10 research outputs found
Precision Electron-Beam Polarimetry using Compton Scattering at 1 GeV
We report on the highest precision yet achieved in the measurement of the
polarization of a low energy, (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 A, ~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.Comment: 9 pages, 7 figures, published in PR
A novel comparison of Moller and Compton electron-beam polarimeters
We have performed a novel comparison between electron-beam polarimeters based on Moller and Compton scattering. A sequence of electron-beam polarization measurements were performed at low beam currents (\u3c 5 mu A) during the Qweakexperiment in Hall-Cat Jefferson Lab. These low current measurements were bracketed by the regular high current ( 180 mu A) operation of the Compton polarimeter. All measurements were found to be consistent within experimental uncertainties of 1% or less, demonstrating that electron polarization does not depend significantly on the beam current. This result lends confidence to the common practice of applying Moller measurements made at low beam currents to physics experiments performed at higher beam currents. The agreement between two polarimetry techniques based on independent physical processes sets an important benchmark for future precision asymmetry measurements that require sub-1% precision in polarimetry. (C) 2017 The Authors. Published by Elsevier B.V
SPECTRA OF RADIATION EMITTED FROM OPEN-ENDED AND CLOSED CARBON NANOTUBES EXPOSED TO MICROWAVE FIELDS
A novel comparison of Møller and Compton electron-beam polarimeters
We have performed a novel comparison between electron-beam polarimeters based on Møller and Compton scattering. A sequence of electron-beam polarization measurements were performed at low beam currents (<5 μA) during the Qweak experiment in Hall-C at Jefferson Lab. These low current measurements were bracketed by the regular high current (180 μA) operation of the Compton polarimeter. All measurements were found to be consistent within experimental uncertainties of 1% or less, demonstrating that electron polarization does not depend significantly on the beam current. This result lends confidence to the common practice of applying Møller measurements made at low beam currents to physics experiments performed at higher beam currents. The agreement between two polarimetry techniques based on independent physical processes sets an important benchmark for future precision asymmetry measurements that require sub-1% precision in polarimetry