Production Of X ray

August 28, 2026 3 Min Read

Production of X Rays-

INTRODUCTION-

When the electrons are accelerated to energies in excess of 5KeV and are than directed onto a target surface, X-rays may be emitted. The production of X ray principally from rapid deceleration of the electrons when they interact with the nucleus of the target atoms. These X-rays are known as ‘Bremsstrahlung’ or braking radiation. The essential features of a simple, low output, X-ray tube are shown in Figure 2.1 and comprise:

1.A heated metal filament to provide a copious supply of electron by thermionic emission and to act as a cathode

2. An evacuated chamber across which a potential difference can be applied

3. A metal anode (the target) with a high efficiency for conversion of electron energy into X-ray photons

4. A thinner window in the chamber wall that will be transparent to most of the X-rays

Electrical Supply to the Tube-

This tube will be energised by an electrical supply generator with the following features:
• An input transformer to adjust primary and secondary voltages
• A high voltage transformer to provide up to 150 kV
• A rectifier system to convert alternating current (AC) to direct current (DC)
• A low voltage transformer providing 8–12 V for the filament heating
• A timing mechanism for terminating exposures

Essential features of a simple, stationary anode X-ray tube. Note that for simplicity only X-ray photons passing through the window are shown. In practice they are emitted in all directions.

Thermionic emission-

Thermionic emission (archaically known as the Edison effect) is the flow of charged particles called thermions from a charged metal or a charged metal oxide surface, caused by thermal vibrational energy overcoming the electrostatic forces holding electrons to the surface.

Factors affecting the rate of thermionic emission-

The number of electrons emitted per second from a surface depends on the following three factors:
1. The nature of the metal surface: Lower the work function of the metal, greater is the rate of emission of electrons from its surface.
2. The temperature of the surface: Higher the temperature of the surface, greater is the rate of emission of electrons from the surface.
3. The surface area of the metal: Larger the surface area of the metal emitting the electrons, greater is the rate of emission of electrons.

INTERACTION OF ELECTRON WITH MATTER-

When electron with high kinetic energy strike on the tagret material than it loss it’s energy than more part of it’s energy convert into heat(99%) and some part of radiation (<1%). By interaction between the electron and matter there are two types of Radiation emit.

1.Bremsstrahlung Interaction

2.Characteristic radiation

Characteristic radiation-

Characteristic radiation is a type of energy emission relevant for X-ray production. This energy emission happens when a fast-moving electron collides with a K-shell electron, the electron in the K-shell is ejected (provided the energy of the incident electron is greater than the binding energy of K-shell electron) leaving behind a ‘hole’. An outer shell electron fills this hole (from the L-shell, M-shell, etc. ) with an emission of a single x-ray photon, sometimes called a characteristic photon, with an energy level equivalent to the energy level difference between the outer and inner shell electron involved in the transition.

The bremsstrahlung x-rays-

The bremsstrahlung x-rays are emitted when electrons get decelerated when fired against a metal target. These charged particles emit bremsstrahlung radiation in the form of photons or bremsstrahlung x-rays. The continuous spectrum formed due to the bombardment of electrons lies in the x-ray region of the electromagnetic spectrum. The energy peaks of the x-ray spectrum tend to shift towards higher frequencies with the increase in energy of the electrons. Often the bombarding electrons also eject electrons from the inner atomic shells of the target metal. The vacancies are quickly filled by dropping electrons from the higher atomic shells. As a result, bremsstrahlung x-rays are emitted.