INFN/LNL, Legnaro (PD), Italy
FRIB, East Lansing, Michigan, USA
JLAB, Newport News, Virginia, USA
The superconducting driver and post-accelerator linacs of the FRIB project, the large scale radioactive beam facility under construction at MSU, require the construction of about 400 low-beta Quarter-wave (QWR) and Half-wave resonators (HWR) with four different optimum velocities. 1st and 2nd generation prototypes of β=0.041 and 0.085 QWRs and β=0.53 HWRs have been built and tested, and have more than fulfilled the FRIB and ReA design goals. The present cavity surface preparation at MSU allowed production of low-beta cavities nearly free from field emission. The first two cryostats of β=0.041 QWRs are now in operation in the ReA3 linac. A 3rd generation design of the FRIB resonators allowed to further improve the cavity parameters, reducing the peak magnetic field in operation and increasing the possible operation gradient , with consequent reduction of the number of required resonators. The construction of the cavities for FRIB, which includes three phases for each cavity type (development, pre-production and production runs) has started. Cavity design, construction, treatment and performance will be described and discussed.
Michigan State University designs and establishes FRIB as a DOE Office of Science National User Facility in support of the mission of the Office of Nuclear Physics.
INFN/LNL, Legnaro (PD), Italy
FRIB, East Lansing, Michigan, USA
The Quarter-Wave Resonators (QWR) section of the FRIB superconducting driver linac is required to accelerate Uranium beam up to 16 MeV/u in two different charge states simultaneously. This puts severe requirements on resonators alignment and field quality, in order to avoid beam losses and emittance growth. In particular, QWR beam steering can cause transverse oscillations of the beam centroid which reduce the linac acceptance and induces emittance growth. We have studied, with an analytical model and with 3D beam dynamics simulations, correction methods for the FRIB QWRs steering. We found that cavity shifting can provide effective steering cancellation in FRIB QWRs without need of cavity shape modifications, and allows to eliminate transverse beam oscillations and to improve beam quality. Calculation and simulation methods and results will be presented and discussed.
Michigan State University designs and establishes FRIB as a DOE Office of Science National User Facility in support of the mission of the Office of Nuclear Physics.
FRIB, East Lansing, Michigan, USA
JLAB, Newport News, Virginia, USA
Thermal analysis of the FRIB cryomodule design is performed to determine the heat load to the cryogenic plant, to minimize the cryogenic plant load, to simulate thermal shield cool down as well as to determine the pressure relief sizes for failure conditions. Static and dynamic heat loads of the cryomodules are calculated and the optimal shield temperature is determined to minimize the cryogenic plant load. Integrated structural and thermal simulations of the 1100-O aluminium thermal shield are performed to determine the desired cool down rate to control the temperature profile on the thermal shield and to minimize thermal expansion displacements during the cool down. Pressure relief sizing calculations for the SRF helium containers, solenoids, helium distribution piping, and vacuum vessels are also described.
Michigan State University designs and establishes FRIB as a DOE Office of Science National User Facility in support of the mission of the Office of Nuclear Physics.
FRIB, East Lansing, Michigan, USA
JLAB, Newport News, Virginia, USA
An advanced, modular bottom-supported cryomodule design is described which is highly optimized for mass-production and efficient precision-assembly. The FRIB driver linac uses 4 types of superconducting resonators and 2 solenoid lengths which in turn require 7 individual cryomodule configurations. To meet alignment tolerances a precision-machined bolted cryomodule rail system is described. A novel, kinematic mounting system of the cold mass is introduced which allows for thermal contractions while preserving alignment. A first prototype will incorporate a wire position monitor for alignment verification. The cold alignment structure is supported by composite posts which also function as thermal isolators. The cryogenic system provides separate 2 K and 4.5 K liquid helium lines to cavities and solenoids. Details of the JT valves, heat exchanger, cool-down circuit and junction to cryogenic line will be provided. Transient cool-down was simulated for stresses and buckling failure. A 1100-O Aluminum shield is used as a thermal radiation shield. The paper also describes cryomodule interfaces with the linac tunnel, the RF input cables, and the cryogenic distribution system.
Michigan State University designs and establishes FRIB as a DOE Office of Science National User Facility in support of the mission of the Office of Nuclear Physics.