Phenomenological Formula Extends Loss Factor Predictions for Rectangular Tapered Collimators Across Optical and Inductive Regimes
The paper delivers a geometry-aware analytic model for wake losses in tapered collimators that spans short-bunch optical diffraction and long-bunch inductive regimes. It is grounded in systematic parametric scans with two independent codes and supplies closed-form expressions ready for accelerator design codes. Main limitation is the absence of experimental beam measurements; confirmation in a real accelerator would strengthen applicability.
The work extends an earlier axisymmetric formula to rectangular geometries by linking the scaling parameter μ d²/(σ_s L) to a Fresnel number derived from diffraction and image-charge electrodynamics. This explains the exact doubling of μ from 0.2 to 0.4 between geometries and validates the expression for realistic chamber widths rather than idealized flat plates. For longer bunches the authors identify the optical-to-inductive transition and supply an analytic loss-factor formula tied to the lowest relevant mode cutoff.
Rahman et al.: Within 18 months, loss-factor measurements at a high-energy linac test stand will confirm the μ=0.4 rectangular coefficient to within 10 % for σ_s < 1 mm bunches.
Sources (2)
- [1]Primary Source(https://arxiv.org/abs/2610.33336)
- [2]Supporting Source(https://inspirehep.net/literature/2854321)