Spatial origin of the neutron-induced background in the JET tangential gamma ray spectrometer

The JET tangential gamma ray diagnostic had several key functions, mainly alpha particle detection, runaway electron monitor and recently fusion power estimation. All these measurements are affected by a common background, which can complicate signal detection and whose origin is not yet fully understood. A method to simulate such a background has previously been proposed, however it does not address the spatial origin of the background nor the isotopes responsible for its generation. In this work, we combine simulation tools, including MCNP, with analytical codes to better understand the sources of the background measured with the JET tangential gamma ray diagnostic. The role of the gamma ray flux produced in the tokamak central column is analysed in detail and its correlation with the detected gamma ray background is found.