FRIB, East Lansing, Michigan, USA
BNL, Upton, Long Island, New York, USA
ANL, Argonne, Illinois, USA
The Facility for Rare Isotope Beams (FRIB) at Michigan State University is building a heavy ion linac to produce rare isotopes by the fragmentation method. The linac will accelerate ions up to U to energies above 200 MeV/u with beam powers up to 400 kW. At energies between 16 and 20 MeV/u the ions will be stripped to higher charge states to increase the energy gain downstream in the linac. The main challenges in the stripper design are due to the high power deposited by the ions in the stripping media (~ 30 MW/cm3) and radiation damage if solids are used. For that reason self-recovering stripper media must be used. The baseline stripper choice is a high-velocity, thin film of liquid lithium with an alternative option of a helium gas stripper. We present in this paper the status of the R&D and construction of the final stripper. Extensive experimental work has been performed on both options.
FRIB, East Lansing, Michigan, USA
FRIB is using a charge stripper in folding segment 1 to increase the number of charge states of particles to enhance the acceleration efficiency. To control possible emittance growth after the charge stripper, the 3-dimensional on-stripper beam size should be as small as possible. The original 2-cavity-HWR (HWR stands for half wave resonator) rebuncher cryomodule is responsible for the longitudinal focusing before stripper. In order to accept and transport the beam downstream to linac segment 2, another kind of 3-cavity-QWR (QWR stands for quarter wave resonator) rebuncher cryomodule is baselined after the stripper. However, two kinds of cryomodules would increase the cost in design, therefore would be quite inefficient. In this paper, the FRIB lattice with only single-type 4-cavity-QWR rebuncher cryomodule in folding segment 1 is discussed. Positions of lattice elements are adjusted to accommodate the new type of cryomodule. Beam dynamics is optimized to meet the on-stripper beam requirement. The lattice is then adjusted and rematches.
FRIB, East Lansing, Michigan, USA
The FRIB driver linac is a front runner for the future high power hadron linacs, making a full use of CW, superconducting acceleration from very low β. Accelerator Driven Nuclear Waste Transmutation System (ADS), International Fusion Material Irradiation Facility (IFMIF), Project-X type proton accelerators for high energy physics and others may utilize the technologies developed for the design, construction, commissioning and power ramp up of the FRIB linac. Although each technology has been already well developed individually (except for charge stripper), their integration is another challenge. In addition, extremely high Bragg peak of uranium beams (several thousand times as high as that of proton beams) gives rise to one of the biggest challenges in many aspects. This report summarizes these challenges and their mitigations, emphasizing the commonly overlooked features.