A Transparent Detector for n_TOF Neutron Beam Monitoring

In order to obtain high precision cross-section measurements using the time-of-flight technique, it is important to know with good accuracy the neutron fluence at the measuring station. The detector dedicated to these measurements should be placed upstream of the detectors used for capture and fission cross-section measurements. The main requirement is to reduce the material of the detector as much as possible, in order to minimize the perturbation of the neutron beam and, especially, the background produced by the device itself. According to these considerations, a new neutron detector equipped with a small-mass device based on MicroMegas ``Micro-bulk{''} technology has been developed as a monitoring detector for the CERN n\_TOF neutron beam. A description of the different characteristics of tins innovative concept of transparent detector for neutron beam monitoring is presented. The result obtained in the commissioning of the new spallation target of the n\_TOF facility at CERN is shown, compared with simulations performed with the FLUKA code.