FT3 - An experiment to study burning plasma physics issues in deuterium plasmas

A conceptual study is presented for a substantial upgrade of the Frascati Tokamak Upgrade (FTU) up to B = 8 T, I = 6 MA, and R [approximately equal to] 1.3 m to study burning plasma (BP) issues in deuterium plasmas operating up to an equivalent DT gain close to Q = 2 in the ELMy H-mode and to Q = 5 with an internal transport barrier (ITB). The effect of alpha particles is simulated by ~1 MeV fast 3He minority heating produced by ion cyclotron resonance heating (20 MW). Thanks to the high-density values ([approximately equal to]4 × 1020 m-3), the FT3 plasmas are characterized by short electron-ion equipartition time (60 ms in the ELMy H-mode scenario) and slowing-down time (44 ms), with respect to the energy confinement time of ~340 ms, a feature characteristic of BP experiments but not always satisfied with present tokamak devices. Advanced scenarios at 5 T with fully noninductive current drive can be investigated with a steady-state current density profile achieved in <5 s. The aim of FT3 is to prepare ITER operation and to provide a test bed for the development of the ITER auxiliary system and diagnostics. Elements of the scientific program are as follows: the investigation of energetic particle collective effects, optimization of H-mode scenarios, development of improved H-mode scenarios and scenarios with ITBs, magnetohydrodynamic and transport studies in ITER-relevant conditions, and study of edge plasma dynamics. FT3 can use all the existing facilities available in Frascati and could be constructed in ~5 yr.