# Ultrafast Large Angle Beamstrahlung Monitor

## TL;DR

This paper presents a novel ultrafast method using nonlinear frequency mixing to measure and optimize beam collision timing and length in a collider, enhancing beam diagnostics.

## Contribution

It introduces a new technique for real-time, high-precision monitoring of beamstrahlung time profiles using nonlinear frequency mixing.

## Key findings

- Achieved 1% accuracy in measuring beam timing and length.
- Demonstrated the method's effectiveness for collider collision optimization.
- Provided a diagnostic tool for beam-beam collision monitoring.

## Abstract

The analysis of beamstrahlung radiation, emitted from a beam of charged particles due to the electromagnetic interaction with a second beam of charged particles, provides a diagnostic tool that can be used to monitor beam-beam collisions in a $e^{+}e^{-}$ storage ring. In this paper we show that the beamstrahlung time profile is related to the timing of the collisions and the length of the beams, and how its measurement can be used to monitor and optimize collisions at the interaction point of the SuperKEKB collider. To measure the time dependence of beamstrahlung, we describe a method based on nonlinear frequency mixing in a nonlinear crystal of beamstrahlung radiation with photons from a pulsed laser. We demonstrate that the method allows to measure and optimize the relative timing and length of the colliding bunches with 1% accuracy.