Instrument for precision long-term β-decay rate measurements

Area of Science:

• Nuclear Physics
• Experimental Physics

Background:

• Precision measurements of radioactive decay rates are essential for fundamental physics research.
• Recent claims suggest small annual variations in decay rates, necessitating highly stable experimental conditions.

Purpose of the Study:

• To describe a novel experimental setup for precise relative beta-decay rate measurements.
• To evaluate the impact of environmental factors on decay rate measurements.
• To provide data for testing hypotheses of annual variations in nuclear decay rates.

Main Methods:

• Utilized automated sample changers with high spatial precision for positioning radioactive samples.
• Employed Geiger-Müller (GM) tubes and NaI scintillators as detector sets.
• Housed the apparatus in a sealed chamber with controlled pressure, humidity, and temperature to mitigate environmental variations.

Main Results:

• Achieved low statistical uncertainties: few times 0.01% per day for GM detectors and ~0.01% per hour for NaI detectors.
• Demonstrated that uncontrolled atmospheric pressure variations can induce a 0.1% annual signal in GM detector count rates.
• Showed that NaI scintillator detector count rates are not discernibly influenced by natural pressure or plausible temperature variations.

Conclusions:

• The developed experimental setup provides high precision for beta-decay rate measurements.
• Environmental stabilization is critical for detecting subtle variations in decay rates, particularly for GM detectors.
• NaI scintillators offer superior stability against common environmental fluctuations compared to GM tubes.