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.
FRIB, East Lansing, Michigan, USA
A study has been initiated at Michigan State University (MSU) to relate the surface preparation of Superconducting Radio Frequency (SRF) resonators and surface particle counts, using niobium samples. During fabrication, undesired surface roughness can develop on the internal surfaces of the resonators. The final cavity finish will be product of material forming, machining, welding, chemistry, high-pressure rinsing, and handling of the niobium material. This study will document niobium samples treated with MSU standard processing procedures; first measuring the surface roughness, then polishing samples with defined techniques, processing, and measuring surface particle counts. The samples will include as received niobium, machined surfaces, welded surfaces, and surfaces with characterized surface imperfections (scratches).
FRIB, East Lansing, Michigan, USA
The β=0.53 half wave resonator is being developed for the Facility for Rare Isotope Beams. One MSU prototype resonator and four industry made resonators have been fabricated. The proposed surface treatment is buffered chemical polishing (BCP) and high pressure rinsing with ultra pure water. The BCP process is being optimized to achieve resonator performance goals during certification testing. Research is focused on the improvement of the damaged layer removal (uniformity), the heat exchanger design, and the quality of BCP acid solution. Several etches have been completed on the half wave resonators and process data, such as removal rate, temperature profiles, and niobium concentration in solution collected. The process data was studied versus the vertical test results; maximum accelerating voltage, quality factor and field emission onset voltage. The chemistry fixture development and process data versus test results will be presented.
FRIB, East Lansing, Michigan, USA
The Michigan State University (MSU) Superconducting Radio Frequency (SRF) cavity processing and coldmass assembly infrastructure is being upgraded to meet the production needs of multiple SRF projects, including the driver linac for the Facility for Rare Isotope Beams and the MSU Reaccelerator. The objective is to modify the current infrastructure to increase throughput and optimize the process workflow, while minimizing impact to the overall preproduction schedule. Facility upgrades include a cleanroom addition, chemistry room addition, part etching lab, cleanroom preparation area, and a new ultra pure water system. New handling fixtures and specialized tools are being implemented. Methods are being developed to streamline the workflow, increase repeatability, enhance process safety and reduce cross contamination and waste. The proposed work center layout, process capabilities, optimized workflow strategies, and plans for continuous improvement will be presented.