Measurements of deuteron density profiles in JET

The plasma purity, deuteron density nD and deuteron temperature TD are the governing parameters in determining the rate of thermonuclear fusion. The Lawson criterion ndτeTD>5.1021 m-3keV sec (τe=energy confinement time) is usually applied to assess the fusion product needed for a nuclear reactor. In practice, the electron density and temperature are frequently used in the above criterion because they are the more easily measured. However, in high power neutral beam heated discharges, the ion temperature can exceed the electron temperature by more than a factor of two. Additionally, the high power density on material surfaces can lead to a considerable impurity influx. At JET a number of diagnostics are applied to measure these quantities. Three different spectroscopic methods are employed to derive profiles of the deuterium density and ion temperature of the bulk plasma. A further independent technique of obtaining the deuteron density relies on measurements of neutron emission. (author) 5 refs., 5 figs