Speaker
Description
Muon collider (MuC) is a promising, yet challenging, pathway to achieve a 10TeV collider at the energy frontier. The current MuC design requires ionization cooling to shrink the beam emittance and accomplish the target luminosity. One key component in the ionization cooling channel is the NCRF cavity which replenishes the longitudinal energy and provides the longitudinal focusing. Overcoming the limit on the cavity gradient imposed by the surrounding strong magnetic field is critical for the performance of the MuC. One unique feature of this cavity is the thin beam window covering the cavity aperture. The beam window increases the cavity shunt impedance and reduces RF breakdown probability. In this poster, we will present recent study progress on two effects of the beam window, the emittance growth due to the scattering and the wakefield enhanced by the closed aperture.
To study the muon scattering in the beam window and the resulting emittance dilution, we use GEANT4 simulation with analytical benchmarking. We simulate the window at different stages in the rectilinear cooling lattice, and it is shown that the scattering effect is negligible at the early stages and becomes significant in the later stages of the post-merging section. The comparison between two window materials, Be and Al, indicates the Al window needs to be at about a quarter of the thickness of the Be window to have the same amount of emittance dilution.
We also show that with the beam aperture completely covered by the window, the CST wakefield solver is no longer suitable for this calculation. Instead, we deploy the CST PIC solver to calculate the EM field generated by the muon beam passing through the cavity and use post-processing methods to resolve the wake potential with a Python wrapper script. The wakefields due to the cavity geometry and the beam space charge are separately characterized.
| What category does your poster fit in? | Acceleration |
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