Jun 13 – 17, 2022
Berkeley, CA
US/Pacific timezone

Measuring the $^{40}$K Feeding to the Ground State of $^{40}$Ar

Not scheduled
Berkeley, CA

Berkeley, CA

Lawrence Berkeley National Laboratory
Oral Poster Presentations Poster Session


Bertis Rasco (Oak Ridge National Laboratory)


Experimental nuclear physicists are well acquainted with the ubiquitous 1461 keV background $\gamma$ ray from the first-forbidden unique electron-capture decay of $^{40}$K to $^{40}$Ar. The third-forbidden unique beta decay to the $^{40}$Ca ground state is also well known. Not so well known is the third-forbidden unique electron-capture decay channel directly to the $^{40}$Ar ground state. This small decay branch has never been directly measured. Predicted intensities and experimental upper limits are highly variable (0-0.8%). This decay channel can be an important background for many rare-event searches, (such as DAMA, ANAIS-112, COSINE-100, SABRE, COSINUS, etc...). This exotic decay branch is also a limiting factor in $^{40}$K based geochronological dating.
The KDK (Potassium (K) Decay (DK)) experimental group is an international collaboration dedicated to perform the first measurement of this undetected $^{40}$K decay branch. The KDK group has created an enriched $^{40}$K source that the low-energy x rays can escape, built a silicon drift detector to measure the x rays, and integrated both into a highly efficient $\gamma$-ray detector, Oak Ridge National Laboratory's Modular Total Absorption Spectrometer (MTAS).
The KDK setup has been calibrated, tested, and the enriched $^{40}$K source was measured for 45 days.
We report on the experimental details and the current state of analyzing the unblinded KDK data.

Primary author

Bertis Rasco (Oak Ridge National Laboratory)

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