Electron Beam Technology- Use: Electron Beam Melting Furnace & Electron Microscopes.- How Electron are Produce and make a Beam?-

Electron sources (Gun)Function: To provide an intense beam of high energy electrons.

Two main types of gun.

(1) Thermionic Electron gun. (2) Field Emission gun.

Thermionic Electron Gun Setup

Hot Cathode: Via thermionic emission the heated hot cathode generates a cloud of electrons. (Made up of Tungsten or Lanthanum hexaboride)

Anode: The high voltage between cathode and anode charges the anode positive. So the electric field accelerates the electrons in the direction of the anode.

Heater Voltage: The filament voltage heats the hot cathode so there thermionic emission of electrons is possible

Wehnelt Cylinder: The Wehnelt cylinder focuses the beam. It is charged negative and so the electric field focuses the electron beam in the middle.

Accelerating Voltage: The acceleration voltage generates an electric field between hot cathode and anode. This field accelerates the electrons in the direction of the anode.

Electron Beam: When filament voltage and acceleration voltage are on the electron gun generates a fine beam of fast electrons. This beam is not visible to the unaided eye.

Evacuated Glass Cylinder: The glass tube is evacuated so the electrons do not interact with other particle or atoms.

Function of an Electron Gun

Electron beam technology Free electrons in a vacuum can be manipulated by electric

and magnetic fields to form a fine beam. At the spot of collision of the beam, particles of solid-state matter, most of the kinetic energy of the electrons is converted into heat.

The main advantage of this method is that, the possibility of rapid local heating can be precisely controlled electronically.

The high concentration of energy in a small volume of matter can be reached in this way.

This can lead to results in very fast increases of temperature at the spot of impact, causing the melting or even evaporation of any material, depending on working conditions.

Electron Beam Furnace: In vacuum, the electron beam provides a great source of heat which

can be utilized to melt or modify any material. This ensures that the purest materials can be produced and refined in

electron beam vacuum furnaces. For the production or refinement of rare and refractory metals the

vacuum furnaces are of smaller volume, but for steels, large furnaces with capacity measured in metric tons and electron beam power in megawatts exist in industrialized countries.