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Experimental proof that uniformly accelerated charges radiate 
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#1
Sep512, 01:52 AM

P: 303

Hello friends,
I recently, was reading all about the accelerating charges and radiation, but somehow the classical electrodynamics treatment is still inadequate, that is, the radiation reaction force(derived for oscillating charges) vanishes for uniformly accelerating charges. In this view, people tried to investigate self interaction during acceleration, but all in vain because of undefinable quantities at the position of the charge. Now, in between all this do we even have any experiment that confirms the presence of radiation for uniformly accelerated charges. If yes, then does it stick to the Larmor's formula of power dissipation ? Thanks in advance 


#2
Sep512, 03:00 AM

P: 1,115




#3
Sep512, 03:44 AM

P: 303

Ofcourse having put that aside, we have the accelerating charges in EM fields and radiation due to acceleration. Now, you are right in saying that if there is some radiation due to uniformly accelerating electrons it is extremely small and cannot be detected(radiation). But I think there could be ways around it, if instead of the radiation we track the energy of these charge particles in uniform acceleration and deceleration experiments. Whereas, on the other hand, the term uniform acceleration itself is quite complicated, when we include relativity(increase in mass) in static fields, the acceleration should converge to zero when we approach the speed 'c' , Moreover, if there is any radiation during uniform acceleration and therefore radiation reaction force, it would most probably depend on the magnitude of acceleration which would again make the original acceleration nonuniform. And if we extend it further, this nonuniform acceleration again induce radiation and radiation reaction by the known formula. In this light how good is the question about uniform acceleration and radiation ? 


#4
Sep512, 04:35 AM

P: 1,115

Experimental proof that uniformly accelerated charges radiate



#5
Sep512, 06:11 AM

P: 303

[itex]E  (e^2 a c^2/6{\pi}) = m_e c^2(γ1)[/itex] and for appropriately chosen E of the accelerator and its length, it seems the other two energy comes close for 1.05≤γ≤1.1 and normal accelerations(a). If I did everything correctly. Therefore, now by injecting these accelerated particles in a magnetic fields and separating them by their energies can easily show if the particles radiated or not. If I assume my calculations are correct. 


#6
Sep512, 06:33 AM

Sci Advisor
P: 2,470

Are we talking uniform in magnitude and direction? Or magnitude only? Because for later, an electron passing through a bend in an accelerator (E.g. JLab) is a fine example.



#7
Sep512, 06:56 AM

P: 1,115




#8
Sep512, 07:49 AM

P: 303




#9
Sep512, 08:11 AM

P: 303

We did not have point charges when Maxwell's equations were formulated ! and classical electrodynamics is all about point charges. 


#10
Sep512, 10:18 AM

P: 1,115




#11
Sep612, 07:47 AM

P: 1,020

you can see some theoretical arguments here.however it is really messy.http://www.mathpages.com/home/kmath528/kmath528.htm



#12
Sep612, 08:02 AM

Sci Advisor
P: 5,541



#13
Sep612, 08:17 AM

Mentor
P: 11,869

That's not uniform acceleration (constant magnitude and direction).



#14
Sep612, 09:33 AM

P: 303




#15
Sep612, 09:35 AM

P: 303




#16
Sep612, 09:41 AM

P: 1,115




#17
Sep612, 11:14 AM

P: 303




#18
Sep612, 11:50 AM

P: 1,115

F_{rad} is proportional only to da/dt, hence formally vanishes for uniform a = du/dt. My feeling is the problem stems from the unrealistic assumption uniform acceleration has 'always been there'. Drop that, and radiation must be happening. But as to what extent, too much subtle arguing either way for me to place any bets. 


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