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Activity standardization of 32Si at PTB
Karsten Kossert1, Mario Veicht2, Ionut Mihalcea2
1Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116, Braunschweig, Germany.
Summary
Researchers addressed 32Si sample instability and measurement discrepancies using liquid scintillation counting. A new stable sample composition was developed, improving activity determination for future 32Si half-life measurements.
Area of Science:
- Nuclear physics and metrology
- Radioactivity measurement techniques
Background:
- Accurate activity concentration determination of 32Si is crucial for nuclear research.
- Liquid scintillation (LS) counting is a primary method for such measurements.
- Challenges include sample stability and inter-method discrepancies.
Purpose of the Study:
- To investigate and resolve issues with 32Si sample stability in LS counting.
- To identify and correct discrepancies between TDCR and CIEMAT/NIST efficiency tracing methods.
- To establish a reliable method for 32Si activity determination for half-life studies.
Main Methods:
- Liquid scintillation (LS) counting techniques, including Triple-to-Double Coincidence Ratio (TDCR) and CIEMAT/NIST efficiency tracing.
- Systematic study of various sample compositions and long-term measurements.
- Spectral analysis for identifying radioactive impurities.
Main Results:
- Identified sample instability due to an adsorption-like effect, but early measurements are usable with increased uncertainty.
- Discrepancies between LS methods were linked to low-energetic impurities, particularly tritium.
- A new stable LS sample composition (15 mL Ultima Gold, 1 mL 0.5 mol/L HCl) was developed.
Conclusions:
- Developed a stable LS sample composition for 32Si, crucial for accurate measurements.
- Resolved discrepancies by identifying and correcting for tritium impurity.
- Paved the way for a new 32Si half-life determination within the SINCHRON project.