Paper  Title  Page 

SURDI1  Computational Challenges in ESS  1 


The European Spallation Source, to be built in Lund, Sweden, will be based on a superconducting proton linac. Toplevel linac parameters of 2.5 GeV energy, 50 mA pulse current, 14 Hz pulse repetition rate and 2.86 ms pulse length result in 5 MW average beam power and 125 MW peak power. General challenges for the accelerator design and construction range from minimizing beam losses to prototyping, manufacturing and installing the large quantity of RF power soures. The presentation will give an overview of the ESS project and give specific examples of computational challenges related to the beam dynamics of the linac.  
Slides SURDI1 [11.623 MB]  
MOAAI1  Project Overview and Computational Needs to Measure Electric Dipole Moments at Storage Rings  7 


The discovery of a nonzero EDM (Electric Dipole Moment) would be a signal for “new physics” beyond the standard model. EDM experiments with charged particles are only possible at storage rings. As a first step towards EDM searches in storage rings we proposed R&D work to be carried out at the Cooler Synchrotron COSY, then perform a first direct EDM measurement of a charged particle in a storage ring at COSY and on a longer time scale construct a dedicated storage ring. Full spintracking simulations of the entire experiment are absolutely crucial to explore the feasibility of the planned experiments. It is planned to use the COSYINFINITY code and its updates to include higherorder nonlinearities, normal form analysis, symplectic tracking and especially spin tracking upon incorporation of RFE/B spin flippers into the code. Adding the spin degree of freedom substantially enhances the need for the computing power. In order to study subtle effects and simulate particle and spin dynamics during the storage and buildup of the EDM signal, one needs customtailored fast trackers capable of following up to 100 billion turns for samples of up to 10^{6} particles.  
Slides MOAAI1 [3.341 MB]  
MOABI1 
Beam Optics Analysis of Largeacceptance Superconducting Inflight Separator BigRIPS at RIKEN RI Beam Factory  


The BigRIPS inflight separator serves to produce rare isotope (RI) beams at RIKEN RI Beam Factory, in which studies of exotic nuclei are extensively made. It is characterized by large acceptances and twostage structure, allowing efficient production of RI beams using inflight fission and high resolving power in particle identification (PID). The large acceptances are achieved by using irondominated superconducting quadrupoles with large apertures and high poletip fields. The PID is made in the secondstage of BigRIPS, in which precise momentum measurement is performed by trajectory reconstruction using ionoptical transfer maps and measured iontrajectories. Elaborate beam optics calculation and analysis are essential to tune ion optics and achieve high PID resolving power, because the quadrupoles have large fringefield regions and their field distribution varies largely as the iron is saturated. The optics calculation has to be made based on precise field map data measured as a function of field strength. In this talk we outline computational needs in the BigRIPS separator, emphasizing the method and analysis of beam optics calculations and comparison with measurements.  
Slides MOABI1 [4.126 MB]  
WEP07  Traveling Poles Elimination Scheme and Calculations of External Quality Factors of HOMs in SC Cavities  152 


Funding: Funded by EU FP7 Research Infrastructure Grant No. 227579 and funding approved by German Federal Ministry of Research & Education, Project: 05K10HRC The main scope of this work is the automation of the extraction procedure of the external quality factors Qext of Higher Order Modes (HOMs) in Superconducting (SC) radio frequency cavities [*]. The HOMs are generated by charged particle beams traveling at the speed of light through SC cavity. The HOMs decay very slowly, depending on localization inside the structure and celltocell coupling, and may influence succeeding charged particle bunches. Thus it is important, at the SC cavity design optimization stage, to calculate the Qext of HOMs. The Traveling Poles Elimination (TPE) scheme has been used on scattering parameters spectra to obtain external quality factors. The combination of Coupled SParameter Calculations (CSC) method and vector fitting procedure allows us to study very complicated structures in much better details and almost automated extraction of HOMs' Qext factors. The results are also reasserted by careful eigenmode analysis of the SC cavity. The SParameter and eigenmode simulations were performed using CST Microwave Studio. *Axel Neumann et al., "Status of the HOM Calculations for the BERLinPro Main Linac Cavity", FRAAC3 (this conference) 

THP01 
SRF Cavity and Cryomodule Design with ACE3P  


Funding: USDOE Based on the conformal higher finiteelement method implemented on parallel computing platforms, ACE3P is extending its capabilities to meet the computational needs for the design of SRF cavities and cryomodules. These requirements include accurate electromagnetic field computations to obtain the optimal cavity shape for maximum accelerating gradient and to find the high order modes (HOMs) excited by the bunch train in a cavity chain. In addition, multipacting simulation is important to the SRF cavity and coupler development as well as electromechanical calculations to model the Lorentz force detuning. Results from ACE3P efforts that address these effects for the design of SRF cavity and cryomodule will be presented. 

FRAAI1  Computational Needs for RF Design of Superconducting Cavities  270 


Funding: Operated by Fermi Research Alliance, LLC under Contract No.DEAC0207CH11359 with the U.S. Department of Energy. 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 electromechanical 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. 

Slides FRAAI1 [8.162 MB]  
FRAAC3  Status of the HOM Calculations for the BERLinPro Main Linac Cavity  278 


Funding: Work supported by Federal Ministry for Research and Education BMBF under contract 05K10HRC The Berlin Energy Recovery Linac Project (BERLinPro) is designed to develop and demonstrate CW LINAC technology and expertise required to drive nextgeneration Energy Recovery Linacs (ERLs). Strongly higher order mode (HOM) damped multicell 1.3 GHz cavities are required for the main linac. The cavity under study is an integrated design of the Cornell base cell with JLab HOM waveguide couplers. Modifications to the end group design have also been pursued, including the substitution of one waveguide by a HZBmodified TTFIII power coupler. In this talk the progress in HOM calculations to avoid beambreakup instabilities for the favored cavity structure will be presented. 

Slides FRAAC3 [15.439 MB]  