Measuring apparatus for degree of spin polarization of an electron beam

Claim 1

Apparatus for determining the degree of spin polarization of an electron beam, in which there are provided a monocrystal of electrically conducting or semiconducting material having a surface disposed perpendicularly to the radiation direction of said electron beam and formed parallel to a crystal structure plane designed to scatter the electrons of said beam, and also means for measuring the intensity of backscattering of electrons by the monocrystal in two respective directions at complementary angles to said radiation direction of said beam, having the improvement consisting in that: (a) first means for accelerating or decelerating electrons, consisting of a plurality of electron lens elements of tubular or of diaphragm form at different electrical potentials are provided for accelerating or decelerating the electrons of said beam to velocities suitable for monochromatizing said electrom beam to a degree required in a subsequent stage; (b) monochromatizing means downstream of said first accelerating or decelerating means are provided for monochromatizing said electron beam; (c) second means for accelerating or decelerating electrons, consisting of electron lenses of tubular or diaphragm form, are provided and located downstream of said monochromatizing means for adjusting the energy to a value required for the scattering of the electrons of the monochromatized beam and for focussing the beam on said surface of said monocrystal; (d) said monocrystal is arranged next in line downstream of said second accelerating or decelerating means; (e) said means for measuring electron backscattering intensity consists essentially of at least one pair of detectors for measuring the intensity of electron beams backscattered at complementary angles from said surface of said monocrystal, and (f) means interposed between said surface of said monocrystal and said backscattering intensity measuring means are provided for separating or deviating the low-energy portion of the backscattered electrons produced by ineleastic interaction of electrons of said beam with said monocrystal.