ANL, Argonne, Illinois
Northern Illinois University, DeKalb, Illinois
A pepper-pot - scintillator screen system has been developed and used to measure the emittance of ion beams extracted from the high-intensity permanent magnet ECR ion source. The system includes a fast beam shutter with a minimum dwell time of 18 ms to reduce the degradation of CsI(Tl) scintillator by DC ion beam irradiation, a CCD camera with a variable shutter speed in the range of 1 μs to 65 s. On-line emittance measurements are performed by an application code developed on LabVIEW platform. The sensitivity of the device is sufficient to measure the emittance of DC ion beams with current densities down to ~100 nA/cm2. The emittance of all ion species extracted from the ECR ion source and post-accelerated to an energy of 75-90 keV/charge have been measured downstream of the LEBT. As the mass-to-charge ratio of ion species is increased, the normalized RMS emittances in both transverse phase planes are reduced from 0.3-0.7 pi mm*mrad for light ions to 0.07-0.13 pi mm*mrad for highly charged 209Bi ions. Most measurements show a complicated structure of multiple images of individual holes. The latter can be mitigated or even avoided in some cases by re-tuning ion source parameters.
ANL, Argonne, Illinois
Northern Illinois University, DeKalb, Illinois
A prototype injector capable of producing multiple-charge-state heavy-ion beams has been constructed at ANL. The injector consists of an ECR ion source, a 100-kV platform and an achromatic Low Energy Beam Transport (LEBT) system. Several charge states of bismuth ions from the ECR have been extracted, accelerated to an energy of 1.8 MeV, separated and then recombined into a high quality beam ready for further acceleration. This technique allows us to double heavy-ion beam intensity in a high-power driver linac for a future radioactive beam facility. Another application is in post-accelerators of radioactive ions based on charge breeders. The intensity of rare isotope beams can be doubled or even tripled by the extraction and acceleration of multiple charge state beams. Experimental results of multiple-charge state beam studies will be reported.