NSCL, East Lansing, Michigan
The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) is currently constructing its new reaccelerated beam facility- ReA3. ReA3 will provide unique low energy rare isotope beams by stopping fast, separated rare isotopes in different stopping systems, and then reaccelerating them in a linac. ReA3 will provide pioneering beams for research in one of the pillars of the next-generation rare isotope facility FRIB that will be hosted at MSU. The main components of ReA3 are a linear cryogenic gas cell to stop the fast beams produced by projectile fragmentation, an Electron Beam Ion Trap (EBIT) charge state booster, a compact accelerator using a room temperature RFQ and a superconducting linac using quarter wave resonators. An achromatic beam transport and distribution line towards the new experimental area will complete ReA3. Beams from ReA3 will range in energy from 0.3 to 6 MeV/u. The maximum energy is 3 MeV/u for heavy nuclei such as uranium, and 6 MeV/u for ions with A<50 as the charge state of the ions can be adjusted by the EBIT. The overall concept and status of ReA3 will be presented in particular emphasizing on the SRF-linac.
Michigan State University, East Lansing
NSCL, East Lansing, Michigan
MSU, East Lansing, Michigan
Superconducting radio frequency (SRF) cavities are often formed from fine-grain niobium sheet produced by forging and rolling of ingots that contain very large grains. Texture heterogeneity is consistently observed in such sheets, and is related to heterogeneous deformation and recrystallization of the large grains in the ingot. Relationships between the deformed, recovered, and recrystallized microstructures are required to eventually produce a homogeneous recrystallization texture. Effects of dislocations and grain boundaries on recrystallization and recovery are examined in several kinds of samples: Differently oriented single crystal and bicrystal samples deformed by uniaxial tension and heat treated, and a bicrystal rolled to various reductions and then heat treated. Active slip systems, dislocation substructures, recovery, and recrystallization will be examined by orientation imaging microscopy at incremental stages of deformation, and compared with crystal plasticity model predictions, to determine the influence of dislocation substructure on the orientations of recrystallized grains.
NSCL, East Lansing, Michigan
INFN/LNL, Legnaro, Padova
FZJ, Jülich
A superconducting linac for re-acceleration of exotic ions is being constructed at Michigan State University (MSU). The re-accelerator will initially be used by the MSU Coupled Cyclotron Facility; it will later become part of the Facility for Rare Isotope Beams at MSU. The re-accelerator will include two types of superconducting quarter-wave resonators (QWRs) to accelerate from 0.6 MeV per nucleon (MeV/u) to up to 3 MeV/u for uranium ("ReA3"), with a subsequent upgrade path to 12 MeV/u ("ReA12"). The QWRs (80.5 MHz, optimum beta = 0.041 and 0.085, made from bulk niobium) are similar to the cavities used at INFN-Legnaro for ALPI and PIAVE. They include stiffening elements and passive dampers to mitigate fluctuations in the resonant frequency. Eight beta = 0.041 QWRs have been fabricated; welding of the helium vessels and RF testing is in progress. Another eight beta = 0.085 QWRs are needed. Three cryomodules are needed to reach 3 MeV/u. Fabrication and assembly of the first cryomodule (the rebuncher, with one beta = 0.041 QWR and two superconducting solenoids) is complete. This paper will cover production efforts, test results so far, and future plans.
FZJ, Jülich
NSCL, East Lansing, Michigan
A superconducting linac for re-acceleration of exotic ions is under development at Michigan State University. Two types of superconducting quarter-wave resonators (80.5 MHz, optimum beta = 0.041 and 0.085) will be used for re-acceleration to energies of up to 3 MeV per nucleon initially, with a subsequent upgrade path to 12 MeV per nucleon. Structural design is an important aspect of the overall cavity and cryomodule implementation. The structural design must include stiffening elements, the tuning mechanism, and the helium vessel. The main mechanical design optimization goal is to minimize the shift in the cavity's resonant frequency due to the Lorentz force, bath pressure fluctuations, and microphonic excitation. Structural analyses of the MSU quarter-wave resonators will be presented in this paper. Stiffening measures will be explored. The numerical predictions will be compared to test results on prototype cavities.
NSCL, East Lansing, Michigan
FRIB, East Lansing, Michigan
The 2007 Long Range Plan for Nuclear Science had as one of its highest recommendations the “construction of a Facility for Rare Isotope Beams (FRIB) a world-leading facility for the study of nuclear structure, reactions, and astrophysics. Experiments with the new isotopes produced at FRIB will lead to a comprehensive description of nuclei, elucidate the origin of the elements in the cosmos, provide an understanding of matter in the crust of neutron stars, and establish the scientific foundation for innovative applications of nuclear science to society.” A superconducting heavy-ion driver linac will be used to provide stable beams of >200 MeV/u at beam powers up to 400 kW that will be used to produce rare isotopes. Experiments can be done with rare isotope beams at velocities similar the driver linac beam, at near zero velocities after stopping in a gas cell, or at intermediate velocities (0.3 to 12 MeV/u) through reacceleration. An overview of the design proposed for implementation of the DOE national users facility FRIB on the campus of Michigan State University will be presented.