Linear particle accelerator

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linear particle accelerator (often abbreviated as linac ) is a type of particle accelerator that accelerates particles or charged subatomic ions to a high speed by subjecting them to a series of potential electric oscillations along a linear straight line. Principles for such a machine were proposed by Gustav Ising in 1924, while the first machine working was built by Rolf WiderÃÆ'¸e in 1928 at RWTH University Aachen. Linac has many applications: they produce X-rays and high-energy electrons for therapeutic purposes in radiation therapy, functioning as particle injectors for higher-energy accelerators, and used directly to achieve the highest kinetic energy for light particles (electrons and positrons) for particle physics.

The design of linac depends on the type of particle being accelerated: electrons, protons or ions. Linac ranges in size from a cathode ray tube (which is a linac type) to a 3.2-kilometer (2.0-mile) linac at the SLAC National Accelerator Laboratory in Menlo Park, California.

Video Linear particle accelerator

Construction and operation

View animated diagrams. A linear particle accelerator consists of the following parts:

• Vacant hollow space containing other components. It is evacuated with a vacuum pump so that the accelerated particles will not collide with the air molecules. The length will vary with the app. If the device is used for the production of X-rays for inspection or therapy, the pipe may be only 0.5 to 1.5 meters in length. If the tool becomes an injector for a synchrotron, its length may be about ten meters. If the device is used as the main accelerator for nuclear particle investigation, it may be several thousand meters in length.
• The particle source (S) . The design of the source depends on the particles being accelerated. Electrons are generated by cold cathode, hot cathode, photocathode, or radio frequency (RF) ion source. Protons are generated in ion sources, which can have many different designs. If the heavier particles have to be accelerated, (for example, uranium ions), a special ion source is required. The source has a high voltage supply to inject particles into the beamline.
• Extend along the pipeline from the source is a series of open cylindrical (C1, C2, C3, C4) open cylinders , increasing in length by the distance from the source. Particles from the source pass through this electrode. The length of each electrode is determined by the frequency and power of the driving and particle resources to be accelerated, so that the particles pass through each electrode in one half cycle of the acceleration voltage. The particle mass has a large effect on the length of the cylindrical electrode; for example, electrons are much lighter than protons and usually require smaller cylindrical electrode parts because of their rapid acceleration.
• The target (not shown) with which the particle collides, is located at the end of the acceleration electrode. If electrons are accelerated to produce X-rays then a tungsten target of cooling water is used. Various target materials are used when protons or other nuclei are accelerated, depending on special investigation. Behind the targets are the various detectors to detect the particles generated from the incoming particle collisions with the target atoms. Many linacs act as early accelerator stages for larger particle accelerators such as synchrotrons and storage rings, and in this case after leaving the electrodes, the accelerated particles enter the next accelerator stage.
• An electronic oscillator and amplifier (G) that produces a high-frequency radio frequency AC voltage (usually thousands of volts) applied to the cylindrical electrode. This is the acceleration voltage that produces an electric field that accelerates particles. As shown, the opposite phase voltage is applied to the sequential electrode. A high power accelerator will have a separate supply to power each of the electrodes, all synchronized to the same frequency.

As shown in the animation, the oscillation voltage applied to the alternative cylindrical electrode has the opposite polarity (180 ° out of phase), so that the adjacent electrode has the opposite voltage. This creates an oscillating electric field (E) in the gap between each pair of electrodes, which gives force to the particles as they pass through, energizing them by accelerating them. The particle source injects a group of particles into the first electrode after each voltage cycle, when the charge on the electrode is opposite to the charge on the particles. The electrodes are made with the correct length so that the accelerated particles take one half cycle to pass through each electrode. Whenever a group of particles passes through the electrode, the oscillating voltage changes the polarity, so that when the particles reach the gap between the electric field electrodes in the right direction to accelerate them. Therefore the particles accelerate to a faster velocity each time they pass between the electrodes; there is a small electric field inside the electrode so that the particle runs at a constant speed in each electrode.

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${\ displaystyle E = qNV_ {p}} Â Â$

volt elektron, di mana ${\ displaystyle N}  ÂÂ$ adalah jumlah elektroda yang dipercepat dalam mesin.

At speeds near the speed of light, additional speed increases will become small, with energy emerging as an increase in particle mass. In the accelerator section where this happens, the length of the tubular electrode will be almost constant. Additional magnetic or electrostatic magnetic elements can be incorporated to ensure that the beam remains at the center of the pipe and its electrodes. Very long accelerators can maintain proper alignment of their components through the use of laser-guided servo systems.

Maps Linear particle accelerator

Benefits

Linear accelerators can produce higher particle energy than previous electrostatic particle accelerators used when created; Cockcroft-Walton accelerator and Van de Graaff generator. In this machine, the particle is only accelerated once by the applied voltage, so that the particle energy in the electron volts equals the acceleration voltage on the engine, which is limited to several million volts by insulation damage. In linac, the particles are accelerated several times by the applied voltage, so that the particle energy is not limited by the accelerated voltage.

High power linacs are also being developed for the production of electrons at relativistic speeds, necessary because the fast electrons moving in the arc will lose energy through synchrotron radiation; this limits the maximum power that can be given to an electron in a given size synchrotron. Linac is also capable of producing exceptional output, producing an almost continuous flow of particles, while the synchrotron will only periodically raise particles to enough energy to get a "shot" at the target. (The bursts can be stored or stored in the ring at the energy to give the experimental electronic time to work, but the average output current is still limited.) The high density of the output makes the linac very attractive for use in loading ring storage facilities with particles in preparation for particle to particle collision. High mass output also makes practical devices for the production of antimatter particles, which are generally difficult to obtain, only a small part of the target collision product. These can then be stored and used further to study the decay of the antimatter material.

medical Linac

Linac-based radiation therapy for cancer therapy started with the first patient care in 1953 in London at Hammersmith Hospital, with an 8 MV engine built by Metropolitan-Vickers, as the first dedicated medical line. Moments later in 1955, MV 6 linac therapy from different machines was being used in the United States.

Linac medical class accelerates electrons using waveguide tuned-cavities, where RF power creates standing waves. Some linacs have short waveguides and are mounted vertically, while higher energy engines tend to have horizontal, long waveguide and magnetic bending to alter the rays vertically in the direction of the patient. Medical Linac uses electron monoenergetic electrons between 4 and 25 MeV, giving X-ray output with energy spectrum up to and including electron energy when electrons are directed to high-density targets (such as tungsten). Electrons or X-rays can be used to treat benign and malignant diseases. The LINAC produces a reliable, flexible and accurate beam of radiation. LINAC's flexibility is a potential advantage over cobalt therapy as a treatment tool. In addition, the device can only be turned off when not in use; no source needs a heavy shield - although the treatment room itself requires large shields on walls, doors, ceilings, etc. to prevent the release of scattered radiation. The use of high-powered engines (& gt; 18Ã, MeV) continuously can cause significant amounts of radiation within the metal parts of the engine head after engine power is removed (ie active sources and necessary precautions must be taken). observed).

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Applications for the development of medical isotopes

The expected scarcity associated with Mo-99, and the technetium-99m medical isotope obtained from it, has also illuminated the linear accelerator technology to produce Mo-99 from unenriched Uranium-235 through neutron bombing. This will enable the medical isotope industry to produce this important isotope with a sub-critical process. Aging facilities, such as Chalk River Laboratories in Ontario Canada, which currently still produce the most Mo-99 from the highly enriched Uranium-235 can be replaced by this new process. In this way, the sub-critical loading of uranium salt dissolved in heavy water with subsequent neutron photo bombings and the extraction of the target product, Mo-99, will be achieved.

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Disadvantages

• The device length limits the location where someone can be placed.
• A large number of their associated driver devices and power supplies are required, increasing the cost of construction and maintenance of this section.
• If the acceleration cavity wall is made of a material that normally performs and a large accelerated field, the wall resistivity converts the electrical energy into heat rapidly. On the other hand, superconductors also require constant cooling to keep them below their critical temperature, and the acceleration plane is limited by quenches. Therefore, high energy accelerators such as SLAC, still the world's longest (in various generations), are run with short pulses, limiting average current outputs and forcing experimental detectors to handle data coming in short bursts.

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See also

src: cdn.abclocal.go.com

References

src: home.cern

External links

• Linear Particle Accelerator (LINAC) animation by Ionactive
• 2MV Tandetron linear particle accelerator in Ljubljana, Slovenia

Source of the article : Wikipedia