Session GH: Instrumentation II

9:00 AM–11:48 AM, Saturday, October 28, 2006
Gaylord Opryland Room: Cheekwood F

Chair: Joe Hamilton, Vanderbilt University

Abstract ID: BAPS.2006.DNP.GH.11

Abstract: GH.00011 : The Polarized $^3$He Target for the Measurement of $G_E^n$ at high $Q^2$ in Hall A

11:00 AM–11:12 AM

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Author:

Ameya Kolarkar
(University of Kentucky)

In early 2006, the Jefferson Lab experiment E02-013 successfully collected data to measure the neutron electric form factor $G_E^n$ at the four-momentum transfer values in the range of 1.2 to 3.5~(GeV/c)$^2$. It used a polarized $^3$He target and a polarized electron beam at energies up to 3.2 GeV to study the semi-exclusive $^3\hspace*{-1.2pt}\vec{H\hspace*{-1.2pt}e} (\vec{e},e^\prime n)$ scattering reaction in quasi-elastic kinematics. The electrons were detected in the BigBite spectrometer and the recoiling neutrons in an array of scintillators. The data will be used to extract $G_E^n$ from the transverse asymmetry $A_T$. The expected statistical accuracy for $\Delta G_E^n/G_{Dipole}$ is 0.04 for these values of $Q^2$. To reduce the systematic uncertainties in $A_T$, the magnetic field direction was measured to better than 2 mrad with a newly developed air-floated compass. For the first time at JLab, the $^3$He target was polarized using spin-exchange with rubidium \emph{and} potassium. A uniform magnetic field was generated in the target region by a newly developed iron enclosure. Nuclear Magnetic Resonance (NMR) and Electron Paramagnetic Resonance (EPR) techniques were used to measure target polarization. Polarizations in excess of 50\% were achieved during running conditions. This talk will focus on various aspects of the target.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2006.DNP.GH.11