Preliminary calibration procedure for the Phase1 neutron and gamma-ray diagnostics of the Divertor Tokamak Test (DTT) facility

• Absolute calibration of DTT NAS & NYM with 252 Cf & 14 MeV compact neutron generator. • NAS: 4 vertical positions below each irradiation end, ≤1 % error on counts. • NYM: central-ring scan with 12 positions on equatorial plane, ≤3 % error on counts. • Expected count rates calculated combining MCNP fluxes & detector characteristics. • MCNP simulations optimize source placement and irradiation time for calibration. Neutron and gamma-ray diagnostics are of key importance for measuring neutron and gamma-ray yields, fluxes and neutron energy distribution in a tokamak. Their calibration is critical for accurate measurements in fusion devices such as the Divertor Tokamak Test (DTT) facility, to be constructed at Frascati in Italy. This paper presents the preliminary calibration procedure for the Neutron Yield Monitors (NYM) and Neutron Activation System (NAS) of this machine. Using neutron sources such as ²⁵²Cf and a Deuterium-Tritium compact neutron generator, the calibration process involves detailed MCNP simulations to optimize source placement and measurement duration. Drawing insights from other devices like the Joint European Torus and the Frascati Tokamak Upgrade, the paper explores various calibration scenarios to enhance experimental time efficiency. A staggered approach is proposed, in which the DD calibration is scheduled after the installation of the larger components in the tokamak, and the DT calibration, if necessary, will be postponed before the start-up of the high-power operations where the triton burn-up component is expected to be much higher than during the low-power phase. This strategy reduces resource demand for the start-up phase and allows for ongoing research to improve the calibration process and diagnostic performance of DTT.