Electromagnetic effects of equatorially misaligned RF cavities

Abstract

One of the most challenging problems in modern particle accelerator systems is the manufacture of RF cavities within the desired tolerance limits. In this study experimental and computational investigations to quantify the effects of transversal half-cell misalignments on the fundamental accelerator cavity parameters and beam dynamics are presented. Equivalent circuit components of an equatorially misaligned single-cell aluminum elliptical cavity are obtained from the measured data and are employed to calculate longitudinal impedance and modal wake function. Critical coupling and bead-pull measurements are performed at the TM010-like mode frequency, 2.45 GHz for the quality factor and shunt impedance of the high-β cavity. We report equivalent circuit analysis for higher-order modes and variations of the equivalent circuit components with respect to considered misalignment errors for the MICE experiment's muon cooling cavity. It is shown that using the equivalent circuit model decreases the computational load significantly for the wake field simulations of resonator cavities. Good agreement between simulations and measurements in terms of accelerating cavity parameters and impedances is illustrated.

Cost-effective experiments with additively manufactured waveguide and cavities in the S-band

“…At this point we note that, conductivity calculations from the measured quality factor includes the effect of surface roughness. However, the differences in between R sh /Q values between the current work and [31] is due to the surface roughness and difficulties occur for tape coating of curvy surfaces. As seen in table 4, the costeffective fabrication method, can be used for roughness studies in various areas in addition to prototyping of accelerator cavities with a very low margin of error.…”

“…For the second experimental research, we manufactured a single-cell TESLA-shaped elliptical cavity utilizing FDM technology with ABS material to demonstrate the applicability of a 3D printed structure covered with conductive tape for accelerator cavity prototyping by measuring the selected fundamental parameters. Additionally, we investigate the effect of the surface roughness due to the use of conductive tape on the cavity parameters and, for the quantification of equatorial misalignment by comparing current results with those presented in the previously reported paper [31].…”

“…Such certain bumps or concave regions at the intersection regions may cause cavity surface destruction as a result of field instabilities for the high beam current operations in the high power regimes. Within this frame, to understand the mentioned effect, a replica of the single-cell cavity, which was employed for the measurements in [31], is printed and coated with conductive tape as a prototype, see figure 5(a). Two halfcells of our cavity can be connected via screws and nuts.…”