Measurements of undulator radiation power noise and comparison with $\textit{ab initio}$ calculations

TL;DR

This paper presents a generalized formula for fluctuations in undulator radiation power due to electron bunch phase-space variations, validated through experiments at Fermilab's IOTA storage ring, with implications for beam diagnostics.

Contribution

It introduces a new formula accounting for beam divergence effects on radiation power fluctuations and experimentally verifies it in a real accelerator setting.

Findings

Validated the generalized fluctuation formula experimentally.

Demonstrated the impact of beam divergence on radiation noise.

Discussed potential applications in beam instrumentation.

Abstract

Generally, turn-to-turn fluctuations of synchrotron radiation power in a storage ring depend on the 6D phase-space distribution of the electron bunch. This effect is related to the interference of fields radiated by different electrons. Changes in the relative electron positions and velocities inside the bunch result in fluctuations in the total emitted energy per pass in a synchrotron radiation source. This effect has been previously described assuming constant and equal electron velocities before entering the synchrotron radiation source. In this paper, we present a generalized formula for the fluctuations with a non-negligible beam divergence. Further, we corroborate this formula in a dedicated experiment with undulator radiation in the Integrable Optics Test Accelerator (IOTA) storage ring at Fermilab. Lastly, possible applications in beam instrumentation are discussed.