Impacts of pellets injected from the low-field side on plasma in ITER

Journal Article · Sat Jan 15 00:00:00 EST 2011 · Plasma Physics Reports

DOI:https://doi.org/10.1134/S1063780X10121086· OSTI ID:22047567

Wisitsorasak, A ^[1]; Onjun, T ^[2]

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1. Mahidol University, Faculty of Science (Thailand)
2. Thammasat University, School of Manufacturing Systems and Mechanical Engineering, Sirindhorn International Institute of Technology (Thailand)

Impacts of pellets injected from the low-field side (LFS) on plasma in ITER are investigated using the 1.5D BALDUR integrated predictive modeling code. In these simulations, the pellet ablation is described using the neutral gas shielding (NGS) model. The pellet ablation model is coupled with the plasma core transport model, which is a combination of the MMM95 anomalous transport model and NCLASS neoclassical transport model. The boundary conditions are assumed to be at the top of the pedestal, in which the pedestal parameters are predicted using a pedestal model based on the theoretical-based pedestal width scaling (either magnetic and flow shear stabilization width scaling, or flow shear stabilization width scaling, or normalized poloidal pressure width scaling) and the infinite-n ballooning mode pressure gradient limit. These pedestal models depend sensitively on the density at the top of the pedestal, which can be strongly influenced by the injection of pellets. The combination of the MMM95 and NCLASS models, together with the pedestal and NGS models, is used to simulate the time evolution of the plasma current, ion and electron temperatures, and density profiles for ITER standard type-I ELMy H-mode discharges during the injection of LFS pellets. It is found that the injection of pellets results in a complicated plasma scenario, especially in the outer region of the plasma and the plasma conditions at the boundary in which the pellet has an impact on increasing the plasma edge density, but reducing the plasma edge temperature. The LFS pellet has a stronger impact on the edge as compared to the center. For fusion performance, the pellet can result in either enhancement or degradation, depending sensitively on the pellet parameters; such as the pellet size, pellet velocity, and pellet frequency. For example, when a series of deuterium pellets with a size of 0.5 cm, velocity of 1 km/s, and frequency of 2 Hz are injected into the ITER plasma from the LFS, the plasma performance, evaluated in terms of Q{sub fusion}, can increase to 72% of that before the use of pellets. It is also found that the injection of pellets results in an increase in the ion and electron densities, but does not enhance the central plasma density. On the other hand, it results in the formation of another peak of the plasma density in the outer region near the plasma edge. The formation of the density peak results in the reduction of plasma transports near the edge by decreasing the contributions of ion-temperature-gradient and trapped electron modes, as well as kinetic ballooning modes.

• OSTI ID: 22047567
• Journal Information: Plasma Physics Reports, Vol. 37, Issue 1; Other Information: Copyright (c) 2011 Pleiades Publishing, Ltd.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-780X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BALLOONING INSTABILITY
BOUNDARY CONDITIONS
COMPUTERIZED SIMULATION
DEUTERIUM
EDGE LOCALIZED MODES
ELECTRIC CURRENTS
ELECTRON DENSITY
ELECTRON TEMPERATURE
FUEL PELLETS
H-MODE PLASMA CONFINEMENT
ION TEMPERATURE
ITER TOKAMAK
NEOCLASSICAL TRANSPORT THEORY
PLASMA
PLASMA DENSITY
PLASMA SIMULATION
PRESSURE GRADIENTS
SHEAR
TEMPERATURE GRADIENTS
TRAPPED ELECTRONS