A multiaperture electron filter for volume-type H− ion source

Negative light ion beams have been used widely in many applications over the past decades. One of the most popular methods of producing H− and D− beams is the so-called volume production, in which a plasma is contained in a multicusp magnetic field. The beam is extracted using an electric field applied in the extraction gap. Accompanying the negative ions is up to 100 times greater number of electrons, which have to be removed from the beam. This is usually done by placing a transverse magnetic field in the extraction region. With this method the electrons can be quite effectively removed from the beam. The problem is that we dump a high intensity, high energy electron beam in the extraction electrode and dissipate a lot of power in the process. The negative ion beam is also deflected in this strong magnetic field which has to be corrected either by tilting the source compared to the extraction or by adding an opposite transverse magnetic field. In the latter method the beam is laterally displaced from th...