High brightness H+ and H- sources

The brightness and emittance of a beam of ions can depend on the transverse ion temperature, lens aberrations, scattering collisions as well as other factors in the beam transport line. However, it is the transverse ion temperature, which arises in the plasma source, which determines the minimum value of the emittance and hence the beam brightness as the other contributions can be eliminated by careful design. The plasma discharge both creates the positive and negative ions and then heats them to a temperature which is a function of the plasma molecular chemistry (for H+) as well as the plasma density and electron temperature. The authors describe these processes and also methods whereby the discharge can be modified to reduce the effective ion temperature and hence raise the beam brightness