Design of neutron and gamma ray diagnostics for the start-up phase of the DTT tokamak

The Divertor Tokamak Test (DTT) facility, which is under design for construction in Frascati (Italy), will produce neutron yield up to 1.3*1017 n/s at full power (H-mode scenario). This calls for an accurate design and selection of the 2.5 MeV neutron diagnostic systems and detectors which can give the comprehensive exploitation of the high neutron fluxes. Measurements of 14 MeV neutrons (which are about 1% of the total neutron yield) coming from the triton burn-up will also be performed. DTT will reach its best performances after a preliminary phase, needed to assess and improve the machine parameters. Here we present the neutron and gamma-ray diagnostics systems which are under design for the initial start-up phase of DTT. The design work benefits from the experience gathered by the community on high power tokamak such as JET. These systems, also called day-1 diagnostics, are: i) Neutron flux monitors which measure the 2.5 and 14 MeV neutron yields, ii) Neutron/Gamma camera for the reconstruction of the neutron and gamma ray emission profile of the plasma, iii) Hard x-ray monitors for measurements of the bremsstrahlung radiation produced by runway electrons in the 1-40 MeV energy range.