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

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


Overview

Overview

  • Internal Conversion

  • 139La Decay Scheme

  • 139Ba Source

  • Data Collection

  • Spectral Analysis

  • Impurity Analysis

  • K X-Ray Analysis

  • aK Calculations

  • Preliminary Results

  • Summary

  • Acknowledgements


Internal conversion

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


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

139La Decay Scheme


139 ba source

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


Data collection

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


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

Spectral Analysis

  • Source A, Sept. 2005 irradiation, spectrum 1

    • 52.7 min elapsed time / 46.9 min live time (~0.6 half lives)


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

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


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

K X-Ray Analysis

Spectrum 1, 0.88 hr

- largely 139La x-rays

Spectrum 9, 15.87 hr

- source impurity x-rays


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

K X-Ray Analysis

spectrum 1

Lanthanum K x-ray region

spectrum 9, scaled

Impurities:

152Eum152Sm

152Eu  152Sm

152Eum  152Eu

153Sm  153Eu


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

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.


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

Preliminary Results

Source A, Sept. 2005 Irradiation

Source B, July 2006 Irradiation

Theoretical Calculations


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

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


Acknowledgements

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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