SLAC, Menlo Park, California, USA
Track3P is the particle tracking module of ACE3P, a 3D parallel finite element electromagnetic code suite developed at SLAC which has been implemented on the US DOE supercomputers at NERSC to simulate large-scale complex accelerator designs. Using the higher-order cavity fields generated by ACE3P codes, Track3P has been used for analyzing multipacting (MP) in accelerator cavities. The prediction of the MP barriers in the ICHIRO cavity at KEK was the first Track3P benchmark against measurements. Using a large number of processors, Track3P can scan through the field gradient and cavity surface efficiently, and its comprehensive postprocessing tool allows the identifications of both the hard and soft MP barriers and the locations of MP activities. Results from applications of this high performance simulation capability to accelerators such as the Quarter Wave Resonator for FRIB, the 704 MHz SRF gun cavity for BNL ERL and the Muon cooling cavity for Muon Collider will be presented.
KU Leuven, Kortrijk, Belgium
The dependence of the eigenfrequencies of a superconductive cavity on its geometry are represented by a stochastic response surface model. The model is constructed on the basis of both information on the eigenfrequencies as on their sensitivities with respect to the geometry. The eigenmodes are calculated using the 2D or 3D finite element method or finite integration technique. The stochastic representation does not only model uncertainties on the geometrical parameters but also inaccuracies of the eigenmode solvers, e.g. due to remeshing. Variations or optimisations of the geometry are carried out on the surrogate model. The model allows an efficient evaluation of microphoning and Lorentz detuning of accelerator cavities.
DELTA, Dortmund, Germany
HZB, Berlin, Germany
Elliptical cavities have been a standard in SRF linac technology for 30 years. In this work, we present a novel approach [1] using Bezier spline profile curves. By using different degrees of spline curves, the number of free parameters can be varied to suit a given problem (endcell tuning, basecell figures of merit), thus leading to a high flexibility of the spline approach. As a realistic example, a cubic spline SRF multicell cavity geometry is calculated and the figures of merit are optimized for the operational mode. We also present an outline for HOM endcell optimization that can be realized using available 2D solvers.
[1] B. Riemann et al., "SRF multicell cavity design using cubic and higher order spline cavity profiles", T 80.9, Verhandlungen DPG Göttingen 2012
Fermilab, Batavia, USA
The computational approaches assure essential guidance and order for the design of a superconducting cavities and cryomodules. The nature of superconductivity requires precise surface electromagnetic fields computation in order to design the cavity shape with a maximum accelerating gradient. At the same time the thickness of the cavity shell is limited by the ability to cool it down the temperature of liquid He, which makes the mechanical stability of the cavity and liquid He vessel assembly extremely important. Hence, it demands a self consistent electro-mechanical optimization in order to minimize microphonics and/or Lorentz force detuning phenomena. Specific challenges are an estimation of RF losses caused by the interaction of the passing beam with SC cavity and a multipactor analysis in the SC cavity and RF coupler. Finally the irregular time structure of a beam train with its own dense spectra may stochastically induce HOM fields in a cavity which results the beam emittance dilution. The study of these effects leads to specifications of SC cavity and cryomodule and can significantly impact on the efficiency and reliability of the superconducting linac operation.
