THE DRIFT SOURCE : A NEGATIVE ION SOURCE MODULE FOR DC MULTI-AMPERES ION BEAMS

International audienceThe concept of a modular large size ion source is under investigation in our laboratory for the development of the very intense (tens of amperes) negative ion (D-) beams needed for neutral beam injection in Thermonuclear Fusion Research. The basic idea is to develop a compact small ion source producing the required ion flux (20-30mA/cm 2) over a total surface of about 200cm 2 and designed in such a way that it can easily juxtaposed with other identical modules. A large negative ion source of any size (up to several m 2) and shape could be realised as a set of several modules. The anticipated advantage of this concept is the minimisation of the risk inherent in a large extrapolation in size (e.g. »1.0m 2 for ITER) of the present ion sources. In this context, we have developed and tested a source module, called the DRIFT source, whose main properties are presented in this paper. The particular magnetic field configuration of this module ensures, in a simplified way, a very good plasma confinement allowing operation of the source at very low filling pressures. Up to now, a Dcurrent of 1A (20mA/cm 2) 50keV energy, 1s pulse length, was obtained with Caesium vapour seeding at 0.15Pa source pressure with an arc power of 2.5kW/litre (12kW)