S. Bricker

Experimental study of a 322 MHz v/c=0.28 niobium spoke cavity

The Rare Isotope Accelerator (RIA) will accelerate heavy ions to >400 MeV/u using an array of superconducting cavities. A proposed linac design based on harmonics of 80.5 MHz will require six cavity types to cover the entire velocity range: three quarter wave resonators, one spoke cavity (half wave resonator), and two 6-cell elliptical cavities. A prototype 322 MHz niobium spoke with optimum velocity of 0.28 c has been fabricated. Each spoke would generate over 1 MV at 4 K for acceleration from v/c=0.20 to 0.40. Details of the design and experimental study are presented.

Cryomodule Design for A Superconducting Linac with Quarter-Wave, Half-Wave and Focusing Elements

The Rare Isotope Accelerator (RIA) driver linac is designed to accelerate heavy ions up to 400 MeV/u (β = v/c = 0.72) with a beam power up to 400 kW [1]. To obtain these intensities, partially stripped ions are accelerated in a 1400 MV superconducting linac. A design based on the 80.5 MHz harmonic requires six cavity types. A rectangular cryomodule design with a cryogenic alignment rail can accommodate all of the superconducting cavity and magnet types for RIA. A prototype 2-cavity cryomodule for the RIA elliptical cavities was designed in 2003 [2] and tested in 2004 [3]. This cryomodule design is suitable for all 3 elliptical cavity types. A similar cryomodule design has been developed for the lower-β quarter-wave and half-wave cavities for RIA. The cavities are interspersed with superconducting magnets for focusing, with 2 cavities between magnets for the quarter-wave cryomodules and 4 cavities between magnets for the halfwave cryomodules. A prototype low-β cryomodule was designed and is now under construction. The prototype module is large enough for 2 cavities and 2 magnets. The cryomodule design will be presented in this paper, along with the current status of assembly and testing of the cavities, magnets, and cryomodule.

Single crystal and large grain niobium research at Michigan State University

As Superconducting Radio Frequency (SRF) technology is used in more accelerator designs, research has focused on increasing the efficiency of these accelerators by pushing gradients and investigating cost reduction options. Today, most SRF structures are fabricated from high purity niobium. Over years of research, a material specification has been derived that defines a uniaxial, fine grain structure for SRF cavity fabrication. Most recently a push has been made to investigate the merits of using single or large grain niobium as a possible alternative to fine grain niobium. Michigan State University (MSU), in collaboration with Fermi National Accelerator Laboratory (FNAL) and Thomas Jefferson National Accelerator Facility (JLAB), is researching large grain niobium via cavity fabrication processes and testing, as well as exploring materials science issues associated with recrystallization and heat transfer. Single‐cell 1.3 GHz (β=0.081) cavities made from both fine and large grain niobium were compared bot...

Specification and design of a 2 K helium system for cryomodule and cavity tests at FRIB

The Facility for Rare Isotope Beams (FRIB) will be a new User Facility for Nuclear Science. The facility is funded by the Department of Energy (DOE) Office of Science and Michigan State University (MSU) and will be constructed on the campus of MSU. The main accelerator for the FRIB project will be a superconducting linac constructed of 52 cryomodules, housing 344 superconducting radio frequency (SRF) cavities. All of the SRF cavities must be operated at superfluid helium temperatures of 2 K. During FRIB fabrication, and prior to the commissioning of the FRIB cryoplant, all cavities and cryomodules must be tested as part of the FRIB quality assurance program. To meet the requirements of FRIB production, upgrades to the existing SRF infrastructure at the National Superconducting Cyclotron Lab (NSCL) must be designed and commissioned. These upgrades include: two additional test Dewars, a FRIB cryomodule testing bay, and a cryogenic system capable of supporting the 2 K cryogenic load, including sub atmospheric pumps, heat exchangers, and JT valves. Transfer lines connecting these new additions will also be designed and fabricated. This paper describes these new systems and show that they will meet FRIB requirements as well as maintaining flexibility for future changes.The Facility for Rare Isotope Beams (FRIB) will be a new User Facility for Nuclear Science. The facility is funded by the Department of Energy (DOE) Office of Science and Michigan State University (MSU) and will be constructed on the campus of MSU. The main accelerator for the FRIB project will be a superconducting linac constructed of 52 cryomodules, housing 344 superconducting radio frequency (SRF) cavities. All of the SRF cavities must be operated at superfluid helium temperatures of 2 K. During FRIB fabrication, and prior to the commissioning of the FRIB cryoplant, all cavities and cryomodules must be tested as part of the FRIB quality assurance program. To meet the requirements of FRIB production, upgrades to the existing SRF infrastructure at the National Superconducting Cyclotron Lab (NSCL) must be designed and commissioned. These upgrades include: two additional test Dewars, a FRIB cryomodule testing bay, and a cryogenic system capable of supporting the 2 K cryogenic load, including sub atmospheri...