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Trim excess tape to minimize impurities. K shell. L shell. e- ~10 -18 s. g -ray. New precise a K measurement as a part of a test of internal conversion theory 166 keV transition in 139 La. Hole. x-ray. e- ~10 -17 s. Source A. Lanthanum K x-ray region. spectrum 1.

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Trim excess tape to minimize impurities

K shell

L shell

e-

~10-18 s

g-ray

New precise aK measurement as a part of a test of internal conversion theory166 keV transition in 139La

Hole

x-ray

e-

~10-17 s

Source A

Lanthanum K x-ray region

spectrum 1

spectrum 9, scaled

Impurities:

152Eum152Sm

152Eu  152Sm

152Eum  152Eu

Adhesive Mylar tape, 3.81 mm

Ba++(aq) + 2NO3-(aq)

Insulin

Mylar tape, 12.7 mm

g-ray

Ka

Kb

x-rays

Source A

Source B

7.0 mm

0.5 in

Source ready to be irradiated

Theoretical Calculations

Internal Conversion, Overview

  • Nuclear de-excitation energy transferred to an electron

    • Electron is emitted, followed by x-ray

    • Competes with g-ray emission

  • Internal Conversion Coefficient (ICC)

    • K-shell

    • I = intensityw = fluorescence yielde = detector efficiency

  • Impact

    • Nuclear decay schemes

      • Spin and parity assignments

      • Transition rates

      • Branching ratios

    • Detector calibration

139La Decay Scheme

C.M. Balonek, University at Buffalo

J.C. Hardy, N. Nica, Texas A&M University Cyclotron Institute

But Why?

  • Various ICC calculations disagree with one another and with experiment by several percent

  • Few ICC measurements have uncertainties under 1%

  • We will measure K-shell ICC values of three different transitions to better than 1% precision

    • ICCs for the 127.55 keV E3 transition from 134Csm and the661.657 keV M4 transition in 137Ba, have already been measured

    • 165.858 keV M1 transition in 139La is the third and final case

K X-Ray Analysis

  • Overlay of two spectra is used to identify impurities

  • Spectrum 1 (47 min) is largely 139La x-rays

  • Spectrum 9 (16 hr) contains x-rays from source impurities

  • Identified 3 different 152Eu transitions that contribute to this x-ray region

Spectral Analysis

  • Peaks identified according to energy and parent nuclei properties

  • 139Ba source produces strong peak at 166 keV

  • 139La K x-rays are another area of interest (29-42 keV)

    • Need to analyze impurities to accurately integrate this region

Source Preparation and Irradiation

Source Preparation

  • Ba(NO3)2(aq) placed on insulin-coated Mylar tape to produce micron-thick film of barium nitrate

    • Insulin aids in production of homogeneous film

  • Adhesive Mylar tape placed on film following solvent evaporation

  • Created two sources: A and B

  • Irradiated sources by neutron activation

    • Texas A&M Nuclear Science Center

  • Measured resulting x and g-rays

    • Germanium detector

      • Texas A&M University Cyclotron Institute

      • Relative photopeak efficiencies calibrated to 0.15%

    • 17 spectra recorded between ~1 and 24 hours after activation

Source A, spectrum 1 (47 min)

Preliminary Results

  • wK = K-shell fluorescence yield, 0.905(4)*

  • NK, Ng = total number of K x or g-rays found by integration of spectra

  • eK, eg = known detector efficiencies at energies of interest

*E. Schönfeld, H. Jaben, NIM A 369 (1996) 527.

A sincere thank you to Dr. John C. Hardy and Dr. Ninel Nica for their endless advisement throughout this project


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