Author: Rybarcyk, L.
Paper Title Page
TUPWA067 Beam Emittance Growth Effects in High-intensity RFQ 1859
  • Y.K. Batygin, R.W. Garnett, L. Rybarcyk
    LANL, Los Alamos, New Mexico, USA
  Beam dynamics in an RFQ are strongly affected by coupling between transverse and longitudinal particle oscillations. The adiabatic process of high-intensity bunched beam formation results in equipartitioning in the RFQ, which determines the longitudinal beam emittance. Avoiding parametric resonances is an important design criterion to prevent significant emittance growth of the beam. Manufacturing errors can result in beam emittance growth and reduction of beam transmission. This paper will present the results of a study where analytical and numerical evaluations were performed to determine the effect of the aforementioned factors on beam quality in a high-current RFQ.  
THPWO094 Electromagnetic and Multi-particle Beam Dynamics Modeling of 4-Rod RFQs 3978
  • S.S. Kurennoy, R.W. Garnett, L. Rybarcyk
    LANL, Los Alamos, New Mexico, USA
  Detailed 3D modeling of the recently commissioned FNAL 4-rod RFQ was performed with the CST Studio Suite. The RFQ model is based on the CAD files used for its fabrication, which are imported in CST Studio. The electromagnetic (EM) analysis was done with MicroWave Studio (MWS) and the beam dynamics modeled with Particle Studio (PS) using the MWS-calculated fields. Realistic matched input CW beam distributions, generated externally with up to 10K particles per RF period and up to 70 RF periods long, are injected in the RFQ for PS simulations. The EM analysis reveals some interesting features of the RFQ fields; their origin and influence on the beam parameters is studied. In particular, the end-gap longitudinal field, which is usually not taken into account when an RFQ is designed with standard codes, can change the output beam energy. Our CST modeling results helped explain and successfully resolve some problems encountered in the FNAL RFQ commissioning. We plan to use a similar approach to evaluate a new 4-rod RFQ that will become a part of an upgraded front end of the LANSCE linac.