How do ions get accelerated repeatedly in a cyclotron?

[lightuplightup]

Hi- does anyone know much about Cyclotrons?I don't know how to answer the following point:

Describe how ions could be accelerated to high energies if they could be made to move in a circular path inside the dees so that they repeatedly moved across the electric field, the direction of which was reversing every half revolution.

I think I am not understanding because of the way it is worded.

Any help or suggestions appreciated

 

[maverick280857]

The space between the dees is used to accelerate the electron using an electric field antiparallel to the direction of intended motion of the electron. The magnetic field inside the dees exerts a sideways deflecting force on the electrons changing the direction of their velocities but not changing the speeds at all (since the magnetic force and the velocity are orthogonal).

Then check: http://en.wikipedia.org/wiki/Cyclotron

Cheers
Vivek

 

[OlderDan]

Hi- does anyone know much about Cyclotrons?I don't know how to answer the following point:

Describe how ions could be accelerated to high energies if they could be made to move in a circular path inside the dees so that they repeatedly moved across the electric field, the direction of which was reversing every half revolution.

I think I am not understanding because of the way it is worded.

Any help or suggestions appreciated

A positive ion in an electric field experiences a force in the direction of the field. A negative ion experiences a force in the opposite direction of the field. The same ion moving through a magnetic field experiences a force perpendicular to the magentic field and the velocity causing it to follow a circular path if the field and velocity are constant. In the cyclotron, the magnetic field turns the ion back into the gap between the dees where the electric field exists. In order for the ion to be accelerated every time it returns to the gap, the direction of the electric field must be reversed every half revolution of the ions.

You could give some thought to what must happen to the magnetic field to keep turning the ion as it speeds up, or what will happen to the radius of the ion path if the magnetic field is constant.