6.3 Long pulse operation

Meeting the pumping requirements of the injectors during very long pulse operation is very difficult, even with a substantial reduction of the gas flow into the ion source and no gas into the neutraliser. The only systems that can provide the required pumping speed are cryopumps, and possibly non-evaporable getters (NEGs), and neither of those actually pumps gas out of the injector. Consequently, such pumps require regular regeneration to avoid possible explosions and/or to avoid saturation of the pumps. As no way has yet been developed to allow an injector to continue operation whilst the pumps are regenerated, the only option is to take the injector off-line during the regeneration. That problem could be overcome by having one "excess" injector, so that of the n injectors installed, only n 1 injectors are ever operating, and each injector is regenerated in turn.
