Paper  Title  Page 

MOPWO001  Moment Method Beam Dynamics Code Development: Extended for Radio Frequency Quadrupole Simulations  879 


Funding: This research is funded by grant “KUL 3E100118” “Electromagnetic Field Simulation for Future Particle Accelerators”, project FP7Euratom No. 269565 and the Belgian Nuclear Research Centre (SCK•CEN). A Radio Frequency Quadrupole (RFQ) enables acceleration of a continuous lowvelocity hadron beam, combining velocity independent electric focusing and adiabatic bunching, resulting in highcurrent compact bunches with nearly 100% capture and transmission efficiency. With virtually no postconstruction tuning capabilities, an RFQ design phase requires all transient parameters (machining tolerances, thermomechanical deformation factors). This allows the determination of acceptable tolerances on input and output beam characteristics, of major importance in beam availability and beam trip prevention, and makes fast beam dynamics simulation codes incorporating RFQs indispensable. This article presents the implementation and validation of an RFQ beam line element into VCode, a moment method beam dynamics simulation code. VCode time integrates the Vlasov equation for an initial particle distribution represented by a discrete set of characteristic moments, accounting for all exerting internal and external forces. VCode delivers highly accurate beam dynamics results with precision and efficiency advantages in terms of average or rms beam dimensions, projected emittances or total energy. 

MOPWO006  Eigenmode Computation for the GSI SIS18 Ferrite Cavity  894 


Funding: Supported by GSI At the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt the heavyion synchrotron SIS18 is operated to further accelerate stable nuclei of elements with different atomic numbers. Two ferriteloaded cavity resonators are installed within this ring. During the acceleration phase their resonance frequency has to be adjusted to the revolution frequency of the heavyions to reflect their increasing speed. To this end, dedicated biased ferritering cores are installed inside the cavities for a broad frequency tuning. By properly choosing a suited bias current, the differential permeability of the ferrite material is modified, which finally enables to adjust the eigenfrequency of the resonator system. Consequently, the actual resonance frequency strongly depends on the magnetic properties of the ferrites. The goal of the current study is to numerically determine the lowest eigensolutions of the GSI SIS18 ferriteloaded cavity. For this purpose, a new solver based on the Finite Integration Technique has been developed. 

MOPWO007  Numerical Calculation of Electromagnetic Fields in Acceleration Cavities Under Precise Consideration of Coupler Structures  897 


Funding: Work supported by BMBF under contract 05H12RD5 The acceleration with superconducting radio frequency cavities requires dedicated couplers to transfer energy from the radio frequency source to the beam. Simultaneously, higher order mode couplers are installed to effectively suppress parasitic modes. Therefore, the numerical eigenmode analysis based on realvalued variables is no longer suitable to describe the dissipative acceleration structure. At the Computational Electromagnetics Laboratory (TEMF) a robust parallel eigenmode solver to calculate the eigenmodes in the lossy acceleration structure is available. This eigenmode solver is based on complexvalued finite element analysis and utilizes basis functions up to the second order on curved tetrahedral elements to enable the high precision elliptical cavity simulations. The eigenmode solver has been applied to the TESLA 1.3 GHz accelerating cavity to determine the resonance frequency, the quality factor and the corresponding field distribution for all 192 eigenmodes up to the 5th dipole passband (3.12 GHz). 
