  We study the topological structure of the SU(2) vacuum at zero temperature:
topological susceptibility, size, shape and distance distributions of the
instantons. We use a cooling algorithm based on an improved action with scale
invariant instanton solutions. This algorithm needs no monitoring or
calibration, has an inherent cut off for dislocations and leaves unchanged
instantons at physical scales. The physical relevance of our results is checked
by studying the scaling and finite volume dependence. We obtain a
susceptibility of (200(15) MeV)^4. The instanton size distribution is peaked
around 0.43fm, and the distance distribution indicates a homogeneous, random
spatial structure.
