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Fluorescence Yield of Cosmic Rays at Various Altitudes

Fluorescence Yield of Cosmic Rays at Various Altitudes. Melissa May Maestas Riverton High School March 7, 2003. Cosmic Rays. Mostly charged particles from outer space Two predominant components protons Iron nuclei. 2. 3. Cosmic Ray Detector.

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Fluorescence Yield of Cosmic Rays at Various Altitudes

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  1. Fluorescence Yield of Cosmic Rays at Various Altitudes Melissa May Maestas Riverton High School March 7, 2003

  2. Cosmic Rays • Mostly charged particles from outer space • Two predominant components • protons • Iron nuclei 2

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  4. Cosmic Ray Detector • Fluorescence light from particle shower can be detected by fast, sensitive cameras (“eyes”) on clear, moonless nights Schematic of twin “eyes” imaging an air shower 4

  5. HiRes • HiRes: High Resolution Fly’s Eye Group • A collaboration of eight universities • Mission: measure Ultra-High Energy Cosmic Rays • Photons are detected with photo-multiplier tubes (PMTs) 5

  6. HiRes Detector • 66 detector units each consisting of 2m diameter mirror and 256 PMTs • Each PMT views 1 degree cone of sky 6

  7. A 25 Microsecond Movie of An Air Shower(playback at 1/500,000 speed) 7

  8. FLASH • FLASH: Fluorescence from Air in Showers • Experiment to measure more precisely the fluorescence yield • Calibration of HiRes technique • Energy measured from amount of light detected • Beam pulses of ~billion electrons sent through chamber of gas • Various pressures • PMT signal measured 8

  9. Stanford Linear Accelerator Center • 2-mile accelerator • 3x1010 eV electrons in pulses of ~109 particles • Site of FLASH experiment 9

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  11. Chamber 11

  12. Experiment • Experiment involved 30 people including two month preparation period between April-June, 2002 • Data collected during 3 week “run” in June, 2002 at SLAC • Additional calibration analysis still in progress to this date • My part in this effort included PMT calibration, data analysis and preparation for next FLASH run 12

  13. Experiment / Hypothesis • FLASH experiment simulated particle showers from cosmic rays • Hypothesis: Fluorescence yield would: • Increase as pressure increases • Decrease as altitude increases • Shower particles/electrons likely to interact more if more molecules present 13

  14. Analysis Procedure • Data selections made for pressure dependence analysis • Plotted: • Full pressure range to find settings used • Each pressure distribution to find its mean • Digitized PMT signal at each pressure • Mean PMT signals vs. mean pressures • Converted pressure to altitude • P(z)=Poe-mgz/KT 14

  15. Pressure Number of electron pulses Pressure - Torr 15

  16. Lowest Pressure Range Number of electron pulses Pressure - Torr 16

  17. Signal at Lowest Pressure Range Number of electron pulses PMT Signal - ADC Counts 17

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  20. Discussion • Result: Yield increases at low pressures but levels off at higher pressures • Hypothesis supported at low pressures • Higher yield - more molecules per unit length for shower particles/electrons to interact with • Hypothesis not supported at higher pressures • Maybe: At low pressures, only amount of gas affects signal • Maybe: At higher pressures, gas molecules interact with each other, interfering with electrons 20

  21. Future Improvements & Experiments • Convert ADC counts to number of photons per electron • Calibration project currently underway • Examine Various Beam charge ranges • Higher beam charge - higher yield, same relationship?? • Part 2 of FLASH: Summer of 2003 • wavelength dependence • shower depth dependence 21

  22. Acknowledgments • Dr. Charles Jui • Dr. John N. Matthews • Dr. Petra Huentemeyer • John Hinton • Justin Findlay • Cigdem Ozkan • The HiRes Collaboration 22

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