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Background Study in NDBD

Background Study in NDBD. Ming Shao. sources. environmental gamma radioactivity cosmic rays Neutrons Radon contamination of materials which detectors and their shielding are made of …. methods.

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Background Study in NDBD

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  1. Background Study in NDBD Ming Shao

  2. sources • environmental gamma radioactivity • cosmic rays • Neutrons • Radon • contamination of materials which detectors and their shielding are made of • …

  3. methods • 􀂾 Cosmic veto shielding • 􀂾 Underground locations • 􀂾 Detector construction using screened low-background materials • 􀂾 Detector construction using electroformed copper • 􀂾 Ultra-pure shielding materials • 􀂾 Low-cosmic-ray exposure DBD material, and copper … • 􀂾 DBD element enrichment • 􀂾 Signal processing • 􀂾 Detector segmentation • …

  4. Example: Majorana • Germanium crystals • Electroformed copper module • Close-in part • Thick shield of lead • Neutron-absorbing blanket • Active cosmic-ray veto shield

  5. Background model • Critical to the design and execution of the NDBD experiment • Guide the pre-commissioning efforts in detector • Acquisition system design • Sensitivity calculation -> physical goal • Depend on experiment method • Combine empirical and theoretic data

  6. Background reduction in Majorana • Ge background • Cosmogenic backgrounds in Ge • Neutrons at Altitude • Enrichment • Primordial (Potassium, Uranium and Thorium) • Backgrounds in Cu • Cosmogenic Activities in the Copper • Backgrounds in Pb • Other Materials

  7. Cosmogenic backgrounds in Ge

  8. Neutrons at Altitude - rate calculation

  9. Cosmogenic activation stages

  10. Primordial radioactivity • Uranium-238 • Thorium-232 • (Polonium-210) • Characteristic Alpha peak can be used for background estimation

  11. Cu • superior material for ultra-low background • Cu electroplating • Cosmogenic activation • Natural activities (208Tl and 214Bi)

  12. Pb • Gamma reduction • Ultra-low background Pb in inner detector • Normal lead outside

  13. Other materials • Outer: low dust situation to prevent contamination of the inner shield during maintenance • Inner: thermal insulators and structural parts (plastic), wires, electrical contacts (metalized plastic), and vacuum seals (indium) • Commercially purchased • screened and stored

  14. |<m>| ~35 meV

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