FRIB, East Lansing, Michigan, USA
The Facility for Rare Isotope Beams driver linac provides CW beams of all the stable ions (from protons to uranium) with a beam power of 400 kW and a minimum beam energy of 200 MeV/u in order to produce a wide variety of rare isotopes, mainly for nuclear physics study. The low beam emittances, both transverse and longitudinal, are key performance requirements, together with beam stability. These are required for efficiently separating one isotope from another, the reason for choosing this linac configuration. Multi-charge states (five charge states for the uranium case) are accelerated for maximizing the beam current, while keeping the low emittances. The efficient acceleration of high beam currents from 0.5 MeV/u through the superconducting linac is, needless to say, one of the biggest challenges. The beam power is more than 200 times higher than existing similar SC heavy ion linac. In particular, the SC cavities are difficult to protect from heavy ion beam damage, which can be 30 times larger locally than a proton beam with the same beam power. Other challenges peculiar to the FRIB linac will be presented, together with the solutions.
TUPP046
FRIB, East Lansing, Michigan, USA
The double-folded FRIB driver linac will accelerate ion beams with multiple charge states simultaneously to maximize output beam power. Therefore, the two 180-degree bending sections, connecting the three superconducting linac segments, are designed to transport beam achromatically and isochronously. Quadrupoles combined with sextupoles were used in the previous design to save space in the tight bending sections. Further detailed design show these combined function magnets were complicated. We thus revisited the design recently with separate function magnets. In this paper, we will compare the design between the two schemes, present the beam simulation results. We will also discuss the optimization procedures on the design of the new separate function magnets.
FRIB, East Lansing, Michigan, USA
FRIB is a $730M heavy ion accelerator project and a very large scale machine for many nuclear physics users. The civil construction started on March 17th 2014. The SRF system design and development have completed. The machine is to be in early completion end of 2019. FRIB accelerates ion species up to 238U with energies of no less than 200MeV/u and provides a beam power up to 400kW. Four SRF cavity families are used from β=0.041, 0.085 (QWRs) to 0.29 and 0.53 (HWRs). 8T superconducting solenoids are installed in the cryomodules for space effective strong beam focusing. The biggest challenges are in accelerating the high-power heavy ion beams from the very low energy to medium energy and the stable operation for large user community. The SRF cryomodule design addressed three critical issues: high performance, stable operation and easy maintainability, which chose several unique technical strategies, e.g.2K operation, bottom up cryomodule assembly, local magnetic shielding and so on. This talk will include high performance cavity R&D, local magnetic shielding, flux trapping by solenoid fringe field, and bottom up cryomodule assembly.
