Tale of the tape

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chelle
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Tale of the tape

Post by chelle » Tue Oct 26, 2010 5:34 pm

Check out this funny (upcoming) article: http://www.sciencenews.org/view/generic ... f_the_tape_
Tale of the tape
Humble desk adhesive is a tiny particle accelerator

Forget fancy particle accelerators — a cheaper tool for emitting X-rays is right there in the office supply cabinet. Pulling back Scotch tape emits X-rays, the same high-energy light emanating from airport security scanners and the interiors of galaxy clusters, ...
I like this part:
No need to worry about radiation exposure at the office — at atmospheric pressure, where air molecules bustle, the electrons quickly run into other particles before they can radiate X-rays.
... just to point out that collisions on top of our atmosphere or on the moon are a different thing than tests here down on earth.
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Re: Tale of the tape

Post by CharmQuark » Tue Oct 26, 2010 6:42 pm

Nice link Chelle :thumbup:
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Stephen
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Re: Tale of the tape

Post by Stephen » Wed Oct 27, 2010 7:46 am

The moon is not protected by an atmosphere, therefore the arguments remains valid.

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chelle
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Re: Tale of the tape

Post by chelle » Wed Oct 27, 2010 9:36 am

Stephen wrote:The moon is not protected by an atmosphere, therefore the arguments remains valid.
I don't think you have read the article or the quote, I'll post it again:
... at atmospheric pressure, where air molecules bustle, the electrons quickly run into other particles before they can radiate X-rays.
When referring to the Moon, when high energetic particles collide with the moons surface, a large amount of collision-energy such as bremsstrahlung as mentioned in the article (see quote below) gets lost into space, because there is no atmospheric pressure. Same thing for the top of our atmosphere where energy get's lost into space.
The field jump-starts free electrons in the neighborhood, accelerating them fast enough to emit X-ray photons. This bremsstrahlung radiation is like that created in the bellies of particle accelerators as they whip charged particles around near the speed of light.
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Re: Tale of the tape

Post by Stephen » Wed Oct 27, 2010 10:45 am

I read your quote - the reasonable conclusion does not change.

Even if some of the energy gets lost, 5,000,000,000 years of much more energetic collisions is enough time for the moon to be destroyed or turned into strangelets soup.

Besides - what is the specific disaster scenario you are concerned about?

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chelle
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Re: Tale of the tape

Post by chelle » Wed Oct 27, 2010 1:26 pm

Stephen wrote:I read your quote - the reasonable conclusion does not change.

Even if some of the energy gets lost, 5,000,000,000 years of much more energetic collisions is enough time for the moon to be destroyed or turned into strangelets soup.

Besides - what is the specific disaster scenario you are concerned about?
All my concerns of an autocatalytic event have already been widely expressed and discussed in other posts so you can sniff through those if you want to know what my concerns are.

I only posted this topic here because it speaks about how atmospheric differences play a significant roll when dealing with 'particles'. In reference you can check this post of me in the 'Sparks' topic: viewtopic.php?p=3855#p3855
To come back to the lhc and cosmic rays and the arguments of high altitude, cold, atmospheric pressure etc. I would like to refer to this safety report of a fire in a bar in Holland where branches on the ceiling caused an enormous short fire on New Years eve. If you read the report it says at page 6: "When comparing tests 1a and 1b it can be noticed that relatively small details have enormous consequences for the overall fire behavior. " (see pdf: http://www.dgmr.nl/uploads/media/dehemel.pdf + fire)
And regarding the Flux, that is also something that I mentioned plenty of times before:
A good overview graph showing the cosmic ray flux as a function of energy can be found here: http://en.wikipedia.org/wiki/Cosmic_ray

Look at the first plot on the right. It shows a graph of flux, measured in number of particles per square meter per second per steradian per GeV (10^9 eV), on the vertical axis, versus particle energy, in electron volts, on the horizontal axis. You will see that the largest flux is at low energy (about 10^9 eV), where the flux is about 1000 particles/m^2-s-sr-GeV. That is, in one square meter, looking over the whole upper half of the sky (2 pi = 6.2 sr), in a bandwidth of 1 GeV, one sees 1000 particles every second. That is very small compared to the luminosity of the LHC, which is somewhere around 10^30 collisions per square centimeter per second. The protons in the LHC have an energy of around 3.5 x 10^12 eV (3.5 TeV). Going back to the cosmic ray plot, you see that the flux of particles with energies around 10^12 eV is much lower, around 10^-3, that is, 0.001 particle/m^2-s-sr-GeV, or about 3 particles per square meter per steradian per GeV per *hour*.

The next question you had concerns the number of particles created in cosmic ray showers. That is a much more complicated question, but the general trend is that higher energy cosmic rays produce more secondary particles. So while cosmic rays with energies of a few GeV may produce a handful of particles, the highest energy cosmic rays, around 10^19 eV, produce showers containing billions of particles. A somewhat technical overview on cosmic ray showers can be found here: http://pdg.lbl.gov/2007/reviews/cosmicrayrpp.pdf

The flux of cosmic ray shower particles versus particle type is seen in Figure 24.3. The horizontal axis this time is atmospheric depth, which is zero at the highest altitudes, and about 1000 grams per square centimeter near sea level. Near sea level the cosmic ray secondary particles are mostly neutrinos and muons (about 100 particles per square meter per second per steradian), with smaller amounts of protons, neutrons, electrons, positrons, and pions.

btwI would like to clarify that the ratio of energies between 10^18 and 10^9 eV is *not* double, but rather a factor of 10^9 (that is, a billion times). Remember, when dividing numbers in scientific notation, one subtracts the exponents.
reference link: viewtopic.php?p=5556#p5556
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