Extraction probability of negative ions from hydrogen ion sources - Effects of filter magnetic field and gas pressure

Trajectories of H(-) ions are calculated numerically by solving the 3D motion equation, including effects of collisional destruction, elastic collisions and charge exchange collisions. According to these trajectories, extraction probability of H(-) ions produced at any location inside the source and energy of extracted H- ions are discussed as a function of gas pressure. Effects of production zone and filter magnetic field on extraction probability are also discussed. The probability for surface produced H(-) ions keeps nearly the constant value, and that for volume produced H(-) ions decreases with gas pressure. The kinetic energy of extracted H(-) ions is reduced mainly by charge exchange collision.