Extraction Gap
         
The optical quality of the beam depends upon the extraction region of the source-lens combination.  The Duoplasmatron source and extraction gap are designed to operate as a unit and optimize the efficiency of this Pierce extraction region.
         
The lens insulators are optically shielded from the ion beam to prevent surface charging or contamination from the vacuum system. This prevents the formation of spark tracks on the insulators which lead to lens voltage breakdown.
         
The divergence of the beam from the ion source is related to the extraction geometry and extraction voltage. The gap geometry provides a strong electric field region to efficiently extract ions from the source plasma resulting in a superior quality beam.
         
         
Einzel Lens
         
The Einzel lens is a three element electrostatic cylindrical tube lens with the center electrode elevated near to source potential. Operated in this manner, the lens is a classical saddle point Einzel lens which decelerates the divergent beam from the source and extraction gap and then re-accelerates it back to the extraction energy. The result is a strong focusing action. The focal length is determined by the voltage applied to the
center electrode.
         
The electrodes are removable for cleaning. In addition, all the insulators are easily removable for cleaning or replacement. The lens is housed in a box which has a port on the bottom for mounting a vacuum pump.
         
         
30 Degree Mass Analysis Magnet
         
The 30 degree electromagnet is a double focusing system with corrections for fringe field effects. It is a highly uniform field magnet with high mass resolution and is capable of analyzing light ions. A highly stable magnet power supply results in excellent beam positional stability.
         
                     Mass energy product, MxE/Zē          > 320 keV AMIJ
                     Mass resolution                                  M/? M  > 16
         
         
Deceleration Gap
         
The deceleration gap is a single gap structure across which the final beam energy is impressed. The beam is brought to a cross over at this gap and is mass analyzed at the resolving aperture located in the structure. The gap is a low optical strength coupling element which introduces only small variations in the optical properties of the beam.  While holding the extraction voltage across the extraction gap constant at optimum value




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