PFPO plasma scenarios for exploration of long pulse operation in ITER

Abstract

Long Pulse Scenarios (LPS) in ITER foreseen during the Pre-Fusion Power Operation (PFPO) phase of the ITER Research Plan (IRP) are assessed using 1.5D transport simulations within the ASTRA framework. Such assessment is required to predict the operational space for LPS operation in PFPO, as well as to evaluate which physics processes for LPS operation during Fusion Power Operation (FPO) could be studied during PFPO. An important aspect in the development of LPSs in PFPO is to minimize lifetime consumption of the Central Solenoid (CS) for these scenarios. The maximum pulse length achievable for LPSs in PFPO with no consumption of CS lifetime (currents in CS coils ≤ 30 kA per turn) has been assessed for a range of heating schemes and heating mixes, confinement regimes (L-mode and H-mode) and for helium and hydrogen plasmas. The operational space of LPS and pulse length has been explored through density scans with the Heating and Current Drive (H&CD) mix required for the FPO Q ≥ 5 steady-state plasma scenario (namely Neutral Beam Injection (NBI) and Electron Cyclotron Heating (ECH)) including acceptable shine through losses on the first wall for both helium and hydrogen plasmas. Fast particle physics aspects that are common between FPO plasmas and LPS PFPO H-mode plasmas at low densities are studied including MHD stability analysis with the KINX code and non-perturbative critical gradient model based on high-n toroidal Alfven eigenmodes (TAE) stability kinetic ballooning code HINST calculations.

Development and application of a predictive model for advanced tokamak scenario design

“…For a typical AUG AT scenario it is ~1.5 s, making this approach acceptable. However, in future larger machines such as ITER a much larger current diffusion time of a few hundred seconds (estimated based on values from [8]) is expected, requiring an alternative solution.…”

Determining the access to H–mode in the ITER pre–fusion and fusion power operation phases at low plasma current with full–radius TGLF–SAT2 simulations of L–mode plasmas

“…These studies have covered both the first phase with ECRH only at one third of the nominal magnetic field and the following phase at half of the nominal magnetic field with additional Neutral Beam Injection (NBI) heating [32,33]. Very recently, integrated transport simulations have been also dedicated to ITER PFPO discharge scenarios in order to explore the operational space for long pulse operation [34].…”