Linear accelerator

Linear accelerator was created thanks to idea of a Norwegian engineer Rolf Wideroe, who constructed the first linear accelerator based on gradual acceleration of charged particles by an electric field. It was in 1927.

Distribution of linear accelerators

 * 1) electrostatic- according to voltage sources
 * 2) Cockcroft-Walton´s accelerator
 * 3) Van de Graaf accelerator
 * 4) high frequency-according to type of wave
 * 5) accelerator with gradual wave
 * 6) accelerator with standing wave

Electrostatic linear accelerator
They are composed of a voltage sources, hollow vacuum accelerator tube and a target, which is hit by accelerated particles.

Ion source releases particles into the system. Charged particles pass through a series of cylindrical electrodes with gradually increasing in lenght. It is because of compensation for increasing particle velocity. Between the electrodes is gradually increasing high voltage U. A charged particle with charge is accelerated repeatedly by electric field to energy E. Spaces between electrodes direct the flying particles into the narrow sheaf, which falls on target. The target becomes the source of X-RAY.

Cockcroft-Walton´s accelerator
An important component of Cockcroft-Waltonś accelerator is voltage multiplier, which will increase the obtained energy on roughly 4 MeV.

Van de Graff accelerator
Van de Graff accelrator transmits the charges through an insulating belt to high voltage electrode, which is connected with accelerator tube. Energy of particles is getting higher to 10 MeV.

High frequency linear accelerator
High frequency linear accelerator is based on accelerating particles whithout need of high voltage. The source is eliminates paticles into the space of cylindric electrodes. They are attached to alternating electric voltage. The even cylindres are connected to one pole of high frequency source and the second pole contains odd rolls.

When positive charged particle gets into the space of the first electrode with negativ potential, it gains certain energy and speed. Frequency of alternating voltage must be same as polarity of cylinder. When the polarity of cylinder is changed( positive potential), it occurse a shift of particle into the space, which is between cylinders. Subsequently, the second electorde with negative potential is speeding up the particles and it will supply them with energy and speed.

The lenght of electrodes must enhance depending on speed of accelerated particle. Particle acceleration occurs in space between cylindric elecetrodes. Particles are moving inside of cylinder. It is based on an inertia. Particles, which are accelerated in this way, can gain energy about 100MeV. Accelerated particles fall on target. High-energy bremsstrahlung is created when the particles hit the target.

Linear accelerator with gradual wave
The accelerated tube is created by waveguide. There we can find circular apertures, which have in the midle a hole. Electrones are released from source and collide with carrier electromagnetic wave. Its phase speed is smaller than the speed of light. In this way they come under the influence of the accelerating field permanently.

Linear accelerator with standing wave
Particles, which are accelerated by high- frequency linear accelerator, must be bounced back in the end of accelerated path and thereby arises standing wave with large force field. It speeds up the electrones to 10 MeV with frequence 100-100 000 Hz.

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