1 / 23

Motivation

Motivation. GERDA: Enriched 76 Germanium in Diodes (86%) Neutron capture in 76 Ge may cause background in the region of interest (Q ββ =2039 keV). Motivation. GERDA: Enriched 76 Germanium in Diodes (86%)

leala
Download Presentation

Motivation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Motivation • GERDA: • Enriched 76Germanium in Diodes (86%) • Neutron capture in 76Ge may cause background in the region of interest (Qββ=2039 keV) Blaubeuren Georg Meierhofer

  2. Motivation • GERDA: • Enriched 76Germanium in Diodes (86%) • Neutron capture in 76Ge may cause background in the region of interest (Qββ=2039 keV) • Measurement of cross section and prompt γ-spectrum of 76Ge Blaubeuren Georg Meierhofer

  3. Decay after neutron capture 76Ge 77Gem σ ~ 90 mb + n t1/2 = 53 s Q = 2702 keV Q = 6072 keV 159 keV 76Ge 77Ge 77As 77Se σ ~ 60 mb Q = 2702 keV Q = 682 keV + n t1/2 = 11.8 h t1/2 = 38 h Blaubeuren Georg Meierhofer

  4. Decay after neutron capture - prompt gammas - Peak at 2040.71 keV in 76Ge from inelastic scattering 76Ge 77Gem σ ~ 90 mb + n t1/2 = 53 s Q = 2702 keV Q = 6072 keV 159 keV 76Ge 77Ge 77As 77Se σ ~ 60 mb Q = 2702 keV Q = 682 keV + n t1/2 = 11.8 h t1/2 = 38 h Blaubeuren Georg Meierhofer

  5. Decay after neutron capture - prompt gammas - Peak at 2040.71 keV in 76Ge from inelastic scattering 76Ge 77Gem σ ~ 90 mb + n t1/2 = 53 s Q = 2702 keV Q = 6072 keV 159 keV 76Ge 77Ge 77As 77Se σ ~ 60 mb Q = 2702 keV Q = 682 keV + n t1/2 = 11.8 h t1/2 = 38 h - Peak at 2037.76 keV Blaubeuren Georg Meierhofer

  6. Known spectrum • Sn = 6072 keV • Expected > 200% per n • Intensity ~ 36% per n Blaubeuren Georg Meierhofer

  7. Known spectrum • Sn = 6072 keV • Expected > 200% per n • Intensity ~ 36% per n • Cross sections: • 76Ge 150 mbarn • 73Ge 15 000 mbarn • natGe 2 300 mbarn Blaubeuren Georg Meierhofer

  8. Prompt γ-Spectrum of natGe Molnar et. Al. Budapest Reactor Blaubeuren Georg Meierhofer

  9. Rates in GERDA • r = Φ*σ*n • Φ = 6,1 n/cm2/y (muon induced flux) • After 20-30 collisions neutrons are thermalised • Φ = 0,56 n/cm2/y • n = 7,9 x 1024 • σ = 150 mb Blaubeuren Georg Meierhofer

  10. Rates in GERDA • r = Φ*σ*n • Φ = 6,1 n/cm2/y (muon induced flux) • After 20-30 collisions neutrons are thermalised • Φ = 0,56 n/cm2/y • n = 7,9 x 1024 • σ = 150 mb • r = 0,7 n-capture/kg/y Blaubeuren Georg Meierhofer

  11. PGAA (Prompt Gamma Activation Analysis) Blaubeuren Georg Meierhofer

  12. PGAA (Prompt Gamma Activation Analysis) PGAA allows element analysis without destruction of the sample with very high sensitivity Blaubeuren Georg Meierhofer

  13. Our Setup Blaubeuren Georg Meierhofer

  14. Rates at FRM II • Sample: • 2 g of GeO2 (86% 76Ge) • Flux of cold neutrons (λ ~ 5 Å) • Φ = 8 X 109 n/cm2/s • σ = 10 barn People involved: University of Tübingen P. Grabmayr J. Jochum University of Cologne J. Jolie P. Kudejova FRM II K. Zeitelhack Blaubeuren Georg Meierhofer

  15. Rates at FRM II • Sample: • 2 g of GeO2 (86% 76Ge) • Flux of cold neutrons (λ ~ 5 Å) • Φ = 8 X 109 n/cm2/s • σ = 10 barn • > 108 n-capture/s People involved: University of Tübingen P. Grabmayr J. Jochum University of Cologne J. Jolie P. Kudejova FRM II K. Zeitelhack Blaubeuren Georg Meierhofer

  16. At this Moment • Experimental setup not finalized • First measurement with reduced neutron flux Φ = 5 x 108 n/cm2/s done • Measurement of the wavelength spectrum running (TOF) Blaubeuren Georg Meierhofer

  17. Blaubeuren Georg Meierhofer

  18. Blaubeuren Georg Meierhofer

  19. Spectrum with neutron beam Blaubeuren Georg Meierhofer

  20. Background with empty target Blaubeuren Georg Meierhofer

  21. Spectrum after irradiation with neutrons 77Ge Blaubeuren Georg Meierhofer

  22. Conclusion • 0,7 n-capture/kg/y • Two known peaks close to 2039 keV - 2037 keV (decay of 77Ge) - 2040 keV (inelastic scattering on 76Ge) - prompt γ-lines from n-capture on 76Ge? • Precise determination of neutron flux and spectrum • Production run after completion of setup • Coincidence measurements for better understanding of the prompt decay scheme Improvement of veto properties for GERDA Blaubeuren Georg Meierhofer

More Related