Originally posted by timebombted
Interesting article, thanks.
Do you know what a 100kg or 250kg detector actually is or how it works? I like to read about this sort of stuff, although its not my branch of science, so certainly no expert.
How do they know the particles are dark matter?
If you can shed any more light, it will be much appreciated.
Right now I think its a statistical game, the results will have to be independently verified. I think the detector is a photomultiplier tube or avalanche diode detector, the solid state equivalent and detects brief flashes of light when one particle interacts with another head on.
Its how they detect neutrino's, same idea. They mentioned in the article there would be seaonal variations if its dark matter so they hope to corrolate cycling up and down of hits depending on what part of the year the planet is aiming at, so its a long boring road collecting flashes. Like the first neutrino detector, it was not very sensitive and you might get one hit a week or so making it a very long term affair and these dark matter particles are even less reactive than neutrino's so you can see the problem, need lots of detectors shielded by about a mile of solid rock to keep out stray cosmic rays and such. The Neutrino detectors now are giant pools of ultra pure liquid, might just be DI water but not sure. Sometimes a neutrino (very seldom) it hits a particular atom dead nuts and turns into another atom, but in the process the breakdown causes a tiny flash which the photomultiplier tube amplifies enough to record. So you build up a track record of where they originate, mostly from the sun, but there are other experiments that are detecting neutrino's emitted by nuclear reactors, a detector or string of them a few miles from the reactor, I think the fluid is C CL4, Carbon Tetrachloride, the cleaning fluid. I think one way used to be if the chlorine atom takes a direct hit it transmutates into something else and they can be detected by running all the fluid through a spectrum analyzer, looking for a needle in a haystack for sure, 3 or 4 atoms gotten zonked from Chlorine to ??, anyway detectable. That was the old way I think. Now they just use sensitive light detectors.
Ok, the detector in this case is Sodium Iodide, presumably transparent, a solid block of it 100Kg and 250 Kg, not sure how big that would be but its probably one extremely pure crystal grown into a boule. So a dark matter whacks one of the atoms, they didn't say which, and it interacts, not sure if it actually transmutates or not but gives of a pulse of light barely detectable and maxes in June and minumized signals in december as the theory goes, the earth is either running into them or away from them relatively speaking as the sun makes its way around the galaxy so every 6 months there will be a minima and maxima and thats what they claim to have seen after a 7 year run. And of course these results are met with more than a little bit of scepticism🙂