Development of a windowless multi-wire proportional chamber (MWPC) counting system for measuring extended-area beta...

Area of Science:

• Metrology
• Nuclear Instrumentation
• Radiation Detection

Background:

• The Korea Research Institute of Standards and Science (KRISS) previously utilized a multi-wire proportional counter (MWPC) as a national standard for radioactivity measurements.
• The existing system, while accurate (<1% uncertainty), had limitations in electric-field uniformity for extended-area sources.

Purpose of the Study:

• To develop and characterize a novel windowless MWPC counting system with improved performance for measuring the surface emission rate of extended-area radioactive sources.
• To enhance the electric-field uniformity and reduce measurement uncertainty compared to previous MWPC systems.

Main Methods:

• A new anode and guard plane design was implemented to achieve better electric-field uniformity within the (250×200)mm² sensitive volume.
• The stable operating conditions for the new MWPC system were investigated.
• Uncertainty analysis was performed using an extended-area 36Cl source.

Main Results:

• The new MWPC design demonstrated superior electric-field uniformity.
• The system achieved a relative combined standard uncertainty of 0.23% for surface emission rate measurements.
• This represents a 50% improvement in uncertainty compared to the previous-generation KRISS MWPC system.

Conclusions:

• The developed windowless MWPC counting system offers significantly improved accuracy and precision for measuring surface emission rates of extended-area sources.
• This advancement contributes to enhanced metrology capabilities in radioactivity standardization.