FRIB, East Lansing, Michigan, USA
Component damage caused by particle beam is an important issue in the design of a high power accelerator, particularly a superconducting linac. The FRIB driver linac must deliver a beam on target of approximately 1 mm in diameter, increasing beam energy density significantly compared to other SRF linacs. Because dE/dx of heavy ion beam is several ten times larger than proton or electron beam, the situation is more severe: at full power, 400 kW, a uranium beam may cause accelerator structure damage in less than 40 μs. A fast response machine protection system is necessary, in additional to special protection design, very careful linac beam tuning and operation. In this paper, temperature rise of niobium and stainless steel at different beam incident angles are compared, and thermal stress analyzed for nominal FRIB beam at different energy. Protection designs are also briefly discussed.
FRIB, East Lansing, Michigan, USA
The Facility for Rare Isotope Beams (FRIB) will utilize a powerful, superconducting heavy-ion driver linac to provide stable ion beams from protons to uranium, at energies of > 200 MeV/u at a beam power of up to 400 kW. ECR ion sources installed above ground will be used to provide highly charged ions, that will be transported into the linac tunnel approx. 10 m below ground. For the heaviest ions, two charge states will be accelerated to about 0.5 MeV/u using a room-temperature 80.5 MHz RFQ and injected into a superconducting cw linac, consisting of 112 quarter-wave (80.5 MHz) and 229 half-wavelength (322 MHz) cavities, installed inside 52 cryomodules operating at 2K. A single stripper section will be located at about 17 MeV/u (for uranium). Transverse focusing along the linac will be achieved by 9 T superconducting solenoids within the same cryostat as the superconducting rf accelerating structures. This paper describes the matured linac design, as the project is progressing towards a Department of Energy performance baseline definition in 2012. Development status of the linac subcomponents are presented with emphasis on the superconducting RF components.
