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
Superconducting quarter-wave resonators and half-wave resonators are being prototyped and fabricated at Michigan State University (MSU) in effort to support the Facility for Rare Isotope Beams (FRIB) project. FRIB requires a 200 MeV per nucleon driver linac, operating 345 resonators at two frequencies (80.5 and 322 MHz) and four betas (0.041, 0.085, 0.29, and 0.53). FRIB cavity development work is underway, with the prototyping of all four resonators, including helium vessel design, stiffening strategy, and tuner interface. In addition, the acquisition strategy for FRIB resonators is being finalized, and the technology transfer program is being initiated. The status of the resonator production effort will be presented in this paper, including an overview of the acquisition strategy for FRIB.
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
Michigan State University is developing and testing quarter wave resonators for a superconducting linac which will be used to reaccelerate exotic ions to 3 MeV per nucleon or higher (ReA3). Eight quarter wave resonators with an optimum velocity of β = v/c = 0.085 and a resonant frequency of 80.5 MHz are required for the third cryomodule, which will complete the first stage of the reaccelerator linac. Approximately 100 additional β = 0.085 resonators of the same design will be required for the Facility for Rare Isotope Beams (FRIB). Results of Dewar testing to characterize the RF performance of the resonators will be presented in this paper.
MSU, East Lansing, USA
Michigan State University, East Lansing, USA
FRIB, East Lansing, Michigan, USA
(MSU), East Lansing, USA
The phonon peak in the thermal conductivity kpp of high purity niobium is an unknown function of heat treatment temperature Th and RRR, amongst other variables. The relationship between Th and kpp of large grain niobium is investigated using two sets of four specimens. The specimens of Set 1 were randomly cut from four ingot discs with different RRR. These specimens were subjected to different heat treatments. Specimens of Set 2 were cut from the same grain of an ingot disc, with the heat flow direction of each specimen along the same crystal orientation. Each of these specimens was subjected to one heat treatment, at a temperature ranging between 600 C and 1200 C, while maintaining a constant temperature for an interval of 2 hours for each specimen. Results from the specimens of Set 1 show that there is no change in kpp after heating at 140 C for 48 hours. Set 1 specimens also show that for a given heat treatment protocol, the maximum in kpp shows a monotonic dependence on RRR. Results from the specimens of Set 2 suggest that the phonon conduction response to heat treatments for 2 hours shows no increase for Th < 600 C and plateaus at Th > 1000 C.
NSCL, East Lansing, Michigan, USA
FRIB, East Lansing, Michigan, USA
Michigan State University, East Lansing, USA
JLAB, Newport News, Virginia, USA
FRIB, East Lansing, Michigan, USA
Niowave, Inc., Lansing, Michigan, USA
Large grain niobium is being examined for fabricating superconducting radiofrequency cavities as an alternative to using rolled sheet with fine grains. It is desirable to know the grain orientations of a niobium ingot slice before fabrication, as this allows heterogeneous strain and surface roughness effects arising from etching to be anticipated. Characterization of grain orientations has been done using orientation imaging microscopy (OIM), which requires destructive extraction of pieces from an ingot slice. Use of a Laue camera allows nondestructive characterization of grain orientations, a process useful for evaluating slices and deformation during the manufacturing process. Five ingot slices from CBMM, Ningxia, and Heraeus are compared. One set of slices was deformed into a half cell and the deformation processes that cause crystal rotations have been investigated and compared with analytical predictions. The five ingot slices are compared in terms of their grain orientations and grain boundary misorientations, indicating no obvious commonalities, which suggests that grain orientations develop randomly during solidification.