An analytical expression was derived for describing the divertor target power during ELMs based on the model discussed in [W. Fundamenski, R.A. Pitts, Plasma Phys. Control. Fus. 48 (2006) 109] where the power load arises from a Maxwellian distribution of particles released into the SOL region. The paper discusses a comparable simple extension of the model by introducing a non-zero characteristic velocity of the Maxwellian distributed particles. This way the experimentally observed temporal evolution as well as the in/out energy imbalance can be described. The extended model named free-streaming-particle (FSP) approach predicts a dependence of the ELM in/out energy balance of the pedestal Mach number as well as an inversion of the in/out balance by a change of the field line helicity as observed experimentally. From the FSP approach the value for EτIR (see text) is predicted to be 18–25% in good agreement to the experimental data. A comparison to the various discussed mechanism for the ELM in/out asymmetry is presented.
- Fusion energy