arXiv subjects
Publications and source records attributed to N. Juntong.
The design of both higher order mode (HOM) and fundamental power (FP) couplers for a unique New Low Surface Field (NLSF) cavity is presented. Here we present a study which uses ILC baseline couplers. The Balleyguier method of calculating external quality factor is used and the results validated using both Microwave studio and HFSS.
We analyse higher order modes in the 3.9 GHz bunch shaping cavities recently installed in the FLASH facility at DESY. We report on recent experimental results on the frequency spectrum from probe based measurements made at CMTB at DESY. These are compared to those predicted by finite difference and finite element computer codes. This study is focused mainly on the dipole component of the multi-pole expansion of the wakefield.. The modes are readily identifiable as single-cavity modes provided the frequencies of these modes are below the cut-off of the inter-connecting beam pipes. The modes above cut-off are coupled to the 4 cavities and are distinct from single cavity modes
We present an optimized geometry for a 1.3 GHz superconducting cavity in which the surface electromagnetic fields have been minimized and the bandwidth of the fundamental mode has been maximized. We refer to this design as the New Low Surface Field (NLSF) cavity. Earlier work focused on properties of the fundamental mode. Here we additionally study higher order modes (HOMs), means of damping them, and short range wake fields. A two-band circuit model is employed in order to facilitate rapid characterization of cavity HOMs.
Results are presented on an alternative cavity to the ILC baseline design of TESLA-style SRF main accelerating linacs. This re-optimised shape enhances the bandwidth of the accelerating mode and has reduced surface electric and magnetic fields, compared to the baseline design and some current high gradient designs. Detailed simulations on the e.m. fields for the New Low Surface Field (NLSF) cavity, including end-cell and coupler designs, are reported. The re-distributed dipole modes are also discussed.
The main linacs of the ILC consist of nine-cell cavities based on the TESLA design. In order to facilitate reaching higher gradients we have re-designed the cavity shape. This leads to a reduction, comparable to several current designs, in both the ratio of the surface electric field to the accelerating field (Es/Ea) and the magnetic field to the accelerating field (Bs/Ea). The bandwidth of the accelerating mode is also optimized. This new shape, which we refer to as the New Low Surface Field (NLSF) design, bears comparison with the Ichiro, Re-entrant and LSF designs.