What is Particle Accelerator?

A Particle accelerator is a device used for increasing the kinetic energy of electrically charged particles.

The accelerators are the important instruments in conducting research concerning particles such as mesons, anti-proton, and anti-neutron.

Van de Graff generator

Cyclotron

Synchrocyclotron

Betatron

Electron-Synchrotron

Alternating Synchrotron

Linear Accelerator

E.O Lawrence and M.S Livingston invented this Device at Berkeley (united state) in1931.

Cyclotron is the earliest and simplest accelerator, and also called the magnetic resonance oscillator.

Cyclotron is used to accelerate Positive Charged particles.

Cyclotrons produce very high energy Charge Particles.

E.O Lawrence awarded a noble prize for the development of the cyclotron.

In Electric Field a charged particle is accelerated.

In Magnetic field a charged particle can be turned around.

In magnetic field the magnetic force acts as a centripetal force.

Cyclotrons accelerate Charged particle beam using a high alternating voltage oscillator which is applied between two "D“ shaped electrodes (also called "Dees")

The cyclotron consists of two flat semicircular metallic boxes D1 and D2 called the Dees on account of their shape like the letter D.

The two Dees are separated by a narrow gap.

The Dees are connected to the terminals of a high frequency oscillator, so that a potential of several million cycle per second is applied between the Dees, which act as an electrode.

Oscillator establishes an alternating electric field in the gap between the Dees, i.e. the electric field is once directed towards D1 and then towards D2

Thus D1 and D2 become alternating positive and negative at the same rate.

A source is placed at the center of the Dees which supplies a positive ion to accelerate.

These Dees are mounted inside a vacuum chamber; the chamber is mounted horizontally between the pole pieces (N&S) of a huge electromagnet capable of producing a vertical field.

Adnan Shahzada M.Sc Physics, University of Peshawar

The positive ions emitted from the source will be accelerated in the gap towards the Dee which is negative at that time.

Let it be D2 Since, there is no electric field inside the Dees, the positive ion move with constant velocity along circles of constant radius under the influence of magnetic field which is perpendicular the Dees.

If the ions emerge from D2 , the polarity of the applied potential is reversed, the positive ions will again face the negative Dee and thus will be again accelerated by the Electric in the gap.

Since, there velocity is increased, they will now move through along D1 Circular arc of greater radius.

Here, the time passage to complete the semi –circle in the D1 remains the same as in D2.

In this way the positive ions move faster and faster moving in ever – expanding circles until they reach the outer edge of the Dees, where they are deflected by deflector flat and strike the target.

Here it should be remembered that the time required for the positive ions to make one complete turn within Dees is equal to the time period of the oscillator.

RadiusThe magnetic force acting on the charge particle is

given by

As this force acts as centripetal force, so we have

Above equation represents the radius of the circular path followed by the charged particle inside the magnetic field

Note: Radius at each turn increase due to increase in velocity, therefore it behaves like the spiral.

Angular velocity

Above equation represents the angular velocity

Frequency

Above equation represents the frequency of circulating charge

Time Period

This is the required time period of circulating charge.

Note: From the calculation we came to know that the Frequency and Time period are independent of radius.

Kinetic Energy

This is the required kinetic energy of the circulating ion.

It cannot accelerate neutron, because neutron do not have any charge.

It cannot accelerate electron because of its small mass.

Cyclotron is used to bombard nuclei with energetic particles and observe the nuclear reactions.

Cyclotron is used for different radioactive tests in hospitals for diagnosis. Like in the treatment of Cancer.

Introduction to Atomic and Nuclear Physics By Henry Semat and John R. Albright

Introduction to Nuclear Physics By Kenneth S. Krane

Introduction to Nuclear physics by Irving kaplan

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