ILC Beam Energy Measurement by means of Laser Compton Backscattering

TL;DR

This paper proposes a new non-invasive laser Compton backscattering method for precise, real-time beam energy measurement at the International Linear Collider, utilizing a compact spectrometer layout and advanced detectors.

Contribution

It introduces a novel, compact Compton spectrometer design with high spatial resolution detectors and simulation validation for accurate beam energy measurement.

Findings

Supports use of infrared or green lasers with quartz fiber detectors.

Achieves beam energy measurement precision of 10^{-4} or better.

Provides a feasible method for bunch-by-bunch energy monitoring during collisions.

Abstract

A novel, non-invasive method of measuring the beam energy at the International Linear Collider is proposed. Laser light collides head-on with beam particles and either the energy of the Compton scattered electrons near the kinematic end-point is measured or the positions of the Compton backscattered $\gamma$-rays, the edge electrons and the unscattered beam particles are recorded. A compact layout for the Compton spectrometer is suggested. It consists of a bending magnet and position sensitive detectors operating in a large radiation environment. Several options for high spatial resolution detectors are discussed. Simulation studies support the use of an infrared or green laser and quartz fiber detectors to monitor the backscattered photons and edge electrons. Employing a cavity monitor, the beam particle position downstream of the magnet can be recorded with submicrometer precision. Such a scheme provides a feasible and promising method to access the incident beam energy with precisions of $10^{-4}$ or better on a bunch-to-bunch basis while the electron and positron beams are in collision.