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Bremsstrahlung - electron acceleration or deceleration?

Deceleration
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Both
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Author Topic: Bremsstrahlung: Acceleration / Deceleration?  (Read 71290 times)

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NC Bound

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Re: Bremsstrahlung: Acceleration / Deceleration?
« Reply #50 on: Apr 26, 2007, 01:22 »
Bremsstrahlung
  Radiation emitted by a charged particle under acceleration. In particular, the term is used for radiation caused by decelerations (the word is German for braking radiation) when passing through the field of atomic nuclei (external bremsstrahlung). Radiation emitted by a charged particle moving in a magnetic field is called synchrotron radiation.
The energy emitted by an accelerated particle is proportional to 1/m2, with m the rest mass of the particle; bremsstrahlung therefore plays a particularly important role for light particles; up to energies of 100 GeV, bremsstrahlung contributes substantially to energy loss in matter only for electrons. At the critical energy  , for electrons approximately given by   MeV/Z, the average energy loss by radiation and by ionization is the same (Z is the atomic number of the traversed material).
The energy spectrum of  rays due to bremsstrahlung of electrons decelerated in the field of atomic nuclei depends on the energy levels of the atomic electrons, due to the screening effect they have on the moving particle, and on the particle velocity. The spectrum extends up to quanta of the energy of the moving particle. In the high-energy limit the probability density is given by
 
where k = radiated energy, x = path length, X0 = radiation length, and F is a slowly varying function not very different from unity, that can be approximated by
 
with R=1-k/E. 
To a reasonable approximation, the amount of energy radiated per energy interval is constant.
Integration of the above formula results in the average energy loss per unit length which comes out to be
 
(this is more or less the definition of the radiation length X0).
In the relativistic limit, the radiated energy is contained in a narrow cone of average half-angle
 
independent of radiated energy.
The term internal bremsstrahlung is used to describe the radiation of non-virtual quanta, i.e. photons or gluons, by particles participating in an interaction. The formulae given for internal bremsstrah lung in electron scattering in the relativistic limit are
 
 
where  is the square of the four-momentum transfer, m the particle mass and F(E,k) has been given above.
In high-energy physics, bremsstrahlung has been put to use in constructing photon beams. Coherent bremsstrahlung on crystals with incident energetic electron beams has produced photon beams with energies > 200 GeV/c

Offline SloGlo

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Re: Bremsstrahlung: Acceleration / Deceleration?
« Reply #51 on: Apr 27, 2007, 09:53 »
Ya gotta love these kinda posts...  now what color is green???

green iz dat part uva spectrum witch kin be found by squaring da inverse uva wavelangth expulsion (meashured by columbs per cc/4) phrum da collision of yellow 'n blu photons.   sheeesh..............
« Last Edit: Apr 27, 2007, 09:54 by SloGlo »
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dew the best ya kin, wit watt ya have, ware yinze are!

Offline Rennhack

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Re: Bremsstrahlung: Acceleration / Deceleration?
« Reply #52 on: Apr 04, 2009, 02:19 »
Here is an update, wikipedia has a good explanation:

Source: http://en.wikipedia.org/wiki/Bremsstrahlung


Bremsstrahlung from German bremsen "to brake" and Strahlung "radiation", i.e. "braking radiation" or "deceleration radiation"), is electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus. The term is also used to refer to the process of producing the radiation. Bremsstrahlung has a continuous spectrum. The phenomenon was discovered by Nikola Tesla during high frequency research he conducted between 1888 and 1897.

Bremsstrahlung may also be referred to as free-free radiation. This refers to the radiation that arises as a result of a charged particle that is free both before and after the deflection (acceleration) that causes the emission. Strictly speaking, bremsstrahlung refers to any radiation due to the acceleration of a charged particle, which includes synchrotron radiation; however, it is frequently used (even when not speaking German) in the more narrow sense of radiation from electrons stopping in matter.

The word Bremsstrahlung is retained from the original German to describe the radiation which is emitted when electrons are decelerated or "braked" when they are fired at a metal target. Accelerated charges give off electromagnetic radiation, and when the energy of the bombarding electrons is high enough, that radiation is in the X-ray region of the electromagnetic spectrum. It is characterized by a continuous distribution of radiation which becomes more intense and shifts toward higher frequencies when the energy of the bombarding electrons is increased.

Outer Bremsstrahlung
"Outer bremsstrahlung" is the term applied in cases where the energy loss by radiation greatly exceeds that by ionization as a stopping mechanism in matter. This is seen clearly for electrons with energies above 50 keV.

Inner Bremsstrahlung
"Inner bremsstrahlung" is the term applied to the less frequent case of radiation emission during beta decay, resulting in the emission of a photon of energy less than or equal to the maximum energy available in the nuclear transition. Inner bremsstrahlung is caused by the abrupt change in the electric field in the region of the nucleus of the atom undergoing decay, in a manner similar to that which causes outer bremsstrahlung. In electron and positron emission the photon's energy comes from the electron/nucleon pair, with the spectrum of the bremsstrahlung decreasing continuously with increasing energy of the beta particle. In electron capture the energy comes at the expense of the neutrino, and the spectrum is greatest at about one third of the normal neutrino energy, reaching zero at zero energy and at normal neutrino energy.

Beta particle-emitting substances sometimes exhibit a weak radiation with continuous spectrum that is due to both outer and inner bremsstrahlung, or to one of them alone.


Secondary radiation
Bremsstrahlung is a type of "secondary radiation", in that it is produced as a result of stopping (or slowing) the primary radiation (beta particles). In some cases, e.g. 32P, the Bremsstrahlung produced by shielding this radiation with the normally used dense materials (e.g. lead) is itself dangerous; in such cases, shielding must be accomplished with low density materials, e.g. Plexiglass (lucite), plastic, wood, or water; because the rate of deceleration of the electron is slower, the radiation given off has a longer wavelength and is therefore less penetrating.


Source: http://en.wikipedia.org/wiki/Bremsstrahlung
« Last Edit: Apr 04, 2009, 04:02 by Rennhack »

B.PRESGROVE

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Re: Bremsstrahlung: Acceleration / Deceleration?
« Reply #53 on: Apr 04, 2009, 12:37 »
Bremsstrahlung is a type of "secondary radiation", in that it is produced as a result of stopping (or slowing) the primary radiation (beta particles). In some cases, e.g. 32P, the Bremsstrahlung produced by shielding this radiation with the normally used dense materials (e.g. lead) is itself dangerous; in such cases, shielding must be accomplished with low density materials, e.g. Plexiglass (lucite), plastic, wood, or water; because the rate of deceleration of the electron is slower, the radiation given off has a longer wavelength and is therefore less penetrating.

In the Nuke Pharmacy world I now work in we deal with this on a regular basis.  There are certain "doses", drugs, that once active cannot be put into a lead pig due to the increase in gamma radiation.  We inturn must use a thick plastic pig in order to transport the meds.  It was funny because on of the guys I work with didnt understand this consept and put the dose in a lead lined pig only to cause the 110 to start chirpin like crazy.  He of cousre thought he had contaminated the whole world, but after simple explaining he understood.  Great thread on this topic.  Not many folks understand this unless they have delt with it first hand.
« Last Edit: Apr 04, 2009, 12:38 by B.PRESGROVE »

atomicarcheologist

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Re: Bremsstrahlung: Acceleration / Deceleration?
« Reply #54 on: Apr 04, 2009, 12:50 »
Bremsstrahlung
 

I noticed that all the formulae in this post have been eliminated.  Does anyone have them to post?

Offline Rennhack

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Re: Bremsstrahlung: Acceleration / Deceleration?
« Reply #55 on: Apr 04, 2009, 03:49 »
I noticed that all the formulae in this post have been eliminated.  Does anyone have them to post?
http://en.wikipedia.org/wiki/Bremsstrahlung

 


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