Experimental study of the characteristics of D- and H- beams produced by a multi-hole multi-ampere accelerator at energies up to 105 keV

The acceleration of D- and H- beams has been studied at energies of up to 105 keV, with currents of the order of 2 A, in multi-second pulses. The optimum extraction voltage has been studied as a function of the beam energy and current. The perveance of the negative ion accelerator has been measured over a wide range of operating conditions with H- and D- beams. The experimental results have been compared to beam optics calculations performed with the SLACAD negative ion code developed at Cadarache: a good agreement has been found. Strong perturbations of negative ion beamlet trajectories have been evidenced in the case of large gap, large aspect ratio accelerators. A comparison between merged beamlets and multi-hole accelerators has been performed. The observed linear increase of the stray accelerated electron current with the extraction voltage has been explained by simulation with a Monte-Carlo code developed at Cadarache