Beam energy measurement at linear colliders using spin precession

TL;DR

This paper proposes a method to measure beam energy at linear colliders by analyzing spin precession caused by bending, achieving high precision through Compton scattering, and discusses related measurement procedures and error sources.

Contribution

It introduces a novel technique for beam energy measurement using spin precession and Compton scattering, with detailed analysis of measurement accuracy and potential error sources.

Findings

Measurement accuracy of about 10^{-5} achieved

Spin precession angle directly proportional to beam energy

Discussion of plasma focusing effects in energy measurement

Abstract

Linear collider designs foresee some bends of about 5-10 mrad. The spin precession angle of one TeV electrons on 10 mrad bend is 23.2 rad and it changes proportional to the energy. Measurement of the spin direction using Compton scattering of laser light on electrons before and after the bend allows determining the beam energy with an accuracy about of 10^{-5}. In this paper the principle of the method, the procedure of the measurement and possible errors are discussed. Some remarks about importance of plasma focusing effects in the method of beam energy measurement using Moller scattering are given.