Cadarache Laboratory Studies of a Neutral Beam Injector with Energy Recovery

The design of a new type of neutral beam injector that recovers the energy of the unneutralized part of the beam, developed at Cadarache Laboratory, is presented. The experimental work done since 1987 is also reviewed. In a recent joint Japan Atomic Energy Research Institute (JAERI)/Commissariat à l'Energie Atomique experiment, the injector was operated with extracted deuterium ion beams of up to 85 keV/35 A and 100 keV/14 A by utilizing a plasma generator developed at JAERI that supplies up to a 94% monoatomic ion content. From energy recovery measurements, an improvement in the injector electrical power efficiency by up to 25% for a 100-keV deuterium beam operated with a 6 × 10¹⁵ mol/cm² neutralizer gas target thickness is deduced.