Development of a high-pressure, gas-filled ion source for a radioactive beam facility

The National Superconducting Cyclotron Laboratory (NSCL) produces radioactive nuclear beams (RNBs) by in-flight fragmentation of fast ion beams. This method produces nuclei more exotic (having a more extreme neutron-proton ratio) than methods at other RNB facilities. However, the resulting beams, by comparison, have other characteristics, such as very high velocities, which can be less desirable for certain nuclear science experiments. It was the goal of the research in this work to construct an ion source which would capture the fast exotic beams produced at the NSCL, and re-emit them near thermal velocities for use in precision experiments, thus expanding the capabilities of a fragmentation facility.; We have developed a new high efficiency, high pressure, gas filled ion source for radioactive ions. The source utilizes a high pressure (∼1 bar) helium gas cell which stops fast (∼100 MeV/nucleon) radioactive ions. These exotic nuclei are thermalized in the helium and extracted with a combination of electrodes and gas flow through a nozzle. The ions will then be captured in a radiofrequency quadrupole rod structure in a differentially pumped expansion chamber and then transported downstream for use in precision nuclear science experiments.; Presented in this volume are the preparations, results and interpretation of the stopping and extraction efforts. The features and operation of the major components will be addressed. For radioactive beams spanning a large range of masses (A ∼ 40 to 120), the source has shown the ability to stop (typically) 30–70% of the ions introduced into the gas cell. The combined stopping and extraction efficiency has been shown to be approximately 0.5%. These results demonstrate that this source will be useful in providing a low-energy, high-quality ion beam to precision experiments for many new nuclides produced in the NSCL Coupled Cyclotron Facility despite their short half-life (down to ∼100 ms) and low production rate (as low as ∼100/s). In addition, this method of stopping fast beams shows promise for use in future radioactive beam facilities such as RIA (the Rare Isotope Accelerator). Finally, future work and planned improvements are presented.