ECR Plasma in a Stuffed Cusp Field

A stuffed cusp field with a torus ECR surface is obtained by adding a toroidal stuffer field onto a simple cusp field. Results of the production of ECR plasma in this field is described. With sweeping the stuffer current, I_is start to increase when the ECR surface forms closed torus, and reaches up several times of one without the stuffer current. Only in this closed case, X-rays (> 3 keV) are detected by NaI scintillator. These disappear when an obstacle is inserted inside ECR torus, suggesting that the ECR torus is of primary importance to produce and maintain energetic electrons. A peak density and temperature measured by a floating double probe reach up to n_e ≃ 2 × 10¹²cm^–3 and T_e ≃ 25eV at a low Ar pressure of p ≃ 7.3 × 10^–6Torr with the microwave power of 380W.