Touschek#191
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When a line is generated through MAD-X sequence conversion, the line end up having markers sequencename$start and sequencename$end. In the line table these are present, but they do not have an associated s position and this causes an error!
Prevented sampling of particles with |δ|>LMA in Touschek MC by reducing the
longitudinal cutoff per element where needed:
nz_eff = min(nz, 0.9 * min(|δN|, δP) / σδ)
This ensures sampled δ stays strictly within the LMA,
avoiding pathological small-angle events with huge weights that distorted
RMC/RP and Touschek lifetime estimates.
- Adjustment is local: only elements with tight acceptance are clamped
- Prints a warning when nz_eff < nz
- Restores stable RMC/RP≈1 and meaningful lifetime results
giadarol
requested changes
Apr 29, 2026
giadarol
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Apr 29, 2026
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Please add a Touscheck chapter in Physics Guide
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All requested changes have been applied. I will open a pull request in xsuite to include information about Touschek in the Xsuite documentation and in the Xsuite physics guide. |
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Description
This PR introduces the possibility to perform Monte Carlo simulations of Touschek scattering in xfields.
It provides:
a new
TouschekScatteringbeam element implementing a Monte Carlo Touschek scattering kernel,a
TouschekManagerthat configures Touschek scattering centers using optics and a supplied local momentum aperture profile,a
TouschekCalculatorthat evaluates Piwinski Touschek scattering rates and integrated per-section rates, used to correctly weight scattered macroparticles.This enables end-to-end Touschek studies within Xsuite, including generation of Touschek-scattered particles, tracking, Touschek loss maps analysis, and Touschek lifetime evaluations.
Checklist
Mandatory:
Optional: