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How strong is gamma radiation ?

  1. Oct 22, 2012 #1
    Several elementary particles emits gamma radiation
    Where can I read more about the different magnitude?
     
  2. jcsd
  3. Oct 22, 2012 #2

    mfb

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    The amount of emitted radiation per particle number (or atom, or whatever is radiating) can be calculated from the lifetime of the particle. To get the emitted energy, you can multiply that with the energy of the photons.
    You can find formulas at Wikipedia or in any textbook.
     
  4. Oct 22, 2012 #3
    Gamma rays are very strong, very damaging ionizing radiation to humans and among the most powerful decay products. Gamma rays are simply highly energetic electromagnetic radiation, very high frequency at x-ray level and higher, which can result from the decay of energetic atomic nuclei.


    good discussion here:
    http://en.wikipedia.org/wiki/Gamma_radiation
     
  5. Oct 23, 2012 #4
    You said at x ray level or higher... If its at the frequency level of x ray then how do we know its gamma ray? And not x ray?
     
  6. Oct 23, 2012 #5
    Straight off the Wikipedia for Gamma-rays:

    "The distinction between X-rays and gamma rays has changed in recent decades. Originally, the electromagnetic radiation emitted by X-ray tubes almost invariably had a longer wavelength than the radiation (gamma rays) emitted by radioactive nuclei. Older literature distinguished between X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10−11 m, defined as gamma rays. However, with artificial sources now able to duplicate any electromagnetic radiation that originates in the nucleus, as well as far higher energies, the wavelengths characteristic of radioactive gamma ray sources vs. other types, now completely overlap. Thus, gamma rays are now usually distinguished by their origin: X-rays are emitted by definition by electrons outside the nucleus, while gamma rays are emitted by the nucleus."

    Exceptions to this rule:
    "Exceptions to this convention occur in astronomy, where gamma decay is seen in the afterglow of certain supernovas, but other high energy processes known to involve other than radioactive decay are still classed as sources of gamma radiation. A notable example is extremely powerful bursts of high-energy radiation normally referred to as long duration gamma-ray bursts, which produce gamma rays by a mechanism not compatible with radioactive decay. These bursts of gamma rays, thought to be due to the collapse of stars called hypernovas, are the most powerful events so far discovered in the cosmos."
     
  7. Oct 25, 2012 #6
    Use the exponential or decay formula to calculate the disintegration per second.
    Cheers, Rajini
     
  8. Oct 25, 2012 #7

    QuantumPion

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    Completely incorrect. Alpha particles are far more energetic and damaging than gamma rays. So are neutrons.
     
  9. Oct 25, 2012 #8
    I wouldn't say completely incorrect, only partially. It depends upon where the isotope is depisted (internally or externally). Alphas are only internal hazards, and except for extremely energetic ones in very close proximity to skin, not an external hazard. Betas have an actual range inside the human body, whereas photons are only attenuated, so have a tendency to deposit all their energy in teh body rather than be just attenuated. Neutrons have higher Q factor than photons (but less than alphas) and are both internal and external hazards (though how one could get internally deposited radioisotopes thatemit neutrons is beyond me).

    Now, as for what to watch out for, the only stuff an everyday person might be exposed to inadvertantly are alphas, betas, and gammas, so, yes, alphas are generally the worst since this implies contamination of some sort, which is a risk for internal deposition.
     
  10. Oct 25, 2012 #9
    Short halflife spontaneous fission.

    Though that is going to be accompanied by fission fragments. What is the Q factor of fission fragments?

    Biochemically, where will lanthanides and therefore heavy actinides like californium go in a living human body?
     
  11. Oct 25, 2012 #10
    Fission fragments have a Q factor of 20. But spontaneous fission is a small branch ratio for those that undergo SF, and most of these are alpha emitters anyway.
     
  12. Oct 25, 2012 #11

    davenn

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    NO, every reference I read tells me that gamma rays are much more energetic that Alpha particles. And that is bourne out by the fact that it takes a heck of a lot of shielding to stop them, compared to a sheet of paper for an Alpha particle

    The danger from Alpha particles comes from their damage to tissue. Because of their large size, thay dump/loose much more, to all their enery on contact. And ONLY if you are very close ( a few cm's from the source). Any further distance and its easy for the Alpha particle to pick up free electrons and become Helium atoms again

    Where as the much smaller gamma rays pass through and loose much less of their energy.
    The catch22 is tho, that because the gamma ray passes right through the body, it causes a long narrow path of damage, rather than a localised and larger damage area of the Alpha particle

    Dave
     
  13. Oct 25, 2012 #12
    That is correct. Since the alpha particles are much slower, the damage they cause is closer together. Two shocks to DNA that are close together is harder to repair than one isolated shock.
     
  14. Oct 25, 2012 #13

    Vanadium 50

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    More penetrating, not more energetic.

    Most alphas are 5 MeV or so. Gamma rays from common radioactive sources are around 1 MeV.
     
  15. Oct 25, 2012 #14

    davenn

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    hey Vanadium50
    all the ref's I read also stated more energetic maybe they need revised ;)

    it got me doing more searching, wiki says....

    from Britannica...


    OK interesting.... I find it fascinating that a lower energy partical has better penetrating power than a higher energy one.
    I have to assume that this has to do with the tiny size of the gamma photo compared to the huge bulk of a Helium nucleus

    Dave
     
  16. Oct 26, 2012 #15
    Alpha particles are less penetrating because they are charged particles and therefore have a definite range in matter. A general rule of thumb for the range of alpha particles in air (0° and 760 torr) used by health physicists for alpha particles is R (in cm) = 0.56E (where E is the energy in MeV) if E < 4 MeV, and R = 1.24E-2.62 (4MeV<E<8MeV). Bet particles have another rule of thumb, but photons are exponentially attenuated, so theoretically, have infinite range.
     
  17. Oct 26, 2012 #16
    Cm-250 - halflife 8300 years. 80 % spontaneous fission (the other branches are 11 % α, 9 % β).
    Cf-254 - halflife 60 days (not much shorter than Po-210, so definite chance of internal poisoning). 99,69% spontaneous fission, 0,31% alpha.
     
  18. Oct 26, 2012 #17

    QuantumPion

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    The amount of shielding required to block radiation has nothing to do with how energetic or dangerous it is. It takes a astronomical amount of shielding to stop neutrinos but they are clearly not anywhere near as energetic or dangerous as gammas or alphas.
     
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