Neutron imaging system established at rochester (NY) evaluation of the neutrons gamma signal noise ratio

摘要

Within the framework of the CEA/DOE collaboration, an experimental campaign took place in Rochester (N Y in U.S.A.), on the laser installation OMEGA. The aim of this compaign was to test a neutron imaging system. The purpose of this equipment is to form the image of the neutron source which is created by inertial confinement fusion of a deuterium-tritium mixture, in order to determine the space distribution of the emission of the neutrons. A neutron imaging device, based on the method known as "Penumbral Imaging" including a pinhole, a scintillator, a device of transport of image, an image intensifier (Micro Chanel Plate) and a CCD array, was studied at C. E. A. The goal of this report is to study, on one hand, the schielding of the CCD againts the neutrons of the source and the gammas created at the chamber wall due to direct irradiation and, on the other hand, to evaluate the level of the interfering signal neutrons and gamma diffused by the environment. This interfering signal decreases the dynamics of measurement and increases the signal noise ratio. It is thus important to control it well. All calculations were made using the code Monte Carlo MCNP.