"Cherenkov radiation is electromagnetic radiation emitted when a charged particle (such as an electron) passes through an insulator at a constant speed greater than the speed of light in that medium. The characteristic blue glow of nuclear reactors is due to Cherenkov radiation.
Cherenkov radiation results when a charged particle, most commonly an electron, travels through a dielectric (electrically insulating) medium with a speed greater than that at which light (photons) propagates in the same medium.
In normal circumstances, these photons destructively interfere with each other and no radiation is detected. However, when a disruption which travels faster than light is propagating through the medium, the photons constructively interfere and intensify the observed radiation
A common analogy is the sonic boom of a supersonic aircraft or bullet. The sound waves generated by the supersonic body propagate at the speed of sound itself; as such, the waves cannot propagate away from the body and form a shock front.
In a similar way, a charged particle can generate a photonic shock wave as it travels through an insulator."
I've read about this before, cool stuff.
ReplyDeleteDo neutrinos also emit Cherenkov radiation if they collide with a particle?
There is this group of 6 particles called leptons: the electron and electron-neutrino, muon and muon-neutrino, tauon and tauon-neutrino (and all their anti-particles). Leptons do not "use" the strong nuclear force, like quarks. The neutrinos only interact via the weak nuclear force, which makes interactions so rare, because the weak force is very weak.
ReplyDeleteThe electron is stable while muon and tau decay fast, which is why the electron is the most common particle.
When a high energy electron-neutrino interacts with a proton via the weak force, it creates an electron. A muon-neutrino a muon, etc.
This electron, muon or tauon created by its corresponding neutrino travels fast and creates Cherenkov radiation (photons).
These photons are converted to electrons, and amplified, in the detectors. Every detector acts as one pixel and is about 40 cm in diameter. Basically a square km CCD of 5 thousand pixels.
The intensity, direction and sharpness of the Cherenkov light cone can be reconstructed from this signal and provides information about the type of neutrino, its direction and energy.
An awful lot of other interactions are involved that make this far more complicated, but this is the main neutrino detection mechanism.
* square = cubic
ReplyDeleteIt seems like you're doing your homework :)
ReplyDeleteSo every detector is a pixel and the detectors are spread widely apart? That ice must be really clear to transmit the light so far.
The noise you are working on, does it come from noisy detectors, or do other phenomena also cause light under the ice?
There will be about 70 vertical strings with each ~70 detectors (called DOMs), spaced 16 m apart. 125 m between each string.
ReplyDeletePicture of DOM (Digital Optical Module), one pixel. The bottom half is the detector, looking through the Earth. I touched one :)
The ice is very clear, except for the ice in the drill hole, where the water refroze again around the string and detectors. This contains bubbles. There are also some layers of dust in the ice.
I'm not yet working on anything :) For what I understand now, the noise/background mostly comes from solar/atmospheric neutrinos and muons. These were interesting for older neutrino detectors, but we want to find neutrinos from outside the solar system now. Possible sources are gamma ray burst, supernovas, active galactic nuclei, cosmic rays, dark matter (WIMPS) and other exotic particles and unknown phenomena.
Also, scattering of light in the ice makes it possible for light not coming from below to hit the detectors.
I can't yet really answer your question though.
Here is an overview of IceCube, showing the strings and the scale. The detectors start at 1450m.
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