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Experiment Research

E04-018: Elastic Electron Scattering Off 3He and 4He at large momentum transfers

Experiment E04-018 will measure elastic electron scattering from the stable isotopes of helium: helium-3 and helium-4. Helium-3 is made up of two protons and one neutron; helium-4 is made up of two protons and two neutrons. These two isotopes are amongst the simplest nuclei that contain both protons and neutrons.

In elastic scattering, the incident electron collides with the stationary helium target nucleus and is deflected from its initial direction. The impact of the collision makes the helium nucleus recoil. The deflected electron and the recoiling nucleus are detected in two state-of-the-art magnetic spectrometers, the Hall A High Resolution Spectrometers (HRS), comprised of superconducting electromagnets and particle detectors.

The experiment will extract the "charge form factor" of helium-3 and helium-4 and the "magnetic form factor" of helium-3. The charge form factor of a nucleus provides direct information for the distribution of electric charge inside it. The magnetic form factor of a nucleus provides direct information for its magnetization distribution.

Comparisons between the form factor data currently being collected in this experiment and theoretical calculations will provide fundamental tests on our knowledge and understanding of the force between nucleons and the inner workings of nuclei, advancing our understanding of the internal structure and dynamics of the nucleus.

E04-018 Technical Paper (.pdf)