Energy analysis of negative hydrogen ions using detached electrons

An electron of a negative hydrogen ion (H−) can be easily detached by collisions with an external laser beam or residual gas molecules in the beam line, because its electron affinity is small (0.754 eV). The detached electrons provide information about the original negative hydrogen ions and should have the same velocity as the original hydrogen ions. By measuring the energy of the detached electrons, the energy of a negative hydrogen-ion beam can be estimated. A preliminary experimental result of an energy analysis of a H− beam using detached electrons is presented.