Blowing Bubbles: The Hunt For Dark Matter Is On At SNOLAB
May 3, 2013

Dark Matter Detector To Search For Evidence In Tiny Bubbles

John P. Millis, Ph.D. for — Your Universe Online

The search for dark matter has been heating up over the last year or so. First, researchers using the Fermi Gamma-ray Telescope announced that a preliminary analysis of the soft gamma-ray data suggested evidence of dark matter annihilations coming from the galactic center.

Then, early results from the Alpha Magnetic Spectrometer found an excess of positrons in their data, an expected signature of dark matter interactions. Follow-up on these studies is underway in an attempt to solidify the results, and interpret the data.

In the meantime, a new dark matter experiment is underway in which dark matter particles could potential be directly measured. The experiment, known as COUPP-60, sits a mile and a half underground in Ontario, Canada.

Part of the SNOLAB underground science laboratory, the experiment has such an unusual location in order to shield it from the immense flux or light and charged particles that penetrate our atmosphere. Only electrically neutral particles, such as neutrons, and other exotic matter will make it that far. Then, the COUPP-60 detector is submerged in 7,000 gallons of water, further isolating it from unwanted particle interactions.

The hope is that only exotic matter, such as potential dark matter particles, can then reach the detector.

Within the detector itself, a mixture of purified water and CF3I — a compound used in fire extinguishers — is held at a temperature and pressure just about boiling point. Yet, the system will not actually begin to bubble. For that an additional amount of energy is needed.

A particle, ideally dark matter, passing through the chamber would provide just enough energy to create a bubble. The data then has to be analyzed to determine what kind of particle passed through the chamber.

The greatest challenge is that, under the best of circumstances, only a few dark matter events are expected to be measured per year. The experiment is now up and running, and scientists are reporting that they have seen their first bubbles.

There is still much work to be done, and it is a long road ahead to gather enough data to know with any confidence that dark matter is being detected. But since the pursuit of science cannot be rushed, we will have to be patient.