Optical excitation of ultra-relativistic partially stripped ions

TL;DR

This paper investigates the optical excitation of ultra-relativistic partially stripped ions at CERN for the Gamma Factory, analyzing their electronic structures, excitation regimes, and photon emission efficiency through analytical and numerical methods.

Contribution

It provides a detailed spectroscopic analysis and excitation schemes for ions used in the Gamma Factory, identifying different interaction regimes and estimating photon emission efficiency.

Findings

Two regimes of ion-light interaction identified

Analytical and numerical estimates of photon emission efficiency

Spectroscopic properties of selected ions analyzed

Abstract

The Gamma Factory (GF) initiative aims at the construction of a unique experimental tool exploiting resonant interaction of light with ultra-relativistic partially stripped ions (PSI) stored in circular accelerators at CERN. Resonant excitation of high-energy electronic transitions in the ions is achieved through Doppler-boosting (by twice the Lorentz factor; from hundred to several thousand times) of light energy. In order to efficiently excite the ions, and hence generate intense beams of scattered/fluorescent photons, a detailed knowledge of the ions' electronic energy structure and the dynamics of optical excitation is required. Spectroscopic properties of PSI selected for the GF operation, as well as their optical excitation schemes, are investigated. Two regimes of the ion--light interaction are identified, leading to different dynamics of the excitation. The efficiency of the ion--light interaction, as well as the number of photons emitted from a single ion bunch, are estimated, both analytically and numerically, for three ions considered for the GF, i.e.~Li-like ${}^{208}_{\phantom{0}82}$Pb$^{79+}$, Li-like ${}^{40}_{20}$Ca$^{17+}$, and H-like ${}^{208}_{\phantom{0}82}$Pb$^{81+}$.