1 - Nuclear Sciences and Applications - IAEA

IAEA-CN-50/A-III-2 175
available), radiated power profile (Abel inverted bolometer data), the plasma
current, loop voltage, Zeff (visible bremsstrahlung, checked against neutron yield
estimates of the deuterium to electron density ratio) and edge particle confinement
time (Da monitors). Neutral beam heating and neutron yields are calculated
by Monte Carlo methods.
The ion temperature profile is calculated, for example, by assuming an ion
thermal diffusivity proportional to the electron thermal diffusivity. With \i = Xe
(i.e. strongly anomalous ion transport) good agreement is obtained with the
diamagnetic measurement of the total stored energy, with the total neutron yield
and, when available, with measured ion temperature profiles from Charge
Exchange Spectroscopy. Since the electron and ion temperatures are well coupled
to within the experimental uncertainties it is not possible to determine x/xe
better than to within a factor 2. Accordingly, the transport losses are first
represented in terms of the effective, power balance, xe/f- Q/ne v kTeS, defined
as the ratio of total heat flux (including the effects of energy equipartition and
convection) across a surface of area, S, to «e V kTe S.
Typical results are illustrated by the analysis of JET Pulse # 15894. The temporal
variation of xe/f ai - radial positions p = 0.5 and 0.75 is shown in Fig. 12a.
As the neutral beam heating phase begins, xe// increases above its ohmic value,
and then decreases continuously to a level close to its ohmic value at the transition
to the H-phase. Xejj is maintained close to this level during the H-phase
(see also discussion in Ref l23] ).
The spatial profiles of xeff ai selected times throughout the discharge are shown
in Fig. 12b. Again it is seen that xe//^ s similar in the transport dominated region
(0.3