Plasma boundary - the divertor

The divertor, an auxiliary magnetic field that guides the plasma edge to specially equipped collector plates ensures good thermal insulation of the plasma core.

The magnetic field confining the plasma occupies the entire volume of the plasma vessel. Consequently, the plasma also propagates till it touches the vessel wall. The wall then absorbs at the areas of contact – apart from the electromagnetic radiation – the entire energy transported to the outside from the core of the plasma. As the wall is not normally suitable for this purpose, measures have to be taken to bound the plasma in a controlled manner.

The plasma is best safeguarded if the field lines do not impinge direct on the wall, but are directed (or "diverted"), at an appropriate distance from the hot plasma core, to specially equipped plates which collect and neutralise the plasma particles. The neutral gas produced in front of these divertor plates builds up a pressure higher than that in the main plasma volume and can thus be more easily pumped off.

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