I recently read an article about "groundbreaking Australian research in the hunt for dark matter", in which it said:

We use highly purified crystals to detect dark matter. These crystals react when they are struck by dark matter particles and have to kept underground from other forms of radiation so we don’t get false readings. The Stawell Underground Physics Laboratory (SUPL) is being built 1025 meters below ground. Once we have results, we’ll compare those with the results from detectors in other parts of the world.

I'm interested to know what these crystals might be composed of, and what kind of "reaction" is expected - for example, a change in energy level, or momentum?

The research is being undertaken through the Centre of Excellence for Particle Physics at the Terascale (CoEPP). This CoEPP web page hints at the interaction they're looking for, but gives no indication of what the crystals are:

Uncovering dark matter at the LHC is a nontrivial task, because it will not interact with the detectors at all. Instead, we can hope to infer the presence of dark matter particles created at the LHC by ascertaining that something is missing. A spectacular signal is that of the mono-X (where 'X' can signify γ, Z or jets).

In this process, a single Standard Model particle recoils against missing momentum attributed to dark matter particles which escape the detector unseen. CoEPP researchers have performed some preliminary work on mono-Z signals. This work will continue, with a focus on going beyond the effective field theory description by instead looking at simple UV complete models.

I looked through Physics Stack Exchange for potential answers, but the only relevant questions seem to focus on liquid xenon:


Sodium iodide.

The experiment at the Stawell underground lab in Australia is part of the SABRE experiment, where SABRE is an acronym for Sodium Iodide with Active Background Rejection Experiment. This page describes the detectors.

The heart of the SABRE detector is high radio-purity thallium-doped sodium-Iodide (NaI(Tl)) scintillating crystals. Each collision between a Dark Matter particle and a nucleus releases a small amount of energy (<100 keV) that is converted into light.


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