### Résumé du preprint DAPNIA-07-126

DAPNIA-07-126
Piccolo Micromegas: first in-core measurements in a nuclear reactor
J. Pancin, S. Andriamonje, S. Aune, A. Giganon, Y Giomataris, J.F. Lecolley, M. Riallot, R. Rosa
An Accelerator Driven System (ADS) consists in the coupling of an accelerator
with a nuclear reactor. Such systems will need neutron detectors working in
a wide energy range and insensitive to X- and $\\gamma$-rays. Micromegas
technology has been proposed to achieve this goal. The ability of Micromegas
to detect neutrons over a wide energy range has already been demonstrated
and this detector is, under certain conditions, insensitive to $\\gamma$-rays.
A new Micromegas neutron detector called Piccolo Micromegas has been designed
to get integrated neutron fluxes on different energy domains. For the first time,
Piccolo Micromegas has been placed in the core of a nuclear reactor at Casaccia
in Italy. The configuration of the detector will be presented as well as its functioning
and the reasons of its insensitivity to $\\gamma$-rays. The results of the operation
of the detector will also be shown for low reactor power to high reactor power ans
some improvements will be suggested.