Elementary Theory for Optimum Eztraction of Space-Charge-Dominated Ion Beams from Plasma Boundaries
The problem of extracting space-charge-limited ion beams from spherical emission boundaries is analyzed for simple,two electrode,parallel-plate and spherical sector electrode systems by application of Langmuir.Blodgett theory with account taken for the divergent lens effect caused by the aperture in the extraction electrode.Results derived from simulation studies for the three electrode system,designed for use with the Oak Ridge National Laboratory ECR ion source,complement predictions made from elementary analytical theory with or without magnetic field in the extraction region of the source.Under minimum halfangular divergence (minimum emittance) conditions,the plasma emission boundary has an optimum curvature and the perveance,P,(i.e,current density,J+ and extraction gap,d),has an optimum value for a given chargestate.From these studies,we find that the optimum perveance for any electrode system can be determined from the Child-Langmuir relation for the parallel-plate electrode system multiplied by a factor,F with value 0.49≤F≤1.
space-charge dominated beam eztraction theory ion beam eztraction simulation optimum perveance optimum angular divergence
G.D.Alton H.Bilheux
国际会议
The 17th International Workshop on ECR Ion Sources and Their Application(第17届国际ECR离子源研讨会)
兰州
英文
201-205
2006-09-17（万方平台首次上网日期，不代表论文的发表时间）