The Increase of Negative Hydrogen Ions Production in ECR Source by use of the Additional Low-Temperature Emitters of Electrons

Analysis of the mechanisms of formation of negative hydrogen ions in the plasma source, operating at the electron cyclotron resonance, leads to the conclusion about the fundamentally important role played in this process by low-temperature electrons. In the source the negative ion production is realized in two stages. First, hydrogen molecules colliding in a plasma with energetic electrons, are exited to high-laying Rydberg electron states and to high vibration levels in the plasma volume. Further, pulling the low-energy electrons, excited molecules acquire a negative charge. Negative atomic ions result from dissociation of excited negatively charged hydrogen molecules. Necessary for this process, the electrons of low energies are the result of collisions of fast plasma electrons with plasma electrodes. In the presented experiments to further increase the number of low-energy electrons were used electrons, emitted from the heated tungsten filaments and ceramic electrodes LaB6 placed in the chamber of the source. The experiments found that emission of electrons from tungsten heaters have improved stability of the discharge and expanded the range of pressure under which there was a discharge, without changing substantially the magnitude of current of negative ions. The emission of electrons from the LaB6 electrodes increased the current of negative ions from a source more than 3 times.