A linear accelerator or linear particle accelerator in short linac is a particle accelerator. The ions or subatomic particles are accelerated to a very high speed using linac. Here the subatomic particle or ion which is to be accelerated is subjected to a series of oscillating electric potential along linear beamline.
The design and the length of linear particle accelerator vary depending upon the particle that is to be accelerated; Proton, Electron or Ions. The size of linac ranges from cathode ray tube to 2 miles long linac at the SLAC National Accelerator Laboratory situated at Menlo Park, California.
A typical linear accelerator comprises of five major parts. They are-
A vacuum chamber in straight hollow pipe form. They are arranged in series fashion and length will vary depending on the requirement. In order to avoid accelerated particles colliding with air molecules, it is evacuated using a vacuum pump.
A particle source, placed at the beginning of accelerator shoots the charged particles which are to be accelerated. The source has its own high energy voltage source to inject these charged particles into the beamline. The design of the source purely depends on the type of particle that is to be accelerated.
Series of open-ended cylindrical Electrodes are spread along the pipe from the source. Their length increases progressively as we move away from the source. The particles are made to pass through these electrodes. The length of each open-ended cylindrical electrode depends exclusively on the particle which is to be accelerated, its mass and frequency and power of driving power source. It is designed in a way that the accelerated particle has to pass through one open-ended cylindrical electrode in exactly one half of the AC(accelerating) voltage.
A target is placed at the end-stage of the linear accelerator, with which the accelerated particle collide. Various detectors are placed beyond the target to study the particle emerged as a result of the collision of the accelerated particle with target atoms.
An electronic oscillator and an amplifier to high potential generate radio frequency AC voltage. This is the major accelerating voltage which results in the generation of an electric field that is necessary to accelerate the particles. The successive cathodes are supplied with opposite phase voltage, all electrodes are synchronized to the same frequency.
Here in the entire process, there will not be exchange or interference of any source. That is the entire system will be isolated from the surrounding. For simple understanding, one can compare this process to the adiabatic process. The transfer of accelerated particle from one electrode to another can be compared to joule thomson effect.
The application of linear accelerator is many. They are used to attain highest-energy electron or positron(light particles) in particle physics. They serve as a particle injector for higher-energy accelerators. They generate high energy electrons and X-Ray for medical purpose in the treatment of cancer(radiotherapy.)
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