NSCL, East Lansing, Michigan
IAP, Frankfurt am Main
Rare isotope beam (RIB) accelerator facilities provide rich research opportunities in nuclear physics. The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) is constructing a RIB facility, called ReA3. It will provide unique low-energy rare isotope beams by stopping fast RIBs and reaccelerating them in a compact linac. ReA3 comprises gas stopper systems, an Electron Beam Ion Trap (EBIT) charge state booster, a room temperature radio frequency quadrupole (RFQ), a linac using superconducting quarter wave resonators (QWRs) and an achromatic beam transport and distribution line to the new experimental area. Beams from ReA3 will range from 3 MeV/u for heavy ions to about 6 MeV/u for light ions, as the charge state of the ions can be adjusted by the EBIT. ReA3 will initially use beams from NSCL's Coupled Cyclotron Facility (CCF). Later ReA3 will provide reacceleration capability for the Facility for Rare Isotope Beams (FRIB), a new national user facility funded by the Department of Energy (DOE) that will be hosted at MSU. The ReA3 concept and status of ReA3 will be presented, with emphasis on the comissioning of the facility, which is underway.
GSI, Darmstadt
NSCL, East Lansing, Michigan
IAP, Frankfurt am Main
Heavy, highly-charged ions (HCI) with only one or few electrons are interesting systems for precision experiments as for instance tests of the theory of quantum electrodynamics (QED). To achieve high precision, kinetic energy and spatial position of the ions have to be well controlled. This is in contradiction to the production process that employs stripping of electrons at high energies by sending relativistic highly-charged ions with still many electrons through matter. In order to match the production at 400 MeV/u with the requirements of the experiments - stored and cooled HCI at low energy - the linear decelerator facility HITRAP has been built at the experimental storage ring (ESR) at GSI in Darmstadt. The ions are first decelerated in the ESR from 400 to 4 MeV/u, cooled and extracted. The ion beam phase spaces are then matched to an IH-structure, decelerated from 4 to 0.5 MeV/u before a 4-rod RFQ reduces the energy to 6 keV/u. Finally, the HCI are cooled in a Penning trap to 4 K. Extensive ion optical calculations were performed and in recent tests up to one million highly-charged ions have been decelerated from 400 MeV/u to 0.5 MeV/u.
NSCL, East Lansing, Michigan
The US Department of Energy Facility for Rare Isotope Beams (FRIB) at Michigan State University includes a heavy ion superconducting linac capable of accelerating all ions up to uranium with energies higher than 200 MeV/u and beam power up to 400 kW. At an energy of approximately 17 MeV/u we plan to strip the beam to reduce the voltage needed in the rest of the linac to achieve the final energy. The design of the stripper is a challenging problem due to the high power deposited (approximately one kW) in the stripper media by the beam in the small beam size. One of the options being considered is a carbon foil stripper. We have developed a test chamber to study the thermal mechanical properties of different stripping media candidates (amorphous carbon, graphene, diamond). This chamber utilizes an electron beam to deposit powers similar to what the FRIB stripper will see in operation. The thermo-mechanical studies are a necessary condition but not sufficient. The effect of radiation damage must also be studied. We have utilized heavy ions (Pb) from the K500 cyclotron to study this issue. We present in this paper a summary of the requirements and the status of the studies.
NSCL, East Lansing, Michigan
INFN/LNL, Legnaro (PD)
FZJ, Jülich
Niobium quarter-wave resonators (QWRs) and half-wave resonators (HWRs) are being developed at Michigan State University for two projects: a 3 MeV per nucleon superconducting linac for re-acceleration of exotic ions (ReA3, under construction, requiring 15 resonators), and a 200 MeV per nucleon driver linac for the Facility for Rare Isotope Beams (FRIB, under design, requiring 344 resonators). The QWRs (80.5 MHz, optimum beta = 0.041 and 0.085) are required for both ReA3 and FRIB. Both include stiffening elements and frictional dampers. Nine beta = 0.041 QWRs have been fabricated; seven of them have been Dewar tested successfully with a helium vessel for use in ReA3. Production and testing of ten beta = 0.085 QWRs is in progress. The HWRs (322 MHz, optimum beta = 0.29 and 0.53, required for FRIB) are designed for mechanical stiffness and low peak surface magnetic field. A prototype beta = 0.53 HWR has been fabricated, and a prototype beta = 0.29 HWR is planned. This paper will cover the RF and mechanical requirements, the resonator and vessel design, and Dewar testing of production resonators.
NSCL, East Lansing, Michigan
Superconducting quarter-wave resonators, half-wave resonators, and cryomodules are being prototyped and fabricated at Michigan State University (MSU) for two ion linac projects. The 3 MeV per nucleon reaccelerator project (ReA3) is under construction as an upgrade to MSU's nuclear physics research program. ReA3 requires 15 production resonators, housed in three cryostats, with commissioning to begin in 2010. In parallel, MSU is engaged in a future laboratory upgrade, the Facility for Rare Isotope Beams (FRIB). FRIB requires a 200 MeV per nucleon driver linac, which includes 344 resonators (four different betas) housed in 52 cryomodules. FRIB development work is underway, with the prototyping of a FRIB cryomodule planned for early 2011. In addition, the acquisition strategy for FRIB resonators and cryomodules is being finalized, and the technology transfer program is being initiated. The status of the resonator and cryomodule production effort will be presented in this paper, including an overview of the acquisition strategy for FRIB.
NSCL, East Lansing, Michigan
Michigan State University is developing cryomodules for two projects: a 3 MeV per nucleon superconducting linac for re-acceleration of exotic ions (ReA3, under construction, requiring 4 cryomodules), and a 200 MeV per nucleon driver linac for the Facility for Rare Isotope Beams (FRIB, under design, requiring 52 cryomodules). The first two ReA3 cryomodules contain a total of seven quarter-wave resonators for beta = 0.041 and five superconducting solenoids (9 T). These cryomodules have been fabricated and installed, with testing underway. The third ReA3 cryomodule (requiring eight QWRs for beta = 0.085 and three solenoids) is being fabricated. A fourth ReA3 module consisting of a single quarter-wave resonator will be used for matching. A prototype cryomodule for FRIB is being designed for two beta = 0.53 half-wave resonators and one solenoid. The experience so far with system performance of the cryomodules will be described in this paper. Topics will include cavity performance, magnetic shielding, microphonics, cavity tuning, input coupler performance, and thermal loads.