  In the framework of the Neutronic and Nuclear Assessment Task Group of the
MEGAPIE experiment we measured the delayed neutron (DN) flux at the top of the
target. The measurement was proposed mainly for radioprotection purposes since
the DN flux at the top of the target has been estimated to be of the same order
of magnitude as the prompt neutron flux. Given the strong model-dependence of
DN predictions, the measurement of DN contribution to the total neutron
activity at the top of the target was thus desired. Moreover, this measurement
is complementary to the DN experiments performed at PNPI (Gatchina) on solid
lead and bismuth targets. The DN measurement at MEGAPIE was performed during
the start-up phase of the target. In this paper we present a detailed
description of the experimental setup and some preliminary results on decay
spectra.
