Neutron and gamma-ray diagnostics are key DTT systems. Their measurements will provide a direct indication of the generated fusion power, of the dynamics of fast ions and of the runaway electrons level.

The set of neutron and gamma-ray diagnostics includes detectors able to measure the number of neutrons emitted per plasma pulse (Neutron Activation System, NAS) or per unit time (Neutron Yield Monitors, NYM) and their energy (Time Of Flight spectrometer, TOF; fig. 1). In addition, the Neutron and Gamma-ray Camera (NGC; fig. 2) can provide “tomographic images” of the emitted neutrons, the gamma-rays generated by reactions between fast ions and plasma impurities and the runaway electrons.

NAS and NYM will be operative since the first DTT plasma, while TOF and NGC are planned to be installed only in PHASE 2 of DTT operations.

The conceptual design of NAS and NYM and the progress of the preliminary-conceptual design of NGC and TOF have been recently presented by the diagnostic team, composed by scientists from ENEA, CNR and University of Milano-Bicocca. The project includes several innovative technical and technological elements such as the use single Crystal Diamonds (sCD) both as NGC and NYM detectors, the use of innovative inorganic scintillators and a new design of the TOF spectrometer. Thanks to these elements, the system will allow combining spatial and energy measurements of the energetic ions produced by the heating systems, as well as to study tritium ions generated by the fusion reactions.

Figure 1: Layout of the DTT TOF spectrometer.

Fig. 2. Layout of the DTT NGC (left). Detail of one of the two slabs of the NGC collimating unit (right).