MODELING OF GAS-FLOW IN THE SIMULATION OF H- ION-SOURCE

Actual gas supply into the ion source is modeled. Filling pressure is related to gas flow rate and conductance of the H- extraction system. The rate equation for the H-2 molecule with gas inflow and outflow rat es related with the filling pressure are employed in the numerical sim ulation of a negative hydrogen ion source. With the results of numeric al simulation, the H number conservation relation and pressure balance equation are shown to be inaccurate especially for higher electron te mperature. Actually for 5 eV of electron temperature, lost H-2 density amounts to 79% and the pressure becomes 5 times the original pressure of 5 mTorr. Even for a low pressure of 3 mTorr, the lost fraction is 67% for 5 eV of the electron temperature. This inaccuracy is large in high power and even for low pressure operation of the ion source. (C) 1996 American Institute of Physics.