Measurement of photo- and radio-luminescence of thin ThF4 films

TL;DR

This study measures the photo- and radio-luminescence of thin ThF4 films, suggesting their potential use in nuclear clock applications by reducing background noise in luminescence detection.

Contribution

It provides new measurements of ThF4 luminescence in UV and visible ranges and demonstrates their suitability for $^{229m}$Th detection in nuclear clock research.

Findings

Luminescence levels are comparable to PMT dark noise in UV range.

Thin ThF4 films can reduce background noise for $^{229m}$Th detection.

Apparatus developed is ready for direct $^{229m}$Th excitation and decay measurements.

Abstract

We conducted measurements on the photo- and radio-luminescence of thin ThF$_4$ films in both the UV and visible ranges. In the UV range, we found that both luminescences are at a similar level as the internal dark counting noise of the photo-multiplier-tube (PMT). Our results suggest that thin ThF$_4$ crystals could be used as a target for the search for $^{229m}$Th and as a medium for the future nuclear clock. The measurements indicate that using a small and thin ThF$_4$ film can reduce background noise while maintaining the signal at the same level, achieved by increasing the $^{229}$Th enrichment. Our developed apparatus is now ready for direct measurements of $^{229m}$Th excitation and decay in ThF$_4$.