Superconducting RF Cavity Frequency and Field Distribution Sensitivity Simulation
Frequency and electromagnetic field distribution sensitivity of a superconducting RF (SRF) cavity are the fundamental phyical paramethers in cavity and tuner design. At low temperature, the frequency sensitivity can be obtained by measuring prototype cavity, but it is not easy to test the filed distribution sensitivity. This paper presents and describes a simulation method combining ANSYS and SUPERFISH to calculate the cavity frequency and field distribution variation due to cavity’s small deformation caused by mechanical force, radiation force, thermal expansion etc.. As an example, the simulation results of the frequency and field flatness sensitivity on the SNS cavities were confirmed by their test results.
Development of an SRF Reduced-beta Cavity for the Injector of the S-DALINAC Entwicklung einer
A recent major upgrade of the superconducting Darmstadt linear accelerator (S-DALINAC) allowed to conduct the first operational tests in an energy recovery linac (ERL) mode. The ERL operating regime imposes strict requirements for many accelerator components as well as for the accelerated beam quality and the beam energy spread in particular. At present, a significant beam energy spread is being observed in the capture section of the S-DALINAC. In that regard, the capture section part of the S-DALINAC injector needs to be upgraded in order to reduce the beam energy spread growth. In this work, the 6-cell reduced-β cavity development process is discussed and a final cavity design is proposed. The SRF cavity design is not limited by electromagnetic field simulations, but also includes the longitudinal beam dynamics computations and the cavity mechanical model investigation. The main challenge was to find an optimal upgrade solution that would satisfy contradictory requirements with minimised investments costs. The results of multi-physics simulations and qualitative analysis that allowed to make decisions related to the SRF cavity design considerations are discussed. The suggested 6-cell SRF cavity is expected to be manufactured by the end of 2019. The cavity commissioning tests are planned in 2020.
Design of the SNS cavity support structure
The Spallation Neutron Source (SNS) facility utilizes a superconducting linac to provide a 1 GeV H/sup -/ beam with an average power of 2 MW. A critical part of the accelerator structure is the superconducting radio frequency (SRF) niobium. cavities, which are housed in a titanium liquid helium pressure vessel. These vessels maintain the operating temperature of 2.1 Kelvin while facilitating the mechanical support, tuning and alignment of the SRF cavities. The design, fabrication and operation of the superconducting support structure will be presented with an emphasis on the design criteria as they pertain to the operation of the cavity. These criteria will be discussed with respect to the titanium liquid helium pressure vessels, higher order mode couplers, fundamental power coupler, field probe and tuning requirements.