Grant: Subatomic Physics Envelope - Project

The goal of the CANREB facility at TRIUMF is to produce re-accelerated high purity beams of heavy short-lived rare isotopes. This will enable a wide variety of direct reaction studies like nucleon transfer reactions and Coulomb excitation to be performed. The aims include probing the evolution of nuclear shell structure and the unitarity of the CKM matrix, understanding shape coexistence in nuclei, and constrain neutron capture rates relevant for heavy element nucleosynthesis. A suite of state-of-the-art experimental facilities is in place at ISAC for performing these studies. Key requirement for these experiments is the availability of re-accelerated beams with high intensity and purity. This proposal will concentrate on the acceleration of neutron rich Sn isotopes. Experimental proposals for transfer reaction measurements with neutron-rich Sn beams have been evaluated by the TRIUMF experiments evaluation committee (EEC) with high priority but are still waiting for the development which is proposed here. Efficient acceleration of heavy ions in linear accelerators requires highly charged ions. Rare isotopes at an ISOL facility like ISAC and ARIEL at TRIUMF are produced by bombarding solid targets with high energy particle beams. The rare isotopes are extracted as a beam of mainly singly charged ions making charge state breeding essential for the acceleration. Furthermore, the isotope production and the ionization process are not very selective. Isobaric contamination of highly abundant isobars cannot be avoided. In the case of neutron rich Sn isotopes, the background consists mainly of Cs and Ba isotopes. Over the last few years, a new system for the charge state breeding and purification, CANREB (CANadian Rare isotope facility with Electron Beam Ion source) has been set up at TRIUMF. First tests and commissioning have started. An Electron beam ion source (EBIS) is used for the charge state breeding. 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. Highly charged ions are extracted as bunches at a pulse repetition rate of up to 100 Hz. CANREB and the ISAC accelerator will allow accelerator and nuclear physics students to investigate the most advanced radioactive ion post-accelerator system to date. The objective of this proposal is to develop tools and methods to characterize and optimize beam properties to match requirements at the experimental stations. Advanced beam optics simulations codes will be used to model the beam transport throughout the entire chain and outputs will be compared to measurements. It will include the development of methods to manipulate the pulse structure of the extracted ions and optimizing efficiency and purity by applying techniques like breeding to closed atomic shells in the EBIS. Within this proposal those methods will be applied to neutron-rich Sn isotopes.