RE: [Vo]:what is needed to give rise to visible Cherenkov radiation?
The holding tank for the fuel rods is filled with borated water. The neutron-boron reaction produces fast ions, which thermalize by knocking electrons free from water molecules – as does the other isotope decay reactions from the rods. Electrons of about 200-300 keV cause the glow – when they further thermalize. This can happen in air - as well as water – and with the same eerie blue glow. We know the mechanism fairly well, since Cherenkov-like radiation will be generated in an electron microscope, or cyclotron, or other beam line in air. Here is a photo of the blue glow. http://upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Cyclotron_with_glowing_beam.jpg/300px-Cyclotron_with_glowing_beam.jpg From: Bob Cook The Cherenkov radiation I have seen is primarily blue. It is associated with the high energy particles emitted from spent fuel in a water storage pool and I think is associated with the slowing down of the particles in water, as you suggest. I also think it is associated with the neutrons that come from the decay of fission products. The charged particles are slowed down in a short distance. The neutrons cause the bluish glow at a distance from the source. This may also be due to scattering of the blue light which is not absorbed like red in the water. I would agree that the EM radiation that is caused by either charged particles or neutrons is broad band as you suggest. Bob Sent from Windows Mail From: Eric Walker mailto:eric.wal...@gmail.com Sent: Saturday, February 7, 2015 9:20 PM To: vortex-l@eskimo.com On Sat, Feb 7, 2015 at 1:49 PM, mix...@bigpond.com wrote: I have a different question altogether. How does one distinguish between Cherenkov radiation and light emitted by recombining ion - electron pairs? (Where fast particles are responsible for creating the pairs.) I believe Cherenkov radiation is broadband. I read today that it is distinguishable, nonetheless, from bremsstrahlung. In the case of bremsstrahlung you need noticeable acceleration (e.g., a bending motion or a collision), whereas Cherenkov radiation arises from constructive interference when a charged particle exceeds the phase velocity of light in a medium. So you can distinguish the two in the case of a relativistic heavy ion. In that case the trajectory of the ion will be straight (so no bremsstrahlung) but it will give rise to Cherenkov radiation. My understanding is that Cherenkov radiation is broadband because the fast particle slowly decelerates, leading the frequency at which constructive interference to change over time. Please carefully vet anything I have said here. Eric
Re: [Vo]:what is needed to give rise to visible Cherenkov radiation?
Eric-- The Cherenkov radiation I have seen is primarily blue. It is associated with the high energy particles emitted from spent fuel in a water storage pool and I think is associated with the slowing down of the particles in water, as you suggest. I also think it is associated with the neutrons that come from the decay of fission products. The charged particles are slowed down in a short distance. The neutrons cause the bluish glow at a distance from the source. This may also be due to scattering of the blue light which is not absorbed like red in the water. I would agree that the EM radiation that is caused by either charged particles or neutrons is broad band as you suggest. Bob Sent from Windows Mail From: Eric Walker Sent: Saturday, February 7, 2015 9:20 PM To: vortex-l@eskimo.com On Sat, Feb 7, 2015 at 1:49 PM, mix...@bigpond.com wrote: I have a different question altogether. How does one distinguish between Cherenkov radiation and light emitted by recombining ion - electron pairs? (Where fast particles are responsible for creating the pairs.) I believe Cherenkov radiation is broadband. I read today that it is distinguishable, nonetheless, from bremsstrahlung. In the case of bremsstrahlung you need noticeable acceleration (e.g., a bending motion or a collision), whereas Cherenkov radiation arises from constructive interference when a charged particle exceeds the phase velocity of light in a medium. So you can distinguish the two in the case of a relativistic heavy ion. In that case the trajectory of the ion will be straight (so no bremsstrahlung) but it will give rise to Cherenkov radiation. My understanding is that Cherenkov radiation is broadband because the fast particle slowly decelerates, leading the frequency at which constructive interference to change over time. Please carefully vet anything I have said here. Eric
[Vo]:what is needed to give rise to visible Cherenkov radiation?
Hi, What is the flux of fast electrons needed to create the kind of visible Cherenkov radiation seen in pool-type fission reactors? http://upload.wikimedia.org/wikipedia/commons/f/f2/Advanced_Test_Reactor.jpg http://upload.wikimedia.org/wikipedia/commons/6/6b/Cerenkov_Effect.jpg Is it a relatively small amount of activity that will accomplish what is seen in these images, or is a large amount of activity required? I assume it is possible to characterize the flux that will lead to visible Cherenkov radiation in terms along the lines of 10e9 electrons per cm^2 per second. What is the typical energy of the beta particles observed in these images? My understanding is that the betas go back to the decay of fission intermediate products. Is it in the MeV range, or the keV range, or possibly even lower? Eric
Re: [Vo]:what is needed to give rise to visible Cherenkov radiation?
On Sat, Feb 7, 2015 at 1:49 PM, mix...@bigpond.com wrote: I have a different question altogether. How does one distinguish between Cherenkov radiation and light emitted by recombining ion - electron pairs? (Where fast particles are responsible for creating the pairs.) I believe Cherenkov radiation is broadband. I read today that it is distinguishable, nonetheless, from bremsstrahlung. In the case of bremsstrahlung you need noticeable acceleration (e.g., a bending motion or a collision), whereas Cherenkov radiation arises from constructive interference when a charged particle exceeds the phase velocity of light in a medium. So you can distinguish the two in the case of a relativistic heavy ion. In that case the trajectory of the ion will be straight (so no bremsstrahlung) but it will give rise to Cherenkov radiation. My understanding is that Cherenkov radiation is broadband because the fast particle slowly decelerates, leading the frequency at which constructive interference to change over time. Please carefully vet anything I have said here. Eric
Re: [Vo]:what is needed to give rise to visible Cherenkov radiation?
In reply to Eric Walker's message of Sat, 7 Feb 2015 10:12:40 -0800: Hi, [snip] I have a different question altogether. How does one distinguish between Cherenkov radiation and light emitted by recombining ion - electron pairs? (Where fast particles are responsible for creating the pairs.) Hi, What is the flux of fast electrons needed to create the kind of visible Cherenkov radiation seen in pool-type fission reactors? http://upload.wikimedia.org/wikipedia/commons/f/f2/Advanced_Test_Reactor.jpg http://upload.wikimedia.org/wikipedia/commons/6/6b/Cerenkov_Effect.jpg Is it a relatively small amount of activity that will accomplish what is seen in these images, or is a large amount of activity required? I assume it is possible to characterize the flux that will lead to visible Cherenkov radiation in terms along the lines of 10e9 electrons per cm^2 per second. What is the typical energy of the beta particles observed in these images? My understanding is that the betas go back to the decay of fission intermediate products. Is it in the MeV range, or the keV range, or possibly even lower? Eric Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
