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Is there a material that can emit gamma radiation when heated by electricity?

  1. Jan 19, 2013 #1
    Different materials emit different frequencies of radiation when heated by a source of heat such as electricity. Examples include gases and solid filaments that emit infrared, visible and ultraviolet radiation, and the scheelite calcium tungstate filaments used to produce x-rays in fluoroscopes. So is there a material that can emit gamma radiation when powered by electricity?
     
    Last edited: Jan 19, 2013
  2. jcsd
  3. Jan 19, 2013 #2
    No, there's no such material. I'll explain why:

    EM emission by heating, bombardment with electrons, etc., occurs when atoms/molecules get excited into higher energy states and then release that energy in the form of radiation. It can do so all in one go, or in a series of lower energy emissions. I'll assume all the energy is released into one photon, since this is the best case scenario for high energy/frequency radiation being produced. There are a few different modes that can be excited: electronic (promoting electrons to higher energy levels), rotational, and vibrational. Electron energy levels are typically the furthest apart and so this is the mode that gives highest frequency radiation. In each case, the limiting factor is how much energy can be absorbed before breaking the relevant bond. For electronic excitation, at a certain amount of energy the atom is ionized; hence, this is the highest energy photon that can be emitted in this process.

    Typical ionization energies of various elements are on the order of 10 electron volts. Chemical bond strength (which is relevant for rotational and vibrational excitation) are on the order of 1eV, so electronic excitation is the best bet. Plus, since chemical bonding happens due to the electronic structure of the atoms, it's a fair assumption that their energies will never depart very much from typical ionization energies. The element with the highest ionization energy is helium: about 25eV. So the most energetic photon that helium can emit before being ionized has energy 25eV, which through the relation ##E=hf## corresponds to a frequency of about ##6\times10^{15} Hz##. Gamma rays, however, have frequencies of around ##10^{19}Hz## and up, so we're off by over three orders magnitude. The ionization/bond energies of various chemical compounds will all be of about the same order as those of the elements, and certainly won't vary enough to make up a factor of over 1000.

    This is why gamma rays are typically generated by nuclear processes, where the binding energy is much higher—on the order of MeV, or thousands of electron volts.
     
  4. Jan 19, 2013 #3
    Where did you see this?
    As I know, the calcium tungstate is used to detect x-rays and not to produce them.
    A filament in an x-ray source may be used, but to emit electrons and not x-rays. The x-rays are produced by the electrons hitting a target. The energy of the x-rays is mainly due to the electrics fields accelerating the electrons and. It-s not coming from heating the filament.
     
  5. Jan 20, 2013 #4
    So this means that the highest frequency produced directly using electrical energy would be ultraviolet radiation emitted by helium.

    My mistake, for an x-ray emitting process that uses electrical energy, an x-ray tube is needed. The electricity is run through a heating element that is designed to heat up in a vacuum to such a high temperature that the electrons would be ejected out of the element because of thermionic emission. The electrons are then conducted into a copper rod placed inside the tube that acts as the return circuit and the collision of the electrons with the copper rod is what provides the energy that produces the x-rays. The diagram below illustrates the process:

    http://image.wetpaint.com/image/2/sRqDNjdhjWV6xKEB5aBQ2Q81593/GW352H227 [Broken]

    Source: http://www.wikiradiography.com/page/Characteristics+and+Production+of+X-rays

    So is it possible to use x-rays or a lower frequency of radiation to excite an unstable isotope so that it will produce gamma rays, not directly through electricity but because the isotope is being excited by a lower frequency of radiation emitted by a tube containing helium or an x-ray tube, both powered by an electrical source? It is known that neutron activation induces radioactivity by making a stable isotope into an unstable isotope by adding more neutrons to the isotope and this of course results not only in the emission of alpha and beta particles from the decaying isotope but also gamma radiation. Can this process be done using electromagnetic radiation where the isotope's ability to emit gamma radiation is done purely by absorbing the energy of photons and not by adding more neutrons? So that the isotope will not become unstable and decay particles that comprise its atoms but simply absorb lower frequency photons and radiate them as gamma ray photons?
     
    Last edited by a moderator: May 6, 2017
  6. Jan 20, 2013 #5

    mfb

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    The original energy comes from the high voltage between the electrodes, which accelerates the electrons. If you increase this voltage, you can get gamma radiation (where I use the word to describe the energy, not the creation process).

    That could be possible, if you find an isotope with fitting energy levels. The efficiency might be bad, and the ground-state itself would be radioactive (and emitting gamma rays) as well.
    You cannot violate energy conservation. Photon upconversion with x-rays looks... speculative.

    You seem to have some specific application in mind - in that case, it would be interesting to know what you try to do.
     
  7. Jan 20, 2013 #6
    I don't see that the method of heating is important.
    Heat supplied is heat supplied.

    All substances emit electromagnetic radiation, which gamma rays are, of a frequency which rises with their temperature according to well known laws. They do not emit a single frequency due to thermal excitation, but a broad spectrum with defined peak.

    To push this peak upscale so that a significant part includes gamma frequencies would involve very very high temperatures, possibly plasma state materials or beyond.

    Gamma rays are normally generated by other mechanisms.
     
  8. Jan 20, 2013 #7
    Yes of course, the electrons would have to be accelerated to high energies and velocities by a high voltage source first before such high frequencies of radiation can be emitted.

    The idea was to up convert the frequency of the photon using some of the total energy emitted by the radiation source. Maybe some of the low frequency photons could be absorbed by the material and its energy added to the photons to be re-radiated causing the photons to lose energy to the point where they remain in the material. After all there are 2 factors that determine the total energy output of an emitter of radiation and that is the frequency of each individual photon and the rate at which the photons are emitted which is determined by the radiant flux of the emitter. The device that will perform this function could be called a radiation transformer. Analogous to how a step-up transformer can raise voltage but end up lowering current, this radiation transformer can raise the output frequency of the source but lower the radiant flux, maintaining the same net energy output in accordance with the laws of power and energy conservation.

    Anyway thank you for this information. This will be very useful to me and if I have any more questions I will post them here or create a new thread.

    Thank you for the information. This type of method may also work.
     
  9. Jan 20, 2013 #8

    mfb

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    At least with 100% efficiency (=the simple concept you propose) this would violate the second law of thermodynamics.

    For thermal emission: As a rule of thumb, every eV of photon energy requires ~12000K of temperature. To get radiation with 100keV+, you need a temperature above 1 billion K. That can be achieved in particle accelerators and some other high-tech devices.
     
  10. Jan 20, 2013 #9
    The device is definitely not going to achieve 100% efficiency. Losses are to be expected. As a proof of concept, the device simply needs to work even if the losses in energy are considerable.
     
  11. Jan 20, 2013 #10

    nsaspook

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  12. Jan 20, 2013 #11

    mfb

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    That is not just an engineering issue here - the very concept of upconversion needs some mechanism to be inefficient, or you need directed (low-energy) radiation in some way, or something else to account for non-decreasing entropy.
     
  13. Jan 20, 2013 #12

    anorlunda

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    What about synchrotron radiation emitted when a charged particle goes through a magnetic field; is there any theoretical upper limit to the energy of such a photon?
     
  14. Jan 20, 2013 #13

    mfb

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    There is no upper limit. Free-electron lasers use this, for example, but a simple bending magnet has higher-energetic photons.
     
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