Politecnico di Torino - Corso Duca degli Abruzzi, 24 - 10129 Torino, ITALY

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Electron spin polariser

Electron beam polarisationElectron microscopeMagnetic measurementsParticle beam polarisationSPIN filter

Introduction

The invention relates to a method and a system for electron polarisation able to generate a spin polarized output particle beam – at least partially polarized. The system conceived works as efficient spin polarisation filter, can be applied to all particles provided with magnetic spin momentum (i.e. electrons, neutrons, atoms, ions, etc.) and it does not require frequent cathode exchange. The produced polarized beam is stable, has high brightness and can be integrated inside an electron microscope.

Technical features

The already available sources of polarized electrons are limited in brightness and/or polarization purity and require a frequent exchange (stability). Such drawbacks limit their using in electron microscopes or similar apparatus. Our SPIN polariser comprises a system of coupled multipolar magnetic and electric field (hereafter q-filter), an holographic elements for the generation of vortex beams (namely beams carrying Orbital Angular momentum) of the given order and a pinhole or diffractive elements for the selection of electrons with a well-defined orbital angular momentum.  In a first implementation the q-filter is positioned after the holographic element while in a second one the position of the q-filter and hologram is inverted. In this way two beams with opposite polarization can be easily selected. Our technology is compatible with source coherency and monochromaticity.

Possible Applications

  • Academic research;
  • Microscopy of Magnetic materials;
  • New atomic contrast effects in High resolution Microscopy.

Advantages

  • Compatibility with conventional field emitter cathode;
  • Flexibility high brightness or high purity;
  • Easily switch to unpolarised mode;
  • Easily switch of polarization (implementation 2);
  • Accessible fabrication technology.