Start of most sensitive search yet for dark matter axion

April 10, 2018 by Robert Sanders, University of California - Berkeley
The SQUID-based amplifier, which is about a millimeter square, is supercooled to be sensitive to faint signals from axions, should they convert into a microwave photon in the ADMX detector. Credit: Sean O'Kelley image

Thanks to low-noise superconducting quantum amplifiers invented at the University of California, Berkeley, physicists are now embarking on the most sensitive search yet for axions, one of today's top candidates for dark matter.

The Axion Dark Matter Experiment (ADMX) reported results today showing that it is the world's first and only experiment to have achieved the necessary sensitivity to "hear" the telltale signs of axions.

The milestone is the result of more than 30 years of research and development, with the latest piece of the puzzle coming in the form of a quantum device that allows ADMX to listen for axions more closely than any experiment ever built.

John Clarke, a professor of physics in the graduate school at UC Berkeley and a pioneer in the development of sensitive magnetic detectors called SQUIDs (superconducting quantum interference devices), developed the two decades ago. ADMX scientists, with Clarke's input, have now incorporated it into the ADMX detector at the University of Washington, Seattle, and are ready to roll.

"ADMX is a complicated and quite expensive piece of machinery, so it took a while to build a suitable detector so that they could put the SQUID amplifier on it and demonstrate that it worked as advertised. Which it did," Clarke said.

The ADMX team published their results online today in the journal Physical Review Letters.

"This result signals the start of the true hunt for axions," said Andrew Sonnenschein at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois, the operations manager for ADMX. "If dark 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."

A cutaway rendering of the ADMX detector, which can detect axions producing photons within its cold, dark interior. Credit: ADMX collaboration

Dark matter: MACHOs, WIMPs or axions?

Dark matter is the missing 84 percent of matter in the universe, and physicists have looked extensively for many possible candidates, most prominently massive compact halo objects, or MACHOs, and weakly interacting massive particles, or WIMPs. Despite decades of searching for MACHOs and WIMPs, scientists have struck out; they can see the effects of dark matter in the universe, in how galaxies and stars within galaxies move, but they can't see dark matter itself.

Axions are becoming the favored alternative, in part because their existence would also solve problems with the standard model of particle physics today, including the fact that the neutron should have an electric dipole moment, but doesn't.

Like other dark-matter candidates, axions are everywhere but difficult to detect. Because they interact with ordinary matter so rarely, they stream through space, even passing through the Earth, without "touching" . ADMX employs a strong magnetic field and a tuned, reflective box to encourage axions to convert to microwave-frequency photons, and uses the quantum amplifier to "listen" for them. All this is done at the lowest possible temperature to reduce background noise.

Clarke learned of a key stumbling block for ADMX in 1994, when meeting with physicist Leslie Rosenberg, now a professor at the University of Washington and chief scientist for ADMX, and Karl van Bibber, now chair of UC Berkeley's Department of Nuclear Engineering. Because the axion signal would be very faint, any detector would have to be very cold and "quiet." Noise from heat, or thermal radiation, is easy to eliminate by cooling the detector down to 0.1 Kelvin, or roughly 460 degrees below zero Fahrenheit. But eliminating the noise from standard semiconductor transistor amplifiers proved difficult.

They asked Clarke, would SQUID amplifiers solve this problem?

Listening for dark matter: How ADMX employs cold cavities and SQUID amplifiers to find the elusive axion. Credit: University of Washington, Seattle

Supercold amplifiers lower noise to absolute limit

Though he had built SQUID amplifiers that worked up to 100 MHz frequencies, none worked at the gigahertz frequencies needed, so he set to work to build one. By 1998, he and his collaborators had solved the problem, thanks in large part to initial funding from the National Science Foundation and subsequent funding from the Department of Energy (DOE) through Lawrence Berkeley National Laboratory. The amplifiers on ADMX were funded by DOE through the University of Washington.

Clarke and his group showed that, cooled to temperatures of tens of milliKelvin above absolute zero, the Microstrip SQUID Amplifier (MSA) could achieve a noise that was quantum limited, that is, limited only by Heisenberg's Uncertainty Principle.

"You can't do better than that," Clarke said.

This much quieter technology, combined with the refrigeration unit, reduced the noise by a factor of about 30 at 600 MHz so that a signal from the axion, if there is one, should come through loud and clear. The MSA currently in operation on ADMX was fabricated by Gene Hilton at the National Institute of Standards and Technology in Boulder, Colorado, and tested, calibrated and packaged by Sean O'Kelley, a graduate student in Clarke's research group at UC Berkeley.

The ADMX team plans to slowly tune through millions of frequencies in hopes of hearing a clear tone from photons produced by axion decay.

"This result plants a flag," said Rosenberg. "It tells the world that we have the sensitivity, and have a very good shot at finding the . No new technology is needed. We don't need a miracle anymore, we just need the time."

Clarke noted too that the high-frequency, low-noise quantum SQUID amplifiers he invented for ADMX have since been employed in another hot area of physics, to read out the superconducting quantum bits, or qubits, for quantum computers of the future.

Explore further: New result draws on 30 years of research and development and begins the definitive search for axion particles

More information: N. Du et al. Search for Invisible Axion Dark Matter with the Axion Dark Matter Experiment, Physical Review Letters (2018). DOI: 10.1103/PhysRevLett.120.151301

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kurtstocklmeir
1 / 5 (4) Apr 11, 2018
for years I have talked about this - gravity gets more strong as it travels there is not any dark matter - all forces get more strong as they travel - because all forces get more strong as they travel a lot of not normal things happen like it is hard to see electric dipole moment associated with a neutron Kurt Stocklmeir
antialias_physorg
4 / 5 (4) Apr 11, 2018
for years I have talked about this - gravity gets more strong as it travels

Erm whut? First you say "for years I have talked about this" and then you go on to say something that is nowhere in the article?

all forces get more strong as they travel

Funnily all experiments, ever, say otherwise. So either you are wrong or reality is wrong...I wonder which?

(Note that if what you claim were actually true it would be supremely easy to build a perpetuum mobile...so off you go to the patent office...shoo )
tallenglish
1 / 5 (2) Apr 15, 2018
Axions don't exist, dark matter is not something special - it is just the same stuff as normal matter, with one very specific difference. How it travels moves to matter with respect to time, if we think of matter as always moving forwards, dark matter is always moving backwards. Thats why it never interacts and is dark in the first place, but like matter it will bend spacetime (just in the opposite way - so it will make halos around galaxies, and connect them).

Until science stops this confirmational bias that is so common and actually starts thinking outside the box as it were (pun intended), we will never understand anything more than what we can see as we refuse to look for it.

Simple idea - time can go in any direction and is no different to the rules we ally to the spacial dimensions, in fact the very idea of a multiverse requires it. All the matter and light we can see is simply moving in the same direction (aka in phase), nothing more special than that.
Joe1963
1 / 5 (1) Apr 17, 2018
I think that at a certain galactic distance, gravity reverses and the galaxies begin pushing against each other. This would do away with cosmological expansion, dark matter, and dark energy. This is a claim that can be easily tested:

A revised gravity equation looks like this (I have made an adjustment compared to my last version):

F = (1.047 X 10^-17) m1m2 [-cos(Θ)] / r^2 where tan Θ = r / (1.419 X 10^22)

In my Reddit article linked below I explain the math behind reasoning why gravity might behave in this strange way. Please do not dismiss the idea until you see the justification.

https://www.reddi...tter_is/
jimmybobber
3 / 5 (4) Apr 17, 2018
"for years I have talked about this - gravity gets more strong as it travels there is not any dark matter - all forces get more strong as they travel - because all forces get more strong as they travel a lot of not normal things happen like it is hard to see electric dipole moment associated with a neutron Kurt Stocklmeir"

Proof?

Benni
3.7 / 5 (3) Apr 17, 2018
for years I have talked about this - gravity gets more strong as it travels there is not any dark matter - all forces get more strong as they travel - because all forces get more strong as they travel a lot of not normal things happen like it is hard to see electric dipole moment associated with a neutron Kurt Stocklmeir


It is easily proven that the force of gravity & electro-magnetism CHANGES in accordance with the Inverse Square Law.
Whydening Gyre
4.5 / 5 (2) Apr 17, 2018
"for years I have talked about this - gravity gets more strong as it travels there is not any dark matter - all forces get more strong as they travel - because all forces get more strong as they travel a lot of not normal things happen like it is hard to see electric dipole moment associated with a neutron Kurt Stocklmeir"

Proof?


Gravity doesn't get any "weaker". Or stronger, for that matter. It's just spread out over a much larger area/volume. Think about it for a bit - it'll come to you....
jimmybobber
4 / 5 (4) Apr 17, 2018
i get it i'm asking him for proof!
inverse square law. Common sense.
Whydening Gyre
not rated yet Apr 18, 2018
i get it i'm asking him for proof!
inverse square law. Common sense.

Sorry, JB. Thought I was answering ol' Kurt, there...
kurtstocklmeir
1 / 5 (1) Apr 24, 2018
all forces get stronger as they travel - when I write these things I am not trying to get people to think my theories are good - I am trying to create records for my theories - physics people like to steal theories - I would like to talk about George - around 1990 I told George that gravity electric fields and magnetic fields are tachyons - George said if gravitons are tachyons they have negative momentum and that can explain attraction associated with gravity - I think George was the first person to explain attraction of any force - any moron knows if gravitons create attraction for particles gravitons will get more momentum in direction they are moving for conservation of momentum this is 1 of my old theories - God will punish people who are fools - fools talk when they do not know what they are talking about - it is not worth it to get punishment from God just to insult people and say dumb things - there is not 1 person around this place who knows any thing Kurt Stocklmeir

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