CRT-Cathode Ray Tube
Table of Contents
CRT full form- Cathode Ray Tube
A display screen known as a Cathode Ray Tube (CRT) creates images using a video signal. This particular vacuum tube produces images when an electron beam fired through electron guns collides with a phosphorescent surface. To put it another way, the CRT produces the beams, accelerates them at high speed, and deflects them to produce the images on the phosphorous screen, making the beam visible.
Working of CRT
The movement of electron beams is necessary for the CRT to function. The electron guns produce highly accelerated, razor-sharply focused electrons. When this fast electron beam hits the fluorescent screen, it produces a bright spot.
The beam travels through two pairs of electrostatic deflection plates after leaving the electron gun. When the voltage was applied across these plates, the beams were refracted. The first pair of plates raises the beam, and the second pair of plates shifts it from side to side. The electron can move both horizontally and vertically independently, allowing it to be placed anywhere on the screen. In order to allow the emitted electron to easily move freely from one end of the tube to the other, the working components of a CRT are enclosed in a vacuum glass envelope.
Construction of CRT
The crucial components of the CRT are the Electrons Gun Assembly, Deflection Plate Assembly, Fluorescent Screen, Glass Envelope, and Base. The electron beam is emitted by the electron gun and strikes the phosphorescent screen after passing through deflecting plates. Below is a detailed explanation of each component.
Electrons Gun Assembly
The electron beams come from an electron gun. The heater, cathode, grid, pre-accelerating anode, focusing anode, and accelerating anode are all components of an electron gun. The highly emitted cathode is where the electrons are released. The cathode is shaped like a cylinder, and a layer of strontium and barium oxide is deposited at its end. This layer causes a high emission of electrons at the tube’s end. In the tiny grid, the electron passes through the electron. With a central hole that is coaxial with the CRT axis, this control grid is constructed of nickel material. The electron from the electron gun has a high positive potential that is applied across the pre-accelerating and accelerating anodes as it travels through the control grid.
By using a focusing anode, the beam is focused. The focusing and accelerating electrodes are each cylindrical and have a small opening in the middle. The beams pass through the vertical and horizontal deflecting plates after leaving the focusing anode. The focusing anode is connected to the lower voltage of approximately 500V, while the pre-accelerating and accelerating anodes are connected to the positive high voltage of about 1500V.The electron beam can be focused using one of two techniques. Both the Electrostatic Focussing Beam and the Electromagnetic Focusing fall under this category.
Electrostatic Deflection Plates
Only one direction results in the uniform electrostatic field being produced by the deflection plate. Electrons won’t move in the other directions because the electron beam entering the deflection plates will only accelerate in one direction.
Screen For CRT
The face plate refers to the CRT’s front. The CRT’s face plate is entirely made of fiber optics, which has unique properties. The phosphor is applied to the faceplate’s internal surface. The electrical energy is transformed into light energy by the phosphorous. When the electron beams hit the phosphorous crystal, its energy level increases. Cathodoluminescence is the name given to this phenomenon. Fluorescence is the name for the light that results from the excitation of phosphorous. So The phosphorous crystals return to their original positions after the electron beam stops, at which point they emit a quantum of light energy known as phosphorescence or persistence.
The aqueous graphite solution known as Aquadag is attached to the anode’s secondary. So The secondary emitted electrons that are required to maintain the electrical equilibrium of the CRT screen are collected by the Aquadag.