ESTIMATES OF THE MAXIMUM RADIATED POWER IN A TOKAMAK DIVERTOR

Using energy balance arguments, the maximum power which can be lost by volume processes in a tokamak divertor has been calculated. A simple ID model is used for parallel heat conduction in the scrape-off layer. It is shown that when radiation is added to the power balance, solutions are often thermally unstable. Conduction remains a powerful loss mechanism for plasma temperatures at the target greater than or equal to 10 eV. The maximum power which can be lost by radiation or other volume processes decreases with increasing plasma density, but increases with increasing input power. It is difficult to make the fractional power radiated exceed 50% for typical divertor parameters.