VARIABLE ENERGY CYCLOTRON CENTRE


The Variable Energy Cyclotron Centre (VECC) at Kolkata under the Department of Atomic Energy had been set up for research and development in the fields of nuclear physics, nuclear chemistry, radiation biology and material science etc. In addition to advanced research in basic sciences, work is also carried out in various applied fields. The cyclotron is capable of producing proton rich isotopes which are not produced by reactors. Exploration is done on the medical uses by exposing tumors directly to the charged particle beam and also by producing radioactive nuclides which have applications in nuclear diagnosis and therapeutic purposes.

Cyclotron:The cyclotron is a cyclic charged particle accelerator. The concept of cyclotron was originated by E.O. Lawrence in 1929. In a cyclotron, alternating electric field (voltage) is applied between two "Dee" shaped hollow electrode (that is when one electrode is positive then the other one is negative) which provides acceleration to the positively charged particles. Dee shaped hollow electrodes are placed between north and south poles of an electro-magnet. The magnetic field helps to bend the charged particles path in circular orbit. The charged particles are produced in an ion source located in the centre of the cyclotron. During acceleration, the pressure in the accelerating chamber is maintained around 2 x 10-6 torr (1 torr = 1mm of Hg)..

Principle: The time taken by the particles or particle revolution frequency, inside the hollow electrode to complete one semicircular path (which is governed by the magnetic field) is made equal to the reversal of the alternating voltage applied in the hollow electrodes. So every time particles reaching the Dee edge will find favorable electrode polarity for acceleration. .

Cyclotrons at Kolkata At present, there are two cyclotrons which are accelerating light and light heavy ions. One of them is called as room temperature cyclotron and the other one is superconducting cyclotron. Typical energy of the accelerated particles from room temperature cyclotron is 80 MeV alpha and 20 MeV proton. The accelerated charged particles energy is much higher in superconducting cyclotron compare to room temperature cyclotron.