Precision Electron-Beam Polarimetry using Compton Scattering at 1 GeV

Abstract

We report on the highest precision yet achieved in the measurement of the polarization of a low energy, $\mathcal{O}$(1 GeV), electron beam, accomplished using a new polarimeter based on electron-photon scattering, in Hall~C at Jefferson Lab. A number of technical innovations were necessary, including a novel method for precise control of the laser polarization in a cavity and a novel diamond micro-strip detector which was able to capture most of the spectrum of scattered electrons. The data analysis technique exploited track finding, the high granularity of the detector and its large acceptance. The polarization of the $180\mu$A, $1.16$~GeV electron beam was measured with a statistical precision of $<$~1\% per hour and a systematic uncertainty of 0.59\%. This exceeds the level of precision required by the \qweak experiment, a measurement of the vector weak charge of the proton. Proposed future low-energy experiments require polarization uncertainty $<$~0.4\%, and this result represents an important demonstration of that possibility. This measurement is also the first use of diamond detectors for particle tracking in an experiment.

arXiv comment9 pages, 7 figures, published in PRX

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Cited by in corpus (12)

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• Electron polarization in ultrarelativistic plasma current filamentation instabilities
• Single-shot determination of spin-polarization for ultrarelativistic electron beams via nonlinear Compton scattering
• Stochasticity in radiative polarization of ultrarelativistic electrons in an ultrastrong laser pulse
• First Determination of the 27Al Neutron Distribution Radius from a Parity-Violating Electron Scattering Measurement
• Strong signature of one-loop self-energy in polarization resolved nonlinear Compton scattering
• Measurement of the Beam-Normal Single-Spin Asymmetry for Elastic Electron Scattering from ${}^{12}$C and ${}^{27}$Al
• Precision Measurement of the Beam-Normal Single-Spin Asymmetry in Forward-Angle Elastic Electron-Proton Scattering
• Parity-Violating Inelastic Electron-Proton Scattering at Low $Q^2$ Above the Resonance Region
• Ultra-High precision Compton polarimetry at 2 GeV