, R. Mann, J. P. Grandin, J. Ullrich affiliations Fakult\"at f\"ur Physik, Universit\"at Freiburg, 79104 Freiburg, Germany Institut f\"ur Theoretische Physik, Universit\"at Frankfurt, 60054 Frankfurt, Germany Centre Interdisciplinaire Recherche avec les Ions Lourds, 14040 Caen, France Institut f\"ur Kernphysik, Universit\"at Frankfurt, 60486 Frankfurt,Germany Gesellschaft f\"ur Schwerionenforschung, 64291 Darmstadt, Germany summary Double ionisation of helium by the impact of 100 MeV/u C$^{6+}$ ions has been studied in a kinematically complete experiment. For small momentum transfers, the electron angular distribution shows a pattern similar to that in photoionisation. Calculations in the Born approximation plus shake-off using a Hartree-Fock ground state wavefunction agree well with the oberved distributions if the interaction between the outgoing electrons is accounted for.