Predicting temperature and density profiles in tokamaks

Abstract

A fixed combination of theory-based transport models, called the Multi-Mode Model, is used in the BALDUR [C. E. Singer et al., Comput. Phys. Commun. 49, 275 (1988)] transport simulation code to predict the temperature and density profiles in tokamaks. The choice of the Multi-Mode Model has been guided by the philosophy of using the best transport theories available for the various modes of turbulence that dominate in different parts of the plasma. The Multi-Mode model has been found to provide a better match to temperature and density profiles than any of the other theory-based models currently available. A description and partial derivation of the Multi-Mode Model is presented, together with three new examples of simulations of the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire et al., Phys. Plasmas 2, 2176 (1995)]. The first simulation shows the strong effect of recycling on the ion temperature profile in TFTR supershot simulations. The second simulation explores the effect of a plasma current ramp—where the plasma energy content changes slowly on the energy confinement time scale. The third simulation shows that the Multi-Mode Model reproduces the experimentally measured profiles when tritium is used as the hydrogenic isotope in L-mode (low confinement mode) plasmas.

Simulations of density profiles, pellet fuelling and density control in ITER

“…The second type of models are semi-empirical models like the Bohm/gyro-Bohm transport model [14]. The third type of models are physics based models like the GLF23 [2], Weiland [3],or MultiMode transport models [13]. For the study presented in this paper we have adopted the Bohm/gyro-Bohm and the GLF23 transport model.…”

Predictive simulations of ITER including neutral beam driven toroidal rotation

“…The largest contribution to core thermal transport in the MMM95 model is the transport resulting from the driftwave turbulence associated with the ion temperature gradient and trapped electron modes ͑ITG/TEM͒ as described in the 1995 Weiland model. 12 This model includes physical effects due to finite beta, magnetic shear, electron-ion collisions, impurities, and fast ions.…”

“…One of the factors contributing to the prediction of the wide range in ITER performance is the stiffness of the anomalous transport model used in the simulations. ͑Stiffness refers to the rapid growth of the driftwave turbulence transport with increasing temperature gradients above a threshold temperature gradient.͒ Transport driven by drift-wave turbulence, which accounts for most of the anomalous thermal transport observed in present day experiments, has been included in the simulations using different anomalous transport models such as the GLF23, 5,11 MMM95, 12 Weiland, 13 and mixed Bohm/gyro-Bohm 14 transport models.…”

The 2008 Public Release of the International Multi-tokamak Confinement Profile Database

“…The mixed Bohm/gyro-Bohm [131] and Multi-mode (MMM95) [132] models have been compared with 13 L-mode and 22 H-mode discharges from JET, DIII-D and TFTR in references [133] and [134] respectively. These discharges were taken from the profile database, and included systematic scans in ρ * , β, collisionality, isotope mass, κ, power, current and density.…”