Ion Source for the Juelich SNQ-Project

We report on the construction of a hydrogen ion source to provide a proton beam of about 150 mA at an energy of 50 keV. The source is of the magnetic multipole type. The ion density in the extraction plane at a discharge current of 76 A has been determined to be 200 mA/cm2 from the ion saturation current of a Langmuir-probe. The proton fraction in the plasma is as high as 74% at this operation condition as measured by a magnetic momentum mass analyser. The proton fraction in the plasma is related to plasma parameters via a scaling equation to give reasonable agreement.