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New precise a K measurement as a test of internal conversion theory

New precise a K measurement as a test of internal conversion theory. 166 keV transition in 139 La. Christine Balonek Dr. John C. Hardy, Advisor Dr. Ninel Nica, Deputy Advisor August 3, 2006. Overview. Internal Conversion 139 La Decay Scheme 139 Ba Source Data Collection

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New precise a K measurement as a test of internal conversion theory

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  1. New precise aK measurement as a test of internal conversion theory 166 keV transition in 139La Christine Balonek Dr. John C. Hardy, Advisor Dr. Ninel Nica, Deputy Advisor August 3, 2006

  2. Overview • Internal Conversion • 139La Decay Scheme • 139Ba Source • Data Collection • Spectral Analysis • Impurity Analysis • K X-Ray Analysis • aK Calculations • Preliminary Results • Summary • Acknowledgements

  3. L shell e- ~10-18 s K shell g-ray Hole x-ray e- ~10-17 s Internal Conversion • Nuclear de-excitation energy transferred to an electron • Electron is emitted and followed by an x-ray • In competition with g-ray emission • Internal Conversion Coefficient • Impact • Nuclear decay schemes • Spin and parity assignments • Transition rates • Branching ratios • Detector calibration

  4. 139La Decay Scheme

  5. Trim excess tape to minimize impurities Adhesive Mylar tape, 3.81 mm Ba++(aq) + 2NO3-(aq) Insulin Mylar tape, 12.7 mm 139Ba Source • Layer Effects • Attenuation calculations • Back scattering • Source design • Determine number of atoms (mass of sample) required to produce desired g-ray counts • Preparation of sources • Obtain enriched barium • Dilute Ba(NO3)2 in water • Two sources, A and B 7.0 mm 0.5 in Source ready to be irradiated

  6. Data collection Neutron irradiation of source Texas A&M Nuclear Science Center g and x-ray detection Germanium detector, Cyclotron Institute, Texas A&M University Relative photopeak efficiencies calibrated to 0.15% 17 spectra recorded between ~1 and 24 hours after activation g and x-rays 151. mm

  7. Spectral Analysis • Source A, Sept. 2005 irradiation, spectrum 1 • 52.7 min elapsed time / 46.9 min live time (~0.6 half lives)

  8. g-ray Ka Kb x-rays Impurity Analysis x-ray impurities 29.623 keV to 42.290 keV g-ray impurities 163.138 keV to 168.638 keV

  9. K X-Ray Analysis Spectrum 1, 0.88 hr - largely 139La x-rays Spectrum 9, 15.87 hr - source impurity x-rays

  10. K X-Ray Analysis spectrum 1 Lanthanum K x-ray region spectrum 9, scaled Impurities: 152Eum152Sm 152Eu  152Sm 152Eum  152Eu 153Sm  153Eu

  11. aK Calculation • K-shell internal conversion coefficient, aK • wK = K-shell fluorescence yield • 0.905(4)* • NK, Ng = total number of K x or g-rays • Integration of spectra after removal of impurities • eK, eg = detector efficiency for K x or g-rays • Known detector efficiencies at energies of interest *E. Schönfeld, H. Jaben, NIM A 369 (1996) 527.

  12. Preliminary Results Source A, Sept. 2005 Irradiation Source B, July 2006 Irradiation Theoretical Calculations

  13. Summary • Successfully prepared and irradiated two enriched 139Ba sources • Analyzed 17 spectra for impurities based on g-ray energies and parent nuclei properties • Performed quantitative x-ray analysis to subtract impurities • Calculated preliminary values for aK of 139La • More detailed analysis of x-rays needed • Analysis is ongoing • Next: 196Pt irradiation • aK measurement for 197Au

  14. Acknowledgements • Dr. John C. Hardy, Advisor • Dr. Ninel Nica, Deputy Advisor • Hardy Research Group • Victor Golovko, John Goodwin, Victor Iacob, Hyo In Park • Texas A&M Cyclotron Institute REU Program • Dr. Sherry Yennello • Mary Ann Batson

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