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Post by ubique on Feb 3, 2012 7:38:12 GMT -4
Bob, I haven't checked your math but overall it looks right assuming the 1 MeV electrons aren't so energetic as to ever pass completely through the body. Looking at the penetration depths for electrons in water [1], it seems rather an opposite situation: Tissue near the skin surface gets most of the dose. That's why one should calculate the effective dose, as for example testicles will get a high dose, and they are very vulnerable to radiation damage. [1] www.photobiology.com/educational/len/part2.htm
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Post by ubique on Jan 14, 2012 9:23:21 GMT -4
Sure on this? The sources I have seen say that neutrons decay into a proton, an electron, and a neutrino, I'm a physicist by training, which included particle physics, so yes, I'm quite sure. It's an antineutrino, to preserve the lepton count. As there are no leptons before the decay, the lepton number is 0. The number has to be the same after the decay. Electron gives +1 to lepton number, so the other lepton created must be an antiparticle for it to have -1 as the lepton number. Electron capture is a well-known process for decay of certain elements. Yes, there's a neutrino produced too, again to preserve the lepton number; I left it out as it's not really meaningful for the discussion. I'm not sure where the neutrino-antineutrino pair would come from. Rather, if you go to a detailed level, an up-quark in the proton turns into a down-quark by emitting a W-boson (and thus the proton transmutes into a neutron), which interacts with the electron, turning it into a neutrino. Beta decays, closely related to electron capture, are other well-known examples where the weak force transmutes protons and neutrons.
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Post by ubique on Jan 13, 2012 23:58:41 GMT -4
Hello all, first post here! Others have covered main parts of the post below while I waited for the account to be approved, but I'll still add a couple of points: so an astronaut going to the moon would experience a concentrated dose of radiation as he traveled thru the belts followed by continual doses from then on. There would be virtually no space devoid of radiation. so to say that the only danger is the van Allen belt is not valid, in space there would be continuous radiation exposure. Correct, but you'll need to note that the absorbed dose rate is much lower in the cislunar space than during the VARB transit. It's not a problem for a short trip, though it's high enough to cause real trouble for any voyage to Mars, for example. No, it can't be, because solar wind is captured in Earth's magnetic field (and other processes also produce trapped particles). This is not true. Free neutrons will decay to a proton, an electron, and an antineutrino, with a half-life of about 15 min. A proton can absorb an electron and turn into a neutrino, in a process called electron capture.
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