Integrated scenario with type-III ELMy H-mode edge: extrapolation to ITER

Abstract

One of the most severe problems for fusion reactors is the power load on the plasma facing components. The challenge is to develop operation scenarios, which combine sufficient energy confinement with benign heat loads to the plasma facing components. The radiative type-III ELMy H-mode seems a possible solution for such an integrated ITER scenario. Nitrogen seeded type-III ELMy H-modes for the standard inductive scenario and the high beta stationary hybrid scenario are investigated with respect to their transient and steady-state power fluxes to the divertor, confinement properties, edge operational space, core operational space, plasma purity and MHD behaviour. A large database of highly radiative type-III ELMy H-modes on JET is used for extrapolations to ITER. On this basis the transient heat load should be acceptable for ITER. It was found that the scaling of the confinement time with respect to the ion gyroradius is close to the gyro-Bohm scaling. Scalings with respect to the plasma collisionality suggest that the confinement will be good enough for an ITER scenario at 17 MA with a power amplification factor (Q) of 10 and might be marginally good enough for a Q = 10 scenario at 15 MA. Those extrapolations are supported by simulations with an integrated core/edge model COREDIV. In addition the hybrid scenario with type-III edge localized modes has been proven to have improved edge conditions without any modification of the central plasma current profile, indicating it is compatible with a high beta operation for a steady-state ITER Q = 5 scenario.

Plasma surface interactions in impurity seeded plasmas

“…The radiative seeding scenario, which acts predominantly on the inter-ELM power load, needs to be integrated with ELM mitigation. A small ELM scenario which is compatible with impurity seeding and possibly suffices with ITER heat load limits is the type-III ELMy H-mode [41]. Since it generally exhibits reduced confinement, it may require ITER operation at slightly increased current of 17 MA to achieve Q=10.…”

Properties of nitrogen-implanted beryllium and its interaction with energetic deuterium

“…Seeding of impurities to the plasma has been used for various purposes in many tokamak experiments, among others in TEXTOR [5], ASDEX Upgrade [6] and JET [7,8]. In ASDEX Upgrade it became a necessity for high power discharges after installation of the full metal wall.…”

Statistical Characterization and Classification of Edge-Localized Plasma Instabilities

“…Introduction: Edge localised plasma instabilities (ELMs) [1][2][3][4] are almost ubiquitous in high performance magnetically confined fusion (MCF) plasmas. Their phenomenological properties are correlated with the quality of global energy confinement, and the peak energy fluxes onto material surfaces [3][4][5][6]. Key challenges are to statistically characterise these processes sufficiently well that a quantitative distinction between different observed classes of ELMs becomes possible, and to relate this classification to the physical processes responsible for them.…”

“…ELMs offer a rich and diverse experimental phenomenology [1][2][3][4][5][6][7][8]. There is intense theoretical research on the instabilities that may be responsible for triggering them [9], but few unifying principles have been identified.…”

“…As an example we analysed JET plasmas 66105-66109, whose ELM frequency is typical of type III ELMs [2][3][4]6], but whose D α signal is visually similar to that of type I ELMs.…”