JET neutron emissivity reconstruction using the Minimum Fisher Information method for 1 ms temporal resolution

Résumé fourni par la source

Abstract A tomography code based on the Minimum Fisher Regularisation method with a geometry description based on the field of view has been applied to reconstruct the neutron emissivity profiles from measurements performed in 2021 during the second JET deuterium-tritium campaign (DTE2). The Neutron Profile Monitor Upgrade installed at JET offers a unique opportunity for investigating the neutron emissivity in a full poloidal cross-section with unprecedented time resolution (~1 ms), thanks to the availability of digital data reprocessing and the high neutron emission that enables milisecond line-integrated raw data with low statistical error. Measurements of 14.1 MeV neutrons provided by the Bicron BC418 plastic scintillators installed in the JET neutron camera have been used.The analysis focuses on the effect of sawtooth crashes on the neutron emission profiles. Tomography results were compared with 1D reconstructions using two different methods and 10 ms time resolution. The use of the neutron camera data sampled at 1 ms enables the observation of hollowing of the neutron emissivity profiles during the sawtooth crash and their subsequent flattening.

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