Beam emittance measurements at the high current injector at GSI
The high current injector (HSI) was set into operation in 1999. The maximum ratio of mass to charge state of this new injector has been increased from 25 to 65 with a lower injection velocity of 2.2 keV/u (11.7 keV/u before). The space charge limit of the RFQ (0.25*A/ς [mA]) was reached for argon and lighter ions but not for U 4+ or rare isotopes. For that reason further modifications of the high current ion injector, e.g., geometry of the acceleration gap, solenoid for focusing, were necessary. Here we present beam emittance measurements after the acceleration system for different ion species with beam energies up to 150 keV and beam currents up to 100 mA. For the measurements a multicusp ion source with a multiaperture accel–decel extraction system has been used to produce high ion beam currents in low charge states. The commissioning has been made using an Ar+ beam. This ion beam is easy to produce in nearly one charge state with emission current densities up to 150 mA/cm2. The emittance measurements will be presented in view of the two main dependencies: the focussing strength of the acceleration gap and the space charge forces in the acceleration gap. more...
2002 American Institute of Physics. [DOI: 10.1063/1.1430522]
Author: R.Hollinger et al.