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Underground Science


Low Radioactivity Techniques:

Identification and Mitigation of Radioactive Backgrounds for Rare Event Search Experiments and underground science

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logo dessin Radioactivite MDeJesus

Underground Science

Rare event searches and underground science have undergone considerable development over the last 3 decades, mostly dedicated to physics thematics such as the study of solar neutrinos, the search for dark matter and neutrinoless double beta decay. But more recently the study of the impact of cosmic rays and natural radioactivity on microelectronic components, on quantum circuits and even in cell biology is also growing.

  • Dark Matter
  • Double Beta Decay
  • Solar Neutrinos
  • Geo-Science
  • Biology
  • Deep Qubits
  • ...

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Underground Laboratories ↑Top↑

Underground Laboratories
“Comparison of Main UL’s in the World.” ©

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Cosmogenic Activation ↑Top↑

Cosmic Ray Shower Nasa

The cosmogenic activation of materials is the production of radioactive isotopes due to the exposure to cosmic rays. The origin of primary cosmic radiation is galactic and is mainly composed of protons (~87%), alpha-particles (~12%) and nuclei Li, Be, B, C, O and F. The kinetic energy of these galactic particles can extend up to 10^^20 eV reaching the surface of the Earth with significant energies. They interaction with the atmospheric components induces production of new particles: n, H, He, 7Be, 14C, 37Ar, 39Ar, ...

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Neutron Activation ↑Top↑

The Neutron activation of materials is the production of radioactive isotopes in materials submitted to a high neutron flux.

Image to illustrate neutron activation Image to illustrate neutron activation

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Radiopurity of Materials↑Top↑

Image to illustrate Radiopurity SNOLAB Database

The radiopurity of materials is a crucial point for rare event search experiments. A central repository of material radiopurity measurements has been settled and is now available to the community. Experiments are invited to feed the database with they radioassay measurements.

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Shielding Materials ↑Top↑

Roman Lead Discovered off the coasts of Ploumanach
Lead ingots from a Roman shipwreck off the French coast of Ploumanac'h dated to the 4th century AD,. © Philippe Mura/Ministère de la Culture/DRASSM

There is no single material that will stop all radiation or particles. The type and nature of a shield depends on the type and amount of radiation one wishes to attenuate or stop. Alpha particles can easily be stopped by a single sheet of paper and cannot penetrate the outer dead layer of the skin. To attenuate or stop neutrons, light materials with hydrogen atoms will be most effective. Whereas for gammas, high Z materials are best suited. In the context of rare event search experiments, the materials used for shielding must also fulfill drastic radiopurity conditions.

  • Gamma
  • Neutron

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Radiation Detection and Measurement ↑Top↑

Image to illustrate Particle Detectors
Summary of particle detector types ©wikipedia

Depending on the nature of the radiation to be detected and quantified ( α, β, γ, μ, ν ...) different techniques are used.

  • Gamma
  • Beta
  • Alpha
  • Neutron
  • Muon

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Underground Screening Facilities ↑Top↑

Most of the underground laboratories have their own low background facility equipped with instruments able to quantify the radiopurity of materials.

Image to illustrate  LSM low-background detectors room
LSM low-background detectors room
Image to illustrate  BUGS - Boulby Ultra-low Background Material Assay
BUGS facility: Boulby Underground Germanium Suite
Image to illustrate  LNGS Special Techniques Service
LNGS Special Techniques Service
Image to illustrate the LSC Radiopurity Service
LSC Radiopurity Service
Image to illustrate the SNOLAB Low Background Counting Facility
SNOLAB Low Background Counting Facility,
Vue des Alpes Detector

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