Semi - analytical Modeling of the NIO1 Source

NIO1 is a compact and versatile ne gative ion source, with a total current of 130 mA accelerated to 60keV. Negative ions are created inside the plasma, which is inductively coupled by an external RF cylindrical coil operating in the range of 2 ± 0.2 MHz. The plasma is confined in the source chamber (a 50 mm radius cylinder) by a multipole magnetic field and the ions are extracted through a 3x3 matrix of apertures. The use of cesium, to enhance the negative ion production by H 0 bombardment of the surfaces, is foreseen in a second sta ge of the operation, so that at present time the source is operating in a pure volume configuration. This paper presents a set of analytical and numerical models, aimed to describe the main physical phenomena occurring in the source, including the RF coupling with the plasma, the evolution of plasma parameters in the source, the electron and energy distribution under the effect of the magnetic filter field and the accelerated beam optics. With respect to more sophisticated models of negative ion sources here we aimed to develo p fast tools capable of qualitatively describing the response of the system to variations in the basic operating parameters. The findings of these models are finally c omp ared with the first results of NIO1.