A Potential Method for the Production of Ice-XI for Low Mass Dark Matter Detection*

For nearly a century, dark matter has been a topic of excited debate and remains an area of active research. Currently, there are three main avenues of dark matter detection: direct detection, indirect detection for example of decay products, or production in particle accelerators. We focus on a specific material that could be used in the first of these. Ice-XI is a hydrogen-ordered phase of water ice that forms at low temperatures. It is a particularly promising target for use in direct detection of light dark matter, specifically single phonon detection. We describe an attempt to make ice-XI employing minimal specialty equipment: using a KOH dopant and maintaining the sample at or below 72 K for several days via an LN2 bath in a vacuum chamber. The phase transition from ice-Ih to ice-XI is monitored through dielectric measurements of capacitors embedded in the ice samples.

Two week-long tests were performed using ice doped with 0.01 M and 0.05 M KOH. We observed no change in the 0.01 M test, but saw a slight increase in capacitance for the 0.05 M test. From previous studies, we expected the ice-XI phase transition to be accompanied by a rapid decrease in capacitance. Our results indicate that the phase transition did not occur in either test. However, some previous studies observed an initial slight increase before the main decrease in capacitance associated with the phase transition. Therefore, we suspect that this initial transition stage may have occurred in the 0.05 M test, and had the test been left to run longer, we may have observed the main stage of the transition as well.  

While we were unsuccessful in documenting the transition, we believe the methodology to be sound. In future iterations of the experiment, we would either perform the test for longer time periods, or try some combination of higher KOH concentrations, colder temperatures, and/or smaller ice samples which could all accelerate the transition, making it more readily observable with our setup.