NaI(Tl) crystal scintillator encapsulated in two organic-scintillator layers with pulse shape data analysis

TL;DR

This paper presents a novel detector design that encases NaI(Tl) crystals in organic scintillators, protecting against humidity and enabling pulse shape analysis to distinguish radiation signals, with maintained crystal quality over a month.

Contribution

The study introduces a fully encased NaI(Tl) detector with pulse shape analysis for background tagging and humidity protection, demonstrating sustained crystal performance.

Findings

Effective humidity protection of NaI(Tl) crystals.

Pulse shape analysis distinguishes signals from three scintillators.

Crystal emission quality maintained for at least one month.

Abstract

Thallium-doped sodium iodide (NaI(Tl)) crystals are widely used in radiation detection applications, from gamma-ray spectroscopy to particle dark matter searches. However, if the crystal is exposed to relative humidity of even a few percent, its light emission degrades, making the crystal impractical as a detector. Surrounding the crystal with organic scintillators not only protects the surface of the crystal from humid air but also offers a new capability to tag backgrounds such as external gamma rays and surface contaminations. We developed a detector that is constructed by fully encasing a NaI(Tl) crystal in a plastic scintillator and then immersing the plastic-crystal assembly in liquid scintillator. Using data collected from this triple phoswich detector, a pulse shape analysis is able to identify the various radiation signals from the three scintillators. Additionally, we find that the crystal's emission quality is maintained for a month.