1 - Nuclear Sciences and Applications - IAEA

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IAEA-CN-50/A-IV-l 219
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Major radius (m)
FIG. 3. Profiles of electron density at 3.0 and 4.2 s and electron temperature (Thomson scattering) and
ion temperature (charge exchange spectroscopy) at 4.2 s for pellet (P) and no-pellet (NP) cases. Timing
of fuelling and heating as in Fig. 1. Heating power (P): RF - 12.5 MW, NBI - 5 MW;
(NP): RF - 11.5 MW, NBI - 5 MW (pulse numbers: 17749/17747). Solid squares: pellet case ion temperature;
open squares: no-pellet case ion temperature.
plasma core. Similarly the enhancement in central electron and ion heating is
diminished as the neutral beam heating power is increased. At high density in JET,
power deposition profiles for 40keV/nucleon beam heating are not strongly
peaked within the plasma core.
Fig. 3 shows density and temperature profiles after pellet injection and near the
termination of the enhanced period for a pellet and no-pellet pulse. Within a
central region of approximately 0.7m diameter, the profiles differ both in
magnitude and scale length. In the pellet case, although the central value of the
electron density decays from 1.35 to 0.6x 1 CP'ta- 3 during the first 1 s of the heating
pulse, the gradient scale length of the core density perturbation has only increased
from 0.5 to 0.6m. The gradient scale length of the temperature profile, both for
ions and electrons, is more than 2x smaller in the pellet case than in the no-pellet
case. The electron temperature profile differs markedly from a triangular shape.
The concurrence of higher density and temperature within this core plasma
implies enhanced central electron pressure and pressure gradients as illustrated in
Fig. 4. The ideal mhd ballooning stability of the equilibria corresponding to these
3.0 s
4.2s
4.2 s
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