NSCL, East Lansing, Michigan
INFN/LNL, Legnaro, Padova
FZJ, Jülich
A superconducting linac for re-acceleration of exotic ions is being constructed at Michigan State University (MSU). The re-accelerator will initially be used by the MSU Coupled Cyclotron Facility; it will later become part of the Facility for Rare Isotope Beams at MSU. The re-accelerator will include two types of superconducting quarter-wave resonators (QWRs) to accelerate from 0.6 MeV per nucleon (MeV/u) to up to 3 MeV/u for uranium ("ReA3"), with a subsequent upgrade path to 12 MeV/u ("ReA12"). The QWRs (80.5 MHz, optimum beta = 0.041 and 0.085, made from bulk niobium) are similar to the cavities used at INFN-Legnaro for ALPI and PIAVE. They include stiffening elements and passive dampers to mitigate fluctuations in the resonant frequency. Eight beta = 0.041 QWRs have been fabricated; welding of the helium vessels and RF testing is in progress. Another eight beta = 0.085 QWRs are needed. Three cryomodules are needed to reach 3 MeV/u. Fabrication and assembly of the first cryomodule (the rebuncher, with one beta = 0.041 QWR and two superconducting solenoids) is complete. This paper will cover production efforts, test results so far, and future plans.
FZJ, Jülich
NSCL, East Lansing, Michigan
A superconducting linac for re-acceleration of exotic ions is under development at Michigan State University. Two types of superconducting quarter-wave resonators (80.5 MHz, optimum beta = 0.041 and 0.085) will be used for re-acceleration to energies of up to 3 MeV per nucleon initially, with a subsequent upgrade path to 12 MeV per nucleon. Structural design is an important aspect of the overall cavity and cryomodule implementation. The structural design must include stiffening elements, the tuning mechanism, and the helium vessel. The main mechanical design optimization goal is to minimize the shift in the cavity's resonant frequency due to the Lorentz force, bath pressure fluctuations, and microphonic excitation. Structural analyses of the MSU quarter-wave resonators will be presented in this paper. Stiffening measures will be explored. The numerical predictions will be compared to test results on prototype cavities.
FZJ, Jülich
In the low energy part of accelerators the magnets usually alternate accelerating cavities. For these particle energies Half-Wave Resonators are considered. Such layout allows enlargement of the peripherical cavity volume containing RF magnetic field. This results in decreasing the cavity peak surface magnetic field Bpk/Eacc by the factor of two. Additionally, an enlarged dome volume allows an installation of magnetic tuner for cavity frequency adjustment without affection of Bpk/Eacc. The paper reports the results of superconducting Half-Wave Resonator shape developments. A magnetic plunger for cavity frequency tune is investigated. Different cavity shape modifications are suitable also for close situated cavities. The results are applicable for SC RF Quarter-Wave Resonators.
FZJ, Jülich
CEA, Gif-sur-Yvette
The driver of the International Fusion Material Irradiation Facility (IFMIF) consists of two 125 mA, 40 MeV cw deuteron accelerators [1-2]. A superconducting option for the 5 to 40 MeV linac based on Half-Wave Resonators (HWR) has been chosen. The first cryomodule houses 8 The driver of the International Fusion Material Irradiation Facility (IFMIF) consists of two 125 mA, 40 MeV cw deuteron accelerators. A superconducting option for the 5 to 40 MeV linac based on Half-Wave Resonators (HWR) has been chosen. The first cryomodule houses 8 HWR's with resonant frequency of 175 MHz and geometric beta=v/c=0.094. This paper describes the RF design of half-wave length resonator together with structural analyses. Detailed simulations of resonance multipactor discharge in HWR are presented. Due to the required high coupling, the power coupler is located in mid-plane of the cavity. Several cavity tuning options were investigated: the capacitive tuner located in mid-plane and opposite to the power coupler port offers a large tuning range and will be tested first.