Abstract
To date, beam dynamics studies and design of combined zero degree drift tube linac (DTL) structures (Kombinierte Null Grad Struktur; KONUS) have only been carried out in multiparticle codes. Quantities such as the beam envelopes are obtained by averaging over particles, whose tracking is computationally intensive for large bunch populations. Tune computations, which depend on this average, are burdensome to obtain. This has motivated the implementation of a simulation of KONUS DTLs in the code transoptr, whose Hamiltonian treatment of beam dynamics enables the integration of energy gain from the longitudinal electric field on axis while simultaneously elaborating the field in transverse directions to obtain the linear optics. The code also features an in-built space charge capability. The evolution of the beam matrix including longitudinal optics is computed in a reference Frenet-Serret frame through the time-dependent DTL cavity fields. This enables fast envelope simulations for DTLs, resulting in a variable energy sequential tune optimization capability. The implementation methodology and optimization techniques, applicable for any combination of DTL tanks and bunchers, is outlined. Comparisons with the code lorasr, in addition to beam-based $E/A$ measurements of a DTL are presented.
Highlights
Tuning accelerators requires modeling of the beam’s evolution through the machine, producing simulated diagnostic fiducials for on-line comparison
Tune computations, which depend on this average, are burdensome to obtain. This has motivated the implementation of a simulation of KONUS drift tube linac (DTL) in the code TRANSOPTR, whose Hamiltonian treatment of beam dynamics enables the integration of energy gain from the longitudinal electric field on axis while simultaneously elaborating the field in transverse directions to obtain the linear optics
We present in this work the novel drift tube linac (DTL) beam envelope capability in the code TRANSOPTR, in particular its ability to perform constrained optimization problems upon the beam or transfer matrices through a DTL structure
Summary
Tuning accelerators requires modeling of the beam’s evolution through the machine, producing simulated diagnostic fiducials for on-line comparison. The infinitesimal transfer matrix approach means energy gain from a time varying electric field can be directly integrated in TRANSOPTR without resorting to stored “transit time factors.” This method is general; while the ISAC-DTL is shown in this paper, other linacs can be implemented with ease, requiring only the on axis field distributions. The approximation could be improved by combining elements’ matrices with edge-effect matrices that had been derived by integrating the equations of motion and applying them as kicks This “fringe field integral” approach was developed especially by Wollnik and co-workers [28], which otherwise had capabilities and restrictions similar to those of TRANSPORT. TRANSOPTR extended the capability, releasing these constraints, by generalizing those coordinates in a simple way, as will be shown
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