Cyclotron: A cyclotron is a cyclic magnetic resonance accelerator in which an alternating potential difference of a few kV is used to accelerate light positive ions such as protons, deuterons, -particles, etc., but not electrons, to very high energies of the order of a few MeV. It was developed by E. O. Lawrence and M. S. Livingston in 1932.
Principle: The working of the cyclotron is based on the principle of synchronous acceleration to accelerate charged particles which follow a spiral path perpendicular to a constant magnetic field and make multiple passes through the same alternating potential difference, whose frequency is the same as the frequency of revolution of the particles.
Construction of the cyclotron:
(i) Two hollow D-shaped chambers that are open at their straight edges form the electrodes. They are called the dees
(ii) The dees are separated by asmall gap, as shown in Fig 10.14, and a high-frequency (10 Hz to 10 Hz) alternating potential difference (of the order of 10 V to 10 V) is applied between them.
(iii) The whole system is placed in an evacuated chamber between the poles of a large and strong electromagnet (81 T to 2 T).
(iv) The ions to be accelerated are produced in an ion source; a hydrogen tube gives protons, heavy hydrogen (deuterium) gives deuterons while helium gives x-particles. The positive ions are injected near the centre and are accelerated each time they cross the gap between the dees. At the edge of one of the dees, an electrostatic deflector deflects the spiralling particles out of the system to strike a target.
Working of cyclotron
The dees of the cyclotron are separated by a small gap [See Fig. 10.14] and a high-frequency alternating potential difference is applied between them. Light positive ions are injected into the system near the centre.Suppose a positive ion of charge and mass is injected when D, is positive and D is negative. The positive ion will accelerate towards Dy. Inside the dees there is no electric field. Hence imide D, it has a constant speed. The magnetic force of magride gel makes it move in a semicircular path through D. The radius of its whit given by equating the centripetal force to the magnetic force
Let be the time spent by the ion to describe the semicircular path. It is also half the prod of excillation T of the alterating potential difference the ions will be in reman with the electric field in the gap. That is, the ion will emerge from D, at the instant D, becomes negative and will be accelerated towards D, As the ion gains spent in the gap its path in D, has greater radius. This process repeats after every hall cycle of the alternating potential difference and the ion is accelerated each time ches the gap between the dees
The radius of the path of the charged particles increases proportionately with their speed, but the period of evolution remains practically constant. This is true for peed of light in free space)
After a large number of revolutions, the ion reaches the edge of the system where a negatively changed electrostatic deflector plate deflects it out of the system towards the target
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