Abelisation of the Neutron Profile Data at JET using Minimum Fisher Regularisation
Analyses and validation of data from neutron measurements present one of the key contributions of JET to research and development of diagnostic systems for fusion burning plasmas. In this respect the JET neutron profile monitor has a unique importance in deterimining spatial distribution of neutron emissivities. The monitor consist of two cameras, one with ten collimated channels, and another with nine collimated channels providing fan-shaped horizontal and vertical views, respectively. The spatial plasma coverage provided by the neutron profile monitor is adequate for inverse reconstructions, albeit with a rather scarce spatial resolution. Minimum Fisher Regularisation (MFR) has been recently applied at JET for the 2D tomographic reconstruction of the neutron emissivity. This contribution presents the latest extension of the algorithm that allows for emissivity profile reconstruction (abelisation) under the assumption of constant neutron emissivities along magnetic flux surfaces (i.e. full poloidal symmetry). This strong assumption, when realistic, allows for profile analyses even if neutron emissivities are low. The MFR abelisation principle is tested and validated on phantom functions, including simulations of emissivity evolution and random data noise. First analyses of experimental data are presented, with particular interest in their potential use for tritium transport studies.