EFFECT OF ADSORBED MATTER ON INTENSE PULSED ION-BEAM GENERATION

Generation of intense pulsed ion beams with high purity has been studi ed experimentally. Impurity ions in the ion beams were found to be cau sed by adsorbed matter on the anode and residual gas molecules in the diode chamber. The first few shots without breaking vacuum in the diod e chamber were found to be effective to remove the adsorbed matter on the anode, and lead to higher purity of the ion beams. No effect on th e ion beam current was observed upon changing the residual gas pressur e in the range from 10(-2) to 10(-3) Pa or upon leaving the anode in a tmosphere for approximately 10 h. Residual gas molecules in the diode chamber had little effect on the purity of the ion beams. After the fi rst 5 shots, the current of the ion beams was found to be 3.0 kA. The most dominant species in the ion beams was F2+.