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A Mott polarimeter operating at MeV electron beam energies
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Image of FIG. 1.
FIG. 1.

Angular dependence of Sherman function for various energies (Z=79). Solid curves are for pure Coulomb potential, dotted ones for extended nucleus.

Image of FIG. 2.
FIG. 2.

Schematic layout showing installation of the Mott polarimeter at the 3.5 MeV injector of the MAMI RTM cascade. The beam energy can be changed by using a phase shifter (ϕ) in the waveguide between klystron and the third accelerating structure.

Image of FIG. 3.
FIG. 3.

Artists view of Mott polarimeter with magnetic spectrometers. Upward- or downward-scattered electrons are detected under θ = 164°. The observable polarization component is normal to the scattering plane. Upper magnet is partially removed for better visibility of electron trajectory. Shielding and 2 m long vacuum pipe to beam dump are not shown.

Image of FIG. 4.
FIG. 4.

Distribution of asymmetry values obtained by a series of asymmetry measurements. A Gaussian fit to the distribution has a variance of σ = 0.002 which is also the statistical uncertainty of the single measurement.

Image of FIG. 5.
FIG. 5.

Asymmetry vs beam current for various targets (statistical error bars).

Image of FIG. 6.
FIG. 6.

Asymmetry vs foil thickness for various primary beam energies at a fixed scattering angle of 164°. Lines are “rational” fit functions (see text). The fits related to the “exponential” model have been omitted for better visibility.

Image of FIG. 7.
FIG. 7.

Polarization determination for several energies using two different fit functions. Errors (±2σ) are fit uncertainties only.


Generic image for table
Table I.

Efficiency parameters for the different targets at beam energy of 3.5 MeV and scattering angle θ = 164°. The analyzing power for single elastic scattering is S 0 = 0.459.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: A Mott polarimeter operating at MeV electron beam energies