UMAN, Manchester
Results are presented on an alternative cavity to the ILC baseline design of TESLA-style SRF main accelerating linacs. This re-optimised shape enhances the bandwidth of the accelerating mode and has reduced surface electric and magnetic fields, compared to the baseline design and some current high gradient designs. Detailed simulations on the e.m. fields for the New Low Surface Field (NLSF) cavity, including end-cell and coupler designs, are reported. The re-distributed dipole mode distribution is also discussed.
UMAN, Manchester
Modes in the third harmonic cavities, designed and fabricated by FNAL, are analysed and the sensitivity to frequency errors are assessed. A circuit model is employed to model both monopole and dipole bands. The monopole circuit model is enhanced to include successive cell coupling, in addition to the usual nearest neighbour cell coupling.
UMAN, Manchester
CERN, Geneva
Instituut voor Kern- en Stralingsfysica, K. U. Leuven, Leuven
The superconducting upgrade of the REX-ISOLDE radioactive ion beam (RIB) post-accelerator at CERN will utilise a compact lattice comprising quarter-wave resonators (QWRs) and solenoids, accelerating beams in the mass range 2.5 < A/q < 4.5 to over 10 MeV/u. The short and independently phased quarter-wave structures allow for the acceleration of RIBs over a variable velocity profile and provide an unrivalled longitudinal acceptance when coupled with solenoid focusing. The incorporation of the solenoids into the cryomodule shortens the linac, whilst maximising the transverse acceptance, but the application of solenoid focusing in the presence of asymmetric QWR fields can have consequences for the beam quality. The rotation of an asymmetric beam produces an effective emittance growth in the laboratory reference system. We present modifications of the cavity geometry to optimise the symmetry of the transverse fields in the high-beta QWR. A racetrack shaped beam port is analysed and a modification made to the inner conductor with a geometry that will enable a niobium film to be effectively sputtered onto the cavity surface.
UMAN, Manchester
CERN, Geneva
Instituut voor Kern- en Stralingsfysica, K. U. Leuven, Leuven
The upgrade of the ISOLDE machine at CERN foresees a superconducting linac based on two gap independently phased Nb sputtered Quarter Wave Resonators (QWRs) working at 101.28MHz and producing an accelerating field of 6MV/m on axis. A deep study of the fields in the cavity is fundamental in order to pin down the crucial e-m parameters of the structure such as peak fields, quality factor and e-m power dissipated on the cavity wall. Furthermore it is fundamental to provide for an efficient tuning system to the structure. In this paper the full list of the e-m cavity parameters will be reported. The tuning plate design and realization will be described. Finally the frequency measurements with and without tuner plate at room temperature will be presented.