Experiments on the formation and detection of He- ions using a high sensitivity device

A device is described which is essentially made of a duoplasmatron ion source, modified to permit direct extraction of negative ions and of a magnetic sector for the mass or energy analysis of the beam. This device has been tested with He- ions and the influence of some physical parameters on the process of formation of these ions studied. Original features of the device, which make it suitable for the extraction and detection of ions of low abundance and weakly bound ions, are described in detail. (Auth.)