Radio Listens to Detect Dark Matter Axion Particles

Four decades ago, researchers proposed a new low-mass particle that could be critical in answering our questions about dark matter. Now, University of Washington physicists might have a new tool in finding those particles. 

The research came as part of the Axion Dark Matter Experiment (ADMX). The project reported the first time to reach the sensitivity needed to "hear" the signs of dark matter axions. The breakthrough happened after 30 years on the project, and it positions the ADMX system to listen for axions more closely than any other project. A new quantum-enabled device adds to the ADMX system and gives it the 'missing piece' it needed. 

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“If you think of an AM radio, it’s exactly like that,” said Gray Rybka, co-spokesperson for ADMX and assistant professor of physics at the University of Washington. “We’ve built a radio that looks for a radio station, but we don’t know its frequency. We turn the knob slowly while listening. Ideally, we will hear a tone when the frequency is right.”

ADMX serves as an axion haloscope, which is a large, low-noise, radio receiver. Scientists tune the haloscope to various frequencies and listen to the axion signal frequencies. Axions don't often interact with matter. However, with the help of a strong magnetic field and a dark, reflective box, ADMX can successfully hear photons created whenever axions convert electromagnetic waves inside the detector, according to researchers.

This method was originally developed by Pierre Sikivie of the University of Florida in 1983. Since this ADMX idea's creation, experiments and analyses have been done by Fermilab, the University of Rochester and the U.S. Department of Energy's Brookhaven National Laboratory to demonstrate just hope helpful this 'radio' is. 

“The initial versions of this experiment, with transistor-based amplifiers would have taken hundreds of years to scan the most likely range of axion masses. With the new superconducting detectors we can search the same range on timescales of only a few years,” said Gianpaolo Carosi, co-spokesperson for ADMX and scientist at Lawrence Livermore National Laboratory.

“This result plants a flag,” said Leslie Rosenberg, professor of physics at the University of Washington and chief scientist for ADMX. “It tells the world that we have the sensitivity, and have a very good shot at finding the axion. No new technology is needed. We don’t need a miracle anymore, we just need the time.”

ADMX will soon be put to work to test millions of frequencies at a high level of sensitivity. Finding axions could be one of the biggest discoveries regarding dark matter and ultimately the longest standing mysteries of our universe. However, there's a possibility that ADMX does not succeed in its mission in finding axions. In that case, the researchers are prepared to create new and innovative solutions for finding the answers of the galaxy. 

“A discovery could come at any time over the next few years,” said scientist Aaron Chou of Fermilab. “It’s been a long road getting to this point, but we’re about to begin the most exciting time in this ongoing search for axions.”