Investigation of the charge state breeding for the post acceleration of neutron rich Sn isotopes

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The goal of the CANREB facility at TRIMUF is to produce re-accelerated high purity beams of heavy radioactive nuclei. This will enable a wide variety of direct reaction studies to be performed at a suite of state-of-the-art experimental stations at the ISAC II experimental hall. They encompass for example nucleon transfer reactions or Coulomb excitation. The aims of these measurements will include understanding the evolution of nuclear shell structure and shape coexistence in nuclei, to constrain neutron capture rates relevant for heavy element nucleosynthesis, and probing nuclear structure information of super-allowed beta emitters to test the unitarity of the CKM matrix. The key requirement for these experiments to become feasible is the availability of beams of rare isotopes with high intensity and purity.***Efficient acceleration of heavy ions requires them to be in a high charge state. Radioactive ions at an ISOL facility like ISAC or ARIEL at TRIUMF are produced by bombarding solid targets with high energy particle beams. The products diffuse out of the target directly into the ion source. With the ion source in close proximity of the hot target it is impossible to use complicated devices for high charge states. Thus, mostly singly charged ions can be produced and charge state breeding is essential for the acceleration. Furthermore, the isotope production and the ionization processes in general are not very selective. In most cases isobaric contamination of highly abundant isobars cannot be avoided. Within the CANREB project a high resolution mass separator (HRS) will clean up most contaminants in the ion beams from the target stations. An electron beam ion source (EBIS) will be used for the charge state breeding. Its advantage is that ions are created in ultrahigh vacuum, which substantially reduces the contamination from residual gas ions compared to other high charge state ion sources. The entire system contains a radio frequency quadrupole (RFQ) linear Paul trap for bunching before the injection into the EBIS followed by a Nier type mass spectrometer for charge state selection. ***The proposed project will allow accelerator and nuclear physics students and post-docs to investigate the most advanced rare isotope post-accelerator system to date. They will develop simulations of the ion transport from the production target, through the HRS, undergoing charge breeding in the EBIS and leading to beam properties at the experiments. This will be complemented by performing measurements and working out optimized operation conditions, first with stable ions from a test ion source followed by radioactive ions from ISAC or ARIEL. We aim to perform the simulations using neutron-rich Sn beams. Letters of intent for transfer reaction measurements with neutron-rich Sn beams have been evaluated by the TRIUMF SAP-EEC with high priority but are still waiting for the development which is proposed here.