ANL, Argonne, Illinois, USA
We have designed, fabricated and tested two new half-wave resonators following the successful development of a series of niobium superconducting quarter-wave cavities. The half-wave resonators are optimized for β = 0.11 ions, operate at 162.5 MHz and are intended to provide up to 2 MV effective voltage for particles with the optimal velocity. Testing of the first two half-wave resonators is complete with both reaching accelerating voltages greater than 3.5 MV with low-field residual resistances of 1.7 and 2.3 nΩ respectively. The intention of this paper is to provide insight into how Argonne achieves low-residual resistances and high surface fields in low-beta cavities by describing the cavity design, fabrication, processing and testing.
THPB073
ANL, Argonne, Illinois, USA
A superconducting higher harmonic cavity (HHC) is under development for Advanced Photon Source Upgrade based on a Multi-Bend Achromat lattice. The HHC improves the Touschek lifetime and the single bunch current limit by lengthening the bunch. A TESLA-shaped single-cell 1.4 GHz (4th harmonic of the main RF) cavity will be used. Monopole and dipole higher order modes (HOMs) will be extracted primarily along the beam pipes and damped in a pair of ‘beamline’ silicon carbide (SiC) HOM dampers. These water-cooled SiC dampers will be placed just outside of the cryomodule. Maximum power dissipation in both SiC HOM dampers is estimated to be 1.7 kW at the beam current of 200 mA total and 4.2 mA max/bunch with the bunch length of RMS >50 ps. The SiC cylinder is cooled by a precision fit copper sleeve with water cooling channels. The thermal contact conductance at the interface between SiC and copper has been experimentally measured. In this paper, we will present design details of the SiC HOM dampers and experimental results of the thermal contact conductance at the interface.
