The displacement of B from substitutional lattice sites during irradiation with a high energy (650 keV) proton beam is measured by channelling analyses along the and using the 11 B (p, α) 8 Be reaction. The normalized B yield, χ, increases with the ion fluence and saturates at a value (χ F< 1) that depends on the channelling axis, being minimum for channelling along. Therefore, displaced B is not randomly located in the lattice. The displacement rate is shown to be consistent with a model involving Si interstitial–B interaction and to depend on the local Si self-interstitial production rate, rather than long range interstitial migration. This was demonstrated by comparing results from samples with and without a Si layer containing 1 at.% C (known to be a trap for interstitial Si) interposed between the B doped layer and the substrate. The B displacement rate does not change in this sample indicating that self-interstitials …