Magnetic field and refocusing paraxial electrons

In summary: The magnetic force is the other half. Anyway, I'm glad the links helped. :-)In summary, the technical meaning of refocusing paraxial electrons along the direction of magnetic field is using a magnetic field to focus electrons that are traveling nearly parallel to the axis of the system onto the x-axis. This is achieved by manipulating the equations for pitch and using the Lorentz Force to calculate the distance at which the electrons will be refocused.
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paulina
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what is the technical meaning of refocusing paraxial electrons along the direction of magnetic field?
 
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  • #2
I'm not quite sure. It sounds like making the electrons bunch up as they travel through a magnetic field. In optics, paraxial rays are rays which travel nearly parallel to the optical axis, so I assume that paraxial electrons are electrons that are traveling nearly parallel to the axis of the system. I'm not quite sure what "along the direction of the magnetic field" means, as I'm not well versed in EM theory.
 
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  • #3
paulina said:
what is the technical meaning of refocusing paraxial electrons along the direction of magnetic field?

Can you show us the source of this comment? Either post a link or list where you have read it? Was it in the context of Cathode Ray Tube (CRT) displays, or in the context of particle accelerators?
 
  • #4
berkeman said:
Can you show us the source of this comment? Either post a link or list where you have read it? Was it in the context of Cathode Ray Tube (CRT) displays, or in the context of particle accelerators?

there was a question related to this which i although solved but could not find its true meaning...
"In a region of space a uniform magnetic field Bis along the positive X-axis.Electrons are emitted from the origin with a speed 'v' at different angles.Show that the paraxial electrons are refocused on the x-axis at a distance (2.pi..m.v/Be). Here, m is the mass of electron and e the charge on it."
i found the answer by finding the pitch of an electron which has velocity v along x and y-axis ( v i +v j)...
i have no idea if my attempt was right or wrong.
 
  • #5
Can you post your work on this question? Did you use the Lorentz force in your calculatons?
 
  • #6
berkeman said:
Can you post your work on this question? Did you use the Lorentz force in your calculatons?

(mv^2)/r = B.e.v
r = m.v/B.e
so, T = 2.pi.m/B.e
now, p = v.T (p= pitch)
p = 2.pi.m.v/ B.e

i did not use Lorentz force
now answer to my question please... :(
 
  • #7
paulina said:
(mv^2)/r = B.e.v
r = m.v/B.e
so, T = 2.pi.m/B.e
now, p = v.T (p= pitch)
p = 2.pi.m.v/ B.e

i did not use Lorentz force
now answer to my question please... :(

I'm not tracking exactly what you did with those equations (they may be related to the Lorentz Force, but I'm not sure). In any case, I did a quick Google search on this:

refocusing paraxial electrons along the direction of magnetic field

and got this hit list: https://www.google.com/search?sourc...tic+field&gs_l=hp...0.0.0.427...0.ZfAOzJjBBpA

The first 2 hits are to this PF thread of yours, but the rest look to be good explanations of using magnetic fields to focus electron beams. Please see if the first couple explanation hits are useful for you. :-)
 
  • #8
berkeman said:
I'm not tracking exactly what you did with those equations (they may be related to the Lorentz Force, but I'm not sure). In any case, I did a quick Google search on this:

refocusing paraxial electrons along the direction of magnetic field

and got this hit list: https://www.google.com/search?sourceid=navclient&aq=&oq=refocusing paraxial electrons along the direction of magnetic field&ie=UTF-8&rlz=1T4GGLL_enUS301US302&q=refocusing paraxial electrons along the direction of magnetic field&gs_l=hp...0.0.0.427...0.ZfAOzJjBBpA

The first 2 hits are to this PF thread of yours, but the rest look to be good explanations of using magnetic fields to focus electron beams. Please see if the first couple explanation hits are useful for you. :)
well there is no electric field, so no lorentz force...
anyway thanks for the link...
 
  • #9
paulina said:
well there is no electric field, so no lorentz force...
anyway thanks for the link...

There are 2 parts to the Lorentz Force equation, after all... :-)
 
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1. What is a magnetic field?

A magnetic field is a physical phenomenon that is created by moving electric charges. It is a region in space where magnetic forces act on other objects with magnetic properties.

2. How is a magnetic field generated?

A magnetic field is generated by electric currents or by the movement of particles with an electric charge. It can also be created by permanent magnets.

3. What is the role of a magnetic field in refocusing paraxial electrons?

In the context of paraxial electrons, a magnetic field is used to steer and focus the electrons towards a specific target. By applying a magnetic field, the electrons' trajectory can be controlled and they can be directed towards a focal point.

4. What is the difference between a paraxial electron and a non-paraxial electron?

A paraxial electron is an electron that moves along the optical axis of an electromagnetic lens, while a non-paraxial electron moves at an angle to the optical axis. Paraxial electrons are easier to manipulate and focus than non-paraxial electrons.

5. What are some applications of magnetic fields and refocusing paraxial electrons?

Magnetic fields and refocusing paraxial electrons are used in various fields such as microscopy, particle accelerators, and medical imaging. They are also crucial in the development of technologies such as electron beam lithography and electron microscopy.

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