ETEAPOT: symplectic orbit/spin tracking code for all-electric storage rings

TL;DR

The paper introduces ETEAPOT, a symplectic simulation code for long-term orbit and spin tracking in all-electric storage rings, crucial for proton EDM experiments, with exact spin and orbit evolution modeling.

Contribution

ETEAPOT is a novel symplectic code that performs exact tracking of particle orbits and spins in electric storage rings, enabling precise long-term simulations for EDM measurements.

Findings

Code achieves exact spin and orbit tracking in electric rings.

Permits reliable long-term simulation over 1000 seconds.

Maintains symplecticity without artificial adjustments.

Abstract

Proposed methods for measuring the electric dipole moment (EDM) of the proton use an intense, polarized proton beam stored in an all-electric storage ring "trap". At the "magic" kinetic energy of 232.792 MeV, proton spins are "frozen", for example always parallel to the instantaneous particle momentum. This paper describes an accelerator simulation code, ETEAPOT, a new component of the Unified Accelerator Libraries (UAL), to be used for long term tracking of particle orbits and spins in electric bend accelerators, in order to simulate EDM storage ring experiments. Though qualitatively much like magnetic rings, the non-constant particle velocity in electric rings give them significantly different properties, especially in weak focusing rings. Like the earlier code TEAPOT (for magnetic ring simulation) this code performs \emph{exact tracking in an idealized (approximate) lattice} rather than the more conventional approach, which is \emph{approximate tracking in a more nearly exact lattice.} The BMT equation describing the evolution of spin vectors through idealized bend elements is also solved exactly---original to this paper. Furthermore the idealization permits the code to be exactly symplectic (with no artificial "symplectification"). Any residual spurious damping or anti-damping is sufficiently small to permit reliable tracking for the long times, such as the 1000 seconds assumed in estimating the achievable EDM precision.