MRI-R2: Development of A High-Performance Gas-Filled Cyclotron Stopper

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This award will support the development of a new and unique device, at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University, to capture short-lived isotopes produced in nuclear reactions that will facilitate a wide range of new nuclear science. The NSCL is the forefront facility in the US for nuclear science using fast projectile fragments (GeV kinetic energies) and is the world leader in the thermalization and precision mass measurements of these projectile fragments. Nearly a fifth of the chemical elements have been thermalized and measured at the NSCL in the last four years. The NSCL is currently building on this success by expanding its experimental arena for precision studies with thermalized projectile fragments to include laser spectroscopy and, in a major step forward, to low-energy nuclear reactions. Funds from this award will be used to develop a robust gas-stopping concept for projectile fragments, particularly for light-ion and high intensity beams that will be difficult to produce with existing technology. The new gas stopper will slow down and thermalize very high-energy projectile fragments in a large gas filled chamber inside a cyclotron-type magnet. Such a gas-filled cyclotron stopper will be able to provide thermalized ions without regard to their chemical nature, with half-lives as short as tens of milliseconds, and at high incident rates. The development of a novel technique to slow down, capture, and extract these difficult beams using a gas-filled reverse-cyclotron will thus have broad impact by: (1) providing the wide range of beams required for the next generation of precision mass measurements and laser spectroscopy at the NSCL, and (2) allowing unique studies of low-energy nuclear reactions with intense beams of short-lived isotopes that are not available anywhere else in the world. The proposed work will be performed by a collaboration of researchers at MSU, RIKEN (in Japan) and GSI (in Germany) and includes the creation of a break-through device on a three-year timescale. This collaboration has significant expertise in all aspects of the work and the project will foster the technical and scientific exchange among these laboratories. The cyclotron-stopper will be constructed at the NSCL and installed on a dedicated beam line for full-scale testing and subsequent connection to the low-energy arena and re-accelerator. This instrumentation will be a critical component of the NSCL-based research program of many students and postdoctoral scholars.