Precise aK Measurement in 197Pt

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Precise aK Measurement in 197Pt

• A Test of Internal Conversion Theory

Mark Hernberg Advisor Dr. John C. Hardy Mentor
Dr. Ninel Nica
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What Is Internal Conversion?
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Internal Conversion Coefficient

• ICCs are used in the study of
• Nuclear decay schemes
• Spin and parity assignments,
• Transition rates
• Branching ratios
• Detector efficiency calibration

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(No Transcript)
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197mPt Decay
CITATION Nuclear Data Sheets (2005)
From NNDC(BNL) Program ENSDAT
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Source Preparation

• Homogeneous Layer of Sample
• 0.7mg 196Pt dissolved in a solution of aqua-regia
• 96 enriched sample, naturally occurring is only
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• Heated dried to solidify
• Placed on thin layer of Mylar
• Thermal Neutron Activation
• At TRIGA nuclear reactor here on campus
• Activation time of 4 hours

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Oops Activation Problems

• Long sample activation time resulted in an
  excessive level of both impurities and activity.

197mPt
197Pt
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Data Collection

• 17 spectra collected from
• 3 hours to 9 days after activation
• Over 700 million counts
• Average of over 900 counts/sec!
• Relative photopeak efficiencies calibrated to
  0.15

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Detector Info
Source

• 3 Main Events in Detector
• Photoelectric Effect
• Compton Scattering
• Pair Production

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Spectral Analysis
Spectrum 1 8.28 minute run time, 55.4 live
time, 1.2 million total counts
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Spectral Analysis
Spectrum 17 22.1 hour run time, 97.6 live time,
1 million total counts
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Impurity Analysis
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Impurity Analysis

• Check known common impurities-
  like 197Au
• Make educated guesses

• Known Gammas for
• 124Sb
• Energy (keV) Ig()
• 602.7 98.2
• 722.78 10.8
• 1690.9 47.7

• Found Gammas
• Energy (keV) Ig()
• 602.5 97.5
• 722.6 10.4
• 1691.4 47.1

TORI Data from LBNL website (1999)
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Spectral Analysis
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Spectral Analysis
197Au
191m Hg
191m Hg
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Peak Analysis
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aK Calculation

• Full Formula

aK K-shell ICC wK fluorescence yield
0.959(4) NK, Ng peak area eK, eg detector
efficiency
E. Schönfeld, H. Jaben, NIM A 369 (1996) 527.
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Preliminary Results
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To Infinity and Beyond

• Prepare another 196Pt sample, this time with the
  correct activation level.
• Repeat data collection analysis process
• Determine aK to lt1 uncertainty.

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Acknowledgements

• Dr. John C. Hardy
• Dr. Ninel Nica
• Victor Iacob