First Results of Magnetic Filter Field at RF Negative Ion Source

A series simulations and experiments were developed to indicate the influences of the magnetic filter field generated by current flowing through the plasma grid (PG) on the plasma parameters and provide reference for improving the performance of radio frequency (RF) negative ion source. The magnetic flux density was simulated by finite method and verified by the experiments to illustrate the accuracy of model. Several plasma distribution experiments were carried out for different PG currents of magnetic filter field conditions. The investigations show that the electron temperature can be decreased easily below 2 eV with current of 590 A. Electron density homogeneity of 93.8% along the upstream of PG with low-field condition is observed and about 76.7% with relatively large current of 2800 A. The influences of the different magnetic filter fields on the plasma in the extraction region are studied and provide reference for the future upgrade of the magnetic filter field on the RF negative ion source.