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Measurement of the Fluorescence Yield for UHECR study

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Measurement of the Fluorescence Yield for UHECR study

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  1. Measurement of the Fluorescence Yield for UHECR study Gwenaëlle LEFEUVRE APC – Collège de France

  2. Cosmic Rays • Fluorescence • Yield Measurements

  3. Ultra-High Energy Cosmic Rays Energy max. ? Nature ? Origin ? Processes ?

  4. The need of an accurate energy 15 % in energy almost 40 % in flux * E3 !

  5. Air shower Cosmic ray • some 103 hadrons • some 109 electrons Fluorescence (isotropic) Cosmic ray Charged particles Nuclei Electromagnetic part : 90 % of total energy ! Cerenkov cone

  6. Detecting the UHECR • Sampling • extrapolation of cross sections • AGASA, Auger • Fluorescence • development of the shower • HiRes, Auger, EUSO Today : Auger calibration of surface detector by fluorescence

  7. What is the fluorescence ? Excitation e-sh + N2 e- + N2+* + e-sh e- + N2+ N2* e- + N2 e- + N2* Bunner, PhD thesis, 1967

  8. Fluorescence spectrum • « Dry air » (80 % N2, 20% O2), 1 bar • after correction of spectrometer response • electron gun, 1013 e-/s Intensity (rel. unit.) Wavelength (Ulrich, Airlight workshop, 2003)

  9. Yield (photons / m) De-excitation of nitrogen • Radiation • Internal • Collision • Recombination : O2 Null pressure f(P, T) Pressure (hPa) photons / e- / meter

  10. US-Standard 76 atmosphere Temperature Density Pressure

  11. Yield variation with altitude Models Measurements

  12. Yield variation with altitude 13.5 %

  13. Already, my result...

  14. Absolute yield in [300, 430] nm with the best accuracy possible Absolute fluorescence spectrum Objectives To achieve this : need an accurate and absolute calibration of the detectors

  15. the setup

  16. the setup 370 MBq

  17. the setup

  18. the setup

  19. the setup BG3 (Schott) Transmission (%) wavelength (nm)

  20. the setup

  21. the setup

  22. the setup

  23. the setup

  24. the setup

  25. the setup