Measurement of EEDF and distribution of primary electrons in a bucket ion source

A tool for investigating the electron energy distribution function (EEDF) in plasmas was developed and used to study the primary electron behaviour in a bucket type ion source. The spatial variation of the EEDF in filter magnetic fields, which optimize the negative ion production, is extensively studied. It is verified that the high energy component of the EEDF damped over a shorter characteristic length than the low energy component. Similar behaviour is also observed and studied in the cusp regions of the plasma.