| S. Panebianco,O. Bringer, P. Bokov, S. Chabod, F. Chartier, E. Dupont, D. Dore, X. Ledoux, A. Letourneau, L. Oriol, A. Prevost, D. Ridikas, J.-C. Toussaint |
The MEGAPIE project is one of the key experiments towards the feasibility
of Accelerator Driven Systems. On-line operation and post-irradiation analysis
will provide the scientific community with unique data on the behavior of a
liquid spallation target under realistic irradiation conditions. A good neutronics
performance of such a target is of primary importance towards an intense neutron
source, where an extended liquid metal loop requires some dedicated verifications
related to the delayed neutron activity of the irradiated PbBi. In this paper we report
on the experimental characterization of the MEGAPIE neutronics in terms of the prompt
neutron (PN) flux inside the target and the delayed neutron (DN) flux on the top of it.
For the PN measurements, a complex detector, made of 8 microscopic fission chambers,
has been built and installed in the central part of the target to measure the absolute
neutron flux and its spatial distribution. Moreover, integral information on the neutron
energy distribution as a function of the position along the beam axis could be extracted,
providing integral constraints on the neutron production models implemented in transport
codes such as MCNPX. For the DN measurement, we used a standard 3He counter and
we acquired data during the start-up phase of the target irradiation in order to take
sufficient statistics at variable beam power. Experimental results obtained on the PN flux
characteristics and their comparison with MCNPX simulations are presented, together
with a preliminary analysis of the DN decay time spectrum. |
