The Naked Scientists

The Naked Scientists Forum

Author Topic: Questions regarding Bremsstrahlung  (Read 3756 times)

Offline chiralSPO

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 1872
  • Thanked: 143 times
    • View Profile
Questions regarding Bremsstrahlung
« on: 08/11/2014 19:13:08 »
As I understand it, any charged particle that is accelerated (or decelerated) emits electromagnetic radiation called Bremsstrahlung radiation.

Question 1:
Given that most substances are composed of both positively charged and negatively charged particles (protons and electrons) wouldn't any accelerating object emit Bremsstrahlung radiation? Do the effects of the protons and electrons somehow cancel out because of their close proximity? If so how far would the charges need to be separated for the effects to manifest? Would an accelerated ionic lattice (say a salt crystal with ion separation on the order of 120 ) or solution of ions emit?

Question 2:
I am having difficulty thinking about different reference frames involving accelerated particles. For instance, in a particle accelerator or in a plasma orbiting a black hole, an observer outside the system can see (detect) the emitted radiation (synchrotron radiation etc.), but what would an observer that is at rest with respect to the accelerating particles see?


 

Offline evan_au

  • Neilep Level Member
  • ******
  • Posts: 4106
  • Thanked: 245 times
    • View Profile
Re: Questions regarding Bremsstrahlung
« Reply #1 on: 09/11/2014 04:58:43 »
Quote from: chiralSPO
Would an ionic lattice (say a salt crystal with ion separation on the order of 120 ) or solution of ions emit?

Bremsstrahlung radiation only happens when the charged particles comes out of an interaction with less energy than when they approached. This reduction in speed represents a change in energy, which is radiated away by the Bremsstrahlung photon(s).

For electrons and protons in an atom, the electrons keep a constant energy (or absorb/emit a line spectrum as they change orbitals), and so do not emit Bremsstrahlung radiation. The same happens for ionic crystals or solutions of ions.

Bremsstrahlung tends to happen in materials that are hot enough to strip the electrons from the nucleus (a plasma). The electrons zooming by the proton (without capture into an atomic orbital) radiate the continuous spectrum of Bremsstrahlung.
 

Offline JohnDuffield

  • Sr. Member
  • ****
  • Posts: 488
  • Thanked: 1 times
    • View Profile
Re: Questions regarding Bremsstrahlung
« Reply #2 on: 10/11/2014 13:40:50 »
Good answer, evan. If I can just pick up on one small point:

...For instance, in a particle accelerator or in a plasma orbiting a black hole, an observer outside the system can see (detect) the emitted radiation (synchrotron radiation etc.), but what would an observer that is at rest with respect to the accelerating particles see?
A plasma orbiting a black hole isn't accelerating in the Newtonian sense. There's no emitted radiation, just as there's no radiation emitted when an electron falls down.
 

Offline chiralSPO

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 1872
  • Thanked: 143 times
    • View Profile
Re: Questions regarding Bremsstrahlung
« Reply #3 on: 10/11/2014 15:47:41 »
Thanks guys! I think these answers clear up some of my misconceptions. Let me try again to make sure I have this right: the radiation is only released when a charged particle loses kinetic energy due to an interaction with an electric or magnetic field. So this means the radiation emitted by charged particles around a black hole is due to interactions with its magnetic field, not its gravitation field, then?
 

Offline JohnDuffield

  • Sr. Member
  • ****
  • Posts: 488
  • Thanked: 1 times
    • View Profile
Re: Questions regarding Bremsstrahlung
« Reply #4 on: 10/11/2014 16:14:26 »
Let me try again to make sure I have this right: the radiation is only released when a charged particle loses kinetic energy due to an interaction with an electric or magnetic field.
Hmmmn, maybe that's not quite right. When it comes to electromagnetism, the field is the electromagnetic field. What we call an electric or magnetic field are two "aspects" of this. And see Wikipedia where you can read this:

"Bremsstrahlung (German pronunciation: [ˈbʁɛmsˌʃtʁaːlʊŋ] ( listen), from bremsen "to brake" and Strahlung "radiation", i.e. "braking radiation" or "deceleration radiation") is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typically an electron by an atomic nucleus....

Strictly speaking, braking radiation is any radiation due to the acceleration of a charged particle, which includes synchrotron radiation, cyclotron radiation, and the emission of electrons and positrons during beta decay. However, the term is frequently used in the more narrow sense of radiation from electrons (from whatever source) slowing in matter."


See how it emphasis slowing in matter?
 
So this means the radiation emitted by charged particles around a black hole is due to interactions with its magnetic field, not its gravitation field, then?
Not necessarily. We don't actually know that a black hole has a magnetic field. I like Friedwardt Winterberg's firewall myself.

"If the balance of forces holding together elementary particles is destroyed near the event horizon, all matter would be converted into zero rest mass particles which could explain the large energy release of gamma ray bursters..."
 

Offline PmbPhy

  • Neilep Level Member
  • ******
  • Posts: 2760
  • Thanked: 38 times
    • View Profile
Re: Questions regarding Bremsstrahlung
« Reply #5 on: 11/11/2014 02:20:24 »
Quote from: chiralSPO
As I understand it, any charged particle that is accelerated (or decelerated) emits electromagnetic radiation called Bremsstrahlung radiation.

Question 1:
Given that most substances are composed of both positively charged and negatively charged particles (protons and electrons) wouldn't any accelerating object emit Bremsstrahlung radiation?
Not other than black body radiation, Bremsstrahlung radiation. Quantum effects are prevalent on the atomic level and then quantum mechanics is used and that gives a different story.'

Quote from: chiralSPO
Question 2:
I am having difficulty thinking about different reference frames involving accelerated particles. For instance, in a particle accelerator or in a plasma orbiting a black hole, an observer outside the system can see (detect) the emitted radiation (synchrotron radiation etc.), but what would an observer that is at rest with respect to the accelerating particles see?
They wouldn't detect radiation. Radiation is only detected when there is a relative acceleration between charged particle and radiation detector.

I collected a bunch of articles on this. They're listed with their abstracts at:
http://home.comcast.net/~peter.m.brown/ref/falling_charge.htm

You can search for them at http://booksc.org/ if you want to read one or more of them. If you need help understanding them please let me know and I'll take a crack at it. I can't promise anything because they're a bit over my head right now. However I'm familiar with the concepts and in some cases the math.
 

Offline evan_au

  • Neilep Level Member
  • ******
  • Posts: 4106
  • Thanked: 245 times
    • View Profile
Re: Questions regarding Bremsstrahlung
« Reply #6 on: 11/11/2014 20:31:17 »
Quote from: JohnDuffield
A plasma orbiting a black hole .... There's no emitted radiation
I guess this comment was talking about radiation in quantum terms; but in a more steam-age terminology:

Gas orbiting a black hole or neutron star is thought to form an accretion disk. The gas will suffer shear stresses due to the different orbital periods at different distances from the black hole. It forms eddies, and dissipates energy due to viscosity; any local magnetic field will cause additional turbulence.

All of this causes the gas to heat up into a plasma, which will radiate like any hot gas. As the charged particles pass each other at high velocity, they will emit Bremsstrahlung radiation.
« Last Edit: 12/11/2014 09:31:56 by evan_au »
 

Offline Toffo

  • Jr. Member
  • **
  • Posts: 19
    • View Profile
Re: Questions regarding Bremsstrahlung
« Reply #7 on: 18/12/2014 12:09:53 »

Given that most substances are composed of both positively charged and negatively charged particles (protons and electrons) wouldn't any accelerating object emit Bremsstrahlung radiation?


Radiation is produced when positive particle moves forwards and starts feeling a backwards pull from a negative particle, while at the same time the negative particle moves forwards and starts feeling a backwards pull from that same positive particle.

Amout of radiation depends on how confused the particles become regarding each other's positions. ... And that depends on distance and acceleration.

« Last Edit: 18/12/2014 12:11:34 by Toffo »
 

Offline JohnDuffield

  • Sr. Member
  • ****
  • Posts: 488
  • Thanked: 1 times
    • View Profile
Re: Questions regarding Bremsstrahlung
« Reply #8 on: 18/12/2014 20:12:40 »
Quote from: JohnDuffield
A plasma orbiting a black hole .... There's no emitted radiation
I guess this comment was talking about radiation in quantum terms; but in a more steam-age terminology:

Gas orbiting a black hole or neutron star is thought to form an accretion disk. The gas will suffer shear stresses due to the different orbital periods at different distances from the black hole. It forms eddies, and dissipates energy due to viscosity; any local magnetic field will cause additional turbulence.

All of this causes the gas to heat up into a plasma, which will radiate like any hot gas. As the charged particles pass each other at high velocity, they will emit Bremsstrahlung radiation.
Fair enough. What I was trying to get across is that a particle in free fall isn't accelerating in the Newtonian sense. It doesn't radiate. 
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11987
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Re: Questions regarding Bremsstrahlung
« Reply #9 on: 19/12/2014 18:47:53 »
I totally agree Chiral. It is confusing :)
Have a look here.

Does accelerated charge emit photons to all observers?

It will mention Bremsstrahlung radiation as one example. And some of the arguments you might not agree with, but that might be a definition question. As for example if you think conservation of energy demands a 'container universe', and then from where you want to define it. At least that was what I got stuck on :)
 

The Naked Scientists Forum

Re: Questions regarding Bremsstrahlung
« Reply #9 on: 19/12/2014 18:47:53 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums