The hunt for dark matter is about to step up a gear. After 30 years of research and development a new detector is finally ready to start searching for a particle that might comprise the mysterious substance that makes up 84 per cent of the Universe – axions.
These theoretical particles have so far slipped past detectors, but that could be about to change.
The Axion Dark Matter Experiment (ADMX), designed to find these elusive particles, has had its sensitivity vastly improved by the addition of SQUIDs.
These aren’t cephalopods that will float around inside the detector, but incredibly sensitive magnetic detectors known as superconducting quantum interference devices, or SQUIDs, which will act as amplifiers.
They have now been installed and tested, ready to start searching.
“This result signals the start of the true hunt for axions,” says Andrew Sonnenschein from the Fermi National Accelerator Laboratory in Illinois who manages the operation of ADMX.
“If dark matter axions exist within the frequency band we will be probing for the next few years, then it’s only a matter of time before we find them.”
Axions are hypothecial elementary particles that were first invoked to explain an issue with the Standard Model of particle physics.
As the particles have mass but only weakly interact with other forms of matter, they were soon taken up as a candidate for dark matter, the unknown substance that seems to permeate our Universe but which is only effected gravitationally.
However, this also means they only weakly interact with a detector, making them very difficult to find.
The ADMX team plan to use a strong magnetic field that will force to particles, if they exist, to decay into a high frequency microwave photon which the detector can then listen out for.
The problem is that these signals are tiny.
The detector is being kept at 0.1K, a fraction of a degree above absolute zero, which reduces the thermal noise, but the semiconductor amplifiers usually used were far too noisy.
By replacing the amplifiers with SQUIDs the team were able to reduce the noise by a factor of 30.
“This result plants a flag,” says Leslie Rosenburg, from 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.”