precise a k measurement in 197 pt

Precise K Measurement in 197Pt

A Test of Internal Conversion Theory

Mark HernbergAdvisor: Dr. John C. Hardy

Mentor: Dr. Ninel Nica

What Is Internal Conversion?

Internal Conversion•Atomic electron ejection•Followed by characteristic X-ray emission

Gamma Decay•Photon emission

Internal Conversion Coefficient

ICCs are used in the study of: Nuclear decay schemes

Spin and parity assignments, Transition rates Branching ratios

Detector efficiency calibration

197mPt Decay

CITATION:Nuclear Data Sheets (2005)

From NNDC(BNL)Program ENSDAT

346.

5

M4

53.1

E

2

95.41 min

16.58 ns

19.89 hr

268.78 M1+E2

77.35 M1+E2

199.44 M1+E2

81.2%

8.2%

10.6%

15.4 ps

191. ns

stable

Source Preparation

Homogeneous Layer of Sample 0.7mg 196Pt dissolved in a solution of

aqua-regia 96% enriched sample, naturally

occurring is only ~25% 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

Oops – Activation Problems

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

197mPt

197Pt

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%

Detector Info

3 Main Events in Detector:1. Photoelectric Effect2. Compton Scattering3. Pair Production

Source

Spectral Analysis

Spectrum 1: 8.28 minute run time, 55.4% live time, ~1.2 million total counts

Spectral Analysis

Spectrum 17: 22.1 hour run time, 97.6% live time, ~1 million total counts

Impurity Analysis

Impurity Analysis

Known Gammas for

124Sb*Energy (keV) I(%)

602.7 98.2

722.78 10.8

1690.9 47.7

Found Gammas

Energy (keV) I(%)

602.5 97.5

722.6 10.4

1691.4 47.1

*TORI Data from LBNL website (1999)

Check known & common impurities- like 197Au

Make educated guesses:

Spectral Analysis

Spectral Analysis

197Au

191m Hg

191m Hg

Peak Analysis

K

K

KK N

N

1

K

K

KK N

N

1

K Calculation

Full Formula

K K-shell ICC

K fluorescence yield 0.959(4)*

NK, N peak area

K, g detector efficiency

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

Preliminary Results

)13(24.4K

To Infinity and Beyond

Prepare another 196Pt sample, this time with the correct activation level.

Repeat data collection & analysis process

Determine K to <1% uncertainty.

Acknowledgements

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