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A Prototype Detector for Dark Matter in the Milky Way

Dark Matter Detector

The business end of a dark matter detector based on a BGO crystal (right) and a germanium disc (left)

It doesn’t emit electromagnetic radiation and no one really knows what it is, but that hasn’t stopped a team of European researchers from developing a device which scientists will use to detect and determine the nature of the dark matter that makes up 1/4 of the mass of our universe.

The researchers from the University of Zaragoza (UNIZAR) and the Institut d’Astrophysique Spatiale (IAS, in France), made assumptions about the nature of dark matter based on theoretical studies, and developed device called a “scintillating bolometer” to detect the result of interaction of dark matter with material inside the detector.

“One of the biggest challenges in Physics today is to discover the true nature of dark matter, which cannot be directly observed – even though it seems to make up one-quarter of the matter of the Universe. So we have to attempt to detect it using prototypes such as the one we have developed”, Eduardo García Abancéns, a researcher from the UNIZAR’s Laboratory of Nuclear Physics and Astroparticles, tells SINC.

García Abancéns is one of the scientists working on the ROSEBUD project (an acronym for Rare Objects SEarch with Bolometers UndergrounD), an international collaborative initiative between the Institut d’Astrophysique Spatiale (CNRS-University of Paris-South, in France) and the University of Zaragoza, which is focusing on hunting for dark matter in the Milky Way.

The scientists have been working for the past decade on this mission at the Canfranc Underground Laboratory, in Huesca, where they have developed various cryogenic detectors (which operate at temperatures close to absolute zero: ?273.15 °C). The latest is a “scintillating bolometer”, a 46-gram device that, in this case, contains a crystal “scintillator”, made up of bismuth, germinate and oxygen (BGO: Bi4Ge3O12), which acts as a dark matter detector.

Naturally, to build any type of dark matter detector, the researchers had to make some assumptions about the nature of the dark matter itself.  The detection technique developed by the researchers is based on a number of theoretical studies which point to particles called WIMPs (Weakly Interacting Massive Particles) as the main constituent of dark matter.

“This detection technique is based on the simultaneous measurement of the light and heat produced by the interaction between the detector and the hypothetical WIMPs which, according to various theoretical models, explain the existence of dark matter”, explains García Abancéns.

The researcher explains that the difference in the scintillation of the various particles enables this method to differentiate between the signals that the WIMPs would produce and others produced by various elements of background radiation (such as alpha, beta or gamma particles).

In order to measure the miniscule amount of heat produced, the detector must be cooled to temperatures close to absolute zero, and a cryogenic facility, reinforced with lead and polyethylene bricks and protected from cosmic radiation as it housed under the Tobazo mountain, has been installed at the Canfranc underground laboratory.

“The new scintillating bolometer has performed excellently, proving its viability as a detector in experiments to look for dark matter, and also as a gamma spectrometer (a device that measures this type of radiation) to monitor background radiation in these experiments”, says García Abancéns.

The scintillating bolometer is currently at the Orsay University Centre in France, where the team is working to optimise the device’s light gathering, and carrying out trials with other BGO crystals.

This study, published recently in the journal Optical Materials, is part of the European EURECA project (European Underground Rare Event Calorimeter Array). This initiative, in which 16 European institutions are taking part (including the University of Zaragoza and the IAS), aims to construct a one-tonne cryogenic detector and use it over the next decade to hunt for the dark matter of the Universe.

Source: FECYT (Spain)

Comments on this entry are closed.

  • Lawrence B. Crowell September 25, 2009, 5:19 PM

    If dark matter is a neutralino, a condensate state of supersymmetric pairs of Higgs and neutrinos, then there might be a tiny interaction with the atomic lattice of the crystal.

    LC

  • Prime September 25, 2009, 11:14 PM

    Seems like a wasteful way to detect dark Current.
    http://www.electric-cosmos.org/electricplasma.htm

    Prime

  • ardeyranger September 26, 2009, 1:52 AM

    Hey Brian – To think that such a neat looking device might detect DM – great story!
    – There’s some funny stuff that slipped through your spell-checker though:
    ‘made up of bismuth, germinate and oxygen’ –

    It should either read:
    made up of bismuth, germanium and oxygen
    or
    made up of bismuth germanate

    with best regards from Germiny ;-)

  • Lawrence B. Crowell September 26, 2009, 4:56 AM

    Prime: Dark matter is not charged or luminous. This is the reason for the adjective “dark.” So EM methods of detection will not work. If one major component of DM are neutralinos, condenstates of supersymmetric pairs of Higgs and neutrinos, then these shoudl interact with ordinary matter by weak forces.

    LC

  • Torbjorn Larsson OM September 26, 2009, 6:23 AM

    This is a nice part of science, where you can exclude stuff even if you don’t yet know exactly what it is. It seems a particular good idea to test for WIMPs first.

    @ ardeyranger, by jirminy, I saw what you did there!

    dark Current

    Sorry, that doesn’t pass my scintillating bollocks-meter.

  • kms September 26, 2009, 4:08 PM

    Phlogiston, methinks.

  • Torbjorn Larsson OM September 26, 2009, 7:44 PM

    Phlogiston, what? DM?

    No, it’s definitely there. Hypothesized as responsible for large structure in the standard cosmology, and tested by astronomical objects such as the Bullet Cluster.

    Phlogiston on the other hand didn’t pass any test at all. (Suggested decreasing mass in burned fuels, when increasing mass from oxide formation was the case.)

    Not only does DM pass first confrontation with observations as opposed to phlogiston, but AFAIU no single tensor or otherwise field explanation is consistent with each individual test of DM.

  • Lawrence B. Crowell September 27, 2009, 5:38 AM

    Dark matter is pretty cold and slow. It moves nowhere near the speed of light. We can surmise this by using statistical mechanics to compute the upper bound on the average momentum of dark matter particles which are held by gravity. For instance with the Bullet galaxy cluster we know that dark matter exist and we can by computing its gravitational lensing estimate how much bulk mass there is in dark matter. We also know that the stuff holds itself together by gravity, and that the particles of the stuff can’t be too fast or else the stuff would “evaporate” from its gravitational “bottle.” So the momentum of the particles is pretty low, making for a rather cold “gas” of stuff.

    Dark matter does not interact via the electromagnetic interaction. So there is not luminous component to it. We understand the electromagnetic interaction interaction better than the others and it is observed on many energy scales. Dark matter is dark and has no EM interaction.

    There might be a whole alternative universe made of matter that id in some manner dual to ordinary matter we observe. This duality is probably supersymmetry, where for every particle we know there are supersymmetric dual particles. These particles might constitute a sort of alternate world we can only readily see by the gravitation of the particle fields (dark matter) which compose it. By there might be a whole alternate world of what I will call “atoms” which interact with each other by an alternative set of gauge-like bosons or “photons.”

    Lawrence B. Crowell

  • Torbjorn Larsson OM September 27, 2009, 9:35 AM

    Satoms, supersymmetric atoms, what a great idea for scifi!

    No, wait, Baxter did that with his “photino birds”. Bummer.

  • Nexus September 28, 2009, 5:09 AM

    “and developed device” should be “and developed a device”.

    Erm, I’ll let myself out…

  • rudeyd September 28, 2009, 11:33 AM

    Fraser,
    I have a question that no one seems to want to acknowledge… much less address with an explanation. I have written to many, many prominent people for a long time and the lack of response from ANYONE is strange.

    The Electric Universe people claim that electricity is never considered when discussing, theorizing, or studying the universe and claim that ignoring it’s effect in the function and origin of the Universe has been, well, almost criminal. They claim that the Big Bang people /science of the Cosmos we all have grown up with is flawed at best, glossed over to protect the BB theory and plain wrong. If I am understanding them correctly, they seem to be militant about being “overlooked – ignored” – ect”

    I have been fascinated all my life with the science of space and Universe and have never seen anything about electricity being what they claim is the “missing link” in the Big Bang and Universe creation mysteries. I realize that they would rub people the wrong way by blatantly claiming the Big Bag people are flat out wrong, but surely the argument has SOME merit. How long did string theory have a giggle factor?

    So my question is: Why is Electricity never part of the equation and why do these people feel like they have been completely ignored?
    A theory is a theory, and all theories usually get their day in court.
    Correct???
    please…….
    If this is a stupid question , at least tell me it’s a stupid question rather than ignore it
    Thanks

  • Torbjorn Larsson OM September 28, 2009, 1:56 PM

    So my question is: Why is Electricity never part of the equation

    As observation and theory, standard cosmology has a long prehistory. The observed expansion of the universe was put into earlier cosmology models based on general relativity together with observations of masses et cetera. Today these can predict the observations well enough without unobserved “EU” mechanisms.

    Among other things expansion resolves one old paradox where EM is weaker than it “should be”. It explains why the sky in a sufficiently large universe isn’t as hot and bright as the surface of stars. Expansion means no equilibrium means less radiation density.

    This shows quite plainly that the universe isn’t based on the natural scale of EM.

    and why do these people feel like they have been completely ignored?

    Because they are nuts?! Crackpots always play the Galilei card to ‘explain’ why they are alone but ‘right’.

  • DrFlimmer September 28, 2009, 2:05 PM

    @ rudeyd

    If I may give you a rather short answer:

    Electromagnetism is NOT left out by any scientist. That is a wrong claim I have also heard quite a lot. In fact, electromagnetism is quite important for many fascinating things in the universe (as I think), like accretion disks and jets.

    The question is: What is more important, electromagnetism or gravitation? And here is what those EU-guys claim:
    You can compare the electrostatic force (basically Coulomb’s law) of two protons with the gravitation between them. What you’ll find is that electromagnetism is 10^39 times (or something like that) stronger. But this really only holds if you compare it between two protons.

    The thing is: Every plasma in the universe contains (almost) the same amount of positive charges and negative charges. So the overall charge of a body is zero, since the charges cancel each other. This means, you can cancel out electromagnetic forces.
    This is impossible with gravitation – there is no “negative” mass. Gravity always adds.
    So, now, compare the forces of a proton with the sun. You will find that the gravitation will now dominate over the electromagnetic force, since the latter is almost zero (leaving aside magnetic effects).

    So, on large scales gravitation dominates of electromagnetic forces (and the other ones, which are much stronger than em forces and very small scales – as you can see, it’s just a matter of size ;) ).

    Again, no scientist will ever ignore fundamental things. This is a stupid claim!

  • Lawrence B. Crowell September 29, 2009, 12:54 PM

    Fresh ideas in science that work become canonical and regarded as in some ways old fashioned. This is even if they work really well, such as quantum mechanics. They may eventually be found to be incomplete and fail outside some domains of observation. Fresh ideas that are bad always remain fresh. They can keep being advanced over and over as something new which breaks the established theories in science.

    Of course electromagnetism is well known by physicists. For Cripe’s sake to get a degree in physics you are drilled on electromagnetism over and over, with repeated courses on the material at more advanced or difficult levels. This does not mean that electromagnetism is EVERYTHING! There are other interactions in the the universe, and other domains such as quantum mechanics or statistical thermodynamics and so forth. The EU people somehow think that a well established area of physics, electromagnetism, is everything, which is their “fresh idea.” In keeping with bad fresh ideas it keeps coming up again and again.

    LC

  • Jon Hanford September 30, 2009, 4:11 AM

    Some great posts on the differences and weaknesses of EU “theory” compared to our current understanding of the cosmos by Larsson, Flimmer and Crowell (sounds like a legal firm :) ). It may also be noted that many EU believers fall back on conspiracy theories to account for the negative view of EU that many astronomers and astrophysicists hold. Also, most ardent employed EU proponents are NOT astronomers or astrophysicists. Added to that is the fact that no single, logical, all-encompassing EU theory exists. As Lawrence Crowell aptly notes “…to get a degree in physics[ or astrophysics ] you are drilled on electromagnetism over and over”.

  • Lawrence B. Crowell September 30, 2009, 1:00 PM

    It is amusing to hear the EU people carry on, as if Stephen Hawking never studied Faraday’s law. They prate on as if they alone know electromagnetism and the rest of us are blind and ignorant to it.

    LC

  • rudeyd October 9, 2009, 2:48 AM

    Thanks for all the info!
    I knew there was a certain amount of “glossing” over the facts a bit, but I couldn’t find that finite fact that explained why most people in the field regard electromagnetism basically a “non-essential” for lack of a better term.

    Looking over those articles again I noticed that the EU people “”smudge”” over the fact that the pos and neg cancel each other out……… : )

    Imagine that! Just like politicians……..

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