Invented by Ernest O. Lawrence, in 1934, cyclotron is a kind of particle accelerator (a machine which uses electromagnetic fields for propagation of charged particles to approx light speed and contain them in a well-defined beam) in which the charged particles get accelerated in an outward direction from the centre, following a spiral path.
Static magnetic field holds the charged particles in a spiral trajectory and the rapidly varying electric field accelerates them. Lawrence was honoured by the Nobel Prize in physics for his invention in 1939.
Cyclotrons remained the most powerful particle accelerator in technology, until the very 1950s. Cyclotrons are used to produce the particle beams in nuclear medicine and also in physics.
WORKING OF A CYCLOTRON
The charged particle beam is accelerated by a cyclotron using a high frequency alternating voltage, applied between two of the hollow ‘D’-shaped sheet metal electrode also known as ‘dees’, inside of the vacuum chamber. A cylindrical space is created for the particles to move by placing the dees face to face, while leaving a narrow gap between them.
The particles are then injected into the centre of the space. Due to the Lorentz force, the magnetic field results in bending of the particle in a circle. The electric field makes the electrons to accelerate between the dees of the magnetic field region. To make the electrons accelerate back across the gap, the field gets reversed at the cyclotron frequency. Using the principle of cyclotron to accelerate electrons, it is known as betatron.
A moving electric charge in a cyclotron continues to move in a circular path, under the influence of a magnetic field which is constant.
APPLICATIONS OF CYCLOTRON
- Cyclotron uses electrical power to accelerate charged particles in the spiral path. This collision of particles results in creation of radioactive isotopes which are further used in the field of medicine, industry and scientific research.
- They are even used in particle therapy to treat cancer. The ion beams from cyclotrons can penetrate the body, killing tumour.
- Cyclotrons are also source of high-energy beams for the nuclear physics experiments.
- Cyclotrons are used to produce positron-emitting isotopes, by bombarding other atoms, which are suitable for PET imaging.
- Cyclotrons can produce a continuous stream of particles at the very target. This is turn makes the power high.