ORNL developments in laser ion sources for radioactive ion beam production
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ORNL developments in laser ion sources for radioactive ion beam production Yuan Liu
© Springer Science+Business Media Dordrecht 2013
Abstract The development of a resonant ionization laser ion source (RILIS) for the production of isotopically pure radioactive ion beams is reported. The application of the laser ion source calls for high elemental selectivity, high efficiency, and fast release of short-lived isotopes. A hot-cavity ion source and three Ti:sapphire lasers pulsed at a 10 kHz rate are employed for the RILIS. The Ti:sapphire lasers have been upgraded with individual pump lasers to eliminate intracavity Pockels cells and output losses due to synchronization delays. The development of ionization schemes for a wide range of elements is important to the success of Ti:sapphire-laser-based RILIS. In off-line studies with stable isotopes, resonant ionization of 14 elements has been studied, leading to new ionization schemes for ten elements. The absolute ionization efficiency of the hot-cavity RILIS has been measured to range from 0.9 % to 40 % for different elements. The mechanisms for ion transportation and confinement in the hot-cavity ion source have been studied using the temporal profiles of the laser-ionized ions. The hot-cavity RILIS has provided beams of neutron-rich 83,85,86 Ga isotopes for beta decay studies and enabled the first measurement of the beta decay of the exotic 86 Ga. Keywords Resonant laser ionization · Ti:sapphire laser · Hot cavity · Ion source · Radioactive ion beam
1 Introduction Experiments with radioactive ion beams (RIBs) will advance our understanding of the structure of nuclei far from stability and enhance the scientific foundation for innovative
Proceedings of the 9th International Workshop on Application of Lasers and Storage Devices in Atomic Nuclei Research “Recent Achievements and Future Prospects” (LASER 2013) held in Poznan, Poland, 13–16 May, 2013 Y. Liu () Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA e-mail: [email protected]
Y. Liu
applications of nuclear science. The Holifield Radioactive Ion Beam Facility (HRIBF) [1] at Oak Ridge National Laboratory (ORNL) was the only accelerated radioactive ion beam (RIB) facility of the ISOL (Isotope Separation On-Line) [2] type in the U.S. The ISOL technique involves a multi-step process in which a high-intensity beam of light ions is used to bombard a thick target to produce nuclei far from stability and those radioactive species are thermally diffused from the target, transported to an ion source, ionized, accelerated to a magnetic isotope separator where they are separated according to mass, and then further accelerated to energies useful for experiments. It can produce high-intensity RIBs with very good phase-space properties. However, the purity of the RIBs is often limited by the isobars produced simultaneously in the target, usually in quantities exceeding the isotopes of interest by orders of magnitudes. The magnetic separator often fails to provide adequate suppression of the undesired is
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