1 - Nuclear Sciences and Applications - IAEA

486
CHEETHAM et al.
0 20 40 60 30 100 120 140 160 180 200
At (ms)
FIG. 2. Temporal evolution of electron temperature at four radii after injection of a pellet into the Hmode
plasma (til5925). The full line is the measured electron temperature using ECE, and the dashed
line is the modelled evolution using the diffusive model with thermal pinch.
also been proposed for modelling of TFTR electron temperature
profiles [10]. Eq.1 then becomes
dWe/dt=div[(nexool|VTe|/(To/a)} 6 +nexo{i+a(r/a) B })VTe] +S -2b-
After pellet injection, evolution of Te(r) takes place initially
in the presence of strong temperature gradients. Thus this
method will be a sensitive test of the VTe dependence of xe-
The initial conditions for solving eq.2a and 2b, the
temperature and density profiles instantly after pellet injection,
are determined from measurements of Te(r), ne(r), pellet
mass, ablation rate and penetration depth. Fig. 1 shows Te(r)
and ne(r) immediately before and after pellet injection. During
evolution of Te(r) the perturbed density profile is assumed to
be stationary. This is justified a posteriori because the density
perturbation travels much more slowly than the temperature
perturbation, as will become clear in the following.
Fig. 2 shows a representative comparison between the
measured and modelled Te(r,t) at four radii for a H-mode plasma,
applying diffusive model with thermal pinch, eq.2a. Assuming
Xe(r), Seff(r) is calculated for the equilibrium pre-pellet
plasma and maintained stationary thereafter. The modelled evolution
of T is found to be sensitive only to the local value of