  Studies attempting to probe the spatial configuration of the valence neutrons
in two-neutron halo nuclei using the technique of intensity interferometry are
described. Following a brief review of the method and its application to
earlier measurements of the breakup of 6He, 11Li and 14Be, the results of the
analysis of a high statistics data set for 6He are presented. The limitations
of the technique, including the assumption of incoherent emission in the
breakup and the sensitivity to the continuum states populated in the
dissociation rather than the ground state, are discussed.
