Ion Source

    SNICS (Source   of  negative   ions by cesium  sputtering)  is  the  widely  used  source  for  the  ion accelerator at the Nuclear Science Centre. The sputter sources uses accelerated cesium ions striking a cold cathode to produce  a negative ion  beam of cathode  material (provided the  material could form negative ions) A tantalum  ionizer immersed in cesium weapor produces cesium ions. Cesium positive ions are  accelerated  towards  the  negatively  biased  cathode,  which  then  accelerate negative ions always from the cathode. A thin layer of cesium condensed on the cathode surface enhances negative ion production. Almost all beams can be produced by SNICS source.

   In general, negative  ion  beam  currents  are  a  function  of the  cathode  composition,  the cathode potential, the cesium ion flux and the cathode temperature (Controlled by cooling fluid (Freon).

   Not all elements form the stable negative ions, and in these cases it is obvious to use molecular ions. Molecular beams have two  disadvantages  in accelerator.    a). They  reduced  the final energy of the beam and  b). the coulomb explosion in the stripper foil. These effects are minimized by choosing the lightest possible  molecule,  such  as hydride. If hydride is not possible, we go for Carbide, Nitride or Oxide.