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Description
A Charge Exchange Recombination Spectroscopy (CXRS) diagnostic for the Divertor Tokamak Test (DTT) is currently under design. DTT is a medium-sized (R = 2.19 m, a = 0.70 m), fully superconducting tokamak, presently under construction at the ENEA Research Center in Frascati, Italy. Thanks to its high external heating power (up to P = 45 MW, provided by a combination of ECRH, ICRH and NBH), DTT aims at reproducing the levels of divertor heat loads expected in ITER and DEMO, with the goal of exploring heat exhaust solutions in fusion-relevant environments. Following the research objectives outlined in the DTT Research Plan, a set of diagnostics was identified to explore ion dynamics and perform transport studies. The CXRS system, extensively used in magnetic confinement devices, provides radially resolved impurity ion temperature ($T_i$), density ($n_Z$) and rotation ($v_i$) profiles. A low-power, non-perturbative Diagnostic Neutral Beam Injector (DNBI) is planned to be installed in DTT after the machine commissioning phase. This will provide a D0 and H0 neutral source for Charge Exchange (CX) reactions with impurity ions. Currently, two CXRS systems, with lines of sight covering the core, mid-radius and edge regions, are under design. A preliminary assessment of the expected Ne CX spectra was performed using the Simulation of Spectra (SoS) code [1], studying the spectrometer response for the DTT plasma scenarios A1, C1 and E1 reported in [2]. These results showed that background signal subtraction is essential to provide reliable CXRS measurements in all three explored DTT scenario, and found an indicative optimal range for the DNBI energy at around 80-90 keV/amu. This work presents updated estimations of the diagnostic spectral response, with an upgraded system geometry, providing an up-to-date model to benchmark previous calculations.
[1] von Hellermann, M. et al. Atoms 2019, 7, 30
[2] I. Casiraghi et al 2023 Plasma Phys. Control. Fusion 65 035017