Cyclotron Basic Construction and Working Principle
Before understanding the basic working principle of Cyclotron it is necessary to understand force on a moving charged particle in a magnetic field and also motion of the charged particle in the magnetic field.
Force on a Moving Charged Particle in a Magnetic FieldWhen a current carrying conductor of length L metre with current I ampere placed perpendicularly in a magnetic field of flux density B Weber per metre square, then the force rather to say magnetic force acting on the conductor would be
Now, let us consider there are total N number of mobile free electrons in the conductor lie in length L metre causing the current I ampere. Where, e is the electric charge of one electron and it is 1.6 × 10-19 coulomb. Now from equation (1) and (2) we get Here, N number of electrons causing current I ampere, and consider that they travel length L metre in time t, therefore drift velocity of the electrons would be
From equation (3) and (4), we get It is the force acting on N number of electrons in the magnetic field hence force on a single electron in that magnetic field can be
Motion of Charged Particle in a Magnetic FieldWhen a charged particle moves in a magnetic field, there would be extreme two conditions. The particle moves either along the direction of the magnetic field or it moves perpendicular to the magnetic field. When the particle moves along the axis of the direction of magnetic field, magnetic force acting on it, Hence there will be no force acting on the particle, hence no change in the velocity of particle and hence it moves in straight line with constant speed.
Now if the charged particle moves perpendicular to the magnetic field then there will be no change in the speed of the particle. This is because the force acting on the particle is perpendicular to the motion of the particle hence the force will not do any work on the particle so there will be no change in the speed of the particle. But this force acting on the particle perpendicular to its motion and the direction of the motion of the particle will change continuously. As a result the particle will move in a in the field in a circular path of a constant radius with constant speed. If the radius of the circular motion is R metre then Now, Hence radius of the motion depends upon the velocity of the motion. Angular speed and time period are constant.
Basics Principle of CyclotronThis concept of motion of charged particle in a magnetic field was successfully employed in an apparatus called cyclotron. Conceptually this device is very simple but it has huge uses in the field of engineering, physics and medicine. This is a charged particle accelerating device. The motion of the charged particle under perpendicular magnetic field is solely applied in the apparatus named cyclotron.
Construction of CyclotronThis device basically has three main constructional parts
- Large sized electromagnet to create uniform magnetic field in between its two face-to-face placed magnetic opposite poles.
- Two low height hollow half cylinders made of high conductive metals. These components of cyclotron are called Dees.
- A high-frequency alternating high voltage source.