7.5 the cyclotron

Question 1

What is the basic theory behind the cyclotron

Answer 1

Frequency of charged particles circling in a magnetic field enables protons to be accelerated to high energies in a circulating beam

Question 2

What is the basic setup of a cyclotron

Answer 2

A source of protons, (ionised hydrogen atoms) is placed at the center of two flat metal boxes open at the diameter. these boxes are connected to high frequency alternating voltage V = V0sin2pift and are situated in a strong vertical magnetic field. this setup is also in a vacuum

Question 3

What happens in a cyclotron step 1

Answer 3

• Charged protons emerge from the central source moving in the horizontal plane enter D1. The path that is followed is semi circular due to the influence of the magnetic field

Question 4

What happens in a cyclotron step 2

Answer 4

When the charged protons next arrive at the narrow gap between the boxes the opposite box will have a negative potential so the protons will be accelerated across the gap by the electric field between the boxes

Question 5

What happens in a cyclotron step 3

Answer 5

They will now enter the second box with extra energy. The charged protons will continue in another semi circle at a higher speed due to the extra energy, (meaning a greater radius), and arrive back at the gap between the boxes where the first box will now be at a negative potential since the voltage supply is alternating at exactly the right frequency.

Question 6

What happens in a cyclotron step 4

Answer 6

Because of step 3 extra energy is again added and the previous steps will repeat with the radius of the proton path increasing each time until they leave the second box tangentially

Question 7

What is the frequency of the alternating voltage

Answer 7

This frequency is twice the frequency of the circulation of the protons

Question 8

Why is a cyclotron accelerating protons only able to reach an energy of 10MeV

Answer 8

The synchronism only lasts so long as mp remains constant

Question 9

How did they overcome the problem relating to the limitations of the cyclotron

Answer 9

synchro-cyclotrons were developed. For these cyclotrons, the frequency of the alternating potential difference was lowered in such a manner as to keep accelerating the protons as their relativistic mass increased.

Question 10

What are some real life uses of cyclotrons.

Answer 10

Cyclotrons can be used to accelerate other positively charged atoms, and they are sometimes used to accelerate the protons used in modern medical treatment such as proton beam therapy