This is ref the postings in the thread viewtopic.php?f=38&t=212&start=10
The plot I usually post up is figure 6 of a paper you can download here; http://www.iop.org/Jet/fulltext/JETP98036.pdf
This is one of the most powerful tokamak runs ever. Only JET and TFTR are equipped to perform DT operation. JET sits behind metres-thick concrete, and work inside the vessel can now only be done by robot.
The figure shows actual results versus simulation. It's a bit tricky to work out whether an experimental neutron came out of a thermal-thermal fusion reaction or a beam-background reaction, so I will take it as read that the simulation below describes it accurately, as it is accurate in the other parameters (power output, &c.).
So if you eyeball the thermonuclear fraction, you'll note that there is very little at the start of the pulse. The fusion power, as much as it is, is dominantly from the fast ions circulating in the toroidal current. This remains the case for almost the entire duration of the pulse!! Overall, it looks to me like most fusions for the whole pulse are beam-target.
Clearly, the tokamak guys have high hopes of pushing this into dominantly thermonuclear with a longer run and they may well achieve that, but for now the beam-target fusion that goes on at the start of the pulse is actually a necessary heat input for the plasma to get it to the thermal temperature required for thermonuclear reactions.