No abstract

A negative ion source that utilizes a porous lanthanum hexaboride surface to generate iodine ions is described. Iodine vapor supplied to the back of the lanthanum hexaboride ionizer from a reservoir percolates through to the front surface where the iodine is evaporated as ions. The peak ion current obtained—2.1 mA at an ion energy of 0.3 keV—leads to a density n≃1010 cm−3.

A _s~nthesized plasma containing no electrons but only positive H+ and negative H Ions has been made from a very intense H-ion source. A rectilinear H-ion beam, extracted from a Penning-type source through a magnetic shield, crosses a gaseous target. By two-electron collisional detachment, positive ions are created which, ~ccord~ng to the gas pressure and target depth, can balance the negative current mtenslty of the negative remaining ions. Precautions have been taken to avoid any pollution by electrons. Such purely ionic plasma beams have a density in the range 10 12 _10 13 m-3 , with a velocity of the order of 10 6 m/sec. This particular kind of plasma was first obtained in 1970 and reported in 1971.