1 - Nuclear Sciences and Applications - IAEA

56 JET TEAM
o
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Peak density (fieXxi
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Fig. 14 Measured QDD versus mean density.
of this type will not be seen in Q=1 deuterium-tritium experiments either, since
there the a-power is only 17% of the total.
8. Fusion Product and Q
The experimental values of the fusion product (nD 7} TE) are plotted versus
Tt in Figure 13. Also shown are the contours of constant thermonuclear Q, Qth
calculated on the basis of a D-T mixture with the same hydrogen isotype density
and with density and temperature profiles typical of JET experiments (pressure
ratio p/(p)=3). It is assumed that Te = Tt at all radii. Correcting for
impurities by taking only the deuteron density overestimates Qth because the
energy content of the electrons associated with the impurities is not included
in the losses. However for Zefj < 3, the maximum error is 30 %. From the figure
it is clear that conditions close to Qth =0.1 have been achieved.
Fig. 14 shows the directly measured values of QDD versus mean density. Here
the highest values which are at low density are due to beam-plasma interactions.
Scaling these to the planned deuterium beam energy (140keV), accounting for
cross-section and yield changes, the equivalent Qtot for a 50:50 D-T plasma is 0.25.
10